Jump to content

Testosterone: Difference between revisions

From Wikipedia, the free encyclopedia
Content deleted Content added
m Remove unnecessary |display-author= parameters from CS1 templates; using AWB
cite journal → vcite2 journal
Line 57: Line 57:
}}
}}


'''Testosterone''' is a [[steroid hormone]] from the [[androgen]] group and is found in mammals, reptiles,<ref name="pmid16326949">{{cite journal | author = Cox RM, John-Alder HB | title = Testosterone has opposite effects on male growth in lizards (Sceloporus spp.) with opposite patterns of sexual size dimorphism | journal = J. Exp. Biol. | volume = 208 | issue = Pt 24 | pages = 4679–87 | date = December 2005 | pmid = 16326949 | doi = 10.1242/jeb.01948 | url = }}</ref> birds,<ref name="pmid16671011">{{cite journal | author = Reed WL, Clark ME, Parker PG, Raouf SA, Arguedas N, Monk DS, Snajdr E, Nolan V, Ketterson ED | title = Physiological effects on demography: a long-term experimental study of testosterone's effects on fitness | journal = Am. Nat. | volume = 167 | issue = 5 | pages = 667–83 | date = May 2006 | pmid = 16671011 | doi = 10.1086/503054 | laysource = ScienceDaily | layurl = http://www.sciencedaily.com/releases/2006/05/060526083618.htm }}</ref> and other [[vertebrate]]s. In [[mammal]]s, testosterone is secreted primarily by the [[testicles]] of [[male]]s and the [[ovaries]] of [[female]]s, although small amounts are also secreted by the [[adrenal gland]]s. It is the principal male sex [[hormone]] and an [[anabolic steroid]].
'''Testosterone''' is a [[steroid hormone]] from the [[androgen]] group and is found in mammals, reptiles,<ref name="pmid16326949">{{vcite2 journal | vauthors = Cox RM, John-Alder HB | title = Testosterone has opposite effects on male growth in lizards (Sceloporus spp.) with opposite patterns of sexual size dimorphism | journal = J. Exp. Biol. | volume = 208 | issue = Pt 24 | pages = 4679–87 | date = December 2005 | pmid = 16326949 | doi = 10.1242/jeb.01948 | url = }}</ref> birds,<ref name="pmid16671011">{{vcite2 journal | vauthors = Reed WL, Clark ME, Parker PG, Raouf SA, Arguedas N, Monk DS, Snajdr E, Nolan V, Ketterson ED | title = Physiological effects on demography: a long-term experimental study of testosterone's effects on fitness | journal = Am. Nat. | volume = 167 | issue = 5 | pages = 667–83 | date = May 2006 | pmid = 16671011 | doi = 10.1086/503054 | laysource = ScienceDaily | layurl = http://www.sciencedaily.com/releases/2006/05/060526083618.htm }}</ref> and other [[vertebrate]]s. In [[mammal]]s, testosterone is secreted primarily by the [[testicles]] of [[male]]s and the [[ovaries]] of [[female]]s, although small amounts are also secreted by the [[adrenal gland]]s. It is the principal male sex [[hormone]] and an [[anabolic steroid]].


In men, testosterone plays a key role in the development of male reproductive tissues such as the [[testis]] and [[prostate]] as well as promoting secondary sexual characteristics such as increased [[muscle]], [[bone]] mass, and the growth of [[androgenic hair|body hair]].<ref name="Mooradian_ 1987">{{cite journal | author = Mooradian AD, Morley JE, Korenman SG | title = Biological actions of androgens | journal = Endocr. Rev. | volume = 8 | issue = 1 | pages = 1–28 | date = February 1987 | pmid = 3549275 | doi = 10.1210/edrv-8-1-1 | url = }}</ref> In addition, testosterone is essential for health and well-being<ref name="pmid19707253">{{cite journal | author = Bassil N, Alkaade S, Morley JE | title = The benefits and risks of testosterone replacement therapy: a review | journal = Ther Clin Risk Manag | volume = 5 | issue = 3 | pages = 427–48 | date = June 2009 | pmid = 19707253 | pmc = 2701485 | doi = | url = }}</ref> as well as the prevention of [[osteoporosis]].<ref name="pmid19011293">{{cite journal | author = Tuck SP, Francis RM | title = Testosterone, bone and osteoporosis | journal = Front Horm Res | volume = 37 | issue = | pages = 123–32 | year = 2009 | pmid = 19011293 | doi = 10.1159/000176049 | isbn = 978-3-8055-8622-1 | series = Frontiers of Hormone Research }}</ref>
In men, testosterone plays a key role in the development of male reproductive tissues such as the [[testis]] and [[prostate]] as well as promoting secondary sexual characteristics such as increased [[muscle]], [[bone]] mass, and the growth of [[androgenic hair|body hair]].<ref name="Mooradian_ 1987">{{vcite2 journal | vauthors = Mooradian AD, Morley JE, Korenman SG | title = Biological actions of androgens | journal = Endocr. Rev. | volume = 8 | issue = 1 | pages = 1–28 | date = February 1987 | pmid = 3549275 | doi = 10.1210/edrv-8-1-1 | url = }}</ref> In addition, testosterone is essential for health and well-being<ref name="pmid19707253">{{vcite2 journal | vauthors = Bassil N, Alkaade S, Morley JE | title = The benefits and risks of testosterone replacement therapy: a review | journal = Ther Clin Risk Manag | volume = 5 | issue = 3 | pages = 427–48 | date = June 2009 | pmid = 19707253 | pmc = 2701485 | doi = | url = }}</ref> as well as the prevention of [[osteoporosis]].<ref name="pmid19011293">{{vcite2 journal | vauthors = Tuck SP, Francis RM | title = Testosterone, bone and osteoporosis | journal = Front Horm Res | volume = 37 | issue = | pages = 123–32 | year = 2009 | pmid = 19011293 | doi = 10.1159/000176049 | isbn = 978-3-8055-8622-1 | series = Frontiers of Hormone Research }}</ref>


On average, in adult males, levels of testosterone are about 7–8 times as great as in adult females,<ref name="pmid14981046">{{cite journal | author = Torjesen PA, Sandnes L | title = Serum testosterone in women as measured by an automated immunoassay and a RIA | journal = Clin. Chem. | volume = 50 | issue = 3 | pages = 678; author reply 678–9 | date = March 2004 | pmid = 14981046 | doi = 10.1373/clinchem.2003.027565 }}</ref> but, as the metabolic consumption of testosterone in males is greater, the daily production is about 20 times greater in men.<ref name="pmid6025472">{{cite journal | author = Southren AL, Gordon GG, Tochimoto S, Pinzon G, Lane DR, Stypulkowski W | title = Mean plasma concentration, metabolic clearance and basal plasma production rates of testosterone in normal young men and women using a constant infusion procedure: effect of time of day and plasma concentration on the metabolic clearance rate of testosterone | journal = J. Clin. Endocrinol. Metab. | volume = 27 | issue = 5 | pages = 686–94 | date = May 1967 | pmid = 6025472 | doi = 10.1210/jcem-27-5-686 }}</ref><ref name="pmid5843701">{{cite journal | author = Southren AL, Tochimoto S, Carmody NC, Isurugi K | title = Plasma production rates of testosterone in normal adult men and women and in patients with the syndrome of feminizing testes | journal = J. Clin. Endocrinol. Metab. | volume = 25 | issue = 11 | pages = 1441–50 | date = November 1965 | pmid = 5843701 | doi = 10.1210/jcem-25-11-1441 }}</ref> Females are also more sensitive to the hormone.<ref name="isbn0-07-135739-4">{{cite book | author = Dabbs M, Dabbs JM | authorlink = | editor = | others = | title = Heroes, rogues, and lovers: testosterone and behavior | edition = | language = | publisher = McGraw-Hill | location = New York | year = 2000 | origyear = | pages = | quote = | isbn = 0-07-135739-4 | oclc = | doi = | url = | accessdate = }}</ref> Testosterone is observed in most vertebrates. [[Fish]] make a slightly different form called [[11-ketotestosterone]].<ref name="isbn0-87893-617-3">{{cite book | author = Nelson, Randy F. | authorlink = | editor = | others = | title = An introduction to behavioral endocrinology | edition = | language = | publisher = Sinauer Associates | location = Sunderland, Mass | year = 2005 | origyear = | page = 143 | quote = | isbn = 0-87893-617-3 | oclc = | doi = | url = | accessdate = }}</ref> Its counterpart in insects is [[ecdysone]].<ref name="De_Loof_2006">{{cite journal | author = De Loof A | title = Ecdysteroids: the overlooked sex steroids of insects? Males: the black box | journal = Insect Science |date=October 2006 | volume = 13 | issue = 5 | pages = 325–338 | doi = 10.1111/j.1744-7917.2006.00101.x }}</ref> These ubiquitous steroids suggest that [[sex hormone]]s have an ancient evolutionary history.<ref name="Mechoulam_1984">{{cite journal | author = Mechoulam R, Brueggemeier RW, Denlinger DL | title = Estrogens in insects | journal = Journal Cellular and Molecular Life Sciences |date=September 1984 | volume = 40 | issue = 9 | pages = 942–944 | doi = 10.1007/BF01946450 }}</ref>
On average, in adult males, levels of testosterone are about 7–8 times as great as in adult females,<ref name="pmid14981046">{{vcite2 journal | vauthors = Torjesen PA, Sandnes L | title = Serum testosterone in women as measured by an automated immunoassay and a RIA | journal = Clin. Chem. | volume = 50 | issue = 3 | pages = 678; author reply 678–9 | date = March 2004 | pmid = 14981046 | doi = 10.1373/clinchem.2003.027565 }}</ref> but, as the metabolic consumption of testosterone in males is greater, the daily production is about 20 times greater in men.<ref name="pmid6025472">{{vcite2 journal | vauthors = Southren AL, Gordon GG, Tochimoto S, Pinzon G, Lane DR, Stypulkowski W | title = Mean plasma concentration, metabolic clearance and basal plasma production rates of testosterone in normal young men and women using a constant infusion procedure: effect of time of day and plasma concentration on the metabolic clearance rate of testosterone | journal = J. Clin. Endocrinol. Metab. | volume = 27 | issue = 5 | pages = 686–94 | date = May 1967 | pmid = 6025472 | doi = 10.1210/jcem-27-5-686 }}</ref><ref name="pmid5843701">{{vcite2 journal | vauthors = Southren AL, Tochimoto S, Carmody NC, Isurugi K | title = Plasma production rates of testosterone in normal adult men and women and in patients with the syndrome of feminizing testes | journal = J. Clin. Endocrinol. Metab. | volume = 25 | issue = 11 | pages = 1441–50 | date = November 1965 | pmid = 5843701 | doi = 10.1210/jcem-25-11-1441 }}</ref> Females are also more sensitive to the hormone.<ref name="isbn0-07-135739-4">{{cite book | author = Dabbs M, Dabbs JM | authorlink = | editor = | others = | title = Heroes, rogues, and lovers: testosterone and behavior | edition = | publisher = McGraw-Hill | location = New York | year = 2000 | origyear = | pages = | quote = | isbn = 0-07-135739-4 | oclc = | doi = | url = | accessdate = }}</ref> Testosterone is observed in most vertebrates. [[Fish]] make a slightly different form called [[11-ketotestosterone]].<ref name="isbn0-87893-617-3">{{cite book | author = Nelson, Randy F. | authorlink = | editor = | others = | title = An introduction to behavioral endocrinology | edition = | publisher = Sinauer Associates | location = Sunderland, Mass | year = 2005 | origyear = | page = 143 | quote = | isbn = 0-87893-617-3 | oclc = | doi = | url = | accessdate = }}</ref> Its counterpart in insects is [[ecdysone]].<ref name="De_Loof_2006">{{vcite2 journal | vauthors = De Loof A | title = Ecdysteroids: the overlooked sex steroids of insects? Males: the black box | journal = Insect Science |date=October 2006 | volume = 13 | issue = 5 | pages = 325–338 | doi = 10.1111/j.1744-7917.2006.00101.x }}</ref> These ubiquitous steroids suggest that [[sex hormone]]s have an ancient evolutionary history.<ref name="Mechoulam_1984">{{vcite2 journal | vauthors = Mechoulam R, Brueggemeier RW, Denlinger DL | title = Estrogens in insects | journal = Journal Cellular and Molecular Life Sciences |date=September 1984 | volume = 40 | issue = 9 | pages = 942–944 | doi = 10.1007/BF01946450 }}</ref>
{{TOC limit|3}}
{{TOC limit|3}}


Line 77: Line 77:
*Development of [[prostate]] and [[seminal vesicle]]s.
*Development of [[prostate]] and [[seminal vesicle]]s.


During the second trimester, androgen level is associated with [[gender]] formation.<ref name="pmid19403051">{{cite journal | author = Swaab DF, Garcia-Falgueras A | title = Sexual differentiation of the human brain in relation to gender identity and sexual orientation | journal = Funct. Neurol. | volume = 24 | issue = 1 | pages = 17–28 | year = 2009 | pmid = 19403051 | doi = }}</ref> This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. A mother's testosterone level during pregnancy is correlated with her daughter's sex-typical behavior as an adult, and the correlation is even stronger than with the daughter's own adult testosterone level.<ref name="isbn0-8135-3053-9">{{cite book | author = Browne KR | title = Biology at work: rethinking sexual equality | publisher = Rutgers University Press | location = New Brunswick, N.J | year = 2002 | page = 112 | isbn = 0-8135-3053-9 | url = http://books.google.com/books?id=vq_0BUkcZ5MC&lpg=PP1&dq=Biology%20at%20Work%3A%20Rethinking%20Sexual%20Equality&pg=PA112#v=onepage&q&f=false }}</ref>
During the second trimester, androgen level is associated with [[gender]] formation.<ref name="pmid19403051">{{vcite2 journal | vauthors = Swaab DF, Garcia-Falgueras A | title = Sexual differentiation of the human brain in relation to gender identity and sexual orientation | journal = Funct. Neurol. | volume = 24 | issue = 1 | pages = 17–28 | year = 2009 | pmid = 19403051 | doi = }}</ref> This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. A mother's testosterone level during pregnancy is correlated with her daughter's sex-typical behavior as an adult, and the correlation is even stronger than with the daughter's own adult testosterone level.<ref name="isbn0-8135-3053-9">{{cite book | author = Browne KR | title = Biology at work: rethinking sexual equality | publisher = Rutgers University Press | location = New Brunswick, N.J | year = 2002 | page = 112 | isbn = 0-8135-3053-9 | url = http://books.google.com/books?id=vq_0BUkcZ5MC&lpg=PP1&dq=Biology%20at%20Work%3A%20Rethinking%20Sexual%20Equality&pg=PA112#v=onepage&q&f=false }}</ref>


=== Early infancy ===
=== Early infancy ===
''Early infancy androgen effects'' are the least understood. In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–6 months of age.<ref name="pmid4715291">{{cite journal | author = Forest MG, Cathiard AM, Bertrand JA | title = Evidence of testicular activity in early infancy | journal = J. Clin. Endocrinol. Metab. | volume = 37 | issue = 1 | pages = 148–51 | date = July 1973 | pmid = 4715291 | doi = 10.1210/jcem-37-1-148 }}</ref><ref name="pmid1379488">{{cite journal | author = Corbier P, Edwards DA, Roffi J | title = The neonatal testosterone surge: a comparative study | journal = Arch Int Physiol Biochim Biophys | volume = 100 | issue = 2 | pages = 127–31 | year = 1992 | pmid = 1379488 | doi = 10.3109/13813459209035274 }}</ref> The function of this rise in humans is unknown. It has been speculated that "brain [[virilization|masculinization]]" is occurring since no significant changes have been identified in other parts of the body.<ref name="pmid18445234">{{cite journal | author = Dakin CL, Wilson CA, Kalló I, Coen CW, Davies DC | title = Neonatal stimulation of 5-HT(2) receptors reduces androgen receptor expression in the rat anteroventral periventricular nucleus and sexually dimorphic preoptic area | journal = Eur. J. Neurosci. | volume = 27 | issue = 9 | pages = 2473–80 | date = May 2008 | pmid = 18445234 | doi = 10.1111/j.1460-9568.2008.06216.x }}</ref> It is interesting to note that the male brain is masculinized by the aromatization of testosterone into estrogen, which crosses the [[blood–brain barrier]] and enters the male brain, whereas female fetuses have [[alpha-fetoprotein]], which binds the estrogen so that female brains are not affected.<ref name="isbn0-495-60300-7">{{cite book | author = Kalat JW | title = Biological psychology | publisher = Wadsworth, Cengage Learning | location = Belmont, Calif | year = 2009 | pages = | isbn = 0-495-60300-7 | chapter = Reproductive behaviors | chapterurl =http://books.google.com/books?id=ZlSbk5rUY60C&lpg=PA321&ots=PUbcHTdh-A&pg=PA321#v=onepage&q&f=false | page = 321 }}</ref>
''Early infancy androgen effects'' are the least understood. In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–6 months of age.<ref name="pmid4715291">{{vcite2 journal | vauthors = Forest MG, Cathiard AM, Bertrand JA | title = Evidence of testicular activity in early infancy | journal = J. Clin. Endocrinol. Metab. | volume = 37 | issue = 1 | pages = 148–51 | date = July 1973 | pmid = 4715291 | doi = 10.1210/jcem-37-1-148 }}</ref><ref name="pmid1379488">{{vcite2 journal | vauthors = Corbier P, Edwards DA, Roffi J | title = The neonatal testosterone surge: a comparative study | journal = Arch Int Physiol Biochim Biophys | volume = 100 | issue = 2 | pages = 127–31 | year = 1992 | pmid = 1379488 | doi = 10.3109/13813459209035274 }}</ref> The function of this rise in humans is unknown. It has been speculated that "brain [[virilization|masculinization]]" is occurring since no significant changes have been identified in other parts of the body.<ref name="pmid18445234">{{vcite2 journal | vauthors = Dakin CL, Wilson CA, Kalló I, Coen CW, Davies DC | title = Neonatal stimulation of 5-HT(2) receptors reduces androgen receptor expression in the rat anteroventral periventricular nucleus and sexually dimorphic preoptic area | journal = Eur. J. Neurosci. | volume = 27 | issue = 9 | pages = 2473–80 | date = May 2008 | pmid = 18445234 | doi = 10.1111/j.1460-9568.2008.06216.x }}</ref> It is interesting to note that the male brain is masculinized by the aromatization of testosterone into estrogen, which crosses the [[blood–brain barrier]] and enters the male brain, whereas female fetuses have [[alpha-fetoprotein]], which binds the estrogen so that female brains are not affected.<ref name="isbn0-495-60300-7">{{cite book | author = Kalat JW | title = Biological psychology | publisher = Wadsworth, Cengage Learning | location = Belmont, Calif | year = 2009 | pages = | isbn = 0-495-60300-7 | chapter = Reproductive behaviors | chapterurl =http://books.google.com/books?id=ZlSbk5rUY60C&lpg=PA321&ots=PUbcHTdh-A&pg=PA321#v=onepage&q&f=false | page = 321 }}</ref>


=== Pre-peripubertal ===
=== Pre-peripubertal ===
Line 104: Line 104:
*[[Axillary hair]]
*[[Axillary hair]]
*Subcutaneous [[body fat|fat]] in face decreases
*Subcutaneous [[body fat|fat]] in face decreases
*Increased muscle strength and mass<ref name="pmid8637535">{{cite journal | author = Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, Bunnell TJ, Tricker R, Shirazi A, Casaburi R | title = The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men | journal = N. Engl. J. Med. | volume = 335 | issue = 1 | pages = 1–7 | date = July 1996 | pmid = 8637535 | doi = 10.1056/NEJM199607043350101 }}</ref>
*Increased muscle strength and mass<ref name="pmid8637535">{{vcite2 journal | vauthors = Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, Bunnell TJ, Tricker R, Shirazi A, Casaburi R | title = The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men | journal = N. Engl. J. Med. | volume = 335 | issue = 1 | pages = 1–7 | date = July 1996 | pmid = 8637535 | doi = 10.1056/NEJM199607043350101 }}</ref>
*Deepening of voice
*Deepening of voice
*Growth of the [[Adam's apple]]
*Growth of the [[Adam's apple]]
Line 119: Line 119:
====Biological uses====
====Biological uses====
* Testosterone is necessary for normal [[sperm]] development. It activates genes in [[Sertoli cell]]s, which promote differentiation of [[spermatogonia]].
* Testosterone is necessary for normal [[sperm]] development. It activates genes in [[Sertoli cell]]s, which promote differentiation of [[spermatogonia]].
* Regulates acute HPA ([[Hypothalamic–pituitary–adrenal axis]]) response under dominance challenge<ref name="pmid18505319">{{cite journal | author = Mehta PH, Jones AC, Josephs RA | title = The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat | journal = J Pers Soc Psychol | volume = 94 | issue = 6 | pages = 1078–93 | date = June 2008 | pmid = 18505319 | doi = 10.1037/0022-3514.94.6.1078 | url = http://homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/index.cfm.pdf }}</ref>
* Regulates acute HPA ([[Hypothalamic–pituitary–adrenal axis]]) response under dominance challenge<ref name="pmid18505319">{{vcite2 journal | vauthors = Mehta PH, Jones AC, Josephs RA | title = The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat | journal = J Pers Soc Psychol | volume = 94 | issue = 6 | pages = 1078–93 | date = June 2008 | pmid = 18505319 | doi = 10.1037/0022-3514.94.6.1078 | url = http://homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/index.cfm.pdf }}</ref>
* Regulator of cognitive and physical energy
* Regulator of cognitive and physical energy
* Maintenance of muscle trophism
* Maintenance of muscle trophism
* Testosterone regulates the population of [[Thromboxane A2|thromboxane A<sub>2</sub>]] receptors on [[megakaryocytes]] and [[platelets]] and hence platelet aggregation in humans<ref name="pmid15820970">{{cite journal | author = Ajayi AA, Halushka PV | title = Castration reduces platelet thromboxane A2 receptor density and aggregability | journal = QJM | volume = 98 | issue = 5 | pages = 349–56 | date = May 2005 | pmid = 15820970 | doi = 10.1093/qjmed/hci054 | url = }}</ref><ref name="pmid7758179">{{cite journal | author = Ajayi AA, Mathur R, Halushka PV | title = Testosterone increases human platelet thromboxane A2 receptor density and aggregation responses | journal = Circulation | volume = 91 | issue = 11 | pages = 2742–7 | date = June 1995 | pmid = 7758179 | doi = 10.1161/01.CIR.91.11.2742 }}</ref>
* Testosterone regulates the population of [[Thromboxane A2|thromboxane A<sub>2</sub>]] receptors on [[megakaryocytes]] and [[platelets]] and hence platelet aggregation in humans<ref name="pmid15820970">{{vcite2 journal | vauthors = Ajayi AA, Halushka PV | title = Castration reduces platelet thromboxane A2 receptor density and aggregability | journal = QJM | volume = 98 | issue = 5 | pages = 349–56 | date = May 2005 | pmid = 15820970 | doi = 10.1093/qjmed/hci054 | url = }}</ref><ref name="pmid7758179">{{vcite2 journal | vauthors = Ajayi AA, Mathur R, Halushka PV | title = Testosterone increases human platelet thromboxane A2 receptor density and aggregation responses | journal = Circulation | volume = 91 | issue = 11 | pages = 2742–7 | date = June 1995 | pmid = 7758179 | doi = 10.1161/01.CIR.91.11.2742 }}</ref>
* High androgen levels are associated with [[menstrual cycle]] irregularities in both clinical populations and healthy women.<ref name="pmid17039468">{{cite journal | author = Van Anders SM, Watson NV | title = Menstrual cycle irregularities are associated with testosterone levels in healthy premenopausal women | journal = Am. J. Hum. Biol. | volume = 18 | issue = 6 | pages = 841–4 | year = 2006 | pmid = 17039468 | doi = 10.1002/ajhb.20555 }}</ref> See [[libido]].
* High androgen levels are associated with [[menstrual cycle]] irregularities in both clinical populations and healthy women.<ref name="pmid17039468">{{vcite2 journal | vauthors = Van Anders SM, Watson NV | title = Menstrual cycle irregularities are associated with testosterone levels in healthy premenopausal women | journal = Am. J. Hum. Biol. | volume = 18 | issue = 6 | pages = 841–4 | year = 2006 | pmid = 17039468 | doi = 10.1002/ajhb.20555 }}</ref> See [[libido]].


==== Cancer prevention and health risks ====
==== Cancer prevention and health risks ====
* Testosterone does not cause deleterious effects in [[prostate cancer]]. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer.<ref name="pmid19011298">{{cite journal | author = Morgentaler A, Schulman C | title = Testosterone and prostate safety | journal = Front Horm Res | volume = 37 | issue = | pages = 197–203 | year = 2009 | pmid = 19011298 | doi = 10.1159/000176054 | url = | isbn = 978-3-8055-8622-1 | series = Frontiers of Hormone Research }}</ref><ref>{{cite journal | author = Rhoden EL, Averbeck MA, Teloken PE | title = Androgen replacement in men undergoing treatment for prostate cancer | journal = J Sex Med | volume = 5 | issue = 9 | pages = 2202–8 | year = 2008 | pmid = 18638000 | doi = 10.1111/j.1743-6109.2008.00925.x }}</ref><ref>{{cite journal | author = Morgentaler A, Traish AM | title = Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth | journal = Eur Urol | volume = 55 | issue = 2 | pages = 310–20 | year = 2009 | pmid = 18838208 | doi = 10.1016/j.eururo.2008.09.024 }}</ref>
* Testosterone does not cause deleterious effects in [[prostate cancer]]. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer.<ref name="pmid19011298">{{vcite2 journal | vauthors = Morgentaler A, Schulman C | title = Testosterone and prostate safety | journal = Front Horm Res | volume = 37 | issue = | pages = 197–203 | year = 2009 | pmid = 19011298 | doi = 10.1159/000176054 | url = | isbn = 978-3-8055-8622-1 | series = Frontiers of Hormone Research }}</ref><ref>{{vcite2 journal | vauthors = Rhoden EL, Averbeck MA, Teloken PE | title = Androgen replacement in men undergoing treatment for prostate cancer | journal = J Sex Med | volume = 5 | issue = 9 | pages = 2202–8 | year = 2008 | pmid = 18638000 | doi = 10.1111/j.1743-6109.2008.00925.x }}</ref><ref>{{vcite2 journal | vauthors = Morgentaler A, Traish AM | title = Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth | journal = Eur Urol | volume = 55 | issue = 2 | pages = 310–20 | year = 2009 | pmid = 18838208 | doi = 10.1016/j.eururo.2008.09.024 }}</ref>
* Recent studies have shown conflicting results concerning the importance of [[Testosterone and cardiovascular system|testosterone in maintaining cardiovascular health]].<ref name="pmid17285783">{{cite journal | author = Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM | title = Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials | journal = Mayo Clin. Proc. | volume = 82 | issue = 1 | pages = 29–39 | date = January 2007 | pmid = 17285783 | doi = 10.4065/82.1.29 | url = }}</ref><ref name="pmid19464009">{{cite journal | author = Jones TH, Saad F | title = The effects of testosterone on risk factors for, and the mediators of, the atherosclerotic process | journal = Atherosclerosis | volume = 207 | issue = 2 | pages = 318–27 | date = April 2009 | pmid = 19464009 | doi = 10.1016/j.atherosclerosis.2009.04.016 | url = }}</ref> Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and glycemic control.<ref name="pmid18488876">{{cite journal | author = Stanworth RD, Jones TH | title = Testosterone for the aging male; current evidence and recommended practice | journal = Clin Interv Aging | volume = 3 | issue = 1 | pages = 25–44 | year = 2008 | pmid = 18488876 | pmc = 2544367 | doi = | url = }}</ref>
* Recent studies have shown conflicting results concerning the importance of [[Testosterone and cardiovascular system|testosterone in maintaining cardiovascular health]].<ref name="pmid17285783">{{vcite2 journal | vauthors = Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM | title = Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials | journal = Mayo Clin. Proc. | volume = 82 | issue = 1 | pages = 29–39 | date = January 2007 | pmid = 17285783 | doi = 10.4065/82.1.29 | url = }}</ref><ref name="pmid19464009">{{vcite2 journal | vauthors = Jones TH, Saad F | title = The effects of testosterone on risk factors for, and the mediators of, the atherosclerotic process | journal = Atherosclerosis | volume = 207 | issue = 2 | pages = 318–27 | date = April 2009 | pmid = 19464009 | doi = 10.1016/j.atherosclerosis.2009.04.016 | url = }}</ref> Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and glycemic control.<ref name="pmid18488876">{{vcite2 journal | vauthors = Stanworth RD, Jones TH | title = Testosterone for the aging male; current evidence and recommended practice | journal = Clin Interv Aging | volume = 3 | issue = 1 | pages = 25–44 | year = 2008 | pmid = 18488876 | pmc = 2544367 | doi = | url = }}</ref>
*Under dominance challenge, may play a role in the regulation of the [[fight-or-flight response]]<ref name="pmid16928375">{{cite journal | author = Mehta PH, Josephs RA | title = Testosterone change after losing predicts the decision to compete again | journal = Horm Behav | volume = 50 | issue = 5 | pages = 684–92 | date = December 2006 | pmid = 16928375 | doi = 10.1016/j.yhbeh.2006.07.001 | url = }}</ref>
*Under dominance challenge, may play a role in the regulation of the [[fight-or-flight response]]<ref name="pmid16928375">{{vcite2 journal | vauthors = Mehta PH, Josephs RA | title = Testosterone change after losing predicts the decision to compete again | journal = Horm Behav | volume = 50 | issue = 5 | pages = 684–92 | date = December 2006 | pmid = 16928375 | doi = 10.1016/j.yhbeh.2006.07.001 | url = }}</ref>
* Men whose testosterone levels are slightly above average are less likely to have high blood pressure, less likely to experience a heart attack, less likely to be obese, and less likely to rate their own health as fair or poor. However, high testosterone men are more likely to report one or more injuries, more likely to consume five or more alcoholic drinks in a day, more likely to have had a sexually transmitted infection, and more likely to smoke.<ref name="pmid10196726">{{cite journal | author = Booth A, Johnson DR, Granger DA | title = Testosterone and men's health | journal = J Behav Med | volume = 22 | issue = 1 | pages = 1–19 | date = February 1999 | pmid = 10196726 | doi = 10.1023/A:1018705001117 | laysource = CNN | layurl = http://articles.cnn.com/1999-12-03/health/testosterone.wmd_1_testosterone-nanograms-risky-behavior?_s=PM:HEALTH }}</ref>
* Men whose testosterone levels are slightly above average are less likely to have high blood pressure, less likely to experience a heart attack, less likely to be obese, and less likely to rate their own health as fair or poor. However, high testosterone men are more likely to report one or more injuries, more likely to consume five or more alcoholic drinks in a day, more likely to have had a sexually transmitted infection, and more likely to smoke.<ref name="pmid10196726">{{vcite2 journal | vauthors = Booth A, Johnson DR, Granger DA | title = Testosterone and men's health | journal = J Behav Med | volume = 22 | issue = 1 | pages = 1–19 | date = February 1999 | pmid = 10196726 | doi = 10.1023/A:1018705001117 | laysource = CNN | layurl = http://articles.cnn.com/1999-12-03/health/testosterone.wmd_1_testosterone-nanograms-risky-behavior?_s=PM:HEALTH }}</ref>


