|Systematic (IUPAC) name|
(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
|Trade names||Androderm, others|
|Intramuscular injection, transdermal (cream, gel, or patch), sub-Q pellet|
|Bioavailability||Very low (due to extensive first pass metabolism)|
|Biological half-life||2–4 hours|
|Excretion||Urine (90%), feces (6%)|
57-85-2 (propionate ester)
|ATC code||G03BA03 (WHO)|
|Melting point||155 °C (311 °F)|
|SEC combustion||−11080 kJ/mol|
Testosterone is a medication and naturally occurring steroid hormone. As a medication it is used to treat male hypogonadism and certain types of breast cancer. It may also be used to increase athletic ability in the form of doping. It is unclear if the use of testosterone for low levels due to aging is beneficial or harmful. Testosterone can be used as a cream applied to the skin, by injection into a muscle, or be placed in the cheek.
Common side effects from use include acne, swelling, and breast enlargement in males. Serious side effects may include liver toxicity, heart disease, and behavioral changes. Women and children who are exposed may develop virilization. It is recommended that those with prostate cancer should not use the medication. It may cause harm if used during pregnancy or breastfeeding.
Testosterone is made primarily by the testicles in males. Small amounts are also made by the adrenal glands and the ovaries in females. In males it is the main sex hormone and plays an important role in the development of the male reproductive system. In adult males it promotes secondary sexual characteristic including increased muscle growth and body hair. Levels of testosterone are typically more than five times higher in adult males than females.
Testosterone was first isolated in 1935. Rates of use have increased three times in the United States between 2001 and 2011. It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. It is available as a generic medication. The price depends on the form of testosterone used.
- 1 Medical uses
- 2 Non-medical use
- 3 Adverse effects
- 4 Physiological effects
- 4.1 Before birth
- 4.2 Early infancy
- 4.3 Before puberty
- 4.4 Pubertal
- 4.5 Adult
- 4.6 Brain
- 4.7 Aggression and criminality
- 5 Biochemistry
- 6 Mechanism of action
- 7 Related drugs
- 8 Routes of administration
- 9 History
- 10 Society and culture
- 11 Other animals
- 12 See also
- 13 References
- 14 External links
The primary use of testosterone is the treatment of males with too little or no natural testosterone production—males with hypogonadism. This is known as hormone replacement therapy or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range. Decline of testosterone production with age has led to interest in androgen replacement therapy.
Low levels due to aging
Testosterone levels may decline gradually with age. The Food and Drug Administration (FDA) stated in 2015 that neither the benefits nor the safety of testosterone have been established for low testosterone levels due to aging. The FDA has required that labels on testosterone include warnings about increased risk of heart attacks and stroke.
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.[medical citation needed]
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. It is also not usually recommended for improving cognition, the risk of heart disease, bone strength or for generalized well being.
Testosterone has been used to treat depression in men who are of middle age with low testosterone. However, a 2014 review showed no benefit on the mood of the men with normal levels of testosterone or on the mood of the older men with low testosterone.
To take advantage of its virilizing effects, testosterone is often administered to transgender men as part of the hormone replacement therapy, with a "target level" of the average male's testosterone level. Likewise, transgender 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 is used as a form of doping among athletes in order to improve performance. Testosterone is classified as an anabolic agent and is on the World Anti-Doping Agency (WADA) List of Prohibited Substances and Methods. Several application methods for testosterone, including intramuscular injections, transdermal gels and patches, and implantable pellets. Hormone supplements cause the endocrine system to adjust its production and lower the natural production of the hormone, so when supplements are discontinued, natural hormone production is lower than it was originally.
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. Their use is seen as an 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 Canadian professional wrestler Chris Benoit's double murder-suicide in 2007; however, there is no evidence implicating steroid use as a factor in the incident.
Some female athletes may have naturally higher levels of testosterone than others, and may be asked to consent to sex verification and either surgery or drugs to decrease testosterone levels. This has proven contentious, with the Court of Arbitration for Sport suspending the IAAF policy due to insufficient evidence of a link between high androgen levels and improved athletic performance.
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.
The Food and Drug Administration (FDA) stated in 2015 that neither the benefits nor the safety of testosterone have been established for low testosterone levels due to aging. The FDA has required that testosterone pharmaceutical labels include warning information about the possibility of an increased risk of heart attacks and stroke.
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. In addition, an increase of 30% in deaths and heart attacks in older men has been reported. 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. 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. 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). The FDA now requires warnings in the drug labeling of all approved testosterone products regarding deep vein thrombosis and pulmonary embolism.
Up to the year 2010, studies had not shown any effect on the risk of death, prostate cancer or cardiovascular disease; more recent studies, however, do raise concerns. 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."