==== Romantic relationships and fatherhood ====
==== Romantic relationships and fatherhood ====
Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.<ref name="pmid15177709">{{cite journal | author = Marazziti D, Canale D | title = Hormonal changes when falling in love | journal = Psychoneuroendocrinology | volume = 29 | issue = 7 | pages = 931–6 | date = August 2004 | pmid = 15177709 | doi = 10.1016/j.psyneuen.2003.08.006 }}</ref> However, it is suggested that after the "honeymoon phase" ends—about one to three years into a relationship—this change in testosterone levels is no longer apparent.<ref name="pmid15177709" /> Fatherhood also decreases testosterone levels in men, suggesting that the resulting emotional and behavioral changes promote paternal care.<ref>{{cite journal | author = Berg SJ, Wynne-Edwards KE | title = Changes in testosterone, cortisol, and estradiol levels in men becoming fathers | journal = Mayo Clinic Proceedings | volume = 76 | issue = 1 | pages = 582–592 | year = 2001 | pmid = 11393496 | doi = 10.4065/76.6.582 | url = }}</ref> Men who produce less testosterone are more likely to be in a relationship<ref name="pmid16621328">{{cite journal | author = van Anders SM, Watson NV | title = Relationship status and testosterone in North American heterosexual and non-heterosexual men and women: cross-sectional and longitudinal data | journal = Psychoneuroendocrinology | volume = 31 | issue = 6 | pages = 715–23 | date = July 2006 | pmid = 16621328 | doi = 10.1016/j.psyneuen.2006.01.008 }}</ref> and/or married,<ref name = "Booth_Dabbs_1993"/> and men who produce more testosterone are more likely to divorce;<ref name = "Booth_Dabbs_1993">{{cite journal | author = Booth A, Dabbs JM|title=Testosterone and Men's Marriages | journal = Social Forces | year = 1993 | volume = 72 | issue = 2 | pages = 463–477 | doi = 10.1093/sf/72.2.463}}</ref> however, causality cannot be determined in this relationship. Marriage or commitment could cause a decrease in testosterone levels.<ref name=Mazur_Michalek_1998>{{cite journal | author = Mazur A, Michalek J | title = Marriage, Divorce, and Male Testosterone | journal = Social Forces | year = 1998 | volume = 77 | issue = 1 | pages = 315–330 | doi = 10.1093/sf/77.1.315 }}</ref> Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.<ref name=Gray_2004>{{cite journal | author = Gray PB, Chapman JF, Burnham TC, McIntyre MH, Lipson SF, Ellison PT | title = Human male pair bonding and testosterone | journal = Human Nature | year = 2004 | volume = 15 | issue = 2 | pages = 119–131 | doi = 10.1007/s12110-004-1016-6 }}</ref> Married men who engage in bond-maintenance activities such as spending the day with their spouse/and or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.<ref name="pmid15219639">{{cite journal | author = Gray PB, Campbell BC, Marlowe FW, Lipson SF, Ellison PT | title = Social variables predict between-subject but not day-to-day variation in the testosterone of US men | journal = Psychoneuroendocrinology | volume = 29 | issue = 9 | pages = 1153–62 | date = October 2004 | pmid = 15219639 | doi = 10.1016/j.psyneuen.2004.01.008 }}</ref>
Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.<ref name="pmid15177709">{{vcite2 journal | vauthors = Marazziti D, Canale D | title = Hormonal changes when falling in love | journal = Psychoneuroendocrinology | volume = 29 | issue = 7 | pages = 931–6 | date = August 2004 | pmid = 15177709 | doi = 10.1016/j.psyneuen.2003.08.006 }}</ref> However, it is suggested that after the "honeymoon phase" ends—about one to three years into a relationship—this change in testosterone levels is no longer apparent.<ref name="pmid15177709" /> Fatherhood also decreases testosterone levels in men, suggesting that the resulting emotional and behavioral changes promote paternal care.<ref>{{vcite2 journal | vauthors = Berg SJ, Wynne-Edwards KE | title = Changes in testosterone, cortisol, and estradiol levels in men becoming fathers | journal = Mayo Clinic Proceedings | volume = 76 | issue = 1 | pages = 582–592 | year = 2001 | pmid = 11393496 | doi = 10.4065/76.6.582 | url = }}</ref> Men who produce less testosterone are more likely to be in a relationship<ref name="pmid16621328">{{vcite2 journal | vauthors = van Anders SM, Watson NV | title = Relationship status and testosterone in North American heterosexual and non-heterosexual men and women: cross-sectional and longitudinal data | journal = Psychoneuroendocrinology | volume = 31 | issue = 6 | pages = 715–23 | date = July 2006 | pmid = 16621328 | doi = 10.1016/j.psyneuen.2006.01.008 }}</ref> and/or married,<ref name = "Booth_Dabbs_1993"/> and men who produce more testosterone are more likely to divorce;<ref name = "Booth_Dabbs_1993">{{vcite2 journal | vauthors = Booth A, Dabbs JM|title=Testosterone and Men's Marriages | journal = Social Forces | year = 1993 | volume = 72 | issue = 2 | pages = 463–477 | doi = 10.1093/sf/72.2.463}}</ref> however, causality cannot be determined in this relationship. Marriage or commitment could cause a decrease in testosterone levels.<ref name=Mazur_Michalek_1998>{{vcite2 journal | vauthors = Mazur A, Michalek J | title = Marriage, Divorce, and Male Testosterone | journal = Social Forces | year = 1998 | volume = 77 | issue = 1 | pages = 315–330 | doi = 10.1093/sf/77.1.315 }}</ref> Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.<ref name=Gray_2004>{{vcite2 journal | vauthors = Gray PB, Chapman JF, Burnham TC, McIntyre MH, Lipson SF, Ellison PT | title = Human male pair bonding and testosterone | journal = Human Nature | year = 2004 | volume = 15 | issue = 2 | pages = 119–131 | doi = 10.1007/s12110-004-1016-6 }}</ref> Married men who engage in bond-maintenance activities such as spending the day with their spouse/and or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.<ref name="pmid15219639">{{vcite2 journal | vauthors = Gray PB, Campbell BC, Marlowe FW, Lipson SF, Ellison PT | title = Social variables predict between-subject but not day-to-day variation in the testosterone of US men | journal = Psychoneuroendocrinology | volume = 29 | issue = 9 | pages = 1153–62 | date = October 2004 | pmid = 15219639 | doi = 10.1016/j.psyneuen.2004.01.008 }}</ref>


Men who produce more testosterone are more likely to engage in extramarital sex.<ref name=Booth_Dabbs_1993/> Testosterone levels do not rely on physical presence of a partner for men engaging in relationships (same-city vs. long-distance), men have similar testosterone levels across the board.<ref name="pmid16621328" /> Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.<ref name="pmid17196592">{{cite journal | author = van Anders SM, Watson NV | title = Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships | journal = Horm Behav | volume = 51 | issue = 2 | pages = 286–91 | date = February 2007 | pmid = 17196592 | doi = 10.1016/j.yhbeh.2006.11.005 }}</ref>
Men who produce more testosterone are more likely to engage in extramarital sex.<ref name=Booth_Dabbs_1993/> Testosterone levels do not rely on physical presence of a partner for men engaging in relationships (same-city vs. long-distance), men have similar testosterone levels across the board.<ref name="pmid16621328" /> Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.<ref name="pmid17196592">{{vcite2 journal | vauthors = van Anders SM, Watson NV | title = Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships | journal = Horm Behav | volume = 51 | issue = 2 | pages = 286–91 | date = February 2007 | pmid = 17196592 | doi = 10.1016/j.yhbeh.2006.11.005 }}</ref>


==== Testosterone and sexual arousal ====
==== Testosterone and sexual arousal ====
Line 140: Line 140:
It has been found that when testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and [[oxytocin]] levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).<ref name="pmid15177709" />
It has been found that when testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and [[oxytocin]] levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).<ref name="pmid15177709" />


Testosterone levels follow a nyctohemeral rhythm that peaks early each day, regardless of sexual activity.<ref name="pmid5061159">{{cite journal | author = Fox CA, Ismail AA, Love DN, Kirkham KE, Loraine JA | title = Studies on the relationship between plasma testosterone levels and human sexual activity | journal = J. Endocrinol. | volume = 52 | issue = 1 | pages = 51–8 | date = January 1972 | pmid = 5061159 | doi = 10.1677/joe.0.0520051 }}</ref>
Testosterone levels follow a nyctohemeral rhythm that peaks early each day, regardless of sexual activity.<ref name="pmid5061159">{{vcite2 journal | vauthors = Fox CA, Ismail AA, Love DN, Kirkham KE, Loraine JA | title = Studies on the relationship between plasma testosterone levels and human sexual activity | journal = J. Endocrinol. | volume = 52 | issue = 1 | pages = 51–8 | date = January 1972 | pmid = 5061159 | doi = 10.1677/joe.0.0520051 }}</ref>


There are positive correlations between positive orgasm experience in women and testosterone levels where relaxation was a key perception of the experience. There is no correlation between testosterone and men's perceptions of their orgasm experience, and also no correlation between higher testosterone levels and greater sexual assertiveness in either sex.<ref name="pmid19409392">{{cite journal | author = van Anders SM, Dunn EJ | title = Are gonadal steroids linked with orgasm perceptions and sexual assertiveness in women and men? | journal = Horm Behav | volume = 56 | issue = 2 | pages = 206–13 | date = August 2009 | pmid = 19409392 | doi = 10.1016/j.yhbeh.2009.04.007 }}</ref>
There are positive correlations between positive orgasm experience in women and testosterone levels where relaxation was a key perception of the experience. There is no correlation between testosterone and men's perceptions of their orgasm experience, and also no correlation between higher testosterone levels and greater sexual assertiveness in either sex.<ref name="pmid19409392">{{vcite2 journal | vauthors = van Anders SM, Dunn EJ | title = Are gonadal steroids linked with orgasm perceptions and sexual assertiveness in women and men? | journal = Horm Behav | volume = 56 | issue = 2 | pages = 206–13 | date = August 2009 | pmid = 19409392 | doi = 10.1016/j.yhbeh.2009.04.007 }}</ref>


An increase in testosterone levels has also been found to occur in both men and women who have masturbation-induced orgasms.<ref name="pmid10367606">{{cite journal | author = Exton MS, Bindert A, Krüger T, Scheller F, Hartmann U, Schedlowski M | title = Cardiovascular and endocrine alterations after masturbation-induced orgasm in women | journal = Psychosom Med | volume = 61 | issue = 3 | pages = 280–9 | year = 1999 | pmid = 10367606 | doi = 10.1097/00006842-199905000-00005 }}</ref><ref name="pmid135817">{{cite journal | author = Purvis K, Landgren BM, Cekan Z, Diczfalusy E | title = Endocrine effects of masturbation in men | journal = J. Endocrinol. | volume = 70 | issue = 3 | pages = 439–44 | date = September 1976 | pmid = 135817 | doi = 10.1677/joe.0.0700439 }}</ref>
An increase in testosterone levels has also been found to occur in both men and women who have masturbation-induced orgasms.<ref name="pmid10367606">{{vcite2 journal | vauthors = Exton MS, Bindert A, Krüger T, Scheller F, Hartmann U, Schedlowski M | title = Cardiovascular and endocrine alterations after masturbation-induced orgasm in women | journal = Psychosom Med | volume = 61 | issue = 3 | pages = 280–9 | year = 1999 | pmid = 10367606 | doi = 10.1097/00006842-199905000-00005 }}</ref><ref name="pmid135817">{{vcite2 journal | vauthors = Purvis K, Landgren BM, Cekan Z, Diczfalusy E | title = Endocrine effects of masturbation in men | journal = J. Endocrinol. | volume = 70 | issue = 3 | pages = 439–44 | date = September 1976 | pmid = 135817 | doi = 10.1677/joe.0.0700439 }}</ref>


=====Mammalian studies=====
=====Mammalian studies=====
Studies conducted on rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans suffering from sexual arousal deficits such as [[hypoactive sexual desire disorder]].<ref name="pmid20920505">{{cite journal | author = Harding SM, Velotta JP | title = Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats | journal = Horm Behav | volume = 59 | issue = 5 | pages = 666–73 | date = May 2011 | pmid = 20920505 | doi = 10.1016/j.yhbeh.2010.09.009 }}</ref>
Studies conducted on rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans suffering from sexual arousal deficits such as [[hypoactive sexual desire disorder]].<ref name="pmid20920505">{{vcite2 journal | vauthors = Harding SM, Velotta JP | title = Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats | journal = Horm Behav | volume = 59 | issue = 5 | pages = 666–73 | date = May 2011 | pmid = 20920505 | doi = 10.1016/j.yhbeh.2010.09.009 }}</ref>


In one study, almost every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a ''novel'' female. P.J. James et al. investigated the role of genotype on such so-called reflexive testosterone increases in male mice. They also concluded that this response is related to the male's initial level of sexual arousal.<ref name="pmid16828762">{{cite journal | author = James PJ, Nyby JG, Saviolakis GA | title = Sexually stimulated testosterone release in male mice (Mus musculus): roles of genotype and sexual arousal | journal = Horm Behav | volume = 50 | issue = 3 | pages = 424–31 | date = September 2006 | pmid = 16828762 | doi = 10.1016/j.yhbeh.2006.05.004 }}</ref>
In one study, almost every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a ''novel'' female. P.J. James et al. investigated the role of genotype on such so-called reflexive testosterone increases in male mice. They also concluded that this response is related to the male's initial level of sexual arousal.<ref name="pmid16828762">{{vcite2 journal | vauthors = James PJ, Nyby JG, Saviolakis GA | title = Sexually stimulated testosterone release in male mice (Mus musculus): roles of genotype and sexual arousal | journal = Horm Behav | volume = 50 | issue = 3 | pages = 424–31 | date = September 2006 | pmid = 16828762 | doi = 10.1016/j.yhbeh.2006.05.004 }}</ref>


In non-human primates it has been suggested that testosterone in puberty stimulates [[sexual motivation]], which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.<ref name="pmid11534996">{{cite journal | author = Wallen K | title = Sex and context: hormones and primate sexual motivation | journal = Horm Behav | volume = 40 | issue = 2 | pages = 339–57 | date = September 2001 | pmid = 11534996 | doi = 10.1006/hbeh.2001.1696 }}</ref> Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its ''sexual motivation'' decreases, but there is no corresponding decrease in ''ability'' to engage in sexual activity (mounting, ejaculating, etc.).<ref name="pmid11534996"/>
In non-human primates it has been suggested that testosterone in puberty stimulates [[sexual motivation]], which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.<ref name="pmid11534996">{{vcite2 journal | vauthors = Wallen K | title = Sex and context: hormones and primate sexual motivation | journal = Horm Behav | volume = 40 | issue = 2 | pages = 339–57 | date = September 2001 | pmid = 11534996 | doi = 10.1006/hbeh.2001.1696 }}</ref> Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its ''sexual motivation'' decreases, but there is no corresponding decrease in ''ability'' to engage in sexual activity (mounting, ejaculating, etc.).<ref name="pmid11534996"/>


===== Male sexual arousal =====
===== Male sexual arousal =====
Higher levels of testosterone were associated with periods of sexual activity within subjects, but between subjects testosterone levels were higher for less sexually active individuals.<ref name="pmid1275688">{{cite journal | author = Kraemer HC, Becker HB, Brodie HK, Doering CH, Moos RH, Hamburg DA | title = Orgasmic frequency and plasma testosterone levels in normal human males | journal = Arch Sex Behav | volume = 5 | issue = 2 | pages = 125–32 | date = March 1976 | pmid = 1275688 | doi = 10.1007/BF01541869 | url = }}</ref> Men who have sexual encounters with unfamiliar or multiple partners experience large increases of testosterone the morning after.<ref name="pmid12367570">{{cite journal | author = Hirschenhauser K, Frigerio D, Grammer K, Magnusson MS | title = Monthly patterns of testosterone and behavior in prospective fathers | journal = Horm Behav | volume = 42 | issue = 2 | pages = 172–81 | date = September 2002 | pmid = 12367570 | doi = 10.1006/hbeh.2002.1815 }}</ref>
Higher levels of testosterone were associated with periods of sexual activity within subjects, but between subjects testosterone levels were higher for less sexually active individuals.<ref name="pmid1275688">{{vcite2 journal | vauthors = Kraemer HC, Becker HB, Brodie HK, Doering CH, Moos RH, Hamburg DA | title = Orgasmic frequency and plasma testosterone levels in normal human males | journal = Arch Sex Behav | volume = 5 | issue = 2 | pages = 125–32 | date = March 1976 | pmid = 1275688 | doi = 10.1007/BF01541869 | url = }}</ref> Men who have sexual encounters with unfamiliar or multiple partners experience large increases of testosterone the morning after.<ref name="pmid12367570">{{vcite2 journal | vauthors = Hirschenhauser K, Frigerio D, Grammer K, Magnusson MS | title = Monthly patterns of testosterone and behavior in prospective fathers | journal = Horm Behav | volume = 42 | issue = 2 | pages = 172–81 | date = September 2002 | pmid = 12367570 | doi = 10.1006/hbeh.2002.1815 }}</ref>


Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films.<ref>{{cite journal | author = Pirke KM, Kockott G, Dittmar F | title = Psychosexual stimulation and plasma testosterone in man | journal = Arch Sex Behav | volume = 3 | issue = 6 | pages = 577–84 | date = November 1974 | pmid = 4429441 | doi = 10.1007/BF01541140 }}</ref> Men who watch sexually explicit films also report increased optimism and decreased exhaustion.<ref name="pmid4001279">{{cite journal | author = Hellhammer DH, Hubert W, Schürmeyer T | title = Changes in saliva testosterone after psychological stimulation in men | journal = Psychoneuroendocrinology | volume = 10 | issue = 1 | pages = 77–81 | year = 1985 | pmid = 4001279 | doi = 10.1016/0306-4530(85)90041-1 }}</ref> Previous research has found a link between relaxation following sexual arousal and testosterone levels.<ref name="pmid3602262">{{cite journal | author = Rowland DL, Heiman JR, Gladue BA, Hatch JP, Doering CH, Weiler SJ | title = Endocrine, psychological and genital response to sexual arousal in men | journal = Psychoneuroendocrinology | volume = 12 | issue = 2 | pages = 149–58 | year = 1987 | pmid = 3602262 | doi = 10.1016/0306-4530(87)90045-X }}</ref>
Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films.<ref>{{vcite2 journal | vauthors = Pirke KM, Kockott G, Dittmar F | title = Psychosexual stimulation and plasma testosterone in man | journal = Arch Sex Behav | volume = 3 | issue = 6 | pages = 577–84 | date = November 1974 | pmid = 4429441 | doi = 10.1007/BF01541140 }}</ref> Men who watch sexually explicit films also report increased optimism and decreased exhaustion.<ref name="pmid4001279">{{vcite2 journal | vauthors = Hellhammer DH, Hubert W, Schürmeyer T | title = Changes in saliva testosterone after psychological stimulation in men | journal = Psychoneuroendocrinology | volume = 10 | issue = 1 | pages = 77–81 | year = 1985 | pmid = 4001279 | doi = 10.1016/0306-4530(85)90041-1 }}</ref> Previous research has found a link between relaxation following sexual arousal and testosterone levels.<ref name="pmid3602262">{{vcite2 journal | vauthors = Rowland DL, Heiman JR, Gladue BA, Hatch JP, Doering CH, Weiler SJ | title = Endocrine, psychological and genital response to sexual arousal in men | journal = Psychoneuroendocrinology | volume = 12 | issue = 2 | pages = 149–58 | year = 1987 | pmid = 3602262 | doi = 10.1016/0306-4530(87)90045-X }}</ref>


A 2002 study found that testosterone increased in heterosexual men after having had a brief conversation with a woman. The increase in testosterone levels was associated with the degree that the women thought the men were trying to impress them.<ref name=Roney_2003>{{cite journal | author = Roney JR, Mahler SV, Maestripieri D | title = Behavioral and hormonal responses of men to brief interactions with women | journal = Evolution and Human Behavior | year = 2003 | volume = 24 | issue = 6 | pages = 365–375 | doi = 10.1016/S1090-5138(03)00053-9 }}</ref>
A 2002 study found that testosterone increased in heterosexual men after having had a brief conversation with a woman. The increase in testosterone levels was associated with the degree that the women thought the men were trying to impress them.<ref name=Roney_2003>{{vcite2 journal | vauthors = Roney JR, Mahler SV, Maestripieri D | title = Behavioral and hormonal responses of men to brief interactions with women | journal = Evolution and Human Behavior | year = 2003 | volume = 24 | issue = 6 | pages = 365–375 | doi = 10.1016/S1090-5138(03)00053-9 }}</ref>


Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.<ref name="pmid20424057">{{cite journal | author = Miller SL, Maner JK | title = Scent of a woman: men's testosterone responses to olfactory ovulation cues | journal = Psychol Sci | volume = 21 | issue = 2 | pages = 276–83 | date = February 2010 | pmid = 20424057 | doi = 10.1177/0956797609357733 }}</ref> This may be linked to the ''ovulatory shift hypothesis'',<ref name = "Gangestead_2005">{{cite journal | author = Gangestead SW, Thornhill R, Garver-Apgar CE | title = Adaptations to Ovulation: Implications for Sexual and Social Behavior | journal = Current Directions in Psychological Science | volume = 14 | issue = 6 | pages = 312–316 | year = 2005 | doi = 10.1111/j.0963-7214.2005.00388.x }}</ref> where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.
Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.<ref name="pmid20424057">{{vcite2 journal | vauthors = Miller SL, Maner JK | title = Scent of a woman: men's testosterone responses to olfactory ovulation cues | journal = Psychol Sci | volume = 21 | issue = 2 | pages = 276–83 | date = February 2010 | pmid = 20424057 | doi = 10.1177/0956797609357733 }}</ref> This may be linked to the ''ovulatory shift hypothesis'',<ref name = "Gangestead_2005">{{vcite2 journal | vauthors = Gangestead SW, Thornhill R, Garver-Apgar CE | title = Adaptations to Ovulation: Implications for Sexual and Social Behavior | journal = Current Directions in Psychological Science | volume = 14 | issue = 6 | pages = 312–316 | year = 2005 | doi = 10.1111/j.0963-7214.2005.00388.x }}</ref> where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.


In a 1991 study, males were exposed to either visual or auditory erotic stimuli and asked to complete a cognitive task, where the number of errors on the task indicated how distracted the participant was by the stimuli. It concluded that men with lower thresholds for sexual arousal have a greater likelihood to attend to sexual information and that testosterone may have an impact by enhancing their attention to the relevant stimuli.<ref name="pmid1937428">{{cite journal | author = Alexander GM, Sherwin BB | title = The association between testosterone, sexual arousal, and selective attention for erotic stimuli in men | journal = Horm Behav | volume = 25 | issue = 3 | pages = 367–81 | date = September 1991 | pmid = 1937428 | doi = 10.1016/0018-506X(91)90008-6 }}</ref>
In a 1991 study, males were exposed to either visual or auditory erotic stimuli and asked to complete a cognitive task, where the number of errors on the task indicated how distracted the participant was by the stimuli. It concluded that men with lower thresholds for sexual arousal have a greater likelihood to attend to sexual information and that testosterone may have an impact by enhancing their attention to the relevant stimuli.<ref name="pmid1937428">{{vcite2 journal | vauthors = Alexander GM, Sherwin BB | title = The association between testosterone, sexual arousal, and selective attention for erotic stimuli in men | journal = Horm Behav | volume = 25 | issue = 3 | pages = 367–81 | date = September 1991 | pmid = 1937428 | doi = 10.1016/0018-506X(91)90008-6 }}</ref>


[[Sperm competition]] theory: Testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.<ref name="pmid6665072">{{cite journal | author = Hart BL | title = Role of testosterone secretion and penile reflexes in sexual behavior and sperm competition in male rats: a theoretical contribution | journal = Physiol. Behav. | volume = 31 | issue = 6 | pages = 823–7 | date = December 1983 | pmid = 6665072 | doi = 10.1016/0031-9384(83)90279-2 }}</ref> This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.
[[Sperm competition]] theory: Testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.<ref name="pmid6665072">{{vcite2 journal | vauthors = Hart BL | title = Role of testosterone secretion and penile reflexes in sexual behavior and sperm competition in male rats: a theoretical contribution | journal = Physiol. Behav. | volume = 31 | issue = 6 | pages = 823–7 | date = December 1983 | pmid = 6665072 | doi = 10.1016/0031-9384(83)90279-2 }}</ref> This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.


===== Female sexual arousal =====
===== Female sexual arousal =====
Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal.<ref name="pmid12007897">{{cite journal | author = Traish AM, Kim N, Min K, Munarriz R, Goldstein I | title = Role of androgens in female genital sexual arousal: receptor expression, structure, and function | journal = Fertil. Steril. | volume = 77 Suppl 4 | issue = | pages = S11–8 | date = April 2002 | pmid = 12007897 | doi = 10.1016/s0015-0282(02)02978-3 }}</ref> Women's level of testosterone is higher when measured pre-intercourse vs pre-cuddling, as well as post-intercourse vs post-cuddling.<ref name="pmid17320881">{{cite journal | author = van Anders SM, Hamilton LD, Schmidt N, Watson NV | title = Associations between testosterone secretion and sexual activity in women | journal = Horm Behav | volume = 51 | issue = 4 | pages = 477–82 | date = April 2007 | pmid = 17320881 | doi = 10.1016/j.yhbeh.2007.01.003 }}</ref> There is a time lag effect when testosterone is administered, on genital arousal in women. In addition, a continuous increase in vaginal sexual arousal may result in higher genital sensations and sexual appetitive behaviors.<ref name="pmid10665617">{{cite journal | author = Tuiten A, Van Honk J, Koppeschaar H, Bernaards C, Thijssen J, Verbaten R | title = Time course of effects of testosterone administration on sexual arousal in women | journal = Arch. Gen. Psychiatry | volume = 57 | issue = 2 | pages = 149–53; discussion 155–6 | date = February 2000 | pmid = 10665617 | doi = 10.1001/archpsyc.57.2.149 }}</ref>
Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal.<ref name="pmid12007897">{{vcite2 journal | vauthors = Traish AM, Kim N, Min K, Munarriz R, Goldstein I | title = Role of androgens in female genital sexual arousal: receptor expression, structure, and function | journal = Fertil. Steril. | volume = 77 Suppl 4 | issue = | pages = S11–8 | date = April 2002 | pmid = 12007897 | doi = 10.1016/s0015-0282(02)02978-3 }}</ref> Women's level of testosterone is higher when measured pre-intercourse vs pre-cuddling, as well as post-intercourse vs post-cuddling.<ref name="pmid17320881">{{vcite2 journal | vauthors = van Anders SM, Hamilton LD, Schmidt N, Watson NV | title = Associations between testosterone secretion and sexual activity in women | journal = Horm Behav | volume = 51 | issue = 4 | pages = 477–82 | date = April 2007 | pmid = 17320881 | doi = 10.1016/j.yhbeh.2007.01.003 }}</ref> There is a time lag effect when testosterone is administered, on genital arousal in women. In addition, a continuous increase in vaginal sexual arousal may result in higher genital sensations and sexual appetitive behaviors.<ref name="pmid10665617">{{vcite2 journal | vauthors = Tuiten A, Van Honk J, Koppeschaar H, Bernaards C, Thijssen J, Verbaten R | title = Time course of effects of testosterone administration on sexual arousal in women | journal = Arch. Gen. Psychiatry | volume = 57 | issue = 2 | pages = 149–53; discussion 155–6 | date = February 2000 | pmid = 10665617 | doi = 10.1001/archpsyc.57.2.149 }}</ref>


When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not level of cortisol in the female body, and hormonal contraceptives may have an impact on the variation in testosterone response to sexual thoughts.<ref name="pmid21185838">{{cite journal | author = Goldey KL, van Anders SM | title = Sexy thoughts: effects of sexual cognitions on testosterone, cortisol, and arousal in women | journal = Horm Behav | volume = 59 | issue = 5 | pages = 754–64 | date = May 2011 | pmid = 21185838 | doi = 10.1016/j.yhbeh.2010.12.005 }}</ref>
When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not level of cortisol in the female body, and hormonal contraceptives may have an impact on the variation in testosterone response to sexual thoughts.<ref name="pmid21185838">{{vcite2 journal | vauthors = Goldey KL, van Anders SM | title = Sexy thoughts: effects of sexual cognitions on testosterone, cortisol, and arousal in women | journal = Horm Behav | volume = 59 | issue = 5 | pages = 754–64 | date = May 2011 | pmid = 21185838 | doi = 10.1016/j.yhbeh.2010.12.005 }}</ref>


Testosterone may prove to be an effective treatment in female sexual arousal disorders.<ref name="Bolour_2005">{{cite journal | author = Bolour S, Braunstein G | title = Testosterone therapy in women: a review | journal = Int. J. Impot. Res. | volume = 17 | issue = 5 | pages = 399–408 | year = 2005 | pmid = 15889125 | doi = 10.1038/sj.ijir.3901334 }}</ref> Currently there is no FDA approved androgen preparation for the treatment of androgen insufficiency, however it has been used off-label to treat low [[libido]] and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.<ref name="Bolour_2005"/>
Testosterone may prove to be an effective treatment in female sexual arousal disorders.<ref name="Bolour_2005">{{vcite2 journal | vauthors = Bolour S, Braunstein G | title = Testosterone therapy in women: a review | journal = Int. J. Impot. Res. | volume = 17 | issue = 5 | pages = 399–408 | year = 2005 | pmid = 15889125 | doi = 10.1038/sj.ijir.3901334 }}</ref> Currently there is no FDA approved androgen preparation for the treatment of androgen insufficiency, however it has been used off-label to treat low [[libido]] and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.<ref name="Bolour_2005"/>


==== Behavior and personality ====
==== Behavior and personality ====
Testosterone levels play a major role in risk-taking during financial decisions.<ref name="pmid19706398">{{cite journal | author = Sapienza P, Zingales L, Maestripieri D | title = Gender differences in financial risk aversion and career choices are affected by testosterone | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 106 | issue = 36 | pages = 15268–73 | date = September 2009 | pmid = 19706398 | pmc = 2741240 | doi = 10.1073/pnas.0907352106 | bibcode = 2009PNAS..10615268S }}</ref><ref name="Apicella_2008">{{cite journal | author = Apicella CL, Dreber A, Campbell B, Gray PB, Hoffman M, Little AC | title = Testosterone and financial risk preferences | journal = Evolution and Human Behavior | volume = 29 | issue = 6 | pages = 384–390 |date=November 2008 | pmid = | doi = 10.1016/j.evolhumbehav.2008.07.001 | url = }}</ref>
Testosterone levels play a major role in risk-taking during financial decisions.<ref name="pmid19706398">{{vcite2 journal | vauthors = Sapienza P, Zingales L, Maestripieri D | title = Gender differences in financial risk aversion and career choices are affected by testosterone | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 106 | issue = 36 | pages = 15268–73 | date = September 2009 | pmid = 19706398 | pmc = 2741240 | doi = 10.1073/pnas.0907352106 | bibcode = 2009PNAS..10615268S }}</ref><ref name="Apicella_2008">{{vcite2 journal | vauthors = Apicella CL, Dreber A, Campbell B, Gray PB, Hoffman M, Little AC | title = Testosterone and financial risk preferences | journal = Evolution and Human Behavior | volume = 29 | issue = 6 | pages = 384–390 |date=November 2008 | pmid = | doi = 10.1016/j.evolhumbehav.2008.07.001 | url = }}</ref>


=== Brain ===
=== Brain ===
As testosterone affects the entire body (often by enlarging; males have bigger hearts, lungs, liver, etc.), the brain is also affected by this "sexual" differentiation;<ref name="pmid19403051"/> the [[enzyme]] [[aromatase]] converts testosterone into [[estradiol]] that is responsible for [[masculinization]] of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with [[congenital disease]]s of androgen formation or androgen receptor function, to be associated with functional androgen receptors.<ref name="pmid11534997">{{cite journal | author = Wilson JD | title = Androgens, androgen receptors, and male gender role behavior | journal = Horm Behav | volume = 40 | issue = 2 | pages = 358–66 | date = September 2001 | pmid = 11534997 | doi = 10.1006/hbeh.2001.1684 }}</ref>
As testosterone affects the entire body (often by enlarging; males have bigger hearts, lungs, liver, etc.), the brain is also affected by this "sexual" differentiation;<ref name="pmid19403051"/> the [[enzyme]] [[aromatase]] converts testosterone into [[estradiol]] that is responsible for [[masculinization]] of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with [[congenital disease]]s of androgen formation or androgen receptor function, to be associated with functional androgen receptors.<ref name="pmid11534997">{{vcite2 journal | vauthors = Wilson JD | title = Androgens, androgen receptors, and male gender role behavior | journal = Horm Behav | volume = 40 | issue = 2 | pages = 358–66 | date = September 2001 | pmid = 11534997 | doi = 10.1006/hbeh.2001.1684 }}</ref>


There are some differences between a male and female brain (possibly the result of different testosterone levels), one of them being size: the male human brain is, on average, larger.<ref name="pmid17544382">{{cite journal | author = Cosgrove KP, Mazure CM, Staley JK | title = Evolving knowledge of sex differences in brain structure, function, and chemistry | journal = Biol. Psychiatry | volume = 62 | issue = 8 | pages = 847–55 | date = October 2007 | pmid = 17544382 | pmc = 2711771 | doi = 10.1016/j.biopsych.2007.03.001 }}</ref> In a Danish study from 2003, men were found to have a total myelinated fiber length of 176,000&nbsp;km at the age of 20, whereas in women the total length was 149,000&nbsp;km (approx. 15% less).<ref name="pmid12794739">{{cite journal | author = Marner L, Nyengaard JR, Tang Y, Pakkenberg B | title = Marked loss of myelinated nerve fibers in the human brain with age | journal = J. Comp. Neurol. | volume = 462 | issue = 2 | pages = 144–52 | date = July 2003 | pmid = 12794739 | doi = 10.1002/cne.10714 }}</ref>
There are some differences between a male and female brain (possibly the result of different testosterone levels), one of them being size: the male human brain is, on average, larger.<ref name="pmid17544382">{{vcite2 journal | vauthors = Cosgrove KP, Mazure CM, Staley JK | title = Evolving knowledge of sex differences in brain structure, function, and chemistry | journal = Biol. Psychiatry | volume = 62 | issue = 8 | pages = 847–55 | date = October 2007 | pmid = 17544382 | pmc = 2711771 | doi = 10.1016/j.biopsych.2007.03.001 }}</ref> In a Danish study from 2003, men were found to have a total myelinated fiber length of 176,000&nbsp;km at the age of 20, whereas in women the total length was 149,000&nbsp;km (approx. 15% less).<ref name="pmid12794739">{{vcite2 journal | vauthors = Marner L, Nyengaard JR, Tang Y, Pakkenberg B | title = Marked loss of myelinated nerve fibers in the human brain with age | journal = J. Comp. Neurol. | volume = 462 | issue = 2 | pages = 144–52 | date = July 2003 | pmid = 12794739 | doi = 10.1002/cne.10714 }}</ref>


A study conducted in 1996 found no immediate short term effects on mood or behavior from the administration of [[wiktionary:supraphysiological|supraphysiologic]] doses of testosterone for 10 weeks on 43 healthy men.<ref name="pmid8637535"/> Another study found a correlation between testosterone and risk tolerance in career choice among women.<ref>{{cite journal | author = Sapienza P, Zingales L, Maestripieri D | title = Gender differences in financial risk aversion and career choices are affected by testosterone | journal = Proc Natl Acad Sci USA | volume = 106 | issue = 36 | pages = 15268–15273 | year = 2009 | pmid = 19706398 | pmc = 2741240 | doi = 10.1073/pnas.0907352106 | url = http://www.pnas.org/content/early/2009/08/20/0907352106 | bibcode = 2009PNAS..10615268S }}</ref><ref>{{cite web | url = http://www.npr.org/templates/story/story.php?storyId=112334459 | title = Testosterone Affects Some Women's Career Choices | date = August 28, 2009 | publisher = NPR}}</ref>
A study conducted in 1996 found no immediate short term effects on mood or behavior from the administration of [[wiktionary:supraphysiological|supraphysiologic]] doses of testosterone for 10 weeks on 43 healthy men.<ref name="pmid8637535"/> Another study found a correlation between testosterone and risk tolerance in career choice among women.<ref>{{vcite2 journal | vauthors = Sapienza P, Zingales L, Maestripieri D | title = Gender differences in financial risk aversion and career choices are affected by testosterone | journal = Proc Natl Acad Sci USA | volume = 106 | issue = 36 | pages = 15268–15273 | year = 2009 | pmid = 19706398 | pmc = 2741240 | doi = 10.1073/pnas.0907352106 | url = http://www.pnas.org/content/early/2009/08/20/0907352106 | bibcode = 2009PNAS..10615268S }}</ref><ref>{{cite web | url = http://www.npr.org/templates/story/story.php?storyId=112334459 | title = Testosterone Affects Some Women's Career Choices | date = August 28, 2009 | publisher = NPR}}</ref>


The literature suggests that attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for [[dementia]] of the Alzheimer's type,<ref name="pmid15582279">{{cite journal | author = Hogervorst E, Bandelow S, Combrinck M, Smith AD | title = Low free testosterone is an independent risk factor for Alzheimer's disease | journal = Exp. Gerontol. | volume = 39 | issue = 11–12 | pages = 1633–9 | year = 2004 | pmid = 15582279 | doi = 10.1016/j.exger.2004.06.019 }}</ref><ref name="pmid14745052">{{cite journal | author = Moffat SD, Zonderman AB, Metter EJ, Kawas C, Blackman MR, Harman SM, Resnick SM | title = Free testosterone and risk for Alzheimer disease in older men | journal = Neurology | volume = 62 | issue = 2 | pages = 188–93 | date = January 2004 | pmid = 14745052 | doi = 10.1212/WNL.62.2.188 }}</ref><ref name="pmid16785599">{{cite journal | author = Pike CJ, Rosario ER, Nguyen TV | title = Androgens, aging, and Alzheimer's disease | journal = Endocrine | volume = 29 | issue = 2 | pages = 233–41 | date = April 2006 | pmid = 16785599 | doi = 10.1385/ENDO:29:2:233 }}</ref><ref name="pmid15383512">{{cite journal | author = Rosario ER, Chang L, Stanczyk FZ, Pike CJ | title = Age-related testosterone depletion and the development of Alzheimer disease | journal = JAMA | volume = 292 | issue = 12 | pages = 1431–2 | date = September 2004 | pmid = 15383512 | doi = 10.1001/jama.292.12.1431-b }}</ref> a key argument in [[life extension]] medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,<ref name="pmid8817730">{{cite journal | author = Moffat SD, Hampson E | title = A curvilinear relationship between testosterone and spatial cognition in humans: possible influence of hand preference | journal = Psychoneuroendocrinology | volume = 21 | issue = 3 | pages = 323–37 | date = April 1996 | pmid = 8817730 | doi = 10.1016/0306-4530(95)00051-8 }}</ref> where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.
The literature suggests that attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for [[dementia]] of the Alzheimer's type,<ref name="pmid15582279">{{vcite2 journal | vauthors = Hogervorst E, Bandelow S, Combrinck M, Smith AD | title = Low free testosterone is an independent risk factor for Alzheimer's disease | journal = Exp. Gerontol. | volume = 39 | issue = 11–12 | pages = 1633–9 | year = 2004 | pmid = 15582279 | doi = 10.1016/j.exger.2004.06.019 }}</ref><ref name="pmid14745052">{{vcite2 journal | vauthors = Moffat SD, Zonderman AB, Metter EJ, Kawas C, Blackman MR, Harman SM, Resnick SM | title = Free testosterone and risk for Alzheimer disease in older men | journal = Neurology | volume = 62 | issue = 2 | pages = 188–93 | date = January 2004 | pmid = 14745052 | doi = 10.1212/WNL.62.2.188 }}</ref><ref name="pmid16785599">{{vcite2 journal | vauthors = Pike CJ, Rosario ER, Nguyen TV | title = Androgens, aging, and Alzheimer's disease | journal = Endocrine | volume = 29 | issue = 2 | pages = 233–41 | date = April 2006 | pmid = 16785599 | doi = 10.1385/ENDO:29:2:233 }}</ref><ref name="pmid15383512">{{vcite2 journal | vauthors = Rosario ER, Chang L, Stanczyk FZ, Pike CJ | title = Age-related testosterone depletion and the development of Alzheimer disease | journal = JAMA | volume = 292 | issue = 12 | pages = 1431–2 | date = September 2004 | pmid = 15383512 | doi = 10.1001/jama.292.12.1431-b }}</ref> a key argument in [[life extension]] medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,<ref name="pmid8817730">{{vcite2 journal | vauthors = Moffat SD, Hampson E | title = A curvilinear relationship between testosterone and spatial cognition in humans: possible influence of hand preference | journal = Psychoneuroendocrinology | volume = 21 | issue = 3 | pages = 323–37 | date = April 1996 | pmid = 8817730 | doi = 10.1016/0306-4530(95)00051-8 }}</ref> where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.


=== Aggression and criminality ===
=== Aggression and criminality ===
Line 197: Line 197:
A study at the Universities of Zurich and Royal Holloway London with more than 120 experimental subjects has shown that the sexual hormone can encourage fair behavior. For the study subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. Two later studies have empirically confirmed these results.<ref>"Prejudice and truth about the effect of testosterone on human bargaining behaviour" - C. Eisenegger, M. Naef R. Snozzi1, M. Heinrichs & E. Fehr - Nature 463, 356-359 (21 January 2010) | doi:10.1038/nature08711; Received 15 September 2009; Accepted 30 November 2009; Published online 8 December 2009</ref><ref>"New evidence on testosterone and cooperation" - Jack van Honk, Estrella R. Montoya, Peter A. Bos, Mark van Vugt & David Terburg - Nature 485, E4–E5 (24 May 2012) doi:10.1038/nature11136 Received 19 October 2011 Accepted 13 March 2012 Published online 23 May 2012</ref><ref>Eisenegger et al. reply - C. Eisenegger, M. Naef, R. Snozzi, M. Heinrichs & E. Fehr - Nature 485, E5–E6 (24 May 2012) {{DOI|10.1038/nature11137}}</ref>
A study at the Universities of Zurich and Royal Holloway London with more than 120 experimental subjects has shown that the sexual hormone can encourage fair behavior. For the study subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. Two later studies have empirically confirmed these results.<ref>"Prejudice and truth about the effect of testosterone on human bargaining behaviour" - C. Eisenegger, M. Naef R. Snozzi1, M. Heinrichs & E. Fehr - Nature 463, 356-359 (21 January 2010) | doi:10.1038/nature08711; Received 15 September 2009; Accepted 30 November 2009; Published online 8 December 2009</ref><ref>"New evidence on testosterone and cooperation" - Jack van Honk, Estrella R. Montoya, Peter A. Bos, Mark van Vugt & David Terburg - Nature 485, E4–E5 (24 May 2012) doi:10.1038/nature11136 Received 19 October 2011 Accepted 13 March 2012 Published online 23 May 2012</ref><ref>Eisenegger et al. reply - C. Eisenegger, M. Naef, R. Snozzi, M. Heinrichs & E. Fehr - Nature 485, E5–E6 (24 May 2012) {{DOI|10.1038/nature11137}}</ref>


Estradiol is known to correlate with aggression in male mice.<ref name="pmid18280561">{{cite journal | author = Soma KK, Scotti MA, Newman AE, Charlier TD, Demas GE | title = Novel mechanisms for neuroendocrine regulation of aggression | journal = Front Neuroendocrinol | volume = 29 | issue = 4 | pages = 476–89 | date = October 2008 | pmid = 18280561 | doi = 10.1016/j.yfrne.2007.12.003 | url = }}</ref> Moreover, the conversion of testosterone to estradiol regulates male aggression in [[sparrows]] during breeding season.<ref name="pmid11016791">{{cite journal | author = Soma KK, Sullivan KA, Tramontin AD, Saldanha CJ, Schlinger BA, Wingfield JC | title = Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows | journal = J. Comp. Physiol. A | volume = 186 | issue = 7–8 | pages = 759–69 | year = 2000 | pmid = 11016791 | doi = 10.1007/s003590000129 }}</ref>
Estradiol is known to correlate with aggression in male mice.<ref name="pmid18280561">{{vcite2 journal | vauthors = Soma KK, Scotti MA, Newman AE, Charlier TD, Demas GE | title = Novel mechanisms for neuroendocrine regulation of aggression | journal = Front Neuroendocrinol | volume = 29 | issue = 4 | pages = 476–89 | date = October 2008 | pmid = 18280561 | doi = 10.1016/j.yfrne.2007.12.003 | url = }}</ref> Moreover, the conversion of testosterone to estradiol regulates male aggression in [[sparrows]] during breeding season.<ref name="pmid11016791">{{vcite2 journal | vauthors = Soma KK, Sullivan KA, Tramontin AD, Saldanha CJ, Schlinger BA, Wingfield JC | title = Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows | journal = J. Comp. Physiol. A | volume = 186 | issue = 7–8 | pages = 759–69 | year = 2000 | pmid = 11016791 | doi = 10.1007/s003590000129 }}</ref>


== Medical uses ==
== Medical uses ==
The primary use of testosterone is the treatment of males with too little or no natural endogenous testosterone production—males with [[hypogonadism]].{{citation needed|date=October 2014}} This is known as hormone replacement therapy or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range.
The primary use of testosterone is the treatment of males with too little or no natural endogenous testosterone production—males with [[hypogonadism]].{{citation needed|date=October 2014}} This is known as hormone replacement therapy or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range.


Testosterone has also been given for many other purposes besides replacement. Examples include reducing [[infertility]], correcting lack of libido or erectile dysfunction, correcting [[osteoporosis]], encouraging [[penis enlargement|penile enlargement]], encouraging height growth, encouraging [[bone marrow]] stimulation and reversing the effects of [[anemia]], and appetite stimulation. By the late 1940s, testosterone was being touted as an anti-aging wonder drug (e.g., see [[Paul de Kruif]]'s ''The Male Hormone'').<ref name = "de Kruif_1945"/> Decline of testosterone production with age has led to interest in [[androgen replacement therapy]].<ref name="pmid16985841">{{cite journal | author = Myers JB, Meacham RB | title = Androgen Replacement Therapy in the Aging Male | journal = Rev Urol | volume = 5 | issue = 4 | pages = 216–26 | year = 2003 | pmid = 16985841 | pmc = 1508369 | doi = | url = }}</ref>
Testosterone has also been given for many other purposes besides replacement. Examples include reducing [[infertility]], correcting lack of libido or erectile dysfunction, correcting [[osteoporosis]], encouraging [[penis enlargement|penile enlargement]], encouraging height growth, encouraging [[bone marrow]] stimulation and reversing the effects of [[anemia]], and appetite stimulation. By the late 1940s, testosterone was being touted as an anti-aging wonder drug (e.g., see [[Paul de Kruif]]'s ''The Male Hormone'').<ref name = "de Kruif_1945"/> Decline of testosterone production with age has led to interest in [[androgen replacement therapy]].<ref name="pmid16985841">{{vcite2 journal | vauthors = Myers JB, Meacham RB | title = Androgen Replacement Therapy in the Aging Male | journal = Rev Urol | volume = 5 | issue = 4 | pages = 216–26 | year = 2003 | pmid = 16985841 | pmc = 1508369 | doi = | url = }}</ref>


Testosterone may be used as a monotherapy in [[dysthymia]] and minor depression or as an augmentation therapy in major depression in middle-aged men with low testosterone. However, review of the current literature does not show a statistically significant impact on the mood of the men with normal levels of testosterone or on the mood of the older men with low testosterone.<ref name="pmid24501728">{{cite journal | author = Amanatkar HR, Chibnall JT, Seo BW, Manepalli JN, Grossberg GT | title = Impact of exogenous testosterone on mood: a systematic review and meta-analysis of randomized placebo-controlled trials | journal = Ann Clin Psychiatry | volume = 26 | issue = 1 | pages = 19–32 | year = 2014 | pmid = 24501728 | doi = | url = http://www.aacp.com/pdf%2F0214%2F0214ACP%5FAmanatkar%2Epdf }}</ref>
Testosterone may be used as a monotherapy in [[dysthymia]] and minor depression or as an augmentation therapy in major depression in middle-aged men with low testosterone. However, review of the current literature does not show a statistically significant impact on the mood of the men with normal levels of testosterone or on the mood of the older men with low testosterone.<ref name="pmid24501728">{{vcite2 journal | vauthors = Amanatkar HR, Chibnall JT, Seo BW, Manepalli JN, Grossberg GT | title = Impact of exogenous testosterone on mood: a systematic review and meta-analysis of randomized placebo-controlled trials | journal = Ann Clin Psychiatry | volume = 26 | issue = 1 | pages = 19–32 | year = 2014 | pmid = 24501728 | doi = | url = http://www.aacp.com/pdf%2F0214%2F0214ACP%5FAmanatkar%2Epdf }}</ref>


To take advantage of its [[virilizing]] effects, testosterone is often administered to [[transsexual|transsexual men]] as part of the [[Hormone replacement therapy (female-to-male)|hormone replacement therapy]],<ref>{{cite web | url=http://www.nhs.uk/Conditions/Gender-dysphoria/Pages/Treatment.aspx | title=Gender dysphoria - Treatment | publisher=NHS Gov.uk | date=Page last reviewed: 21/05/2012 | accessdate=31 October 2013}}</ref> with a "target level" of the normal male testosterone level. Likewise, [[trans women|transsexual women]] are sometimes prescribed [[antiandrogen|anti-androgens]] to decrease the level of testosterone in the body and allow for the effects of estrogen to develop.
To take advantage of its [[virilizing]] effects, testosterone is often administered to [[transsexual|transsexual men]] as part of the [[Hormone replacement therapy (female-to-male)|hormone replacement therapy]],<ref>{{cite web | url=http://www.nhs.uk/Conditions/Gender-dysphoria/Pages/Treatment.aspx | title=Gender dysphoria - Treatment | publisher=NHS Gov.uk | date=Page last reviewed: 21/05/2012 | accessdate=31 October 2013}}</ref> with a "target level" of the normal male testosterone level. Likewise, [[trans women|transsexual women]] are sometimes prescribed [[antiandrogen|anti-androgens]] to decrease the level of testosterone in the body and allow for the effects of estrogen to develop.


Testosterone therapy may improve the management of [[type 2 diabetes]].<ref name="pmid18772488">{{cite journal | author = Traish AM, Saad F, Guay A | title = The dark side of testosterone deficiency: II. Type 2 diabetes and insulin resistance | journal = J. Androl. | volume = 30 | issue = 1 | pages = 23–32 | year = 2009 | pmid = 18772488 | doi = 10.2164/jandrol.108.005751 | url = }}</ref> Low testosterone has been associated with the development of [[Alzheimer's disease]].<ref name="pmid16785599"/><ref name="pmid15383512"/> A small trial in 2005 showed mixed results in using testosterone to combat the effects of aging.<ref name="pmid18167405">{{cite journal | author = Emmelot-Vonk MH, Verhaar HJ, Nakhai Pour HR, Aleman A, Lock TM, Bosch JL, Grobbee DE, van der Schouw YT | title = Effect of testosterone supplementation on functional mobility, cognition, and other parameters in older men: a randomized controlled trial | journal = JAMA | volume = 299 | issue = 1 | pages = 39–52 | date = January 2008 | pmid = 18167405 | doi = 10.1001/jama.2007.51 | url = }}</ref>
Testosterone therapy may improve the management of [[type 2 diabetes]].<ref name="pmid18772488">{{vcite2 journal | vauthors = Traish AM, Saad F, Guay A | title = The dark side of testosterone deficiency: II. Type 2 diabetes and insulin resistance | journal = J. Androl. | volume = 30 | issue = 1 | pages = 23–32 | year = 2009 | pmid = 18772488 | doi = 10.2164/jandrol.108.005751 | url = }}</ref> Low testosterone has been associated with the development of [[Alzheimer's disease]].<ref name="pmid16785599"/><ref name="pmid15383512"/> A small trial in 2005 showed mixed results in using testosterone to combat the effects of aging.<ref name="pmid18167405">{{vcite2 journal | vauthors = Emmelot-Vonk MH, Verhaar HJ, Nakhai Pour HR, Aleman A, Lock TM, Bosch JL, Grobbee DE, van der Schouw YT | title = Effect of testosterone supplementation on functional mobility, cognition, and other parameters in older men: a randomized controlled trial | journal = JAMA | volume = 299 | issue = 1 | pages = 39–52 | date = January 2008 | pmid = 18167405 | doi = 10.1001/jama.2007.51 | url = }}</ref>


=== Hormone replacement therapy ===
=== Hormone replacement therapy ===
{{Further|Testosterone#Adverse effects|Andropause#Hormone replacement therapy|Androgen replacement therapy#Adverse effects}}
{{Further|Testosterone#Adverse effects|Andropause#Hormone replacement therapy|Androgen replacement therapy#Adverse effects}}
Testosterone levels decline gradually with age in human beings.(see [[andropause]]) The clinical significance of this decrease is debated (see [[andropause]]). There is disagreement about when to treat aging men with testosterone replacement therapy. The [[American Society of Andrology]]'s position is that "testosterone replacement therapy in aging men is indicated when both clinical symptoms and signs suggestive of [[androgen deficiency]] and decreased testosterone levels are present."<ref name="pmid16474019">{{cite journal | title = Testosterone replacement therapy for male aging: ASA position statement | journal = J. Androl. | volume = 27 | issue = 2 | pages = 133–4 | year = 2006 | pmid = 16474019 | doi = }}</ref> The [[American Association of Clinical Endocrinologists]] says "[[Hypogonadism]] is defined as a free testosterone level that is below the lower limit of normal for young adult control subjects. Previously, age-related decreases in free testosterone were once accepted as normal. Currently, they are not considered normal. Males with borderline testosterone levels may benefit from a trial of testosterone.<ref name="pmid12917096">{{cite journal | author = Guay AT, Spark RF, Bansal S, Cunningham GR, Goodman NF, Nankin HR, Petak SM, Perez JB | title = American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of male sexual dysfunction: a couple's problem—2003 update | journal = Endocr Pract | volume = 9 | issue = 1 | pages = 77–95 | year = 2003 | pmid = 12917096 | doi = 10.4158/EP.9.1.77 | url = http://aace.metapress.com/content/9j3jxth5vc3nqd9l/fulltext.pdf }}</ref> Large-scale trials to assess the effectiveness and long-term safety of testosterone are still lacking.<ref name="url_ Cunningham">{{cite web | url = http://www.endocrinetoday.com/view.aspx?rid=29171 | title = Testosterone treatment in aging men | author = Cunningham GR | date = 2008-06-25 | work = | publisher = EndocrineToday.com | accessdate = 2009-07-17}}</ref>
Testosterone levels decline gradually with age in human beings.(see [[andropause]]) The clinical significance of this decrease is debated (see [[andropause]]). There is disagreement about when to treat aging men with testosterone replacement therapy. The [[American Society of Andrology]]'s position is that "testosterone replacement therapy in aging men is indicated when both clinical symptoms and signs suggestive of [[androgen deficiency]] and decreased testosterone levels are present."<ref name="pmid16474019">{{vcite2 journal | vauthors = | title = Testosterone replacement therapy for male aging: ASA position statement | journal = J. Androl. | volume = 27 | issue = 2 | pages = 133–4 | year = 2006 | pmid = 16474019 | doi = }}</ref> The [[American Association of Clinical Endocrinologists]] says "[[Hypogonadism]] is defined as a free testosterone level that is below the lower limit of normal for young adult control subjects. Previously, age-related decreases in free testosterone were once accepted as normal. Currently, they are not considered normal. Males with borderline testosterone levels may benefit from a trial of testosterone.<ref name="pmid12917096">{{vcite2 journal | vauthors = Guay AT, Spark RF, Bansal S, Cunningham GR, Goodman NF, Nankin HR, Petak SM, Perez JB | title = American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of male sexual dysfunction: a couple's problem—2003 update | journal = Endocr Pract | volume = 9 | issue = 1 | pages = 77–95 | year = 2003 | pmid = 12917096 | doi = 10.4158/EP.9.1.77 | url = http://aace.metapress.com/content/9j3jxth5vc3nqd9l/fulltext.pdf }}</ref> Large-scale trials to assess the effectiveness and long-term safety of testosterone are still lacking.<ref name="url_ Cunningham">{{cite web | url = http://www.endocrinetoday.com/view.aspx?rid=29171 | title = Testosterone treatment in aging men | author = Cunningham GR | date = 2008-06-25 | work = | publisher = EndocrineToday.com | accessdate = 2009-07-17}}</ref>


There is not total agreement on the threshold of testosterone value below which a man would be considered [[hypogonadal]]. (Currently, there are no standards as to when to treat women.) Testosterone can be measured as "free" (that is, bioavailable and unbound) or, more commonly, "total" (including the percentage that is chemically bound and unavailable). In the United States, male total testosterone levels below 300&nbsp;ng/dL (10.4&nbsp;nmol/L) from a morning serum sample are generally considered low.<ref name="urlMedlinePlus Medical Encyclopedia: Testosterone">{{cite web | url = http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003707.htm | title = Testosterone | author = Holt EH, Zieve D | authorlink = | date = 2008-03-18 | work = MedlinePlus Medical Encyclopedia | publisher = U.S. National Library of Medicine | pages = | language = | archiveurl = | archivedate = | quote = | accessdate = 2009-07-17}}</ref> Identification of inadequate testosterone in an aging male by symptoms alone can be difficult.
There is not total agreement on the threshold of testosterone value below which a man would be considered [[hypogonadal]]. (Currently, there are no standards as to when to treat women.) Testosterone can be measured as "free" (that is, bioavailable and unbound) or, more commonly, "total" (including the percentage that is chemically bound and unavailable). In the United States, male total testosterone levels below 300&nbsp;ng/dL (10.4&nbsp;nmol/L) from a morning serum sample are generally considered low.<ref name="urlMedlinePlus Medical Encyclopedia: Testosterone">{{cite web | url = http://www.nlm.nih.gov/MEDLINEPLUS/ency/article/003707.htm | title = Testosterone | author = Holt EH, Zieve D | authorlink = | date = 2008-03-18 | work = MedlinePlus Medical Encyclopedia | publisher = U.S. National Library of Medicine | pages = | archiveurl = | archivedate = | quote = | accessdate = 2009-07-17}}</ref> Identification of inadequate testosterone in an aging male by symptoms alone can be difficult.