Testosterone in the presence of a slow-growing prostate cancer is assumed to increase its growth rate. However, the association between testosterone supplementation and the development of prostate cancer is unproven. Nevertheless, physicians are cautioned about the cancer risk associated with testosterone supplementation.
It may accelerate pre-existing prostate cancer growth in individuals who have undergone androgen deprivation. It is recommended that physicians screen for prostate cancer with a digital rectal exam and prostate-specific antigen (PSA) level before starting therapy, and monitor PSA and hematocrit levels closely during therapy.
Ethnic groups have different rates of prostate cancer. Differences in sex hormones, including testosterone, have been suggested as an explanation for these differences. 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.
Adverse effects may also 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. Exogenous testosterone may also cause suppression of spermatogenesis, leading to, in some cases, infertility. Gynecomastia may occur due to testosterone's peripheral conversion to estradiol via aromatase.
Pregnancy and breast feeding
||This section needs more medical references for verification or relies too heavily on primary sources. (June 2016)|
In general, androgens such as testosterone promote protein synthesis and thus growth of tissues with androgen receptors. Testosterone can be described as having virilising and anabolic effects (though these categorical descriptions are somewhat arbitrary, as there is a great deal of mutual overlap between them).
- Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation.
- Androgenic effects include maturation of the sex organs, particularly the penis and the formation of the scrotum in the fetus, and after birth (usually at puberty) a deepening of the voice, growth of facial hair (such as the beard) and axillary (underarm) hair. Many of these fall into the category of male secondary sex characteristics.
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.
Effects before birth are divided into two categories, classified in relation to the stages of development.
The first period occurs between 4 and 6 weeks of the gestation. Examples include genital virilisation such as midline fusion, phallic urethra, scrotal thinning and rugation, and phallic enlargement; although the role of testosterone is far smaller than that of dihydrotestosterone. There is also development of the prostate gland and seminal vessicles.
During the second trimester, androgen level is associated with gender formation. 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.
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. 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. 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.
Before puberty effects of rising androgen levels occur in both boys and girls.
- Adult-type body odor
- Increased oiliness of skin and hair, acne
- Pubarche (appearance of pubic hair)
- Axillary hair
- Growth spurt, accelerated bone maturation
- Hair on upper lip,on chin, and growth of sideburns.
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. The effects include:
- Enlargement of sebaceous glands. This might cause acne.
- Penis or clitoris enlargement
- Increased libido and frequency of erection or clitoral engorgement
- Pubic hair extends to thighs and up toward umbilicus
- Facial hair (sideburns, beard, moustache)
- Loss of scalp hair (Androgenetic alopecia)
- Chest hair, periareolar hair, perianal hair
- Leg hair, armpit hair
- Subcutaneous fat in face decreases
- Increased muscle strength and mass
- Deepening of voice
- Growth of the Adam's apple
- Growth of spermatogenic tissue in testicles, male fertility
- Growth of jaw, brow, chin, nose, and remodeling of facial bone contours, in conjunction with human growth hormone
- Shoulders become broader and rib cage expands
- Completion of bone maturation and termination of growth. This occurs indirectly via estradiol metabolites and hence more gradually in men than women.
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 might decrease in the later decades of adult life.
- Testosterone is necessary for normal sperm development. It activates genes in Sertoli cells, which promote differentiation of spermatogonia.
- Regulates acute HPA (Hypothalamic–pituitary–adrenal axis) response under dominance challenge
- Regulator of cognitive and physical energy
- Maintenance of muscle trophism
- Testosterone regulates the population of thromboxane A2 receptors on megakaryocytes and platelets and hence platelet aggregation in humans
- High androgen levels are associated with menstrual cycle irregularities in both clinical populations and healthy women. See libido.
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.
- Recent studies have shown conflicting results concerning the importance of testosterone in maintaining cardiovascular health. 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.
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. 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. Men who produce less testosterone are more likely to be in a relationship and/or married, and men who produce more testosterone are more likely to divorce; however, causality cannot be determined in this correlation. Marriage or commitment could cause a decrease in testosterone levels. 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. 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.
Men who produce more testosterone are more likely to engage in extramarital sex. 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. 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.
Fatherhood also decreases testosterone levels in men, suggesting that the resulting emotional and behavioral changes promote paternal care. The way testosterone levels change when a child is in distress is indicative of fathering styles. If the levels reduce, then there is more empathy by the father than in fathers whose levels go up.
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).
Testosterone levels follow a nyctohemeral rhythm that peaks early each day, regardless of sexual activity.
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.
Sexual arousal and masturbation in women produce small increases in testosterone concentrations. The plasma levels of various steroids significantly increase after masturbation in men and the testosterone levels correlate to those levels.
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.
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.