=== Insufficiency ===
=== Insufficiency ===
{{Further|Hypogonadism|Androgen deficiency}}
{{Further|Hypogonadism|Androgen deficiency}}
Testosterone insufficiency (also termed hypotestosteronism or hypotestosteronemia) is an abnormally low testosterone production. It may occur because of testicular dysfunction ([[primary hypogonadism]]) or hypothalamic-pituitary dysfunction ([[secondary hypogonadism]]) and may be congenital or acquired.<ref>{{cite journal | author = Gould DC, Petty R | title = The male menopause: does it exist?: For: Some men need investigation and testosterone treatment | journal = West. J. Med. | volume = 173 | issue = 2 | pages = 76–8 | date = August 2000 | pmid = 10924412 | pmc = 1070997 | doi = 10.1136/ewjm.173.2.76 | url = }}</ref> An acquired form of hypotestosteronism is the decline in testosterone levels that occurs by [[aging]], sometimes called "[[andropause]]" in men, as a comparison to the decline in [[estrogen]] that comes with [[menopause]] in women. In Western countries, average testosterone levels are receding in men of all ages.<ref name="pmid17062768">{{cite journal | author = Travison TG, Araujo AB, O'Donnell AB, Kupelian V, McKinlay JB | title = A population-level decline in serum testosterone levels in American men | journal = J. Clin. Endocrinol. Metab. | volume = 92 | issue = 1 | pages = 196–202 | date = January 2007 | pmid = 17062768 | doi = 10.1210/jc.2006-1375 }}</ref><ref name="Dindyal_2007">{{cite journal | author = Dindyal S| title=The sperm count has been decreasing steadily for many years in Western industrialised countries: Is there an endocrine basis for this decrease? | journal=The Internet Journal of Urology | volume=2 |issue=1 | pages=1–21 | year=2007 |url=http://www.ispub.com/journal/the-internet-journal-of-urology/volume-2-number-1/the-sperm-count-has-been-decreasing-steadily-for-many-years-in-western-industrialised-countries-is-there-an-endocrine-basis-for-this-decrease.html}}</ref>
Testosterone insufficiency (also termed hypotestosteronism or hypotestosteronemia) is an abnormally low testosterone production. It may occur because of testicular dysfunction ([[primary hypogonadism]]) or hypothalamic-pituitary dysfunction ([[secondary hypogonadism]]) and may be congenital or acquired.<ref>{{vcite2 journal | vauthors = Gould DC, Petty R | title = The male menopause: does it exist?: For: Some men need investigation and testosterone treatment | journal = West. J. Med. | volume = 173 | issue = 2 | pages = 76–8 | date = August 2000 | pmid = 10924412 | pmc = 1070997 | doi = 10.1136/ewjm.173.2.76 | url = }}</ref> An acquired form of hypotestosteronism is the decline in testosterone levels that occurs by [[aging]], sometimes called "[[andropause]]" in men, as a comparison to the decline in [[estrogen]] that comes with [[menopause]] in women. In Western countries, average testosterone levels are receding in men of all ages.<ref name="pmid17062768">{{vcite2 journal | vauthors = Travison TG, Araujo AB, O'Donnell AB, Kupelian V, McKinlay JB | title = A population-level decline in serum testosterone levels in American men | journal = J. Clin. Endocrinol. Metab. | volume = 92 | issue = 1 | pages = 196–202 | date = January 2007 | pmid = 17062768 | doi = 10.1210/jc.2006-1375 }}</ref><ref name="Dindyal_2007">{{vcite2 journal | vauthors = Dindyal S| title=The sperm count has been decreasing steadily for many years in Western industrialised countries: Is there an endocrine basis for this decrease? | journal=The Internet Journal of Urology | volume=2 |issue=1 | pages=1–21 | year=2007 |url=http://www.ispub.com/journal/the-internet-journal-of-urology/volume-2-number-1/the-sperm-count-has-been-decreasing-steadily-for-many-years-in-western-industrialised-countries-is-there-an-endocrine-basis-for-this-decrease.html}}</ref>


===Women===
===Women===
Testosterone supplementation is effective in the short term for [[hypoactive sexual desire disorder]].<ref name=Wie2014/> Its long term safety, however, is unclear.<ref name=Wie2014>{{cite journal | author = Wierman ME, Arlt W, Basson R, Davis SR, Miller KK, Murad MH, Rosner W, Santoro N | title = Androgen therapy in women: a reappraisal: an endocrine society clinical practice guideline. | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 99 | issue = 10 | pages = 3489–510 | date = Oct 2014 | pmid = 25279570 | doi = 10.1210/jc.2014-2260 }}</ref>
Testosterone supplementation is effective in the short term for [[hypoactive sexual desire disorder]].<ref name=Wie2014/> Its long term safety, however, is unclear.<ref name=Wie2014>{{vcite2 journal | vauthors = Wierman ME, Arlt W, Basson R, Davis SR, Miller KK, Murad MH, Rosner W, Santoro N | title = Androgen therapy in women: a reappraisal: an endocrine society clinical practice guideline. | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 99 | issue = 10 | pages = 3489–510 | date = Oct 2014 | pmid = 25279570 | doi = 10.1210/jc.2014-2260 }}</ref>


Treating low androgen levels with testosterone is not generally recommended in women when it is due to [[hypopituitarism]], [[adrenal insufficiency]], or following surgical removal of the ovaries.<ref name=Wie2014/> It is also not usually recommended for improving cognition, the risk of heart disease, bone strength of generalized well being.<ref name=Wie2014/>
Treating low androgen levels with testosterone is not generally recommended in women when it is due to [[hypopituitarism]], [[adrenal insufficiency]], or following surgical removal of the ovaries.<ref name=Wie2014/> It is also not usually recommended for improving cognition, the risk of heart disease, bone strength of generalized well being.<ref name=Wie2014/>
Line 236: Line 236:


=== Detection of abuse ===
=== Detection of abuse ===
A number of methods for detecting testosterone use by athletes have been employed, most based on a [[urinalysis|urine test]]. These include the testosterone/[[epitestosterone]] ratio (normally less than 6), the testosterone/luteinizing hormone ratio and the [[carbon-13]] / [[carbon-12]] ratio (pharmaceutical testosterone contains less carbon-13 than endogenous testosterone). In some testing programs, an individual's own historical results may serve as a reference interval for interpretation of a suspicious finding. Another approach being investigated is the detection of the administered form of testosterone, usually an ester, in hair.<ref name="pmid19549614">{{cite journal | author = Strahm E, Emery C, Saugy M, Dvorak J, Saudan C | title = Detection of testosterone administration based on the carbon isotope ratio profiling of endogenous steroids: international reference populations of professional soccer players | journal = Br J Sports Med | volume = 43 | issue = 13 | pages = 1041–4 | date = December 2009 | pmid = 19549614 | pmc = 2784500 | doi = 10.1136/bjsm.2009.058669 | url = }}</ref><ref name="pmid20355155">{{cite journal | author = Kicman AT, Cowan DA | title = Subject-based profiling for the detection of testosterone administration in sport | journal = Drug Test Anal | volume = 1 | issue = 1 | pages = 22–4 | date = January 2009 | pmid = 20355155 | doi = 10.1002/dta.14 | url = }}</ref><ref name="pmid19353724">{{cite journal | author = Pozo OJ, Deventer K, Van Eenoo P, Rubens R, Delbeke FT | title = Quantification of testosterone undecanoate in human hair by liquid chromatography-tandem mass spectrometry | journal = Biomed. Chromatogr. | volume = 23 | issue = 8 | pages = 873–80 | date = August 2009 | pmid = 19353724 | doi = 10.1002/bmc.1199 }}</ref><ref name="isbn0-9626523-6-9">{{cite book | author = Baselt RC | title = Disposition of Toxic Drugs & Chemicals in Man | edition = 8th | publisher = Biomedical Publications | location = Foster City, Calif | year = 2008 | origyear = | pages = 1501–1504 | quote = | isbn = 978-0-9626523-7-0 }}</ref>
A number of methods for detecting testosterone use by athletes have been employed, most based on a [[urinalysis|urine test]]. These include the testosterone/[[epitestosterone]] ratio (normally less than 6), the testosterone/luteinizing hormone ratio and the [[carbon-13]] / [[carbon-12]] ratio (pharmaceutical testosterone contains less carbon-13 than endogenous testosterone). In some testing programs, an individual's own historical results may serve as a reference interval for interpretation of a suspicious finding. Another approach being investigated is the detection of the administered form of testosterone, usually an ester, in hair.<ref name="pmid19549614">{{vcite2 journal | vauthors = Strahm E, Emery C, Saugy M, Dvorak J, Saudan C | title = Detection of testosterone administration based on the carbon isotope ratio profiling of endogenous steroids: international reference populations of professional soccer players | journal = Br J Sports Med | volume = 43 | issue = 13 | pages = 1041–4 | date = December 2009 | pmid = 19549614 | pmc = 2784500 | doi = 10.1136/bjsm.2009.058669 | url = }}</ref><ref name="pmid20355155">{{vcite2 journal | vauthors = Kicman AT, Cowan DA | title = Subject-based profiling for the detection of testosterone administration in sport | journal = Drug Test Anal | volume = 1 | issue = 1 | pages = 22–4 | date = January 2009 | pmid = 20355155 | doi = 10.1002/dta.14 | url = }}</ref><ref name="pmid19353724">{{vcite2 journal | vauthors = Pozo OJ, Deventer K, Van Eenoo P, Rubens R, Delbeke FT | title = Quantification of testosterone undecanoate in human hair by liquid chromatography-tandem mass spectrometry | journal = Biomed. Chromatogr. | volume = 23 | issue = 8 | pages = 873–80 | date = August 2009 | pmid = 19353724 | doi = 10.1002/bmc.1199 }}</ref><ref name="isbn0-9626523-6-9">{{cite book | author = Baselt RC | title = Disposition of Toxic Drugs & Chemicals in Man | edition = 8th | publisher = Biomedical Publications | location = Foster City, Calif | year = 2008 | origyear = | pages = 1501–1504 | quote = | isbn = 978-0-9626523-7-0 }}</ref>


== Adverse effects ==
== Adverse effects ==
{{see also|Testosterone#Hormone replacement therapy}}
{{see also|Testosterone#Hormone replacement therapy}}
Whether or not testosterone therapy in men causes important adverse effects was unclear as of 2010.<ref name=Fer2010>{{cite journal | author = Fernández-Balsells MM, Murad MH, Lane M, Lampropulos JF, Albuquerque F, Mullan RJ, Agrwal N, Elamin MB, Gallegos-Orozco JF, Wang AT, Erwin PJ, Bhasin S, Montori VM | title = Clinical review 1: Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 95 | issue = 6 | pages = 2560–75 | date = June 2010 | pmid = 20525906 | doi = 10.1210/jc.2009-2575 }}</ref>
Whether or not testosterone therapy in men causes important adverse effects was unclear as of 2010.<ref name=Fer2010>{{vcite2 journal | vauthors = Fernández-Balsells MM, Murad MH, Lane M, Lampropulos JF, Albuquerque F, Mullan RJ, Agrwal N, Elamin MB, Gallegos-Orozco JF, Wang AT, Erwin PJ, Bhasin S, Montori VM | title = Clinical review 1: Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 95 | issue = 6 | pages = 2560–75 | date = June 2010 | pmid = 20525906 | doi = 10.1210/jc.2009-2575 }}</ref>


===Cardiovascular disease===
===Cardiovascular disease===
On January 31, 2014, reports of strokes, heart attacks, and deaths in men taking FDA-approved testosterone-replacement led the Food and Drug Administration to announce that it would be investigating this issue.<ref>http://www.fda.gov/downloads/Drugs/DrugSafety/UCM383909.pdf</ref> The FDA is requiring warnings in the drug labeling of all approved testosterone products regarding [[deep vein thrombosis]] and [[pulmonary embolism]].<ref>{{cite web |author=Staff |title=FDA adding general warning to testosterone products about potential for venous blood clots|url=http://www.fda.gov/Drugs/DrugSafety/ucm401746.htm|website=[[FDA]]|accessdate=9 October 2014|date=19 June 2014}}</ref>
On January 31, 2014, reports of strokes, heart attacks, and deaths in men taking FDA-approved testosterone-replacement led the Food and Drug Administration to announce that it would be investigating this issue.<ref>http://www.fda.gov/downloads/Drugs/DrugSafety/UCM383909.pdf</ref> The FDA is requiring warnings in the drug labeling of all approved testosterone products regarding [[deep vein thrombosis]] and [[pulmonary embolism]].<ref>{{cite web |author=Staff |title=FDA adding general warning to testosterone products about potential for venous blood clots|url=http://www.fda.gov/Drugs/DrugSafety/ucm401746.htm|website=[[FDA]]|accessdate=9 October 2014|date=19 June 2014}}</ref>


Adverse effects of testosterone supplementation may include increased cardiovascular events (including [[stroke]]s and [[heart attack]]s) and [[death]]s based on three peer-reviewed studies involving men taking testosterone-replacement.<ref>{{cite journal | author = Finkle WD, Greenland S, Ridgeway GK, Adams JL, Frasco MA, Cook MB, Fraumeni JF, Hoover RN | title = Increased Risk of Non-fatal Myocardial Infarction Following Testosterone Therapy Prescription in Men | journal = [[PLoS ONE]] | volume = 9 | issue = 1 | pages = e85805 | date = January 2014 | pmid = 24489673 | pmc = 3905977 | doi = 10.1371/journal.pone.0085805 | url = http://testosteronedruglawyers.com/wp-content/uploads/2014/03/Study-by-Finkle.pdf }}</ref> In addition, an increase of 30% in deaths and heart attacks in older men has been reported.<ref name="pmid24193080">{{cite journal | author = Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM | title = Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels | journal = [[Journal of the American Medical Association]] | volume = 310 | issue = 17 | pages = 1829–36 | year = 2013 | pmid = 24193080 | doi = 10.1001/jama.2013.280386 }}</ref> Due to an increased incidence of adverse cardiovascular events compared to a [[placebo group]], a Testosterone in Older Men with Mobility Limitations (TOM) trial (a [[National Institute of Aging]] randomized trial) was halted early by the [[Data monitoring committee#Safety concerns|Data Safety and Monitoring Committee]].<ref>{{cite journal | author = Basaria S, Coviello AD, Travison TG, Storer TW, Farwell WR, Jette AM, Eder R, Tennstedt S, Ulloor J, Zhang A, Choong K, Lakshman KM, Mazer NA, Miciek R, Krasnoff J, Elmi A, Knapp PE, Brooks B, Appleman E, Aggarwal S, Bhasin G, Hede-Brierley L, Bhatia A, Collins L, LeBrasseur N, Fiore LD, Bhasin S | title = Adverse Events Associated with Testosterone Administration | journal = [[New England Journal of Medicine]] | volume = 363 | issue = 2 | pages = 109–22 | date = Jul 2010 | pmid = 20592293 | pmc = 3440621 | doi = 10.1056/NEJMoa1000485 }}</ref> On January 31, 2014, reports of [[stroke]]s, [[heart attack]]s, and [[death]]s in men taking [[FDA]]-approved testosterone-replacement led the [[Food and Drug Administration]] ([[FDA]]) to announce that it would be investigating the issue.<ref name="FDA-20140131">{{cite web |author=Staff |title=FDA evaluating risk of stroke, heart attack and death with FDA-approved testosterone products |url=http://www.fda.gov/downloads/Drugs/DrugSafety/UCM383909.pdf |publisher=[[U.S. Food and Drug Administration]] |date=January 31, 2014 |format=[[PDF]] |accessdate=September 17, 2014 }}</ref> Later, in September 2014, the [[FDA]] announced, as a result of the "potential for adverse cardiovascular outcomes", a review of the appropriateness and safety of Testosterone Replacement Therapy (TRT).<ref name="NYT-20140917">{{cite news |last=Tavernise |first=Sabrina |title=F.D.A. Panel Backs Limits on Testosterone Drugs |url=http://www.nytimes.com/2014/09/18/health/testosterone-drugs-fda.html |date=September 17, 2014 |work=[[New York Times]] |accessdate=September 18, 2014 }}</ref><ref name="CNN-20140905">{{cite news |author=Staff |title=FDA Panel To Review Testosterone Therapy Appropriateness and Safety |url=http://ireport.cnn.com/docs/DOC-1167887 |date=September 5, 2014 |work=[[CNN News]] |accessdate=September 14, 2014 }}</ref><ref name="FDA-20140903">{{cite web |author=Staff |title=Joint Meeting for Bone, Reproductive and Urologic Drugs Advisory Committee (BRUDAC) and the Drug Safety And Risk Management Advisory Committee (DSARM AC) - FDA background documents for the discussion of two major issues in testosterone replacement therapy (TRT): 1. The appropriate indicated population for TRT, and 2. The potential for adverse cardiovascular outcomes associated with use of TRT |url=http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Drugs/ReproductiveHealthDrugsAdvisoryCommittee/UCM412536.pdf |date=September 17, 2014 |work=[[Food and Drug Administration]] |format=[[PDF]] |accessdate=September 14, 2014 }}</ref>
Adverse effects of testosterone supplementation may include increased cardiovascular events (including [[stroke]]s and [[heart attack]]s) and [[death]]s based on three peer-reviewed studies involving men taking testosterone-replacement.<ref>{{vcite2 journal | vauthors = Finkle WD, Greenland S, Ridgeway GK, Adams JL, Frasco MA, Cook MB, Fraumeni JF, Hoover RN | title = Increased Risk of Non-fatal Myocardial Infarction Following Testosterone Therapy Prescription in Men | journal = [[PLoS ONE]] | volume = 9 | issue = 1 | pages = e85805 | date = January 2014 | pmid = 24489673 | pmc = 3905977 | doi = 10.1371/journal.pone.0085805 | url = http://testosteronedruglawyers.com/wp-content/uploads/2014/03/Study-by-Finkle.pdf }}</ref> In addition, an increase of 30% in deaths and heart attacks in older men has been reported.<ref name="pmid24193080">{{vcite2 journal | vauthors = Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM | title = Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels | journal = [[Journal of the American Medical Association]] | volume = 310 | issue = 17 | pages = 1829–36 | year = 2013 | pmid = 24193080 | doi = 10.1001/jama.2013.280386 }}</ref> Due to an increased incidence of adverse cardiovascular events compared to a [[placebo group]], a Testosterone in Older Men with Mobility Limitations (TOM) trial (a [[National Institute of Aging]] randomized trial) was halted early by the [[Data monitoring committee#Safety concerns|Data Safety and Monitoring Committee]].<ref>{{vcite2 journal | vauthors = Basaria S, Coviello AD, Travison TG, Storer TW, Farwell WR, Jette AM, Eder R, Tennstedt S, Ulloor J, Zhang A, Choong K, Lakshman KM, Mazer NA, Miciek R, Krasnoff J, Elmi A, Knapp PE, Brooks B, Appleman E, Aggarwal S, Bhasin G, Hede-Brierley L, Bhatia A, Collins L, LeBrasseur N, Fiore LD, Bhasin S | title = Adverse Events Associated with Testosterone Administration | journal = [[New England Journal of Medicine]] | volume = 363 | issue = 2 | pages = 109–22 | date = Jul 2010 | pmid = 20592293 | pmc = 3440621 | doi = 10.1056/NEJMoa1000485 }}</ref> On January 31, 2014, reports of [[stroke]]s, [[heart attack]]s, and [[death]]s in men taking [[FDA]]-approved testosterone-replacement led the [[Food and Drug Administration]] ([[FDA]]) to announce that it would be investigating the issue.<ref name="FDA-20140131">{{cite web |author=Staff |title=FDA evaluating risk of stroke, heart attack and death with FDA-approved testosterone products |url=http://www.fda.gov/downloads/Drugs/DrugSafety/UCM383909.pdf |publisher=[[U.S. Food and Drug Administration]] |date=January 31, 2014 |format=[[PDF]] |accessdate=September 17, 2014 }}</ref> Later, in September 2014, the [[FDA]] announced, as a result of the "potential for adverse cardiovascular outcomes", a review of the appropriateness and safety of Testosterone Replacement Therapy (TRT).<ref name="NYT-20140917">{{cite news |last=Tavernise |first=Sabrina |title=F.D.A. Panel Backs Limits on Testosterone Drugs |url=http://www.nytimes.com/2014/09/18/health/testosterone-drugs-fda.html |date=September 17, 2014 |work=[[New York Times]] |accessdate=September 18, 2014 }}</ref><ref name="CNN-20140905">{{cite news |author=Staff |title=FDA Panel To Review Testosterone Therapy Appropriateness and Safety |url=http://ireport.cnn.com/docs/DOC-1167887 |date=September 5, 2014 |work=[[CNN News]] |accessdate=September 14, 2014 }}</ref><ref name="FDA-20140903">{{cite web |author=Staff |title=Joint Meeting for Bone, Reproductive and Urologic Drugs Advisory Committee (BRUDAC) and the Drug Safety And Risk Management Advisory Committee (DSARM AC) - FDA background documents for the discussion of two major issues in testosterone replacement therapy (TRT): 1. The appropriate indicated population for TRT, and 2. The potential for adverse cardiovascular outcomes associated with use of TRT |url=http://www.fda.gov/downloads/AdvisoryCommittees/CommitteesMeetingMaterials/Drugs/ReproductiveHealthDrugsAdvisoryCommittee/UCM412536.pdf |date=September 17, 2014 |work=[[Food and Drug Administration]] |format=[[PDF]] |accessdate=September 14, 2014 }}</ref>


Up to the year 2010, studies had not shown any effect on the risk of death, [[prostate cancer]] or [[cardiovascular disease]];<ref name=Fer2010/><ref>{{cite journal | author = Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM | title = Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials. | journal = Mayo Clinic proceedings. Mayo Clinic | volume = 82 | issue = 1 | pages = 29–39 | date = January 2007 | pmid = 17285783 | doi = 10.4065/82.1.29 }}</ref> more recent studies, however, do raise concerns.<ref>{{cite web|title=Testosterone Products: Drug Safety Communication - FDA Investigating Risk of Cardiovascular Events|url=http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm384225.htm|work=FDA|accessdate=3 February 2014|date=Jan 31, 2014}}</ref> A 2013 study, published in the Journal of the American Medical Association, reported "the use of testosterone therapy was significantly associated with increased risk of adverse outcomes." The study began after a previous, randomized, clinical trial of testosterone therapy in men was stopped prematurely "due to adverse cardiovascular events raising concerns about testosterone therapy safety."<ref name=vigen2013>{{cite journal | author = Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM | title = Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. | journal = Journal of the American Medical Association | volume = 310 | issue = 17 | pages = 1829–36 | date = Nov 6, 2013 | pmid = 24193080 | doi = 10.1001/jama.2013.280386 | url = http://jama.jamanetwork.com/article.aspx?articleid=1764051 | accessdate = 16 June 2014 }}</ref>
Up to the year 2010, studies had not shown any effect on the risk of death, [[prostate cancer]] or [[cardiovascular disease]];<ref name=Fer2010/><ref>{{vcite2 journal | vauthors = Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM | title = Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials. | journal = Mayo Clinic proceedings. Mayo Clinic | volume = 82 | issue = 1 | pages = 29–39 | date = January 2007 | pmid = 17285783 | doi = 10.4065/82.1.29 }}</ref> more recent studies, however, do raise concerns.<ref>{{cite web|title=Testosterone Products: Drug Safety Communication - FDA Investigating Risk of Cardiovascular Events|url=http://www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm384225.htm|work=FDA|accessdate=3 February 2014|date=Jan 31, 2014}}</ref> A 2013 study, published in the Journal of the American Medical Association, reported "the use of testosterone therapy was significantly associated with increased risk of adverse outcomes." The study began after a previous, randomized, clinical trial of testosterone therapy in men was stopped prematurely "due to adverse cardiovascular events raising concerns about testosterone therapy safety."<ref name=vigen2013>{{vcite2 journal | vauthors = Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM | title = Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. | journal = Journal of the American Medical Association | volume = 310 | issue = 17 | pages = 1829–36 | date = Nov 6, 2013 | pmid = 24193080 | doi = 10.1001/jama.2013.280386 | url = http://jama.jamanetwork.com/article.aspx?articleid=1764051 | accessdate = 16 June 2014 }}</ref>


===Cancer===
===Cancer===
Testosterone in the presence of a slow-growing cancer is assumed to increase its growth rate. However, the association between testosterone supplementation and the development of prostate cancer is unproven.<ref name="pmid19863857">{{cite journal | author = Rhoden EL, Averbeck MA | title = Testosterone therapy and prostate carcinoma | journal = Curr Urol Rep | volume = 10 | issue = 6 | pages = 453–9 | date = November 2009 | pmid = 19863857 | doi = 10.1007/s11934-009-0072-1 }}</ref> Nevertheless, physicians are cautioned about the cancer risk associated with testosterone supplementation.<ref name="pmid16006887">{{cite journal | author = Gaylis FD, Lin DW, Ignatoff JM, Amling CL, Tutrone RF, Cosgrove DJ | title = Prostate cancer in men using testosterone supplementation | journal = J. Urol. | volume = 174 | issue = 2 | pages = 534–8; discussion 538 | date = August 2005 | pmid = 16006887 | doi = 10.1097/01.ju.0000165166.36280.60 }}</ref>
Testosterone in the presence of a slow-growing cancer is assumed to increase its growth rate. However, the association between testosterone supplementation and the development of prostate cancer is unproven.<ref name="pmid19863857">{{vcite2 journal | vauthors = Rhoden EL, Averbeck MA | title = Testosterone therapy and prostate carcinoma | journal = Curr Urol Rep | volume = 10 | issue = 6 | pages = 453–9 | date = November 2009 | pmid = 19863857 | doi = 10.1007/s11934-009-0072-1 }}</ref> Nevertheless, physicians are cautioned about the cancer risk associated with testosterone supplementation.<ref name="pmid16006887">{{vcite2 journal | vauthors = Gaylis FD, Lin DW, Ignatoff JM, Amling CL, Tutrone RF, Cosgrove DJ | title = Prostate cancer in men using testosterone supplementation | journal = J. Urol. | volume = 174 | issue = 2 | pages = 534–8; discussion 538 | date = August 2005 | pmid = 16006887 | doi = 10.1097/01.ju.0000165166.36280.60 }}</ref>


Ethnic groups have different rates of [[prostate cancer]].<ref name=Cal2010/> Differences in sex hormones, including testosterone, have been suggested as an explanation for these differences.<ref name=Cal2010>{{cite journal | author = Calistro Alvarado L | title = Population differences in the testosterone levels of young men are associated with prostate cancer disparities in older men | journal = Am. J. Hum. Biol. | volume = 22 | issue = 4 | pages = 449–55 | year = 2010 | pmid = 20087895 | doi = 10.1002/ajhb.21016 }}</ref> This apparent paradox can be resolved by noting that prostate cancer is very common. In autopsies, 80% of 80-year-old men have prostate cancer.<ref name="pmid15495199">{{cite journal | author = Bostwick DG, Burke HB, Djakiew D, Euling S, Ho SM, Landolph J, Morrison H, Sonawane B, Shifflett T, Waters DJ, Timms B | title = Human prostate cancer risk factors | journal = Cancer | volume = 101 | issue = 10 Suppl | pages = 2371–490 | date = November 2004 | pmid = 15495199 | doi = 10.1002/cncr.20408 | laysource = Mercer University School of Medicine | layurl = http://library.med.utah.edu/WebPath/TUTORIAL/PROSTATE/PROSTATE.html }}</ref>
Ethnic groups have different rates of [[prostate cancer]].<ref name=Cal2010/> Differences in sex hormones, including testosterone, have been suggested as an explanation for these differences.<ref name=Cal2010>{{vcite2 journal | vauthors = Calistro Alvarado L | title = Population differences in the testosterone levels of young men are associated with prostate cancer disparities in older men | journal = Am. J. Hum. Biol. | volume = 22 | issue = 4 | pages = 449–55 | year = 2010 | pmid = 20087895 | doi = 10.1002/ajhb.21016 }}</ref> This apparent paradox can be resolved by noting that prostate cancer is very common. In autopsies, 80% of 80-year-old men have prostate cancer.<ref name="pmid15495199">{{vcite2 journal | vauthors = Bostwick DG, Burke HB, Djakiew D, Euling S, Ho SM, Landolph J, Morrison H, Sonawane B, Shifflett T, Waters DJ, Timms B | title = Human prostate cancer risk factors | journal = Cancer | volume = 101 | issue = 10 Suppl | pages = 2371–490 | date = November 2004 | pmid = 15495199 | doi = 10.1002/cncr.20408 | laysource = Mercer University School of Medicine | layurl = http://library.med.utah.edu/WebPath/TUTORIAL/PROSTATE/PROSTATE.html }}</ref>


===Other===
===Other===
Other adverse effects of testosterone supplementation may include increased [[hematocrit]] (which may require [[venipuncture]] in order to treat), exacerbation of [[sleep apnea]] and acceleration of pre-existing [[prostate cancer]] growth in individuals having undergone androgen deprivation.{{citation needed|date=September 2014}} Other adverse effects may include minor side-effects such as acne and oily skin as well as significant hair loss and/or thinning of the hair which may be prevented with [[5-alpha reductase]] inhibitors ordinarily used for the treatment of [[benign prostatic hyperplasia]] such as [[finasteride]] or [[dutasteride]].{{citation needed|date=September 2014}} Exogenous testosterone may also cause suppression of [[spermatogenesis]], leading to infertility.<ref name="pmid1977002">{{cite journal | title = Contraceptive efficacy of testosterone-induced azoospermia in normal men. World Health Organization Task Force on methods for the regulation of male fertility | journal = Lancet | volume = 336 | issue = 8721 | pages = 955–9 | date = October 1990 | pmid = 1977002 | doi = 10.1016/0140-6736(90)92416-F | url = }}</ref> It does increase [[hemoglobin]] levels and decrease [[HDL cholesterol]] levels but it is not clear if these changes are meaningful.<ref name=Fer2010/>
Other adverse effects of testosterone supplementation may include increased [[hematocrit]] (which may require [[venipuncture]] in order to treat), exacerbation of [[sleep apnea]] and acceleration of pre-existing [[prostate cancer]] growth in individuals having undergone androgen deprivation.{{citation needed|date=September 2014}} Other adverse effects may include minor side-effects such as acne and oily skin as well as significant hair loss and/or thinning of the hair which may be prevented with [[5-alpha reductase]] inhibitors ordinarily used for the treatment of [[benign prostatic hyperplasia]] such as [[finasteride]] or [[dutasteride]].{{citation needed|date=September 2014}} Exogenous testosterone may also cause suppression of [[spermatogenesis]], leading to infertility.<ref name="pmid1977002">{{vcite2 journal | vauthors = | title = Contraceptive efficacy of testosterone-induced azoospermia in normal men. World Health Organization Task Force on methods for the regulation of male fertility | journal = Lancet | volume = 336 | issue = 8721 | pages = 955–9 | date = October 1990 | pmid = 1977002 | doi = 10.1016/0140-6736(90)92416-F | url = }}</ref> It does increase [[hemoglobin]] levels and decrease [[HDL cholesterol]] levels but it is not clear if these changes are meaningful.<ref name=Fer2010/>


===Pregnancy and breast feeding===
===Pregnancy and breast feeding===
Line 264: Line 264:
=== Biosynthesis ===
=== Biosynthesis ===
[[File:Steroidogenesis.svg|thumb|left|500px|Human [[steroidogenesis]], showing testosterone near bottom.]]
[[File:Steroidogenesis.svg|thumb|left|500px|Human [[steroidogenesis]], showing testosterone near bottom.]]
Like other [[steroid]] hormones, testosterone is derived from [[cholesterol]] (see figure to the left).<ref name="pmid1307739">{{cite journal | author = Waterman MR, Keeney DS | title = Genes involved in androgen biosynthesis and the male phenotype | journal = Horm. Res. | volume = 38 | issue = 5–6 | pages = 217–21 | year = 1992 | pmid = 1307739 | doi = 10.1159/000182546 | url = }}</ref> The first step in the [[biosynthesis]] involves the oxidative cleavage of the sidechain of cholesterol by [[cholesterol side-chain cleavage enzyme|CYP11A]], a [[mitochondrion|mitochondrial]] [[cytochrome P450]] oxidase with the loss of six carbon atoms to give [[pregnenolone]]. In the next step, two additional carbon atoms are removed by the [[CYP17A1|CYP17A]] enzyme in the [[endoplasmic reticulum]] to yield a variety of C<sub>19</sub> steroids.<ref name="pmid3535074">{{cite journal | author = Zuber MX, Simpson ER, Waterman MR | title = Expression of bovine 17 alpha-hydroxylase cytochrome P-450 cDNA in nonsteroidogenic (COS 1) cells | journal = Science | volume = 234 | issue = 4781 | pages = 1258–61 | date = December 1986 | pmid = 3535074 | doi = 10.1126/science.3535074 | url = | bibcode = 1986Sci...234.1258Z }}</ref> In addition, the 3-hydroxyl group is oxidized by [[3-beta-HSD|3-β-HSD]] to produce [[androstenedione]]. In the final and rate limiting step, the C-17 keto group androstenedione is reduced by [[17Beta Hydroxysteroid dehydrogenase|17-β hydroxysteroid dehydrogenase]] to yield testosterone.
Like other [[steroid]] hormones, testosterone is derived from [[cholesterol]] (see figure to the left).<ref name="pmid1307739">{{vcite2 journal | vauthors = Waterman MR, Keeney DS | title = Genes involved in androgen biosynthesis and the male phenotype | journal = Horm. Res. | volume = 38 | issue = 5–6 | pages = 217–21 | year = 1992 | pmid = 1307739 | doi = 10.1159/000182546 | url = }}</ref> The first step in the [[biosynthesis]] involves the oxidative cleavage of the sidechain of cholesterol by [[cholesterol side-chain cleavage enzyme|CYP11A]], a [[mitochondrion|mitochondrial]] [[cytochrome P450]] oxidase with the loss of six carbon atoms to give [[pregnenolone]]. In the next step, two additional carbon atoms are removed by the [[CYP17A1|CYP17A]] enzyme in the [[endoplasmic reticulum]] to yield a variety of C<sub>19</sub> steroids.<ref name="pmid3535074">{{vcite2 journal | vauthors = Zuber MX, Simpson ER, Waterman MR | title = Expression of bovine 17 alpha-hydroxylase cytochrome P-450 cDNA in nonsteroidogenic (COS 1) cells | journal = Science | volume = 234 | issue = 4781 | pages = 1258–61 | date = December 1986 | pmid = 3535074 | doi = 10.1126/science.3535074 | url = | bibcode = 1986Sci...234.1258Z }}</ref> In addition, the 3-hydroxyl group is oxidized by [[3-beta-HSD|3-β-HSD]] to produce [[androstenedione]]. In the final and rate limiting step, the C-17 keto group androstenedione is reduced by [[17Beta Hydroxysteroid dehydrogenase|17-β hydroxysteroid dehydrogenase]] to yield testosterone.


The largest amounts of testosterone (>95%) are produced by the [[testis|testes]] in men.<ref name="Mooradian_ 1987"/> It is also synthesized in far smaller quantities in women by the [[thecal cells]] of the [[ovary|ovaries]], by the [[placenta]], as well as by the [[zona reticularis]] of the [[adrenal cortex]] and even [[skin]]<ref name="pmid15507105">{{cite journal | author = Zouboulis CC, Degitz K | title = Androgen action on human skin – from basic research to clinical significance | journal = Exp. Dermatol. | volume = 13 Suppl 4 | issue = | pages = 5–10 | year = 2004 | pmid = 15507105 | doi = 10.1111/j.1600-0625.2004.00255.x }}</ref> in both sexes. In the [[testes]], testosterone is produced by the [[Leydig cell]]s.<ref name="pmid58744">{{cite journal | author = Brooks RV | title = Androgens | journal = Clin Endocrinol Metab | volume = 4 | issue = 3 | pages = 503–20 | date = November 1975 | pmid = 58744 | doi = 10.1016/S0300-595X(75)80045-4 | url = }}</ref> The male generative glands also contain [[Sertoli cell]]s, which require testosterone for [[spermatogenesis]]. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific [[plasma protein]], [[sex hormone-binding globulin]] (SHBG).
The largest amounts of testosterone (>95%) are produced by the [[testis|testes]] in men.<ref name="Mooradian_ 1987"/> It is also synthesized in far smaller quantities in women by the [[thecal cells]] of the [[ovary|ovaries]], by the [[placenta]], as well as by the [[zona reticularis]] of the [[adrenal cortex]] and even [[skin]]<ref name="pmid15507105">{{vcite2 journal | vauthors = Zouboulis CC, Degitz K | title = Androgen action on human skin – from basic research to clinical significance | journal = Exp. Dermatol. | volume = 13 Suppl 4 | issue = | pages = 5–10 | year = 2004 | pmid = 15507105 | doi = 10.1111/j.1600-0625.2004.00255.x }}</ref> in both sexes. In the [[testes]], testosterone is produced by the [[Leydig cell]]s.<ref name="pmid58744">{{vcite2 journal | vauthors = Brooks RV | title = Androgens | journal = Clin Endocrinol Metab | volume = 4 | issue = 3 | pages = 503–20 | date = November 1975 | pmid = 58744 | doi = 10.1016/S0300-595X(75)80045-4 | url = }}</ref> The male generative glands also contain [[Sertoli cell]]s, which require testosterone for [[spermatogenesis]]. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific [[plasma protein]], [[sex hormone-binding globulin]] (SHBG).


=== Regulation ===
=== Regulation ===
[[File:Hypothalamus pituitary testicles axis.png|thumb|right|Hypothalamic–pituitary–testicular axis]]
[[File:Hypothalamus pituitary testicles axis.png|thumb|right|Hypothalamic–pituitary–testicular axis]]
In males, testosterone is synthesized primarily in [[Leydig cells]]. The number of Leydig cells in turn is regulated by [[luteinizing hormone]] (LH) and [[follicle-stimulating hormone]] (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of [[17Beta Hydroxysteroid dehydrogenase|17-β hydroxysteroid dehydrogenase]].<ref name="isbn0-9627422-7-9">{{cite book | author = Payne AH, O'Shaughnessy P | authorlink = | editor = Payne AH, Hardy MP, Russell LD | others = | title = Leydig Cell | edition = | language = | publisher = Cache River Press | location = Vienna [Il] | year = 1996 | origyear = | pages = 260–285 | quote = | isbn = 0-9627422-7-9 | oclc = | doi = | url = | chapter = Structure, function, and regulation of steroidogenic enzymes in the Leydig cell }}</ref>
In males, testosterone is synthesized primarily in [[Leydig cells]]. The number of Leydig cells in turn is regulated by [[luteinizing hormone]] (LH) and [[follicle-stimulating hormone]] (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of [[17Beta Hydroxysteroid dehydrogenase|17-β hydroxysteroid dehydrogenase]].<ref name="isbn0-9627422-7-9">{{cite book | author = Payne AH, O'Shaughnessy P | authorlink = | editor = Payne AH, Hardy MP, Russell LD | others = | title = Leydig Cell | edition = | publisher = Cache River Press | location = Vienna [Il] | year = 1996 | origyear = | pages = 260–285 | quote = | isbn = 0-9627422-7-9 | oclc = | doi = | url = | chapter = Structure, function, and regulation of steroidogenic enzymes in the Leydig cell }}</ref>


The amount of testosterone synthesized is regulated by the [[hypothalamic–pituitary–gonadal axis|hypothalamic–pituitary–testicular axis]] (see figure to the right).<ref name="pmid1377467">{{cite journal | author = Swerdloff RS, Wang C, Bhasin S | title = Developments in the control of testicular function | journal = Baillieres Clin. Endocrinol. Metab. | volume = 6 | issue = 2 | pages = 451–83 | date = April 1992 | pmid = 1377467 | doi = 10.1016/S0950-351X(05)80158-2 | url = }}</ref> When testosterone levels are low, gonadotropin-releasing hormone ([[gonadotropin-releasing hormone|GnRH]]) is released by the [[hypothalamus]], which in turn stimulates the [[pituitary gland]] to release FSH and LH. These latter two hormones stimulate the testis to synthesize testosterone. Finally, increasing levels of testosterone through a negative [[feedback]] loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively.
The amount of testosterone synthesized is regulated by the [[hypothalamic–pituitary–gonadal axis|hypothalamic–pituitary–testicular axis]] (see figure to the right).<ref name="pmid1377467">{{vcite2 journal | vauthors = Swerdloff RS, Wang C, Bhasin S | title = Developments in the control of testicular function | journal = Baillieres Clin. Endocrinol. Metab. | volume = 6 | issue = 2 | pages = 451–83 | date = April 1992 | pmid = 1377467 | doi = 10.1016/S0950-351X(05)80158-2 | url = }}</ref> When testosterone levels are low, gonadotropin-releasing hormone ([[gonadotropin-releasing hormone|GnRH]]) is released by the [[hypothalamus]], which in turn stimulates the [[pituitary gland]] to release FSH and LH. These latter two hormones stimulate the testis to synthesize testosterone. Finally, increasing levels of testosterone through a negative [[feedback]] loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively.


Factors affecting testosterone levels include:
Factors affecting testosterone levels include:
* Weight loss may result in an increase in testosterone levels. Fat cells synthesize the enzyme aromatase, which converts testosterone, the male sex hormone, into estradiol, the female sex hormone.<ref name="pmid21849026">{{cite journal | author = Håkonsen LB, Thulstrup AM, Aggerholm AS, Olsen J, Bonde JP, Andersen CY, Bungum M, Ernst EH, Hansen ML, Ernst EH, Ramlau-Hansen CH | title = Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men | journal = Reprod Health | volume = 8 | issue = | page = 24 | year = 2011 | pmid = 21849026 | pmc = 3177768 | doi = 10.1186/1742-4755-8-24 }}</ref>
* Weight loss may result in an increase in testosterone levels. Fat cells synthesize the enzyme aromatase, which converts testosterone, the male sex hormone, into estradiol, the female sex hormone.<ref name="pmid21849026">{{vcite2 journal | vauthors = Håkonsen LB, Thulstrup AM, Aggerholm AS, Olsen J, Bonde JP, Andersen CY, Bungum M, Ernst EH, Hansen ML, Ernst EH, Ramlau-Hansen CH | title = Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men | journal = Reprod Health | volume = 8 | issue = | page = 24 | year = 2011 | pmid = 21849026 | pmc = 3177768 | doi = 10.1186/1742-4755-8-24 }}</ref>
* The secosteroid [[vitamin D]] in levels of 400–1000&nbsp;[[international unit|IU]]/d (10–25&nbsp;µg/d) raises testosterone levels.<ref name="pmid21154195">{{cite journal | author = Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A | title = Effect of vitamin D supplementation on testosterone levels in men | journal = Horm. Metab. Res. | volume = 43 | issue = 3 | pages = 223–5 | date = March 2011 | pmid = 21154195 | doi = 10.1055/s-0030-1269854 }}</ref>
* The secosteroid [[vitamin D]] in levels of 400–1000&nbsp;[[international unit|IU]]/d (10–25&nbsp;µg/d) raises testosterone levels.<ref name="pmid21154195">{{vcite2 journal | vauthors = Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A | title = Effect of vitamin D supplementation on testosterone levels in men | journal = Horm. Metab. Res. | volume = 43 | issue = 3 | pages = 223–5 | date = March 2011 | pmid = 21154195 | doi = 10.1055/s-0030-1269854 }}</ref>
* [[Zinc]] deficiency lowers testosterone levels<ref name="pmid8875519">{{cite journal | author = Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ | title = Zinc status and serum testosterone levels of healthy adults | journal = Nutrition | volume = 12 | issue = 5 | pages = 344–8 | date = May 1996 | pmid = 8875519 | doi = 10.1016/S0899-9007(96)80058-X | url = }}</ref> but over supplementation has no effect on serum testosterone.<ref name="pmid17882141">{{cite journal | author = Koehler K, Parr MK, Geyer H, Mester J, Schänzer W | title = Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement | journal = Eur J Clin Nutr | volume = 63 | issue = 1 | pages = 65–70 | date = January 2009 | pmid = 17882141 | doi = 10.1038/sj.ejcn.1602899 | url = }}</ref>
* [[Zinc]] deficiency lowers testosterone levels<ref name="pmid8875519">{{vcite2 journal | vauthors = Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ | title = Zinc status and serum testosterone levels of healthy adults | journal = Nutrition | volume = 12 | issue = 5 | pages = 344–8 | date = May 1996 | pmid = 8875519 | doi = 10.1016/S0899-9007(96)80058-X | url = }}</ref> but over supplementation has no effect on serum testosterone.<ref name="pmid17882141">{{vcite2 journal | vauthors = Koehler K, Parr MK, Geyer H, Mester J, Schänzer W | title = Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement | journal = Eur J Clin Nutr | volume = 63 | issue = 1 | pages = 65–70 | date = January 2009 | pmid = 17882141 | doi = 10.1038/sj.ejcn.1602899 | url = }}</ref>
* Dominance challenges can, in some cases, stimulate increased testosterone release in men.<ref name="pmid10603287">{{cite journal | author = Schultheiss OC, Campbell KL, McClelland DC | title = Implicit power motivation moderates men's testosterone responses to imagined and real dominance success | journal = Horm Behav | volume = 36 | issue = 3 | pages = 234–41 | date = December 1999 | pmid = 10603287 | doi = 10.1006/hbeh.1999.1542 | url = }}</ref>
* Dominance challenges can, in some cases, stimulate increased testosterone release in men.<ref name="pmid10603287">{{vcite2 journal | vauthors = Schultheiss OC, Campbell KL, McClelland DC | title = Implicit power motivation moderates men's testosterone responses to imagined and real dominance success | journal = Horm Behav | volume = 36 | issue = 3 | pages = 234–41 | date = December 1999 | pmid = 10603287 | doi = 10.1006/hbeh.1999.1542 | url = }}</ref>
* Aging reduces testosterone release.<ref name="pmid16339924">{{cite journal | author = Liu PY, Pincus SM, Takahashi PY, Roebuck PD, Iranmanesh A, Keenan DM, Veldhuis JD | title = Aging attenuates both the regularity and joint synchrony of LH and testosterone secretion in normal men: analyses via a model of graded GnRH receptor blockade | journal = Am. J. Physiol. Endocrinol. Metab. | volume = 290 | issue = 1 | pages = E34–E41 | date = January 2006 | pmid = 16339924 | doi = 10.1152/ajpendo.00227.2005 | url = }}</ref>
* Aging reduces testosterone release.<ref name="pmid16339924">{{vcite2 journal | vauthors = Liu PY, Pincus SM, Takahashi PY, Roebuck PD, Iranmanesh A, Keenan DM, Veldhuis JD | title = Aging attenuates both the regularity and joint synchrony of LH and testosterone secretion in normal men: analyses via a model of graded GnRH receptor blockade | journal = Am. J. Physiol. Endocrinol. Metab. | volume = 290 | issue = 1 | pages = E34–E41 | date = January 2006 | pmid = 16339924 | doi = 10.1152/ajpendo.00227.2005 | url = }}</ref>
* [[Hypogonadism]]
* [[Hypogonadism]]
* Sleep ([[REM dream]]) increases nocturnal testosterone levels.<ref name="pmid18519168">{{cite journal | author = Andersen ML, Tufik S | title = The effects of testosterone on sleep and sleep-disordered breathing in men: its bidirectional interaction with erectile function | journal = Sleep Med Rev | volume = 12 | issue = 5 | pages = 365–79 | date = October 2008 | pmid = 18519168 | doi = 10.1016/j.smrv.2007.12.003 | url = http://www.sono.org.br/pdf/2008_Andersen_Sleep_Med_Rev.pdf }}</ref>
* Sleep ([[REM dream]]) increases nocturnal testosterone levels.<ref name="pmid18519168">{{vcite2 journal | vauthors = Andersen ML, Tufik S | title = The effects of testosterone on sleep and sleep-disordered breathing in men: its bidirectional interaction with erectile function | journal = Sleep Med Rev | volume = 12 | issue = 5 | pages = 365–79 | date = October 2008 | pmid = 18519168 | doi = 10.1016/j.smrv.2007.12.003 | url = http://www.sono.org.br/pdf/2008_Andersen_Sleep_Med_Rev.pdf }}</ref>
* [[Resistance training]] increases testosterone levels,<ref name="url_Marin">{{cite journal | author = Marin DP, Figueira AJ Junior, Pinto LG | year = 2006| title = One session of resistance training may increase serum testosterone and triiodetironine in young men| url = http://journals.lww.com/acsm-msse/Fulltext/2006/05001/One_Session_of_Resistance_Training_May_Increase.2108.aspx| journal = Medicine & Science in Sports & Exercise | volume = 38 | issue = 5 | page = S285 | doi =10.1249/00005768-200605001-01235 }}</ref> however, in older men, that increase can be avoided by protein ingestion.<ref name="pmid18455389">{{cite journal | author = Hulmi JJ, Ahtiainen JP, Selänne H, Volek JS, Häkkinen K, Kovanen V, Mero AA | title = Androgen receptors and testosterone in men—effects of protein ingestion, resistance exercise and fiber type | journal = J. Steroid Biochem. Mol. Biol. | volume = 110 | issue = 1–2 | pages = 130–7 | date = May 2008 | pmid = 18455389 | doi = 10.1016/j.jsbmb.2008.03.030 | url = }}</ref>
* [[Resistance training]] increases testosterone levels,<ref name="url_Marin">{{vcite2 journal | vauthors = Marin DP, Figueira AJ Junior, Pinto LG | year = 2006| title = One session of resistance training may increase serum testosterone and triiodetironine in young men| url = http://journals.lww.com/acsm-msse/Fulltext/2006/05001/One_Session_of_Resistance_Training_May_Increase.2108.aspx| journal = Medicine & Science in Sports & Exercise | volume = 38 | issue = 5 | page = S285 | doi =10.1249/00005768-200605001-01235 }}</ref> however, in older men, that increase can be avoided by protein ingestion.<ref name="pmid18455389">{{vcite2 journal | vauthors = Hulmi JJ, Ahtiainen JP, Selänne H, Volek JS, Häkkinen K, Kovanen V, Mero AA | title = Androgen receptors and testosterone in men—effects of protein ingestion, resistance exercise and fiber type | journal = J. Steroid Biochem. Mol. Biol. | volume = 110 | issue = 1–2 | pages = 130–7 | date = May 2008 | pmid = 18455389 | doi = 10.1016/j.jsbmb.2008.03.030 | url = }}</ref>
*[[Licorice]]. The active ingredient in licorice root, [[glycyrrhizinic acid]] has been linked to small, clinically non-significant decreases in testosterone levels.<ref name="pmid11716893">{{cite journal | author = Josephs RA, Guinn JS, Harper ML, Askari F | title = Liquorice consumption and salivary testosterone concentrations | journal = Lancet | volume = 358 | issue = 9293 | pages = 1613–4 | date = November 2001 | pmid = 11716893 | doi = 10.1016/S0140-6736(01)06664-8 | url = }}</ref> In contrast, a more recent study found that licorice administration produced a substantial testosterone decrease in a small, female-only sample.<ref name="pmid15579328">{{cite journal | author = Armanini D, Mattarello MJ, Fiore C, Bonanni G, Scaroni C, Sartorato P, Palermo M | title = Licorice reduces serum testosterone in healthy women | journal = Steroids | volume = 69 | issue = 11–12 | pages = 763–6 | year = 2004 | pmid = 15579328 | doi = 10.1016/j.steroids.2004.09.005 | url = }}</ref>
*[[Licorice]]. The active ingredient in licorice root, [[glycyrrhizinic acid]] has been linked to small, clinically non-significant decreases in testosterone levels.<ref name="pmid11716893">{{vcite2 journal | vauthors = Josephs RA, Guinn JS, Harper ML, Askari F | title = Liquorice consumption and salivary testosterone concentrations | journal = Lancet | volume = 358 | issue = 9293 | pages = 1613–4 | date = November 2001 | pmid = 11716893 | doi = 10.1016/S0140-6736(01)06664-8 | url = }}</ref> In contrast, a more recent study found that licorice administration produced a substantial testosterone decrease in a small, female-only sample.<ref name="pmid15579328">{{vcite2 journal | vauthors = Armanini D, Mattarello MJ, Fiore C, Bonanni G, Scaroni C, Sartorato P, Palermo M | title = Licorice reduces serum testosterone in healthy women | journal = Steroids | volume = 69 | issue = 11–12 | pages = 763–6 | year = 2004 | pmid = 15579328 | doi = 10.1016/j.steroids.2004.09.005 | url = }}</ref>
* Natural or man-made [[antiandrogens]] including [[spearmint]] tea reduce testosterone levels.<ref name="pmid17310494">{{cite journal | author = Akdoğan M, Tamer MN, Cüre E, Cüre MC, Köroğlu BK, Delibaş N | title = Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism | journal = Phytother Res | volume = 21 | issue = 5 | pages = 444–7 | date = May 2007 | pmid = 17310494 | doi = 10.1002/ptr.2074 | url = }}</ref><ref name="pmid18804513">{{cite journal | author = Kumar V, Kural MR, Pereira BM, Roy P | title = Spearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats&nbsp;– altered levels of gene expression, enzymes and hormones | journal = Food Chem. Toxicol. | volume = 46 | issue = 12 | pages = 3563–70 | date = December 2008 | pmid = 18804513 | doi = 10.1016/j.fct.2008.08.027 | url = }}</ref><ref name="pmid19585478">{{cite journal | author = Grant P | title = Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial | journal = Phytother Res | volume = 24 | issue = 2 | pages = 186–8 | date = February 2010 | pmid = 19585478 | doi = 10.1002/ptr.2900 | url = }}</ref>
* Natural or man-made [[antiandrogens]] including [[spearmint]] tea reduce testosterone levels.<ref name="pmid17310494">{{vcite2 journal | vauthors = Akdoğan M, Tamer MN, Cüre E, Cüre MC, Köroğlu BK, Delibaş N | title = Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism | journal = Phytother Res | volume = 21 | issue = 5 | pages = 444–7 | date = May 2007 | pmid = 17310494 | doi = 10.1002/ptr.2074 | url = }}</ref><ref name="pmid18804513">{{vcite2 journal | vauthors = Kumar V, Kural MR, Pereira BM, Roy P | title = Spearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats&nbsp;– altered levels of gene expression, enzymes and hormones | journal = Food Chem. Toxicol. | volume = 46 | issue = 12 | pages = 3563–70 | date = December 2008 | pmid = 18804513 | doi = 10.1016/j.fct.2008.08.027 | url = }}</ref><ref name="pmid19585478">{{vcite2 journal | vauthors = Grant P | title = Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial | journal = Phytother Res | volume = 24 | issue = 2 | pages = 186–8 | date = February 2010 | pmid = 19585478 | doi = 10.1002/ptr.2900 | url = }}</ref>
* Posing in high-power nonverbal displays through open, expansive postures can increase testosterone levels.<ref name="pmid20855902">{{cite journal | author = Carney DR, Cuddy AJ, Yap AJ | title = Power posing: brief nonverbal displays affect neuroendocrine levels and risk tolerance | journal = Psychol Sci. | volume = 21 | issue = 10 | pages = 1363–1368 | date = October 2010 | pmid = 20855902 | doi = 10.1177/0956797610383437 | accessdate = March 31, 2014 }}</ref>
* Posing in high-power nonverbal displays through open, expansive postures can increase testosterone levels.<ref name="pmid20855902">{{vcite2 journal | vauthors = Carney DR, Cuddy AJ, Yap AJ | title = Power posing: brief nonverbal displays affect neuroendocrine levels and risk tolerance | journal = Psychol Sci. | volume = 21 | issue = 10 | pages = 1363–1368 | date = October 2010 | pmid = 20855902 | doi = 10.1177/0956797610383437 | accessdate = March 31, 2014 }}</ref>


=== Metabolism ===
=== Metabolism ===
Approximately 7% of testosterone is reduced to 5α-[[dihydrotestosterone]] (DHT) by the cytochrome P<sub>450</sub> enzyme [[5-alpha reductase|5α-reductase]],<ref name="pmid8092979">{{cite journal | author = Randall VA | title = Role of 5 alpha-reductase in health and disease | journal = Baillieres Clin. Endocrinol. Metab. | volume = 8 | issue = 2 | pages = 405–31 | date = April 1994 | pmid = 8092979 | doi = 10.1016/S0950-351X(05)80259-9 | url = }}</ref> an enzyme highly expressed in male sex organs and hair follicles.<ref name="Mooradian_ 1987"/> Approximately 0.3% of testosterone is converted into estradiol by [[aromatase]] (CYP19A1)<ref name="pmid12428207">{{cite journal | author = Meinhardt U, Mullis PE | title = The essential role of the aromatase/p450arom | journal = Semin. Reprod. Med. | volume = 20 | issue = 3 | pages = 277–84 | date = August 2002 | pmid = 12428207 | doi = 10.1055/s-2002-35374 | url = }}</ref> an enzyme expressed in the brain, liver, and adipose tissues.<ref name="Mooradian_ 1987"/>
Approximately 7% of testosterone is reduced to 5α-[[dihydrotestosterone]] (DHT) by the cytochrome P<sub>450</sub> enzyme [[5-alpha reductase|5α-reductase]],<ref name="pmid8092979">{{vcite2 journal | vauthors = Randall VA | title = Role of 5 alpha-reductase in health and disease | journal = Baillieres Clin. Endocrinol. Metab. | volume = 8 | issue = 2 | pages = 405–31 | date = April 1994 | pmid = 8092979 | doi = 10.1016/S0950-351X(05)80259-9 | url = }}</ref> an enzyme highly expressed in male sex organs and hair follicles.<ref name="Mooradian_ 1987"/> Approximately 0.3% of testosterone is converted into estradiol by [[aromatase]] (CYP19A1)<ref name="pmid12428207">{{vcite2 journal | vauthors = Meinhardt U, Mullis PE | title = The essential role of the aromatase/p450arom | journal = Semin. Reprod. Med. | volume = 20 | issue = 3 | pages = 277–84 | date = August 2002 | pmid = 12428207 | doi = 10.1055/s-2002-35374 | url = }}</ref> an enzyme expressed in the brain, liver, and adipose tissues.<ref name="Mooradian_ 1987"/>


DHT is a more potent form of testosterone while estradiol has completely different activities (feminization) compared to testosterone (masculinization). Also, testosterone and DHT may be deactivated or cleared by enzymes that hydroxylate at the 6, 7, 15 or 16 positions.<ref name="isbn0-3870-8012-0">{{cite book | author = Trager L | authorlink = | editor = | others = | title = Steroidhormone: Biosynthese, Stoffwechsel, Wirkung | edition = | language = German | publisher = Springer-Verlag | location = | year = 1977 | origyear = | page = 349 | quote = | isbn = 0-387-08012-0 | oclc = | doi = | url = | accessdate = }}</ref>
DHT is a more potent form of testosterone while estradiol has completely different activities (feminization) compared to testosterone (masculinization). Also, testosterone and DHT may be deactivated or cleared by enzymes that hydroxylate at the 6, 7, 15 or 16 positions.<ref name="isbn0-3870-8012-0">{{cite book | author = Trager L | authorlink = | editor = | others = | title = Steroidhormone: Biosynthese, Stoffwechsel, Wirkung | edition = | language = German | publisher = Springer-Verlag | location = | year = 1977 | origyear = | page = 349 | quote = | isbn = 0-387-08012-0 | oclc = | doi = | url = | accessdate = }}</ref>


== Mechanism of action ==
== Mechanism of action ==
The effects of testosterone in humans and other [[vertebrates]] occur by way of two main mechanisms: by activation of the [[androgen receptor]] (directly or as DHT), and by conversion to [[estradiol]] and activation of certain [[estrogen receptor]]s.<ref name="pmid18406296">{{cite journal | author = Hiipakka RA, Liao S | title = Molecular mechanism of androgen action | journal = Trends Endocrinol. Metab. | volume = 9 | issue = 8 | pages = 317–24 | date = October 1998 | pmid = 18406296 | doi = 10.1016/S1043-2760(98)00081-2 | url = }}</ref><ref name="pmid11511858">{{cite journal | author = McPhaul MJ, Young M | title = Complexities of androgen action | journal = J. Am. Acad. Dermatol. | volume = 45 | issue = 3 Suppl | pages = S87–94 | date = September 2001 | pmid = 11511858 | doi = 10.1067/mjd.2001.117429 | url = }}</ref>
The effects of testosterone in humans and other [[vertebrates]] occur by way of two main mechanisms: by activation of the [[androgen receptor]] (directly or as DHT), and by conversion to [[estradiol]] and activation of certain [[estrogen receptor]]s.<ref name="pmid18406296">{{vcite2 journal | vauthors = Hiipakka RA, Liao S | title = Molecular mechanism of androgen action | journal = Trends Endocrinol. Metab. | volume = 9 | issue = 8 | pages = 317–24 | date = October 1998 | pmid = 18406296 | doi = 10.1016/S1043-2760(98)00081-2 | url = }}</ref><ref name="pmid11511858">{{vcite2 journal | vauthors = McPhaul MJ, Young M | title = Complexities of androgen action | journal = J. Am. Acad. Dermatol. | volume = 45 | issue = 3 Suppl | pages = S87–94 | date = September 2001 | pmid = 11511858 | doi = 10.1067/mjd.2001.117429 | url = }}</ref>


Free testosterone (T) is transported into the [[cytoplasm]] of target [[Tissue (biology)|tissue]] [[Cell (biology)|cells]], where it can bind to the [[androgen receptor]], or can be reduced to 5α-[[dihydrotestosterone]] (DHT) by the cytoplasmic enzyme [[5-alpha reductase]]. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of T.<ref name="pmid3762019">{{cite journal | author = Breiner M, Romalo G, Schweikert HU | title = Inhibition of androgen receptor binding by natural and synthetic steroids in cultured human genital skin fibroblasts | journal = Klin. Wochenschr. | volume = 64 | issue = 16 | pages = 732–7 | date = August 1986 | pmid = 3762019 | doi = 10.1007/BF01734339 | url = }}</ref> The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the [[cell nucleus]] and bind directly to specific [[nucleotide]] sequences of the [[chromosome|chromosomal]] DNA. The areas of binding are called [[hormone response element]]s (HREs), and influence transcriptional activity of certain [[gene]]s, producing the androgen effects.
Free testosterone (T) is transported into the [[cytoplasm]] of target [[Tissue (biology)|tissue]] [[Cell (biology)|cells]], where it can bind to the [[androgen receptor]], or can be reduced to 5α-[[dihydrotestosterone]] (DHT) by the cytoplasmic enzyme [[5-alpha reductase]]. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of T.<ref name="pmid3762019">{{vcite2 journal | vauthors = Breiner M, Romalo G, Schweikert HU | title = Inhibition of androgen receptor binding by natural and synthetic steroids in cultured human genital skin fibroblasts | journal = Klin. Wochenschr. | volume = 64 | issue = 16 | pages = 732–7 | date = August 1986 | pmid = 3762019 | doi = 10.1007/BF01734339 | url = }}</ref> The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the [[cell nucleus]] and bind directly to specific [[nucleotide]] sequences of the [[chromosome|chromosomal]] DNA. The areas of binding are called [[hormone response element]]s (HREs), and influence transcriptional activity of certain [[gene]]s, producing the androgen effects.