In non-human primates, it may be that testosterone in puberty stimulates sexual arousal, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females. 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.).
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.
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. Men who watch sexually explicit films also report increased motivation, competitiveness, and decreased exhaustion. Previous research has found a link between relaxation following sexual arousal and testosterone levels.
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.
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. This may be linked to the ovulatory shift hypothesis, 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 work by enhancing their attention to the relevant stimuli.
Sperm competition theory: Testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats. 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.
Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal. Women's level of testosterone is higher when measured pre-intercourse vs pre-cuddling, as well as post-intercourse vs post-cuddling. 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.
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 affect the variation in testosterone response to sexual thoughts.
Testosterone may prove to be an effective treatment in female sexual arousal disorders. 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.
Behavior and personality
The brain is also affected by this sexual differentiation; 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.
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. 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).
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. Another study found a correlation between testosterone and risk tolerance in career choice among women.
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, 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, where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.
Aggression and criminality 
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.
Testosterone is only one of many 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 important role in male aggression. Studies have also found that testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus.
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. However men with high testosterone was significantly 27% less generous in an ultimatum game while men with the lowest testosterone were 560% more generous. The Annual NY Academy of Sciences has also found anabolic steroid use which increase testosterone to be higher in teenagers and this was associated with increased violence. Studies have also found administered testosterone to increase verbal aggression and anger in some participants.
Testosterone is significantly correlated with aggression and competitive behaviour and is directly facilitated by the latter. There are two theories on the role of testosterone in aggression and competition. The first one is the Challenge hypothesis which states that testosterone would increase during puberty thus facilitating reproductive and competitive behaviour which would include aggression. Thus it is the challenge of competition among males of the species that facilitates aggression and violence. Studies conducted have found direct correlation between testosterone and dominance especially among the most violent criminals in prison who had the highest testosterone levels. The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males.
The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression". Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible. The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game. Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.
The rise in testosterone levels during competition predicted aggression in males but not in females. Subjects who interacted with hand guns and an experimental game showed rise in testosterone and aggression. Natural selection might have evolved males to be more sensitive to competitive and status challenge situations and that the interacting roles of testosterone are the essential ingredient for aggressive behaviour in these situations. Testosterone produces aggression by activating subcortical areas in the brain, which may also be inhibited or suppressed by social norms or familial situations while still manifesting in diverse intensities and ways through thoughts, anger, verbal aggression, competition, dominance and to physical violence. Testosterone mediates attraction to cruel and violent cues in men by promoting extended viewing of violent stimuli. Testosterone specific structural brain characteristic can predict aggressive behaviour in individuals.
Estradiol is known to correlate with aggression in male mice. Moreover, the conversion of testosterone to estradiol regulates male aggression in sparrows during breeding season. Rats who were given anabolic steroids that increase testosterone were also more physical aggressive to provocation as a result of "threat sensitivity".
Like other steroid hormones, testosterone is derived from cholesterol (see figure to the left). 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. 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. 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 in both sexes. In the testes, testosterone is produced by the Leydig cells. 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).
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.
The amount of testosterone synthesized is regulated by the hypothalamic–pituitary–testicular axis (see figure to the right). 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 can 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.
- The secosteroid vitamin D in levels of 400–1000 IU/d (10–25 µg/d) raises testosterone levels.
- Zinc deficiency lowers testosterone levels but over supplementation has no effect on serum testosterone.
- Vitamin A deficiency may lead to sub-optimal plasma Testosterone levels.
- Dominance challenges can, in some cases, stimulate increased testosterone release in men.
- Aging may reduce testosterone release.
- Sleep (REM dream) increases nocturnal testosterone levels.
- Resistance training increases testosterone levels, however, in older men, that increase can be avoided by protein ingestion.
- Licorice can decrease the production of testosterone and this effect is greater in females.
- Natural or man-made antiandrogens including spearmint tea reduce testosterone levels.
- Posing in high-power nonverbal displays through open, expansive postures can increase testosterone levels.
98% of testosterone in plasma is bound to protein. 65% is bound to beta-globulin called Gonadal steroid-binding globulin ( GBG) or Sex steroid-binding globulin and 33% to albumin. Plasma testosterone level in the body (free or bound): 10.4-24.3 nmol/L) in adult men. In women:30-70 ng/dL A small amount of circulating testosterone is converted to estradiol, but most of the testosterone is converted to 17-ketosteroids, principally androsterone and its isomer etio-cholanolone, and excreted in urine.
Approximately 7% of testosterone is reduced to 5α-dihydrotestosterone (DHT) by the cytochrome P450 enzyme 5α-reductase, an enzyme highly expressed in male sex organs and hair follicles. Approximately 0.3% of testosterone is converted into estradiol by aromatase (CYP19A1) an enzyme expressed in the brain, liver, and adipose tissues.