Androgen receptors occur in many different vertebrate body system tissues, and both males and females respond similarly to similar levels. Greatly differing amounts of testosterone prenatally, at puberty, and throughout life account for a share of biological [[sexual differentiation|differences]] between males and females.
Androgen receptors occur in many different vertebrate body system tissues, and both males and females respond similarly to similar levels. Greatly differing amounts of testosterone prenatally, at puberty, and throughout life account for a share of biological [[sexual differentiation|differences]] between males and females.
Line 305: Line 305:


== Related drugs ==
== Related drugs ==
Some drugs indirectly target testosterone as a way of treating certain conditions. For example, [[5-alpha-reductase inhibitor]]s such as [[finasteride]] inhibit the conversion of testosterone into [[dihydrotestosterone]] (DHT), a metabolite more potent than testosterone.<ref name="pmid15853706">{{cite journal | author = Bratoeff E, Cabeza M, Ramirez E, Heuze Y, Flores E | title = Recent advances in the chemistry and pharmacological activity of new steroidal antiandrogens and 5 alpha-reductase inhibitors | journal = Curr. Med. Chem. | volume = 12 | issue = 8 | pages = 927–43 | year = 2005 | pmid = 15853706 | doi = 10.2174/0929867053507306 | url = }}</ref> These 5-alpha-reductase inhibitors have been used to treat various conditions associated with androgens, such as [[androgenetic alopecia]] ([[male-pattern baldness]]), [[hirsutism]], [[benign prostatic hyperplasia]] (BPH), and [[prostate cancer]].<ref name="pmid15853706"/> In contrast, [[gonadotropin-releasing hormone antagonist|GnRH antagonists]] bind to [[gonadotropin-releasing hormone receptor|GnRH receptors]] in the [[pituitary gland]], blocking the release of [[luteinising hormone]] (LH) and [[follicle-stimulating hormone]] (FSH) from the pituitary.<ref name="pmid17237842">{{cite journal | author = Engel JB, Schally AV | title = Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone | journal = Nat Clin Pract Endocrinol Metab | volume = 3 | issue = 2 | pages = 157–67 | date = February 2007 | pmid = 17237842 | doi = 10.1038/ncpendmet0399 | url = }}</ref> In men, the reduction in LH subsequently leads to rapid suppression of testosterone release from the [[testes]]. GnRH antagonists have been used for the treatment of prostate cancer.
Some drugs indirectly target testosterone as a way of treating certain conditions. For example, [[5-alpha-reductase inhibitor]]s such as [[finasteride]] inhibit the conversion of testosterone into [[dihydrotestosterone]] (DHT), a metabolite more potent than testosterone.<ref name="pmid15853706">{{vcite2 journal | vauthors = Bratoeff E, Cabeza M, Ramirez E, Heuze Y, Flores E | title = Recent advances in the chemistry and pharmacological activity of new steroidal antiandrogens and 5 alpha-reductase inhibitors | journal = Curr. Med. Chem. | volume = 12 | issue = 8 | pages = 927–43 | year = 2005 | pmid = 15853706 | doi = 10.2174/0929867053507306 | url = }}</ref> These 5-alpha-reductase inhibitors have been used to treat various conditions associated with androgens, such as [[androgenetic alopecia]] ([[male-pattern baldness]]), [[hirsutism]], [[benign prostatic hyperplasia]] (BPH), and [[prostate cancer]].<ref name="pmid15853706"/> In contrast, [[gonadotropin-releasing hormone antagonist|GnRH antagonists]] bind to [[gonadotropin-releasing hormone receptor|GnRH receptors]] in the [[pituitary gland]], blocking the release of [[luteinising hormone]] (LH) and [[follicle-stimulating hormone]] (FSH) from the pituitary.<ref name="pmid17237842">{{vcite2 journal | vauthors = Engel JB, Schally AV | title = Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone | journal = Nat Clin Pract Endocrinol Metab | volume = 3 | issue = 2 | pages = 157–67 | date = February 2007 | pmid = 17237842 | doi = 10.1038/ncpendmet0399 | url = }}</ref> In men, the reduction in LH subsequently leads to rapid suppression of testosterone release from the [[testes]]. GnRH antagonists have been used for the treatment of prostate cancer.


== Routes of administration ==
== Routes of administration ==
[[File:Depo-testosterone 200 mg ml crop.jpg|thumb|Vial of testosterone for intramuscular injection]]
[[File:Depo-testosterone 200 mg ml crop.jpg|thumb|Vial of testosterone for intramuscular injection]]
There are many [[routes of administration]] for testosterone. Forms of testosterone for human administration currently available include injectable (such as testosterone [[cypionate]] or testosterone [[enanthate]] in oil),<ref name="urlTestosterone Information from Drugs.com">{{cite web | url = http://www.drugs.com/testosterone.html | title = Testosterone Information | authorlink = | work = | publisher = Drugs.com | pages = |language = | archiveurl = | archivedate = | quote = | accessdate = }}</ref> oral, [[Cheek|buccal]],<ref name="urlStriant Official FDA information, side effects and uses.">{{cite web | url =http://www.drugs.com/pro/striant.html | title = Striant Official FDA information, side effects and uses |authorlink = | work = | publisher = Drugs.com | pages = | language = | archiveurl = |archivedate = | quote = | accessdate = }}</ref> transdermal skin patches, transdermal creams, gels,<ref name="urlAndroGel Official FDA information, side effects and uses.">{{cite web | url =http://www.drugs.com/pro/androgel.html | title = AndroGel Official FDA information, side effects and uses |authorlink = | work = | publisher = Drugs.com | pages = | language = | archiveurl = |archivedate = | quote = | accessdate = }}</ref><ref name="urlTestim (patches and gel) medical facts from Drugs.com">{{cite web | url = http://www.drugs.com/mtm/testim-patches-and-gel.html | title = Testim (patches and gel) medical facts | authorlink = | work = | publisher = Drugs.com }}</ref> and implantable pellets.<ref name="urlwww.slatepharma.com">{{cite web | url =http://www.slatepharma.com | title = Testopel Pellets | publisher = www.slatepharma.com | pages = | language = | archiveurl = | archivedate = | quote = | accessdate = }}</ref> Roll-on methods and nasal sprays are currently under development.
There are many [[routes of administration]] for testosterone. Forms of testosterone for human administration currently available include injectable (such as testosterone [[cypionate]] or testosterone [[enanthate]] in oil),<ref name="urlTestosterone Information from Drugs.com">{{cite web | url = http://www.drugs.com/testosterone.html | title = Testosterone Information | authorlink = | work = | publisher = Drugs.com | pages = |language = | archiveurl = | archivedate = | quote = | accessdate = }}</ref> oral, [[Cheek|buccal]],<ref name="urlStriant Official FDA information, side effects and uses.">{{cite web | url =http://www.drugs.com/pro/striant.html | title = Striant Official FDA information, side effects and uses |authorlink = | work = | publisher = Drugs.com | pages = | archiveurl = |archivedate = | quote = | accessdate = }}</ref> transdermal skin patches, transdermal creams, gels,<ref name="urlAndroGel Official FDA information, side effects and uses.">{{cite web | url =http://www.drugs.com/pro/androgel.html | title = AndroGel Official FDA information, side effects and uses |authorlink = | work = | publisher = Drugs.com | pages = | archiveurl = |archivedate = | quote = | accessdate = }}</ref><ref name="urlTestim (patches and gel) medical facts from Drugs.com">{{cite web | url = http://www.drugs.com/mtm/testim-patches-and-gel.html | title = Testim (patches and gel) medical facts | authorlink = | work = | publisher = Drugs.com }}</ref> and implantable pellets.<ref name="urlwww.slatepharma.com">{{cite web | url =http://www.slatepharma.com | title = Testopel Pellets | publisher = www.slatepharma.com | pages = | archiveurl = | archivedate = | quote = | accessdate = }}</ref> Roll-on methods and nasal sprays are currently under development.


== History ==
== History ==
A [[testicular]] action was linked to circulating blood fractions&nbsp;– now understood to be a family of androgenic hormones&nbsp;– in the early work on castration and testicular transplantation in fowl by [[Arnold Adolph Berthold]] (1803–1861).<ref name="Berthold_1849">{{cite journal |author = Berthold AA | title = Transplantation der Hoden | trans_title = Transplantation of testis | language = German | journal = Arch. Anat. Physiol. Wissensch. |volume = 16 |issue = |pages = 42–6 | year = 1849 | pmid = | doi= | url =}}</ref> Research on the action of testosterone received a brief boost in 1889, when the Harvard professor [[Charles-Édouard Brown-Séquard]] (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in ''The Lancet'' that his vigor and feeling of well-being were markedly restored but the effects were transient,<ref name="Brown-Sequard_1889">{{cite journal |author = Brown-Sequard CE | title = The effects produced on man by subcutaneous injections of liquid obtained from the testicles of animals |language = | journal = Lancet |volume = 2 | issue = 3438|page = 105| year = 1889 | doi = 10.1016/S0140-6736(00)64118-1| url =}}</ref> and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.
A [[testicular]] action was linked to circulating blood fractions&nbsp;– now understood to be a family of androgenic hormones&nbsp;– in the early work on castration and testicular transplantation in fowl by [[Arnold Adolph Berthold]] (1803–1861).<ref name="Berthold_1849">{{cite journal |author = Berthold AA | title = Transplantation der Hoden | trans_title = Transplantation of testis | language = German | journal = Arch. Anat. Physiol. Wissensch. |volume = 16 |issue = |pages = 42–6 | year = 1849 | pmid = | doi= | url =}}</ref> Research on the action of testosterone received a brief boost in 1889, when the Harvard professor [[Charles-Édouard Brown-Séquard]] (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in ''The Lancet'' that his vigor and feeling of well-being were markedly restored but the effects were transient,<ref name="Brown-Sequard_1889">{{cite journal |author = Brown-Sequard CE | title = The effects produced on man by subcutaneous injections of liquid obtained from the testicles of animals |language = | journal = Lancet |volume = 2 | issue = 3438|page = 105| year = 1889 | doi = 10.1016/S0140-6736(00)64118-1| url =}}</ref> and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.


In 1927, the University of Chicago's Professor of Physiologic Chemistry, Fred C. Koch, established easy access to a large source of bovine testicles — the Chicago stockyards — and recruited students willing to endure the tedious work of extracting their isolates. In that year, Koch and his student, Lemuel McGee, derived 20&nbsp;mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them.<ref name="Gallagher_Koch_1929">{{cite journal | author = Gallagher TF, Koch FC | title = The testicular hormone |journal = J. Biol. Chem. | volume = 84 | issue = 2 | pages = 495–500 |date=November 1929 | pmid = | doi = | url = }}</ref> The group of Ernst Laqueur at the University of Amsterdam purified testosterone from bovine testicles in a similar manner in 1934, but isolation of the hormone from animal tissues in amounts permitting serious study in humans was not feasible until three European pharmaceutical giants—[[Schering]] (Berlin, Germany), [[Organon International|Organon]] (Oss, Netherlands) and [[Novartis|Ciba]] (Basel, Switzerland)—began full-scale steroid research and development programs in the 1930s.
In 1927, the University of Chicago's Professor of Physiologic Chemistry, Fred C. Koch, established easy access to a large source of bovine testicles — the Chicago stockyards — and recruited students willing to endure the tedious work of extracting their isolates. In that year, Koch and his student, Lemuel McGee, derived 20&nbsp;mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them.<ref name="Gallagher_Koch_1929">{{vcite2 journal | vauthors = Gallagher TF, Koch FC | title = The testicular hormone |journal = J. Biol. Chem. | volume = 84 | issue = 2 | pages = 495–500 |date=November 1929 | pmid = | doi = | url = }}</ref> The group of Ernst Laqueur at the University of Amsterdam purified testosterone from bovine testicles in a similar manner in 1934, but isolation of the hormone from animal tissues in amounts permitting serious study in humans was not feasible until three European pharmaceutical giants—[[Schering]] (Berlin, Germany), [[Organon International|Organon]] (Oss, Netherlands) and [[Novartis|Ciba]] (Basel, Switzerland)—began full-scale steroid research and development programs in the 1930s.
[[File:Lavoslav Ružićka 1939.jpg|thumb|180px|Leopold Ruzicka]]
[[File:Lavoslav Ružićka 1939.jpg|thumb|180px|Leopold Ruzicka]]
The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".<ref name="David_1935">{{cite journal | author = David KG., Dingemanse E, Freud J. Laqueur E | title = Über krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron | trans_title = On crystalline male hormone from testicles (testosterone) effective as from urine or from cholesterol | language = German | journal = Hoppe Seylers Z Physiol Chem | volume = 233 | issue = 5–6| page = 281 |date=May 1935 | pmid = | doi = 10.1515/bchm2.1935.233.5-6.281| url = }}</ref> They named the hormone ''testosterone'', from the [[stem (linguistics)|stems]] of ''testicle'' and ''[[sterol]]'', and the [[suffix]] of ''[[ketone]]''. The structure was worked out by Schering's [[Adolf Butenandt]].<ref name="Butenandt_1935a">{{cite journal | author = Butenandt A, Hanisch G | title = Umwandlung des Dehydroandrosterons in Androstendiol und Testosterone; ein Weg zur Darstellung des Testosterons aus Cholestrin | trans_title = About Testosterone. Conversion of Dehydro-androsterons into androstendiol and testosterone; a way for the structure assignment of testosterone from cholestrol | language = German | journal = Hoppe Seylers Z Physiol Chem | volume = 237 | issue = 2| page = 89 | year = 1935 | pmid = | doi = 10.1515/bchm2.1935.237.1-3.89| url = }}</ref><ref name="pmid11176375">{{cite journal | author = Freeman ER, Bloom DA, McGuire EJ | title = A brief history of testosterone | journal = J. Urol. | volume = 165 | issue = 2 | pages = 371–3 | date = February 2001 | pmid = 11176375 | doi = 10.1097/00005392-200102000-00004 | url = }}</ref>
The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".<ref name="David_1935">{{vcite2 journal | vauthors = David KG., Dingemanse E, Freud J. Laqueur E | title = Über krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron | trans_title = On crystalline male hormone from testicles (testosterone) effective as from urine or from cholesterol | language = German | journal = Hoppe Seylers Z Physiol Chem | volume = 233 | issue = 5–6| page = 281 |date=May 1935 | pmid = | doi = 10.1515/bchm2.1935.233.5-6.281| url = }}</ref> They named the hormone ''testosterone'', from the [[stem (linguistics)|stems]] of ''testicle'' and ''[[sterol]]'', and the [[suffix]] of ''[[ketone]]''. The structure was worked out by Schering's [[Adolf Butenandt]].<ref name="Butenandt_1935a">{{vcite2 journal | vauthors = Butenandt A, Hanisch G | title = Umwandlung des Dehydroandrosterons in Androstendiol und Testosterone; ein Weg zur Darstellung des Testosterons aus Cholestrin | trans_title = About Testosterone. Conversion of Dehydro-androsterons into androstendiol and testosterone; a way for the structure assignment of testosterone from cholestrol | language = German | journal = Hoppe Seylers Z Physiol Chem | volume = 237 | issue = 2| page = 89 | year = 1935 | pmid = | doi = 10.1515/bchm2.1935.237.1-3.89| url = }}</ref><ref name="pmid11176375">{{vcite2 journal | vauthors = Freeman ER, Bloom DA, McGuire EJ | title = A brief history of testosterone | journal = J. Urol. | volume = 165 | issue = 2 | pages = 371–3 | date = February 2001 | pmid = 11176375 | doi = 10.1097/00005392-200102000-00004 | url = }}</ref>


The [[chemical synthesis]] of testosterone from cholesterol was achieved in August that year by Butenandt and Hanisch.<ref name="Butenandt_1935b">{{cite journal | author = Butenandt A, Hanisch G | title = Uber die Umwandlung des Dehydroandrosterons in Androstenol-(17)-one-(3) (Testosterone); um Weg zur Darstellung des Testosterons auf Cholesterin (Vorlauf Mitteilung). [The conversion of dehydroandrosterone into androstenol-(17)-one-3 (testosterone); a method for the production of testosterone from cholesterol (preliminary communication)] | journal = Chemische Berichte | year = 1935 | volume = 68 | pages = 1859–1862 | language = German }}</ref> Only a week later, the Ciba group in Zurich, [[Leopold Ruzicka]] (1887–1976) and A. Wettstein, published their synthesis of testosterone.<ref name="Ruzicka_1935">{{cite journal | author = Ruzicka L, Wettstein A | title = Uber die kristallinische Herstellung des Testikelhormons, Testosteron (Androsten-3-ol-17-ol) [The crystalline production of the testicle hormone, testosterone (Androsten-3-ol-17-ol)] | journal = Helvetica Chimica Acta | year = 1935 | volume = 18 | pages = 1264–1275 | language = German | doi=10.1002/hlca.193501801176}}</ref> These independent partial syntheses of testosterone from a cholesterol base earned both Butenandt and Ruzicka the joint 1939 [[Nobel Prize in Chemistry]].<ref name="pmid11176375"/><ref name="pmid7817189">{{cite journal | author = Hoberman JM, Yesalis CE | title = The history of synthetic testosterone | journal = Sci. Am. | volume = 272 | issue = 2 | pages = 76–81 | date = February 1995 | pmid = 7817189 | doi = 10.1038/scientificamerican0295-76 | url = }}</ref> Testosterone was identified as 17β-hydroxyandrost-4-en-3-one (C<sub>19</sub>H<sub>28</sub>O<sub>2</sub>), a solid polycyclic alcohol with a hydroxyl group at the 17th carbon atom. This also made it obvious that additional modifications on the synthesized testosterone could be made, i.e., esterification and alkylation.
The [[chemical synthesis]] of testosterone from cholesterol was achieved in August that year by Butenandt and Hanisch.<ref name="Butenandt_1935b">{{vcite2 journal | vauthors = Butenandt A, Hanisch G | title = Uber die Umwandlung des Dehydroandrosterons in Androstenol-(17)-one-(3) (Testosterone); um Weg zur Darstellung des Testosterons auf Cholesterin (Vorlauf Mitteilung). [The conversion of dehydroandrosterone into androstenol-(17)-one-3 (testosterone); a method for the production of testosterone from cholesterol (preliminary communication)] | journal = Chemische Berichte | year = 1935 | volume = 68 | pages = 1859–1862 | language = German }}</ref> Only a week later, the Ciba group in Zurich, [[Leopold Ruzicka]] (1887–1976) and A. Wettstein, published their synthesis of testosterone.<ref name="Ruzicka_1935">{{vcite2 journal | vauthors = Ruzicka L, Wettstein A | title = Uber die kristallinische Herstellung des Testikelhormons, Testosteron (Androsten-3-ol-17-ol) [The crystalline production of the testicle hormone, testosterone (Androsten-3-ol-17-ol)] | journal = Helvetica Chimica Acta | year = 1935 | volume = 18 | pages = 1264–1275 | language = German | doi=10.1002/hlca.193501801176}}</ref> These independent partial syntheses of testosterone from a cholesterol base earned both Butenandt and Ruzicka the joint 1939 [[Nobel Prize in Chemistry]].<ref name="pmid11176375"/><ref name="pmid7817189">{{vcite2 journal | vauthors = Hoberman JM, Yesalis CE | title = The history of synthetic testosterone | journal = Sci. Am. | volume = 272 | issue = 2 | pages = 76–81 | date = February 1995 | pmid = 7817189 | doi = 10.1038/scientificamerican0295-76 | url = }}</ref> Testosterone was identified as 17β-hydroxyandrost-4-en-3-one (C<sub>19</sub>H<sub>28</sub>O<sub>2</sub>), a solid polycyclic alcohol with a hydroxyl group at the 17th carbon atom. This also made it obvious that additional modifications on the synthesized testosterone could be made, i.e., esterification and alkylation.


The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group<ref name=" Kenyon _1940">{{cite journal | author = Kenyon AT, Knowlton K, Sandiford I, Koch FC, Lotwin,G | title = A comparative study of the metabolic effects of testosterone propionate in normal men and women and in eunuchoidism | journal = Endocrinology | volume = 26| issue = 1 | pages = 26–45 |date=February 1940| doi = 10.1210/Endo-26-1-26 | url = }}</ref> was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",<ref name="pmid10443899">{{cite journal | author = Schwarz S, Onken D, Schubert A | title = The steroid story of Jenapharm: from the late 1940s to the early 1970s | journal = Steroids | volume = 64 | issue = 7 | pages = 439–45 | date = July 1999 | pmid = 10443899 | doi = 10.1016/S0039-128X(99)00003-3 | url = http://www.ingentaconnect.com/content/els/0039128x/1999/00000064/00000007/art00003 }}</ref> and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.<ref name = "de Kruif_1945" >{{cite book | author = de Kruif P | title = The Male Hormone | publisher = Harcourt, Brace| location = New York |year = 1945 |pages = | isbn = | oclc = | doi = }}</ref>
The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group<ref name=" Kenyon _1940">{{vcite2 journal | vauthors = Kenyon AT, Knowlton K, Sandiford I, Koch FC, Lotwin,G | title = A comparative study of the metabolic effects of testosterone propionate in normal men and women and in eunuchoidism | journal = Endocrinology | volume = 26| issue = 1 | pages = 26–45 |date=February 1940| doi = 10.1210/Endo-26-1-26 | url = }}</ref> was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",<ref name="pmid10443899">{{vcite2 journal | vauthors = Schwarz S, Onken D, Schubert A | title = The steroid story of Jenapharm: from the late 1940s to the early 1970s | journal = Steroids | volume = 64 | issue = 7 | pages = 439–45 | date = July 1999 | pmid = 10443899 | doi = 10.1016/S0039-128X(99)00003-3 | url = http://www.ingentaconnect.com/content/els/0039128x/1999/00000064/00000007/art00003 }}</ref> and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.<ref name = "de Kruif_1945" >{{cite book | author = de Kruif P | title = The Male Hormone | publisher = Harcourt, Brace| location = New York |year = 1945 |pages = | isbn = | oclc = | doi = }}</ref>


==Society and culture==
==Society and culture==
Line 326: Line 326:


== References ==
== References ==
{{Reflist|30em}}
{{Reflist|35em}}


==External links==
== External links ==
* [http://gmd.mpimp-golm.mpg.de/Spectrums/8d9c152d-3e30-4c60-8fa7-70fd1213b528.aspx Testosterone MS Spectrum]
* [http://gmd.mpimp-golm.mpg.de/Spectrums/8d9c152d-3e30-4c60-8fa7-70fd1213b528.aspx Testosterone MS Spectrum]
* [http://www.ebi.ac.uk/pdbe-srv/PDBeXplore/ligand/?ligand=FFA Testosterone bound to proteins] in the [[Protein Data Bank|PDB]]
* [http://www.ebi.ac.uk/pdbe-srv/PDBeXplore/ligand/?ligand=FFA Testosterone bound to proteins] in the [[Protein Data Bank|PDB]]

Revision as of 16:53, 3 January 2015

Testosterone
Clinical data
Trade namesAndroderm, Delatestryl
AHFS/Drugs.comMonograph
Pregnancy
category
Routes of
administration
Intramuscular injection, transdermal (cream, gel, or patch), sub-'Q' pellet
ATC code
Legal status
Legal status
Pharmacokinetic data
BioavailabilityLow (due to extensive first pass metabolism)
MetabolismLiver, Testis and Prostate
Elimination half-life2–4 h
ExcretionUrine (90%), feces (6%)
Identifiers
  • (8R,9S,10R,13S,14S,17S)- 17-Hydroxy-10,13-dimethyl- 1,2,6,7,8,9,11,12,14,15,16,17- dodecahydrocyclopenta[a]phenanthren-3-one
CAS Number
  • 58-22-0 checkY
    57-85-2 (propionate ester)
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.336 Edit this at Wikidata
Chemical and physical data
FormulaC19H28O2
Molar mass288.42 g·mol−1
3D model (JSmol)
Specific rotation+110.2°
Melting point155 °C (311 °F)
  • O=C4\C=C2/[C@]([C@H]1CC[C@@]3([C@@H](O)CC[C@H]3[C@@H]1CC2)C)(C)CC4
  • InChI=1S/C19H28O2/c1-18-9-7-13(20)11-12(18)3-4-14-15-5-6-17(21)19(15,2)10-8-16(14)18/h11,14-17,21H,3-10H2,1-2H3/t14-,15-,16-,17-,18-,19-/m0/s1 checkY
  • Key:MUMGGOZAMZWBJJ-DYKIIFRCSA-N checkY
 ☒NcheckY (what is this?)  (verify)

Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles,[2] birds,[3] and other vertebrates. In mammals, testosterone is secreted primarily by the testicles of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid.

In men, testosterone plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle, bone mass, and the growth of body hair.[4] In addition, testosterone is essential for health and well-being[5] as well as the prevention of osteoporosis.[6]

On average, in adult males, levels of testosterone are about 7–8 times as great as in adult females,[7] but, as the metabolic consumption of testosterone in males is greater, the daily production is about 20 times greater in men.[8][9] Females are also more sensitive to the hormone.[10] Testosterone is observed in most vertebrates. Fish make a slightly different form called 11-ketotestosterone.[11] Its counterpart in insects is ecdysone.[12] These ubiquitous steroids suggest that sex hormones have an ancient evolutionary history.[13]

Health effects

In general, androgens promote protein synthesis and growth of those tissues with androgen receptors. Testosterone effects can be classified as virilizing and anabolic, though the distinction is somewhat artificial, as many of the effects can be considered both.

Testosterone effects can also be classified by the age of usual occurrence. For postnatal effects in both males and females, these are mostly dependent on the levels and duration of circulating free testosterone.

Before birth

The prenatal androgen effects occur during two different stages. Between 4 and 6 weeks of the gestation.

During the second trimester, androgen level is associated with gender formation.[14] This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. A mother's testosterone level during pregnancy is correlated with her daughter's sex-typical behavior as an adult, and the correlation is even stronger than with the daughter's own adult testosterone level.[15]

Early infancy

Early infancy androgen effects are the least understood. In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–6 months of age.[16][17] The function of this rise in humans is unknown. It has been speculated that "brain masculinization" is occurring since no significant changes have been identified in other parts of the body.[18] It is interesting to note that the male brain is masculinized by the aromatization of testosterone into estrogen, which crosses the blood–brain barrier and enters the male brain, whereas female fetuses have alpha-fetoprotein, which binds the estrogen so that female brains are not affected.[19]

Pre-peripubertal

Pre- Peripubertal effects are the first observable effects of rising androgen levels at the end of childhood, occurring in both boys and girls.

Pubertal

Pubertal effects begin to occur when androgen has been higher than normal adult female levels for months or years. In males, these are usual late pubertal effects, and occur in women after prolonged periods of heightened levels of free testosterone in the blood.

Adult

Adult testosterone effects are more clearly demonstrable in males than in females, but are likely important to both sexes. Some of these effects may decline as testosterone levels decrease in the later decades of adult life.

Reference ranges for blood tests, showing adult male testosterone levels in light blue at center-left.

Biological uses

Cancer prevention and health risks

  • Testosterone does not cause deleterious effects in prostate cancer. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer.[25][26][27]
  • Recent studies have shown conflicting results concerning the importance of testosterone in maintaining cardiovascular health.[28][29] Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and glycemic control.[30]
  • Under dominance challenge, may play a role in the regulation of the fight-or-flight response[31]
  • Men whose testosterone levels are slightly above average are less likely to have high blood pressure, less likely to experience a heart attack, less likely to be obese, and less likely to rate their own health as fair or poor. However, high testosterone men are more likely to report one or more injuries, more likely to consume five or more alcoholic drinks in a day, more likely to have had a sexually transmitted infection, and more likely to smoke.[32]

Romantic relationships and fatherhood

Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.[33] However, it is suggested that after the "honeymoon phase" ends—about one to three years into a relationship—this change in testosterone levels is no longer apparent.[33] Fatherhood also decreases testosterone levels in men, suggesting that the resulting emotional and behavioral changes promote paternal care.[34] Men who produce less testosterone are more likely to be in a relationship[35] and/or married,[36] and men who produce more testosterone are more likely to divorce;[36] however, causality cannot be determined in this relationship. Marriage or commitment could cause a decrease in testosterone levels.[37] Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.[38] Married men who engage in bond-maintenance activities such as spending the day with their spouse/and or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.[39]

Men who produce more testosterone are more likely to engage in extramarital sex.[36] Testosterone levels do not rely on physical presence of a partner for men engaging in relationships (same-city vs. long-distance), men have similar testosterone levels across the board.[35] Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.[40]

Testosterone and sexual arousal

It has been found that when testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and oxytocin levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).[33]

Testosterone levels follow a nyctohemeral rhythm that peaks early each day, regardless of sexual activity.[41]

There are positive correlations between positive orgasm experience in women and testosterone levels where relaxation was a key perception of the experience. There is no correlation between testosterone and men's perceptions of their orgasm experience, and also no correlation between higher testosterone levels and greater sexual assertiveness in either sex.[42]

An increase in testosterone levels has also been found to occur in both men and women who have masturbation-induced orgasms.[43][44]

Mammalian studies

Studies conducted on rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans suffering from sexual arousal deficits such as hypoactive sexual desire disorder.[45]

In one study, almost every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a novel female. P.J. James et al. investigated the role of genotype on such so-called reflexive testosterone increases in male mice. They also concluded that this response is related to the male's initial level of sexual arousal.[46]

In non-human primates it has been suggested that testosterone in puberty stimulates sexual motivation, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.[47] Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its sexual motivation decreases, but there is no corresponding decrease in ability to engage in sexual activity (mounting, ejaculating, etc.).[47]

Male sexual arousal

Higher levels of testosterone were associated with periods of sexual activity within subjects, but between subjects testosterone levels were higher for less sexually active individuals.[48] Men who have sexual encounters with unfamiliar or multiple partners experience large increases of testosterone the morning after.[49]

Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films.[50] Men who watch sexually explicit films also report increased optimism and decreased exhaustion.[51] Previous research has found a link between relaxation following sexual arousal and testosterone levels.[52]

A 2002 study found that testosterone increased in heterosexual men after having had a brief conversation with a woman. The increase in testosterone levels was associated with the degree that the women thought the men were trying to impress them.[53]

Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.[54] This may be linked to the ovulatory shift hypothesis,[55] where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.

In a 1991 study, males were exposed to either visual or auditory erotic stimuli and asked to complete a cognitive task, where the number of errors on the task indicated how distracted the participant was by the stimuli. It concluded that men with lower thresholds for sexual arousal have a greater likelihood to attend to sexual information and that testosterone may have an impact by enhancing their attention to the relevant stimuli.[56]

Sperm competition theory: Testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.[57] This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.

Female sexual arousal

Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal.[58] Women's level of testosterone is higher when measured pre-intercourse vs pre-cuddling, as well as post-intercourse vs post-cuddling.[59] There is a time lag effect when testosterone is administered, on genital arousal in women. In addition, a continuous increase in vaginal sexual arousal may result in higher genital sensations and sexual appetitive behaviors.[60]

When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not level of cortisol in the female body, and hormonal contraceptives may have an impact on the variation in testosterone response to sexual thoughts.[61]

Testosterone may prove to be an effective treatment in female sexual arousal disorders.[62] Currently there is no FDA approved androgen preparation for the treatment of androgen insufficiency, however it has been used off-label to treat low libido and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.[62]

Behavior and personality

Testosterone levels play a major role in risk-taking during financial decisions.[63][64]

Brain

As testosterone affects the entire body (often by enlarging; males have bigger hearts, lungs, liver, etc.), the brain is also affected by this "sexual" differentiation;[14] the enzyme aromatase converts testosterone into estradiol that is responsible for masculinization of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with congenital diseases of androgen formation or androgen receptor function, to be associated with functional androgen receptors.[65]

There are some differences between a male and female brain (possibly the result of different testosterone levels), one of them being size: the male human brain is, on average, larger.[66] In a Danish study from 2003, men were found to have a total myelinated fiber length of 176,000 km at the age of 20, whereas in women the total length was 149,000 km (approx. 15% less).[67]

A study conducted in 1996 found no immediate short term effects on mood or behavior from the administration of supraphysiologic doses of testosterone for 10 weeks on 43 healthy men.[20] Another study found a correlation between testosterone and risk tolerance in career choice among women.[68][69]

The literature suggests that attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for dementia of the Alzheimer's type,[70][71][72][73] a key argument in life extension medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,[74] where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.

Aggression and criminality

The "evolutionary neuroandrogenic theory" focuses on the hormone testosterone as a factor influencing aggression and criminality and being evolutionarily beneficial during certain forms of competition. In most species, males are more aggressive than females. Castration of males usually has a pacifying effect on their aggressive behavior. In humans, males engage in crime and especially violent crime more than females. Their involvement in crime usually rises in the early teens to mid teens, at the same time as testosterone levels rise. Research on the relationship between testosterone and aggression is difficult, since the only reliable measurement of brain testosterone is by a lumbar puncture that is not done for research purposes. Studies therefore have often instead used more unreliable measurements from blood or saliva.[citation needed]

Most studies support a link between adult criminality and testosterone, although the relationship is modest if examined separately for each sex. Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have also found testosterone to be associated with behaviors or personality traits linked with criminality such as antisocial behavior and alcoholism. Many studies have also been done on the relationship between more general aggressive behavior/feelings and testosterone. About half the studies have found a relationship and about half no relationship.[75]

Testosterone is only one of a myriad of factors that influence aggression and the effects of previous experience and environmental stimuli have been found to correlate more strongly. A few studies indicate that the testosterone derivative estradiol (one form of estrogen) might play an even more important role in male aggression.[75][76][77][78]

It has been empirically shown that boys who had a history of high physical aggression, from age 6 to 12, were found to have lower testosterone levels at age 13 compared with boys with no history of high physical aggression. The former were also failing in school and were unpopular with their peers. Both concurrent and longitudinal analyses indicate that testosterone levels were positively associated with social success rather than with physical aggression.[79]

A study at the Universities of Zurich and Royal Holloway London with more than 120 experimental subjects has shown that the sexual hormone can encourage fair behavior. For the study subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. Two later studies have empirically confirmed these results.[80][81][82]

Estradiol is known to correlate with aggression in male mice.[83] Moreover, the conversion of testosterone to estradiol regulates male aggression in sparrows during breeding season.[84]

Medical uses

The primary use of testosterone is the treatment of males with too little or no natural endogenous testosterone production—males with hypogonadism.[citation needed] This is known as hormone replacement therapy or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range.

Testosterone has also been given for many other purposes besides replacement. Examples include reducing infertility, correcting lack of libido or erectile dysfunction, correcting osteoporosis, encouraging penile enlargement, encouraging height growth, encouraging bone marrow stimulation and reversing the effects of anemia, and appetite stimulation. By the late 1940s, testosterone was being touted as an anti-aging wonder drug (e.g., see Paul de Kruif's The Male Hormone).[85] Decline of testosterone production with age has led to interest in androgen replacement therapy.[86]

Testosterone may be used as a monotherapy in dysthymia and minor depression or as an augmentation therapy in major depression in middle-aged men with low testosterone. However, review of the current literature does not show a statistically significant impact on the mood of the men with normal levels of testosterone or on the mood of the older men with low testosterone.[87]

To take advantage of its virilizing effects, testosterone is often administered to transsexual men as part of the hormone replacement therapy,[88] with a "target level" of the normal male testosterone level. Likewise, transsexual women are sometimes prescribed anti-androgens to decrease the level of testosterone in the body and allow for the effects of estrogen to develop.

Testosterone therapy may improve the management of type 2 diabetes.[89] Low testosterone has been associated with the development of Alzheimer's disease.[72][73] A small trial in 2005 showed mixed results in using testosterone to combat the effects of aging.[90]

Hormone replacement therapy

Testosterone levels decline gradually with age in human beings.(see andropause) The clinical significance of this decrease is debated (see andropause). There is disagreement about when to treat aging men with testosterone replacement therapy. The American Society of Andrology's position is that "testosterone replacement therapy in aging men is indicated when both clinical symptoms and signs suggestive of androgen deficiency and decreased testosterone levels are present."[91] The American Association of Clinical Endocrinologists says "Hypogonadism is defined as a free testosterone level that is below the lower limit of normal for young adult control subjects. Previously, age-related decreases in free testosterone were once accepted as normal. Currently, they are not considered normal. Males with borderline testosterone levels may benefit from a trial of testosterone.[92] Large-scale trials to assess the effectiveness and long-term safety of testosterone are still lacking.[93]

There is not total agreement on the threshold of testosterone value below which a man would be considered hypogonadal. (Currently, there are no standards as to when to treat women.) Testosterone can be measured as "free" (that is, bioavailable and unbound) or, more commonly, "total" (including the percentage that is chemically bound and unavailable). In the United States, male total testosterone levels below 300 ng/dL (10.4 nmol/L) from a morning serum sample are generally considered low.[94] Identification of inadequate testosterone in an aging male by symptoms alone can be difficult.

Insufficiency

Testosterone insufficiency (also termed hypotestosteronism or hypotestosteronemia) is an abnormally low testosterone production. It may occur because of testicular dysfunction (primary hypogonadism) or hypothalamic-pituitary dysfunction (secondary hypogonadism) and may be congenital or acquired.[95] An acquired form of hypotestosteronism is the decline in testosterone levels that occurs by aging, sometimes called "andropause" in men, as a comparison to the decline in estrogen that comes with menopause in women. In Western countries, average testosterone levels are receding in men of all ages.[96][97]

Women

Testosterone supplementation is effective in the short term for hypoactive sexual desire disorder.[98] Its long term safety, however, is unclear.[98]

Treating low androgen levels with testosterone is not generally recommended in women when it is due to hypopituitarism, adrenal insufficiency, or following surgical removal of the ovaries.[98] It is also not usually recommended for improving cognition, the risk of heart disease, bone strength of generalized well being.[98]

Non-medical use

Athletics

Testosterone can be used by an athlete in order to improve performance, but it is considered to be a form of doping in most sports. There are several application methods for testosterone, including intramuscular injections, transdermal gels and patches, and implantable pellets. Supplement of the hormone results in lower metabolic production via the Farquharson phenomenon, creating long-term dependence for improved performance level.[citation needed]

Anabolic steroids (including testosterone) have also been taken to enhance muscle development, strength, or endurance. They do so directly by increasing the muscles' protein synthesis. As a result, muscle fibers become larger and repair faster than the average person's. After a series of scandals and publicity in the 1980s (such as Ben Johnson's improved performance at the 1988 Summer Olympics), prohibitions of anabolic steroid use were renewed or strengthened by many sports organizations. Testosterone and other anabolic steroids were designated a "controlled substance" by the United States Congress in 1990, with the Anabolic Steroid Control Act.[99] Their use is seen as a seriously problematic[citation needed] issue in modern sport, particularly given the lengths to which athletes and professional laboratories go to in trying to conceal such use from sports regulators. Steroid use once again came into the spotlight recently as a result of the Chris Benoit double murder-suicide in 2007, however, there has been no evidence indicating steroid use as a contributing factor.[citation needed]

Some female athletes may have naturally higher levels of testosterone than others, and may be asked to consent to a “therapeutic proposal”, either surgery or drugs, to decrease testosteone levels to a level thought acceptable to compete fairly with others.[100]

Detection of abuse

A number of methods for detecting testosterone use by athletes have been employed, most based on a urine test. These include the testosterone/epitestosterone ratio (normally less than 6), the testosterone/luteinizing hormone ratio and the carbon-13 / carbon-12 ratio (pharmaceutical testosterone contains less carbon-13 than endogenous testosterone). In some testing programs, an individual's own historical results may serve as a reference interval for interpretation of a suspicious finding. Another approach being investigated is the detection of the administered form of testosterone, usually an ester, in hair.[101][102][103][104]

Adverse effects

Whether or not testosterone therapy in men causes important adverse effects was unclear as of 2010.[105]

Cardiovascular disease

On January 31, 2014, reports of strokes, heart attacks, and deaths in men taking FDA-approved testosterone-replacement led the Food and Drug Administration to announce that it would be investigating this issue.[106] The FDA is requiring warnings in the drug labeling of all approved testosterone products regarding deep vein thrombosis and pulmonary embolism.[107]

Adverse effects of testosterone supplementation may include increased cardiovascular events (including strokes and heart attacks) and deaths based on three peer-reviewed studies involving men taking testosterone-replacement.[108] In addition, an increase of 30% in deaths and heart attacks in older men has been reported.[109] Due to an increased incidence of adverse cardiovascular events compared to a placebo group, a Testosterone in Older Men with Mobility Limitations (TOM) trial (a National Institute of Aging randomized trial) was halted early by the Data Safety and Monitoring Committee.[110] On January 31, 2014, reports of strokes, heart attacks, and deaths in men taking FDA-approved testosterone-replacement led the Food and Drug Administration (FDA) to announce that it would be investigating the issue.[111] Later, in September 2014, the FDA announced, as a result of the "potential for adverse cardiovascular outcomes", a review of the appropriateness and safety of Testosterone Replacement Therapy (TRT).[112][113][114]

Up to the year 2010, studies had not shown any effect on the risk of death, prostate cancer or cardiovascular disease;[105][115] more recent studies, however, do raise concerns.[116] A 2013 study, published in the Journal of the American Medical Association, reported "the use of testosterone therapy was significantly associated with increased risk of adverse outcomes." The study began after a previous, randomized, clinical trial of testosterone therapy in men was stopped prematurely "due to adverse cardiovascular events raising concerns about testosterone therapy safety."[117]

Cancer

Testosterone in the presence of a slow-growing cancer is assumed to increase its growth rate. However, the association between testosterone supplementation and the development of prostate cancer is unproven.[118] Nevertheless, physicians are cautioned about the cancer risk associated with testosterone supplementation.[119]

Ethnic groups have different rates of prostate cancer.[120] Differences in sex hormones, including testosterone, have been suggested as an explanation for these differences.[120] This apparent paradox can be resolved by noting that prostate cancer is very common. In autopsies, 80% of 80-year-old men have prostate cancer.[121]

Other

Other adverse effects of testosterone supplementation may include increased hematocrit (which may require venipuncture in order to treat), exacerbation of sleep apnea and acceleration of pre-existing prostate cancer growth in individuals having undergone androgen deprivation.[citation needed] Other adverse effects may include minor side-effects such as acne and oily skin as well as significant hair loss and/or thinning of the hair which may be prevented with 5-alpha reductase inhibitors ordinarily used for the treatment of benign prostatic hyperplasia such as finasteride or dutasteride.[citation needed] Exogenous testosterone may also cause suppression of spermatogenesis, leading to infertility.[122] It does increase hemoglobin levels and decrease HDL cholesterol levels but it is not clear if these changes are meaningful.[105]

Pregnancy and breast feeding

Testosterone is contraindicated in pregnancy and not recommended during breastfeeding.[123]

Biochemistry

Biosynthesis

Human steroidogenesis, showing testosterone near bottom.

Like other steroid hormones, testosterone is derived from cholesterol (see figure to the left).[124] The first step in the biosynthesis involves the oxidative cleavage of the sidechain of cholesterol by CYP11A, a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In the next step, two additional carbon atoms are removed by the CYP17A enzyme in the endoplasmic reticulum to yield a variety of C19 steroids.[125] In addition, the 3-hydroxyl group is oxidized by 3-β-HSD to produce androstenedione. In the final and rate limiting step, the C-17 keto group androstenedione is reduced by 17-β hydroxysteroid dehydrogenase to yield testosterone.

The largest amounts of testosterone (>95%) are produced by the testes in men.[4] It is also synthesized in far smaller quantities in women by the thecal cells of the ovaries, by the placenta, as well as by the zona reticularis of the adrenal cortex and even skin[126] in both sexes. In the testes, testosterone is produced by the Leydig cells.[127] The male generative glands also contain Sertoli cells, which require testosterone for spermatogenesis. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific plasma protein, sex hormone-binding globulin (SHBG).

Regulation

Hypothalamic–pituitary–testicular axis

In males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17-β hydroxysteroid dehydrogenase.[128]

The amount of testosterone synthesized is regulated by the hypothalamic–pituitary–testicular axis (see figure to the right).[129] When testosterone levels are low, gonadotropin-releasing hormone (GnRH) is released by the hypothalamus, which in turn stimulates the pituitary gland to release FSH and LH. These latter two hormones stimulate the testis to synthesize testosterone. Finally, increasing levels of testosterone through a negative feedback loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively.

Factors affecting testosterone levels include:

  • Weight loss may result in an increase in testosterone levels. Fat cells synthesize the enzyme aromatase, which converts testosterone, the male sex hormone, into estradiol, the female sex hormone.[130]
  • The secosteroid vitamin D in levels of 400–1000 IU/d (10–25 µg/d) raises testosterone levels.[131]
  • Zinc deficiency lowers testosterone levels[132] but over supplementation has no effect on serum testosterone.[133]
  • Dominance challenges can, in some cases, stimulate increased testosterone release in men.[134]
  • Aging reduces testosterone release.[135]
  • Hypogonadism
  • Sleep (REM dream) increases nocturnal testosterone levels.[136]
  • Resistance training increases testosterone levels,[137] however, in older men, that increase can be avoided by protein ingestion.[138]
  • Licorice. The active ingredient in licorice root, glycyrrhizinic acid has been linked to small, clinically non-significant decreases in testosterone levels.[139] In contrast, a more recent study found that licorice administration produced a substantial testosterone decrease in a small, female-only sample.[140]
  • Natural or man-made antiandrogens including spearmint tea reduce testosterone levels.[141][142][143]
  • Posing in high-power nonverbal displays through open, expansive postures can increase testosterone levels.[144]

Metabolism

Approximately 7% of testosterone is reduced to 5α-dihydrotestosterone (DHT) by the cytochrome P450 enzyme 5α-reductase,[145] an enzyme highly expressed in male sex organs and hair follicles.[4] Approximately 0.3% of testosterone is converted into estradiol by aromatase (CYP19A1)[146] an enzyme expressed in the brain, liver, and adipose tissues.[4]

DHT is a more potent form of testosterone while estradiol has completely different activities (feminization) compared to testosterone (masculinization). Also, testosterone and DHT may be deactivated or cleared by enzymes that hydroxylate at the 6, 7, 15 or 16 positions.[147]

Mechanism of action

The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors.[148][149]

Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5-alpha reductase. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of T.[150] The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects.

Androgen receptors occur in many different vertebrate body system tissues, and both males and females respond similarly to similar levels. Greatly differing amounts of testosterone prenatally, at puberty, and throughout life account for a share of biological differences between males and females.

The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol. In the bones, estradiol accelerates ossification of cartilage into bone, leading to closure of the epiphyses and conclusion of growth. In the central nervous system, testosterone is aromatized to estradiol. Estradiol rather than testosterone serves as the most important feedback signal to the hypothalamus (especially affecting LH secretion).[citation needed] In many mammals, prenatal or perinatal "masculinization" of the sexually dimorphic areas of the brain by estradiol derived from testosterone programs later male sexual behavior.[citation needed]

Synthetic analogs

A number of synthetic analogs of testosterone have been developed with improved bioavailability and metabolic half life relative to testosterone. Many of these analogs have an alkyl group introduced at the C-17 position in order to prevent conjugation and hence improve oral bioavailability. These are the so-called "17-aa" (17-alkyl androgen) family of androgens such as fluoxymesterone and methyltestosterone.

Some drugs indirectly target testosterone as a way of treating certain conditions. For example, 5-alpha-reductase inhibitors such as finasteride inhibit the conversion of testosterone into dihydrotestosterone (DHT), a metabolite more potent than testosterone.[151] These 5-alpha-reductase inhibitors have been used to treat various conditions associated with androgens, such as androgenetic alopecia (male-pattern baldness), hirsutism, benign prostatic hyperplasia (BPH), and prostate cancer.[151] In contrast, GnRH antagonists bind to GnRH receptors in the pituitary gland, blocking the release of luteinising hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary.[152] In men, the reduction in LH subsequently leads to rapid suppression of testosterone release from the testes. GnRH antagonists have been used for the treatment of prostate cancer.

Routes of administration

Vial of testosterone for intramuscular injection

There are many routes of administration for testosterone. Forms of testosterone for human administration currently available include injectable (such as testosterone cypionate or testosterone enanthate in oil),[153] oral, buccal,[154] transdermal skin patches, transdermal creams, gels,[155][156] and implantable pellets.[157] Roll-on methods and nasal sprays are currently under development.

History

A testicular action was linked to circulating blood fractions – now understood to be a family of androgenic hormones – in the early work on castration and testicular transplantation in fowl by Arnold Adolph Berthold (1803–1861).[158] Research on the action of testosterone received a brief boost in 1889, when the Harvard professor Charles-Édouard Brown-Séquard (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in The Lancet that his vigor and feeling of well-being were markedly restored but the effects were transient,[159] and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.

In 1927, the University of Chicago's Professor of Physiologic Chemistry, Fred C. Koch, established easy access to a large source of bovine testicles — the Chicago stockyards — and recruited students willing to endure the tedious work of extracting their isolates. In that year, Koch and his student, Lemuel McGee, derived 20 mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them.[160] The group of Ernst Laqueur at the University of Amsterdam purified testosterone from bovine testicles in a similar manner in 1934, but isolation of the hormone from animal tissues in amounts permitting serious study in humans was not feasible until three European pharmaceutical giants—Schering (Berlin, Germany), Organon (Oss, Netherlands) and Ciba (Basel, Switzerland)—began full-scale steroid research and development programs in the 1930s.

Leopold Ruzicka

The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".[161] They named the hormone testosterone, from the stems of testicle and sterol, and the suffix of ketone. The structure was worked out by Schering's Adolf Butenandt.[162][163]

The chemical synthesis of testosterone from cholesterol was achieved in August that year by Butenandt and Hanisch.[164] Only a week later, the Ciba group in Zurich, Leopold Ruzicka (1887–1976) and A. Wettstein, published their synthesis of testosterone.[165] These independent partial syntheses of testosterone from a cholesterol base earned both Butenandt and Ruzicka the joint 1939 Nobel Prize in Chemistry.[163][166] Testosterone was identified as 17β-hydroxyandrost-4-en-3-one (C19H28O2), a solid polycyclic alcohol with a hydroxyl group at the 17th carbon atom. This also made it obvious that additional modifications on the synthesized testosterone could be made, i.e., esterification and alkylation.

The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group[167] was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",[168] and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.[85]

Society and culture

A number of lawsuits are currently underway against testosterone manufacturers, alleging a significantly increased rate of stroke and heart attack in elderly men who use testosterone supplements.[169]

References

  1. ^ "FDA-sourced list of all drugs with black box warnings (Use Download Full Results and View Query links.)". nctr-crs.fda.gov. FDA. Retrieved 22 Oct 2023.
  2. ^ Cox RM, John-Alder HB (December 2005). "Testosterone has opposite effects on male growth in lizards (Sceloporus spp.) with opposite patterns of sexual size dimorphism". J. Exp. Biol. 208 (Pt 24): 4679–87. doi:10.1242/jeb.01948. PMID 16326949.
  3. ^ Reed WL, Clark ME, Parker PG, Raouf SA, Arguedas N, Monk DS, Snajdr E, Nolan V, Ketterson ED (May 2006). "Physiological effects on demography: a long-term experimental study of testosterone's effects on fitness". Am. Nat. 167 (5): 667–83. doi:10.1086/503054. PMID 16671011. {{cite journal}}: Unknown parameter |laysource= ignored (help); Unknown parameter |layurl= ignored (help)
  4. ^ a b c d Mooradian AD, Morley JE, Korenman SG (February 1987). "Biological actions of androgens". Endocr. Rev. 8 (1): 1–28. doi:10.1210/edrv-8-1-1. PMID 3549275.
  5. ^ Bassil N, Alkaade S, Morley JE (June 2009). "The benefits and risks of testosterone replacement therapy: a review". Ther Clin Risk Manag. 5 (3): 427–48. PMC 2701485. PMID 19707253.
  6. ^ Tuck SP, Francis RM (2009). "Testosterone, bone and osteoporosis". Front Horm Res. Frontiers of Hormone Research. 37: 123–32. doi:10.1159/000176049. ISBN 978-3-8055-8622-1. PMID 19011293.
  7. ^ Torjesen PA, Sandnes L (March 2004). "Serum testosterone in women as measured by an automated immunoassay and a RIA". Clin. Chem. 50 (3): 678, author reply 678–9. doi:10.1373/clinchem.2003.027565. PMID 14981046.
  8. ^ Southren AL, Gordon GG, Tochimoto S, Pinzon G, Lane DR, Stypulkowski W (May 1967). "Mean plasma concentration, metabolic clearance and basal plasma production rates of testosterone in normal young men and women using a constant infusion procedure: effect of time of day and plasma concentration on the metabolic clearance rate of testosterone". J. Clin. Endocrinol. Metab. 27 (5): 686–94. doi:10.1210/jcem-27-5-686. PMID 6025472.
  9. ^ Southren AL, Tochimoto S, Carmody NC, Isurugi K (November 1965). "Plasma production rates of testosterone in normal adult men and women and in patients with the syndrome of feminizing testes". J. Clin. Endocrinol. Metab. 25 (11): 1441–50. doi:10.1210/jcem-25-11-1441. PMID 5843701.
  10. ^ Dabbs M, Dabbs JM (2000). Heroes, rogues, and lovers: testosterone and behavior. New York: McGraw-Hill. ISBN 0-07-135739-4.
  11. ^ Nelson, Randy F. (2005). An introduction to behavioral endocrinology. Sunderland, Mass: Sinauer Associates. p. 143. ISBN 0-87893-617-3.
  12. ^ De Loof A (October 2006). "Ecdysteroids: the overlooked sex steroids of insects? Males: the black box". Insect Science. 13 (5): 325–338. doi:10.1111/j.1744-7917.2006.00101.x.
  13. ^ Mechoulam R, Brueggemeier RW, Denlinger DL (September 1984). "Estrogens in insects". Journal Cellular and Molecular Life Sciences. 40 (9): 942–944. doi:10.1007/BF01946450.
  14. ^ a b Swaab DF, Garcia-Falgueras A (2009). "Sexual differentiation of the human brain in relation to gender identity and sexual orientation". Funct. Neurol. 24 (1): 17–28. PMID 19403051.
  15. ^ Browne KR (2002). Biology at work: rethinking sexual equality. New Brunswick, N.J: Rutgers University Press. p. 112. ISBN 0-8135-3053-9.
  16. ^ Forest MG, Cathiard AM, Bertrand JA (July 1973). "Evidence of testicular activity in early infancy". J. Clin. Endocrinol. Metab. 37 (1): 148–51. doi:10.1210/jcem-37-1-148. PMID 4715291.
  17. ^ Corbier P, Edwards DA, Roffi J (1992). "The neonatal testosterone surge: a comparative study". Arch Int Physiol Biochim Biophys. 100 (2): 127–31. doi:10.3109/13813459209035274. PMID 1379488.
  18. ^ Dakin CL, Wilson CA, Kalló I, Coen CW, Davies DC (May 2008). "Neonatal stimulation of 5-HT(2) receptors reduces androgen receptor expression in the rat anteroventral periventricular nucleus and sexually dimorphic preoptic area". Eur. J. Neurosci. 27 (9): 2473–80. doi:10.1111/j.1460-9568.2008.06216.x. PMID 18445234.
  19. ^ Kalat JW (2009). "Reproductive behaviors". Biological psychology. Belmont, Calif: Wadsworth, Cengage Learning. p. 321. ISBN 0-495-60300-7. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)
  20. ^ a b Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, Bunnell TJ, Tricker R, Shirazi A, Casaburi R (July 1996). "The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men". N. Engl. J. Med. 335 (1): 1–7. doi:10.1056/NEJM199607043350101. PMID 8637535.
  21. ^ Mehta PH, Jones AC, Josephs RA (June 2008). "The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat" (PDF). J Pers Soc Psychol. 94 (6): 1078–93. doi:10.1037/0022-3514.94.6.1078. PMID 18505319.
  22. ^ Ajayi AA, Halushka PV (May 2005). "Castration reduces platelet thromboxane A2 receptor density and aggregability". QJM. 98 (5): 349–56. doi:10.1093/qjmed/hci054. PMID 15820970.
  23. ^ Ajayi AA, Mathur R, Halushka PV (June 1995). "Testosterone increases human platelet thromboxane A2 receptor density and aggregation responses". Circulation. 91 (11): 2742–7. doi:10.1161/01.CIR.91.11.2742. PMID 7758179.
  24. ^ Van Anders SM, Watson NV (2006). "Menstrual cycle irregularities are associated with testosterone levels in healthy premenopausal women". Am. J. Hum. Biol. 18 (6): 841–4. doi:10.1002/ajhb.20555. PMID 17039468.
  25. ^ Morgentaler A, Schulman C (2009). "Testosterone and prostate safety". Front Horm Res. Frontiers of Hormone Research. 37: 197–203. doi:10.1159/000176054. ISBN 978-3-8055-8622-1. PMID 19011298.
  26. ^ Rhoden EL, Averbeck MA, Teloken PE (2008). "Androgen replacement in men undergoing treatment for prostate cancer". J Sex Med. 5 (9): 2202–8. doi:10.1111/j.1743-6109.2008.00925.x. PMID 18638000.
  27. ^ Morgentaler A, Traish AM (2009). "Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth". Eur Urol. 55 (2): 310–20. doi:10.1016/j.eururo.2008.09.024. PMID 18838208.
  28. ^ Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM (January 2007). "Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials". Mayo Clin. Proc. 82 (1): 29–39. doi:10.4065/82.1.29. PMID 17285783.
  29. ^ Jones TH, Saad F (April 2009). "The effects of testosterone on risk factors for, and the mediators of, the atherosclerotic process". Atherosclerosis. 207 (2): 318–27. doi:10.1016/j.atherosclerosis.2009.04.016. PMID 19464009.
  30. ^ Stanworth RD, Jones TH (2008). "Testosterone for the aging male; current evidence and recommended practice". Clin Interv Aging. 3 (1): 25–44. PMC 2544367. PMID 18488876.
  31. ^ Mehta PH, Josephs RA (December 2006). "Testosterone change after losing predicts the decision to compete again". Horm Behav. 50 (5): 684–92. doi:10.1016/j.yhbeh.2006.07.001. PMID 16928375.
  32. ^ Booth A, Johnson DR, Granger DA (February 1999). "Testosterone and men's health". J Behav Med. 22 (1): 1–19. doi:10.1023/A:1018705001117. PMID 10196726. {{cite journal}}: Unknown parameter |laysource= ignored (help); Unknown parameter |layurl= ignored (help)
  33. ^ a b c Marazziti D, Canale D (August 2004). "Hormonal changes when falling in love". Psychoneuroendocrinology. 29 (7): 931–6. doi:10.1016/j.psyneuen.2003.08.006. PMID 15177709.
  34. ^ Berg SJ, Wynne-Edwards KE (2001). "Changes in testosterone, cortisol, and estradiol levels in men becoming fathers". Mayo Clinic Proceedings. 76 (1): 582–592. doi:10.4065/76.6.582. PMID 11393496.
  35. ^ a b van Anders SM, Watson NV (July 2006). "Relationship status and testosterone in North American heterosexual and non-heterosexual men and women: cross-sectional and longitudinal data". Psychoneuroendocrinology. 31 (6): 715–23. doi:10.1016/j.psyneuen.2006.01.008. PMID 16621328.
  36. ^ a b c Booth A, Dabbs JM (1993). "Testosterone and Men's Marriages". Social Forces. 72 (2): 463–477. doi:10.1093/sf/72.2.463.
  37. ^ Mazur A, Michalek J (1998). "Marriage, Divorce, and Male Testosterone". Social Forces. 77 (1): 315–330. doi:10.1093/sf/77.1.315.
  38. ^ Gray PB, Chapman JF, Burnham TC, McIntyre MH, Lipson SF, Ellison PT (2004). "Human male pair bonding and testosterone". Human Nature. 15 (2): 119–131. doi:10.1007/s12110-004-1016-6.
  39. ^ Gray PB, Campbell BC, Marlowe FW, Lipson SF, Ellison PT (October 2004). "Social variables predict between-subject but not day-to-day variation in the testosterone of US men". Psychoneuroendocrinology. 29 (9): 1153–62. doi:10.1016/j.psyneuen.2004.01.008. PMID 15219639.
  40. ^ van Anders SM, Watson NV (February 2007). "Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships". Horm Behav. 51 (2): 286–91. doi:10.1016/j.yhbeh.2006.11.005. PMID 17196592.
  41. ^ Fox CA, Ismail AA, Love DN, Kirkham KE, Loraine JA (January 1972). "Studies on the relationship between plasma testosterone levels and human sexual activity". J. Endocrinol. 52 (1): 51–8. doi:10.1677/joe.0.0520051. PMID 5061159.
  42. ^ van Anders SM, Dunn EJ (August 2009). "Are gonadal steroids linked with orgasm perceptions and sexual assertiveness in women and men?". Horm Behav. 56 (2): 206–13. doi:10.1016/j.yhbeh.2009.04.007. PMID 19409392.
  43. ^ Exton MS, Bindert A, Krüger T, Scheller F, Hartmann U, Schedlowski M (1999). "Cardiovascular and endocrine alterations after masturbation-induced orgasm in women". Psychosom Med. 61 (3): 280–9. doi:10.1097/00006842-199905000-00005. PMID 10367606.
  44. ^ Purvis K, Landgren BM, Cekan Z, Diczfalusy E (September 1976). "Endocrine effects of masturbation in men". J. Endocrinol. 70 (3): 439–44. doi:10.1677/joe.0.0700439. PMID 135817.
  45. ^ Harding SM, Velotta JP (May 2011). "Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats". Horm Behav. 59 (5): 666–73. doi:10.1016/j.yhbeh.2010.09.009. PMID 20920505.
  46. ^ James PJ, Nyby JG, Saviolakis GA (September 2006). "Sexually stimulated testosterone release in male mice (Mus musculus): roles of genotype and sexual arousal". Horm Behav. 50 (3): 424–31. doi:10.1016/j.yhbeh.2006.05.004. PMID 16828762.
  47. ^ a b Wallen K (September 2001). "Sex and context: hormones and primate sexual motivation". Horm Behav. 40 (2): 339–57. doi:10.1006/hbeh.2001.1696. PMID 11534996.
  48. ^ Kraemer HC, Becker HB, Brodie HK, Doering CH, Moos RH, Hamburg DA (March 1976). "Orgasmic frequency and plasma testosterone levels in normal human males". Arch Sex Behav. 5 (2): 125–32. doi:10.1007/BF01541869. PMID 1275688.
  49. ^ Hirschenhauser K, Frigerio D, Grammer K, Magnusson MS (September 2002). "Monthly patterns of testosterone and behavior in prospective fathers". Horm Behav. 42 (2): 172–81. doi:10.1006/hbeh.2002.1815. PMID 12367570.
  50. ^ Pirke KM, Kockott G, Dittmar F (November 1974). "Psychosexual stimulation and plasma testosterone in man". Arch Sex Behav. 3 (6): 577–84. doi:10.1007/BF01541140. PMID 4429441.
  51. ^ Hellhammer DH, Hubert W, Schürmeyer T (1985). "Changes in saliva testosterone after psychological stimulation in men". Psychoneuroendocrinology. 10 (1): 77–81. doi:10.1016/0306-4530(85)90041-1. PMID 4001279.
  52. ^ Rowland DL, Heiman JR, Gladue BA, Hatch JP, Doering CH, Weiler SJ (1987). "Endocrine, psychological and genital response to sexual arousal in men". Psychoneuroendocrinology. 12 (2): 149–58. doi:10.1016/0306-4530(87)90045-X. PMID 3602262.
  53. ^ Roney JR, Mahler SV, Maestripieri D (2003). "Behavioral and hormonal responses of men to brief interactions with women". Evolution and Human Behavior. 24 (6): 365–375. doi:10.1016/S1090-5138(03)00053-9.
  54. ^ Miller SL, Maner JK (February 2010). "Scent of a woman: men's testosterone responses to olfactory ovulation cues". Psychol Sci. 21 (2): 276–83. doi:10.1177/0956797609357733. PMID 20424057.
  55. ^ Gangestead SW, Thornhill R, Garver-Apgar CE (2005). "Adaptations to Ovulation: Implications for Sexual and Social Behavior". Current Directions in Psychological Science. 14 (6): 312–316. doi:10.1111/j.0963-7214.2005.00388.x.
  56. ^ Alexander GM, Sherwin BB (September 1991). "The association between testosterone, sexual arousal, and selective attention for erotic stimuli in men". Horm Behav. 25 (3): 367–81. doi:10.1016/0018-506X(91)90008-6. PMID 1937428.
  57. ^ Hart BL (December 1983). "Role of testosterone secretion and penile reflexes in sexual behavior and sperm competition in male rats: a theoretical contribution". Physiol. Behav. 31 (6): 823–7. doi:10.1016/0031-9384(83)90279-2. PMID 6665072.
  58. ^ Traish AM, Kim N, Min K, Munarriz R, Goldstein I (April 2002). "Role of androgens in female genital sexual arousal: receptor expression, structure, and function". Fertil. Steril. 77 Suppl 4: S11–8. doi:10.1016/s0015-0282(02)02978-3. PMID 12007897.
  59. ^ van Anders SM, Hamilton LD, Schmidt N, Watson NV (April 2007). "Associations between testosterone secretion and sexual activity in women". Horm Behav. 51 (4): 477–82. doi:10.1016/j.yhbeh.2007.01.003. PMID 17320881.
  60. ^ Tuiten A, Van Honk J, Koppeschaar H, Bernaards C, Thijssen J, Verbaten R (February 2000). "Time course of effects of testosterone administration on sexual arousal in women". Arch. Gen. Psychiatry. 57 (2): 149–53, discussion 155–6. doi:10.1001/archpsyc.57.2.149. PMID 10665617.
  61. ^ Goldey KL, van Anders SM (May 2011). "Sexy thoughts: effects of sexual cognitions on testosterone, cortisol, and arousal in women". Horm Behav. 59 (5): 754–64. doi:10.1016/j.yhbeh.2010.12.005. PMID 21185838.
  62. ^ a b Bolour S, Braunstein G (2005). "Testosterone therapy in women: a review". Int. J. Impot. Res. 17 (5): 399–408. doi:10.1038/sj.ijir.3901334. PMID 15889125.
  63. ^ Sapienza P, Zingales L, Maestripieri D (September 2009). "Gender differences in financial risk aversion and career choices are affected by testosterone". Proc. Natl. Acad. Sci. U.S.A. 106 (36): 15268–73. Bibcode:2009PNAS..10615268S. doi:10.1073/pnas.0907352106. PMC 2741240. PMID 19706398.
  64. ^ Apicella CL, Dreber A, Campbell B, Gray PB, Hoffman M, Little AC (November 2008). "Testosterone and financial risk preferences". Evolution and Human Behavior. 29 (6): 384–390. doi:10.1016/j.evolhumbehav.2008.07.001.
  65. ^ Wilson JD (September 2001). "Androgens, androgen receptors, and male gender role behavior". Horm Behav. 40 (2): 358–66. doi:10.1006/hbeh.2001.1684. PMID 11534997.
  66. ^ Cosgrove KP, Mazure CM, Staley JK (October 2007). "Evolving knowledge of sex differences in brain structure, function, and chemistry". Biol. Psychiatry. 62 (8): 847–55. doi:10.1016/j.biopsych.2007.03.001. PMC 2711771. PMID 17544382.
  67. ^ Marner L, Nyengaard JR, Tang Y, Pakkenberg B (July 2003). "Marked loss of myelinated nerve fibers in the human brain with age". J. Comp. Neurol. 462 (2): 144–52. doi:10.1002/cne.10714. PMID 12794739.
  68. ^ Sapienza P, Zingales L, Maestripieri D (2009). "Gender differences in financial risk aversion and career choices are affected by testosterone". Proc Natl Acad Sci USA. 106 (36): 15268–15273. Bibcode:2009PNAS..10615268S. doi:10.1073/pnas.0907352106. PMC 2741240. PMID 19706398.
  69. ^ "Testosterone Affects Some Women's Career Choices". NPR. August 28, 2009.
  70. ^ Hogervorst E, Bandelow S, Combrinck M, Smith AD (2004). "Low free testosterone is an independent risk factor for Alzheimer's disease". Exp. Gerontol. 39 (11–12): 1633–9. doi:10.1016/j.exger.2004.06.019. PMID 15582279.
  71. ^ Moffat SD, Zonderman AB, Metter EJ, Kawas C, Blackman MR, Harman SM, Resnick SM (January 2004). "Free testosterone and risk for Alzheimer disease in older men". Neurology. 62 (2): 188–93. doi:10.1212/WNL.62.2.188. PMID 14745052.
  72. ^ a b Pike CJ, Rosario ER, Nguyen TV (April 2006). "Androgens, aging, and Alzheimer's disease". Endocrine. 29 (2): 233–41. doi:10.1385/ENDO:29:2:233. PMID 16785599.
  73. ^ a b Rosario ER, Chang L, Stanczyk FZ, Pike CJ (September 2004). "Age-related testosterone depletion and the development of Alzheimer disease". JAMA. 292 (12): 1431–2. doi:10.1001/jama.292.12.1431-b. PMID 15383512.
  74. ^ Moffat SD, Hampson E (April 1996). "A curvilinear relationship between testosterone and spatial cognition in humans: possible influence of hand preference". Psychoneuroendocrinology. 21 (3): 323–37. doi:10.1016/0306-4530(95)00051-8. PMID 8817730.
  75. ^ a b Wright J, Ellis L, Beaver K (2009). Handbook of crime correlates. San Diego: Academic Press. pp. 208–210. ISBN 0-12-373612-9.{{cite book}}: CS1 maint: multiple names: authors list (link)
  76. ^ Goldman D, Lappalainen J, Ozaki N. Direct analysis of candidate genes in impulsive disorders. In: Bock G, Goode J, eds. Genetics of Criminal and Antisocial Behaviour. Ciba Foundation Symposium 194. Chichester: John Wiley & Sons; 1996.
  77. ^ Coccaro E. Neurotransmitter correlates of impulsive aggression in humans. In: Ferris C, Grisso T, eds. Understanding Aggressive Behaviour inn Children. Annals of the New York Academy of Sciences 1996; 794: 82-89
  78. ^ "Estrogen or testosterone increases self-reported aggressive behaviors in hypogonadal adolescents," J. Finkelstein, E. Susman, V. Chinchilli, S. Kunselman, M. R. D'Arcangelo, J. Schwab, L. Demers, L. Liben, G. Lookingbill, and H. E. Kulin, Journal of Clinical Endocrinology and Metabolism, Vol. 82, No. 8, 1997, pp. 2433-2438.
  79. ^ Journal of the American Academy of Child & Adolescent Psychiatry - Volume 35, Issue 10 , Pages 1322-1330, October 1996
  80. ^ "Prejudice and truth about the effect of testosterone on human bargaining behaviour" - C. Eisenegger, M. Naef R. Snozzi1, M. Heinrichs & E. Fehr - Nature 463, 356-359 (21 January 2010) | doi:10.1038/nature08711; Received 15 September 2009; Accepted 30 November 2009; Published online 8 December 2009
  81. ^ "New evidence on testosterone and cooperation" - Jack van Honk, Estrella R. Montoya, Peter A. Bos, Mark van Vugt & David Terburg - Nature 485, E4–E5 (24 May 2012) doi:10.1038/nature11136 Received 19 October 2011 Accepted 13 March 2012 Published online 23 May 2012
  82. ^ Eisenegger et al. reply - C. Eisenegger, M. Naef, R. Snozzi, M. Heinrichs & E. Fehr - Nature 485, E5–E6 (24 May 2012) doi:10.1038/nature11137
  83. ^ Soma KK, Scotti MA, Newman AE, Charlier TD, Demas GE (October 2008). "Novel mechanisms for neuroendocrine regulation of aggression". Front Neuroendocrinol. 29 (4): 476–89. doi:10.1016/j.yfrne.2007.12.003. PMID 18280561.
  84. ^ Soma KK, Sullivan KA, Tramontin AD, Saldanha CJ, Schlinger BA, Wingfield JC (2000). "Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows". J. Comp. Physiol. A. 186 (7–8): 759–69. doi:10.1007/s003590000129. PMID 11016791.
  85. ^ a b de Kruif P (1945). The Male Hormone. New York: Harcourt, Brace.
  86. ^ Myers JB, Meacham RB (2003). "Androgen Replacement Therapy in the Aging Male". Rev Urol. 5 (4): 216–26. PMC 1508369. PMID 16985841.
  87. ^ Amanatkar HR, Chibnall JT, Seo BW, Manepalli JN, Grossberg GT (2014). "Impact of exogenous testosterone on mood: a systematic review and meta-analysis of randomized placebo-controlled trials". Ann Clin Psychiatry. 26 (1): 19–32. PMID 24501728.
  88. ^ "Gender dysphoria - Treatment". NHS Gov.uk. Page last reviewed: 21/05/2012. Retrieved 31 October 2013. {{cite web}}: Check date values in: |date= (help)
  89. ^ Traish AM, Saad F, Guay A (2009). "The dark side of testosterone deficiency: II. Type 2 diabetes and insulin resistance". J. Androl. 30 (1): 23–32. doi:10.2164/jandrol.108.005751. PMID 18772488.
  90. ^ Emmelot-Vonk MH, Verhaar HJ, Nakhai Pour HR, Aleman A, Lock TM, Bosch JL, Grobbee DE, van der Schouw YT (January 2008). "Effect of testosterone supplementation on functional mobility, cognition, and other parameters in older men: a randomized controlled trial". JAMA. 299 (1): 39–52. doi:10.1001/jama.2007.51. PMID 18167405.
  91. ^ "Testosterone replacement therapy for male aging: ASA position statement". J. Androl. 27 (2): 133–4. 2006. PMID 16474019.
  92. ^ Guay AT, Spark RF, Bansal S, Cunningham GR, Goodman NF, Nankin HR, Petak SM, Perez JB (2003). "American Association of Clinical Endocrinologists medical guidelines for clinical practice for the evaluation and treatment of male sexual dysfunction: a couple's problem—2003 update" (PDF). Endocr Pract. 9 (1): 77–95. doi:10.4158/EP.9.1.77. PMID 12917096.
  93. ^ Cunningham GR (2008-06-25). "Testosterone treatment in aging men". EndocrineToday.com. Retrieved 2009-07-17.
  94. ^ Holt EH, Zieve D (2008-03-18). "Testosterone". MedlinePlus Medical Encyclopedia. U.S. National Library of Medicine. Retrieved 2009-07-17.
  95. ^ Gould DC, Petty R (August 2000). "The male menopause: does it exist?: For: Some men need investigation and testosterone treatment". West. J. Med. 173 (2): 76–8. doi:10.1136/ewjm.173.2.76. PMC 1070997. PMID 10924412.
  96. ^ Travison TG, Araujo AB, O'Donnell AB, Kupelian V, McKinlay JB (January 2007). "A population-level decline in serum testosterone levels in American men". J. Clin. Endocrinol. Metab. 92 (1): 196–202. doi:10.1210/jc.2006-1375. PMID 17062768.
  97. ^ Dindyal S (2007). "The sperm count has been decreasing steadily for many years in Western industrialised countries: Is there an endocrine basis for this decrease?". The Internet Journal of Urology. 2 (1): 1–21.
  98. ^ a b c d Wierman ME, Arlt W, Basson R, Davis SR, Miller KK, Murad MH, Rosner W, Santoro N (Oct 2014). "Androgen therapy in women: a reappraisal: an endocrine society clinical practice guideline". The Journal of Clinical Endocrinology and Metabolism. 99 (10): 3489–510. doi:10.1210/jc.2014-2260. PMID 25279570.
  99. ^ "Anabolic Steroid Control Act" (PDF). United States Sentencing Commission. 1990.
  100. ^ Karkazis, Katrina; Jordan-Young, Rebecca (April 11, 2014). "The Trouble With Too Much T". New York Times. Retrieved April 12, 2014.
  101. ^ Strahm E, Emery C, Saugy M, Dvorak J, Saudan C (December 2009). "Detection of testosterone administration based on the carbon isotope ratio profiling of endogenous steroids: international reference populations of professional soccer players". Br J Sports Med. 43 (13): 1041–4. doi:10.1136/bjsm.2009.058669. PMC 2784500. PMID 19549614.
  102. ^ Kicman AT, Cowan DA (January 2009). "Subject-based profiling for the detection of testosterone administration in sport". Drug Test Anal. 1 (1): 22–4. doi:10.1002/dta.14. PMID 20355155.
  103. ^ Pozo OJ, Deventer K, Van Eenoo P, Rubens R, Delbeke FT (August 2009). "Quantification of testosterone undecanoate in human hair by liquid chromatography-tandem mass spectrometry". Biomed. Chromatogr. 23 (8): 873–80. doi:10.1002/bmc.1199. PMID 19353724.
  104. ^ Baselt RC (2008). Disposition of Toxic Drugs & Chemicals in Man (8th ed.). Foster City, Calif: Biomedical Publications. pp. 1501–1504. ISBN 978-0-9626523-7-0.
  105. ^ a b c Fernández-Balsells MM, Murad MH, Lane M, Lampropulos JF, Albuquerque F, Mullan RJ, Agrwal N, Elamin MB, Gallegos-Orozco JF, Wang AT, Erwin PJ, Bhasin S, Montori VM (June 2010). "Clinical review 1: Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis". The Journal of Clinical Endocrinology and Metabolism. 95 (6): 2560–75. doi:10.1210/jc.2009-2575. PMID 20525906.
  106. ^ http://www.fda.gov/downloads/Drugs/DrugSafety/UCM383909.pdf
  107. ^ Staff (19 June 2014). "FDA adding general warning to testosterone products about potential for venous blood clots". FDA. Retrieved 9 October 2014.
  108. ^ Finkle WD, Greenland S, Ridgeway GK, Adams JL, Frasco MA, Cook MB, Fraumeni JF, Hoover RN (January 2014). "Increased Risk of Non-fatal Myocardial Infarction Following Testosterone Therapy Prescription in Men" (PDF). PLoS ONE. 9 (1): e85805. doi:10.1371/journal.pone.0085805. PMC 3905977. PMID 24489673.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  109. ^ Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM (2013). "Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels". Journal of the American Medical Association. 310 (17): 1829–36. doi:10.1001/jama.2013.280386. PMID 24193080.
  110. ^ Basaria S, Coviello AD, Travison TG, Storer TW, Farwell WR, Jette AM, Eder R, Tennstedt S, Ulloor J, Zhang A, Choong K, Lakshman KM, Mazer NA, Miciek R, Krasnoff J, Elmi A, Knapp PE, Brooks B, Appleman E, Aggarwal S, Bhasin G, Hede-Brierley L, Bhatia A, Collins L, LeBrasseur N, Fiore LD, Bhasin S (Jul 2010). "Adverse Events Associated with Testosterone Administration". New England Journal of Medicine. 363 (2): 109–22. doi:10.1056/NEJMoa1000485. PMC 3440621. PMID 20592293.
  111. ^ Staff (January 31, 2014). "FDA evaluating risk of stroke, heart attack and death with FDA-approved testosterone products" (PDF). U.S. Food and Drug Administration. Retrieved September 17, 2014.
  112. ^ Tavernise, Sabrina (September 17, 2014). "F.D.A. Panel Backs Limits on Testosterone Drugs". New York Times. Retrieved September 18, 2014.
  113. ^ Staff (September 5, 2014). "FDA Panel To Review Testosterone Therapy Appropriateness and Safety". CNN News. Retrieved September 14, 2014.
  114. ^ Staff (September 17, 2014). "Joint Meeting for Bone, Reproductive and Urologic Drugs Advisory Committee (BRUDAC) and the Drug Safety And Risk Management Advisory Committee (DSARM AC) - FDA background documents for the discussion of two major issues in testosterone replacement therapy (TRT): 1. The appropriate indicated population for TRT, and 2. The potential for adverse cardiovascular outcomes associated with use of TRT" (PDF). Food and Drug Administration. Retrieved September 14, 2014.
  115. ^ Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM (January 2007). "Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials". Mayo Clinic proceedings. Mayo Clinic. 82 (1): 29–39. doi:10.4065/82.1.29. PMID 17285783.
  116. ^ "Testosterone Products: Drug Safety Communication - FDA Investigating Risk of Cardiovascular Events". FDA. Jan 31, 2014. Retrieved 3 February 2014.
  117. ^ Vigen R, O'Donnell CI, Barón AE, Grunwald GK, Maddox TM, Bradley SM, Barqawi A, Woning G, Wierman ME, Plomondon ME, Rumsfeld JS, Ho PM (Nov 6, 2013). "Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels". Journal of the American Medical Association. 310 (17): 1829–36. doi:10.1001/jama.2013.280386. PMID 24193080. Retrieved 16 June 2014.
  118. ^ Rhoden EL, Averbeck MA (November 2009). "Testosterone therapy and prostate carcinoma". Curr Urol Rep. 10 (6): 453–9. doi:10.1007/s11934-009-0072-1. PMID 19863857.
  119. ^ Gaylis FD, Lin DW, Ignatoff JM, Amling CL, Tutrone RF, Cosgrove DJ (August 2005). "Prostate cancer in men using testosterone supplementation". J. Urol. 174 (2): 534–8, discussion 538. doi:10.1097/01.ju.0000165166.36280.60. PMID 16006887.
  120. ^ a b Calistro Alvarado L (2010). "Population differences in the testosterone levels of young men are associated with prostate cancer disparities in older men". Am. J. Hum. Biol. 22 (4): 449–55. doi:10.1002/ajhb.21016. PMID 20087895.
  121. ^ Bostwick DG, Burke HB, Djakiew D, Euling S, Ho SM, Landolph J, Morrison H, Sonawane B, Shifflett T, Waters DJ, Timms B (November 2004). "Human prostate cancer risk factors". Cancer. 101 (10 Suppl): 2371–490. doi:10.1002/cncr.20408. PMID 15495199. {{cite journal}}: Unknown parameter |laysource= ignored (help); Unknown parameter |layurl= ignored (help)
  122. ^ "Contraceptive efficacy of testosterone-induced azoospermia in normal men. World Health Organization Task Force on methods for the regulation of male fertility". Lancet. 336 (8721): 955–9. October 1990. doi:10.1016/0140-6736(90)92416-F. PMID 1977002.
  123. ^ "Testosterone Pregnancy and Breastfeeding Warnings". Retrieved 1 February 2014.
  124. ^ Waterman MR, Keeney DS (1992). "Genes involved in androgen biosynthesis and the male phenotype". Horm. Res. 38 (5–6): 217–21. doi:10.1159/000182546. PMID 1307739.
  125. ^ Zuber MX, Simpson ER, Waterman MR (December 1986). "Expression of bovine 17 alpha-hydroxylase cytochrome P-450 cDNA in nonsteroidogenic (COS 1) cells". Science. 234 (4781): 1258–61. Bibcode:1986Sci...234.1258Z. doi:10.1126/science.3535074. PMID 3535074.
  126. ^ Zouboulis CC, Degitz K (2004). "Androgen action on human skin – from basic research to clinical significance". Exp. Dermatol. 13 Suppl 4: 5–10. doi:10.1111/j.1600-0625.2004.00255.x. PMID 15507105.
  127. ^ Brooks RV (November 1975). "Androgens". Clin Endocrinol Metab. 4 (3): 503–20. doi:10.1016/S0300-595X(75)80045-4. PMID 58744.
  128. ^ Payne AH, O'Shaughnessy P (1996). "Structure, function, and regulation of steroidogenic enzymes in the Leydig cell". In Payne AH, Hardy MP, Russell LD (ed.). Leydig Cell. Vienna [Il]: Cache River Press. pp. 260–285. ISBN 0-9627422-7-9.{{cite book}}: CS1 maint: multiple names: editors list (link)
  129. ^ Swerdloff RS, Wang C, Bhasin S (April 1992). "Developments in the control of testicular function". Baillieres Clin. Endocrinol. Metab. 6 (2): 451–83. doi:10.1016/S0950-351X(05)80158-2. PMID 1377467.
  130. ^ Håkonsen LB, Thulstrup AM, Aggerholm AS, Olsen J, Bonde JP, Andersen CY, Bungum M, Ernst EH, Hansen ML, Ernst EH, Ramlau-Hansen CH (2011). "Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men". Reprod Health. 8: 24. doi:10.1186/1742-4755-8-24. PMC 3177768. PMID 21849026.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  131. ^ Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A (March 2011). "Effect of vitamin D supplementation on testosterone levels in men". Horm. Metab. Res. 43 (3): 223–5. doi:10.1055/s-0030-1269854. PMID 21154195.
  132. ^ Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ (May 1996). "Zinc status and serum testosterone levels of healthy adults". Nutrition. 12 (5): 344–8. doi:10.1016/S0899-9007(96)80058-X. PMID 8875519.
  133. ^ Koehler K, Parr MK, Geyer H, Mester J, Schänzer W (January 2009). "Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement". Eur J Clin Nutr. 63 (1): 65–70. doi:10.1038/sj.ejcn.1602899. PMID 17882141.
  134. ^ Schultheiss OC, Campbell KL, McClelland DC (December 1999). "Implicit power motivation moderates men's testosterone responses to imagined and real dominance success". Horm Behav. 36 (3): 234–41. doi:10.1006/hbeh.1999.1542. PMID 10603287.
  135. ^ Liu PY, Pincus SM, Takahashi PY, Roebuck PD, Iranmanesh A, Keenan DM, Veldhuis JD (January 2006). "Aging attenuates both the regularity and joint synchrony of LH and testosterone secretion in normal men: analyses via a model of graded GnRH receptor blockade". Am. J. Physiol. Endocrinol. Metab. 290 (1): E34–E41. doi:10.1152/ajpendo.00227.2005. PMID 16339924.
  136. ^ Andersen ML, Tufik S (October 2008). "The effects of testosterone on sleep and sleep-disordered breathing in men: its bidirectional interaction with erectile function" (PDF). Sleep Med Rev. 12 (5): 365–79. doi:10.1016/j.smrv.2007.12.003. PMID 18519168.
  137. ^ Marin DP, Figueira AJ, Pinto LG (2006). "One session of resistance training may increase serum testosterone and triiodetironine in young men". Medicine & Science in Sports & Exercise. 38 (5): S285. doi:10.1249/00005768-200605001-01235. {{cite journal}}: Vancouver style error: suffix in name 2 (help)
  138. ^ Hulmi JJ, Ahtiainen JP, Selänne H, Volek JS, Häkkinen K, Kovanen V, Mero AA (May 2008). "Androgen receptors and testosterone in men—effects of protein ingestion, resistance exercise and fiber type". J. Steroid Biochem. Mol. Biol. 110 (1–2): 130–7. doi:10.1016/j.jsbmb.2008.03.030. PMID 18455389.
  139. ^ Josephs RA, Guinn JS, Harper ML, Askari F (November 2001). "Liquorice consumption and salivary testosterone concentrations". Lancet. 358 (9293): 1613–4. doi:10.1016/S0140-6736(01)06664-8. PMID 11716893.
  140. ^ Armanini D, Mattarello MJ, Fiore C, Bonanni G, Scaroni C, Sartorato P, Palermo M (2004). "Licorice reduces serum testosterone in healthy women". Steroids. 69 (11–12): 763–6. doi:10.1016/j.steroids.2004.09.005. PMID 15579328.
  141. ^ Akdoğan M, Tamer MN, Cüre E, Cüre MC, Köroğlu BK, Delibaş N (May 2007). "Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism". Phytother Res. 21 (5): 444–7. doi:10.1002/ptr.2074. PMID 17310494.
  142. ^ Kumar V, Kural MR, Pereira BM, Roy P (December 2008). "Spearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats – altered levels of gene expression, enzymes and hormones". Food Chem. Toxicol. 46 (12): 3563–70. doi:10.1016/j.fct.2008.08.027. PMID 18804513.
  143. ^ Grant P (February 2010). "Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial". Phytother Res. 24 (2): 186–8. doi:10.1002/ptr.2900. PMID 19585478.
  144. ^ Carney DR, Cuddy AJ, Yap AJ (October 2010). "Power posing: brief nonverbal displays affect neuroendocrine levels and risk tolerance". Psychol Sci. 21 (10): 1363–1368. doi:10.1177/0956797610383437. PMID 20855902. {{cite journal}}: |access-date= requires |url= (help)
  145. ^ Randall VA (April 1994). "Role of 5 alpha-reductase in health and disease". Baillieres Clin. Endocrinol. Metab. 8 (2): 405–31. doi:10.1016/S0950-351X(05)80259-9. PMID 8092979.
  146. ^ Meinhardt U, Mullis PE (August 2002). "The essential role of the aromatase/p450arom". Semin. Reprod. Med. 20 (3): 277–84. doi:10.1055/s-2002-35374. PMID 12428207.
  147. ^ Trager L (1977). Steroidhormone: Biosynthese, Stoffwechsel, Wirkung (in German). Springer-Verlag. p. 349. ISBN 0-387-08012-0.
  148. ^ Hiipakka RA, Liao S (October 1998). "Molecular mechanism of androgen action". Trends Endocrinol. Metab. 9 (8): 317–24. doi:10.1016/S1043-2760(98)00081-2. PMID 18406296.
  149. ^ McPhaul MJ, Young M (September 2001). "Complexities of androgen action". J. Am. Acad. Dermatol. 45 (3 Suppl): S87–94. doi:10.1067/mjd.2001.117429. PMID 11511858.
  150. ^ Breiner M, Romalo G, Schweikert HU (August 1986). "Inhibition of androgen receptor binding by natural and synthetic steroids in cultured human genital skin fibroblasts". Klin. Wochenschr. 64 (16): 732–7. doi:10.1007/BF01734339. PMID 3762019.
  151. ^ a b Bratoeff E, Cabeza M, Ramirez E, Heuze Y, Flores E (2005). "Recent advances in the chemistry and pharmacological activity of new steroidal antiandrogens and 5 alpha-reductase inhibitors". Curr. Med. Chem. 12 (8): 927–43. doi:10.2174/0929867053507306. PMID 15853706.
  152. ^ Engel JB, Schally AV (February 2007). "Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone". Nat Clin Pract Endocrinol Metab. 3 (2): 157–67. doi:10.1038/ncpendmet0399. PMID 17237842.
  153. ^ "Testosterone Information". Drugs.com.
  154. ^ "Striant Official FDA information, side effects and uses". Drugs.com.
  155. ^ "AndroGel Official FDA information, side effects and uses". Drugs.com.
  156. ^ "Testim (patches and gel) medical facts". Drugs.com.
  157. ^ "Testopel Pellets". www.slatepharma.com.
  158. ^ Berthold AA (1849). "Transplantation der Hoden". Arch. Anat. Physiol. Wissensch. (in German). 16: 42–6. {{cite journal}}: Unknown parameter |trans_title= ignored (|trans-title= suggested) (help)
  159. ^ Brown-Sequard CE (1889). "The effects produced on man by subcutaneous injections of liquid obtained from the testicles of animals". Lancet. 2 (3438): 105. doi:10.1016/S0140-6736(00)64118-1.
  160. ^ Gallagher TF, Koch FC (November 1929). "The testicular hormone". J. Biol. Chem. 84 (2): 495–500.
  161. ^ David KG., Dingemanse EK, Freud J Laqueur E (May 1935). "Über krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron". Hoppe Seylers Z Physiol Chem (in German). 233 (5–6): 281. doi:10.1515/bchm2.1935.233.5-6.281. {{cite journal}}: Unknown parameter |trans_title= ignored (|trans-title= suggested) (help); Vancouver style error: punctuation in name 1 (help)
  162. ^ Butenandt A, Hanisch G (1935). "Umwandlung des Dehydroandrosterons in Androstendiol und Testosterone; ein Weg zur Darstellung des Testosterons aus Cholestrin". Hoppe Seylers Z Physiol Chem (in German). 237 (2): 89. doi:10.1515/bchm2.1935.237.1-3.89. {{cite journal}}: Unknown parameter |trans_title= ignored (|trans-title= suggested) (help)
  163. ^ a b Freeman ER, Bloom DA, McGuire EJ (February 2001). "A brief history of testosterone". J. Urol. 165 (2): 371–3. doi:10.1097/00005392-200102000-00004. PMID 11176375.
  164. ^ Butenandt A, Hanisch G (1935). "Uber die Umwandlung des Dehydroandrosterons in Androstenol-(17)-one-(3) (Testosterone); um Weg zur Darstellung des Testosterons auf Cholesterin (Vorlauf Mitteilung). [The conversion of dehydroandrosterone into androstenol-(17)-one-3 (testosterone); a method for the production of testosterone from cholesterol (preliminary communication)]". Chemische Berichte (in German). 68: 1859–1862.
  165. ^ Ruzicka L, Wettstein A (1935). "Uber die kristallinische Herstellung des Testikelhormons, Testosteron (Androsten-3-ol-17-ol) [The crystalline production of the testicle hormone, testosterone (Androsten-3-ol-17-ol)]". Helvetica Chimica Acta (in German). 18: 1264–1275. doi:10.1002/hlca.193501801176.
  166. ^ Hoberman JM, Yesalis CE (February 1995). "The history of synthetic testosterone". Sci. Am. 272 (2): 76–81. doi:10.1038/scientificamerican0295-76. PMID 7817189.
  167. ^ Kenyon AT, Knowlton K, Sandiford I, Koch FC, Lotwin, G (February 1940). "A comparative study of the metabolic effects of testosterone propionate in normal men and women and in eunuchoidism". Endocrinology. 26 (1): 26–45. doi:10.1210/Endo-26-1-26.
  168. ^ Schwarz S, Onken D, Schubert A (July 1999). "The steroid story of Jenapharm: from the late 1940s to the early 1970s". Steroids. 64 (7): 439–45. doi:10.1016/S0039-128X(99)00003-3. PMID 10443899.
  169. ^ Harris, Andrew. "Abbott Labs Sued by Five Men Claiming Androgel Injuries". Bloomberg.com. Bloomberg, L.P. Retrieved 16 June 2014.