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.
Mechanism of action
The effects of testosterone in humans and other vertebrates occur by way of multiple mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Androgens such as testosterone have also been found to bind to and activate membrane androgen receptors.
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. 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). 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.
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. 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. 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. 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.
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.
Routes of administration
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), oral, buccal, transdermal skin patches, transdermal creams, gels, and implantable pellets. Roll-on methods and nasal sprays are currently under development.
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). 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, 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. 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.
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)". 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, at the Chemisches Institut of Technical University in Gdańsk.
The chemical synthesis of testosterone from cholesterol was achieved in August that year by Butenandt and Hanisch. Only a week later, the Ciba group in Zurich, Leopold Ruzicka (1887–1976) and A. Wettstein, published their synthesis of testosterone. These independent partial syntheses of testosterone from a cholesterol base earned both Butenandt and Ruzicka the joint 1939 Nobel Prize in Chemistry. 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 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", 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.
Society and culture
A number of lawsuits are currently (2014) underway against testosterone manufacturers, alleging a significantly increased rate of stroke and heart attack in elderly men who use testosterone supplements.
Testosterone is observed in most vertebrates. Fish make a slightly different form called 11-ketotestosterone. Its counterpart in insects is ecdysone. These ubiquitous steroids suggest that sex hormones have an ancient evolutionary history.
- "Testosterone". Drugs.com. American Society of Health-System Pharmacists. December 4, 2015. Retrieved 3 September 2016.
- Staff (3 March 2015). "Testosterone Products: Drug Safety Communication – FDA Cautions About Using Testosterone Products for Low Testosterone Due to Aging; Requires Labeling Change to Inform of Possible Increased Risk of Heart Attack And Stroke". FDA. Retrieved 5 March 2015.
- Puri D (2014). Textbook of Medical Biochemistry (3 rd ed.). Elsevier Health Sciences. p. 631. ISBN 9788131238059.
- Heffner LJ, Schust DJ (2010). The Reproductive System at a Glance. John Wiley & Sons. p. 17. ISBN 9781405194525.
- Burtis CA, Ashwood ER, Bruns DE (2012). Tietz Textbook of Clinical Chemistry and Molecular Diagnostics (5th ed.). Elsevier Health Sciences. p. 1975. ISBN 978-1-4557-5942-2.
- Taylor WN (2002). Anabolic Steroids and the Athlete (2 ed.). McFarland. p. 180. ISBN 978-0-7864-1128-3.
- Desroches B, Kohn TP, Welliver C, Pastuszak AW (April 2016). "Testosterone therapy in the new era of Food and Drug Administration oversight". Translational Andrology and Urology. 5 (2): 207–12. doi:10.21037/tau.2016.03.13. PMC . PMID 27141448.
- "19th WHO Model List of Essential Medicines (April 2015)" (PDF). WHO. April 2015. Retrieved May 10, 2015.
- Hamilton R (2015). Tarascon Pocket Pharmacopoeia 2015 Deluxe Lab-Coat Edition. Jones & Bartlett Learning. p. 197. ISBN 978-1-284-05756-0.
- Winn, Katherine L. Margo|Robert. "Testosterone Treatments: Why, When, and How? - American Family Physician". www.aafp.org. Retrieved 2016-10-03.
- Myers JB, Meacham RB (2003). "Androgen replacement therapy in the aging male". Reviews in Urology. 5 (4): 216–26. PMC . PMID 16985841.
- Liverman CT, Blazer DG, Institute of Medicine (US) Committee on Assessing the Need for Clinical Trials of Testosterone Replacement Therapy (January 1, 2004). "Introduction". Testosterone and Aging: Clinical Research Directions. National Academies Press (US). doi:10.17226/10852. ISBN 978-0-309-09063-6 – via www.ncbi.nlm.nih.gov.
- Yeap BB, Almeida OP, Hyde Z, Norman PE, Chubb SA, Jamrozik K, Flicker L (May 2007). "In men older than 70 years, total testosterone remains stable while free testosterone declines with age. The Health in Men Study". European Journal of Endocrinology / European Federation of Endocrine Societies. 156 (5): 585–94. doi:10.1530/EJE-06-0714. PMID 17468195 – via PubMed.
- Gould DC, Petty R (Aug 2000). "The male menopause: does it exist?: for: some men need investigation and testosterone treatment". The Western Journal of Medicine. 173 (2): 76–8. doi:10.1136/ewjm.173.2.76. PMC . PMID 10924412.
- 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.
- Amanatkar HR, Chibnall JT, Seo BW, Manepalli JN, Grossberg GT (Feb 2014). "Impact of exogenous testosterone on mood: a systematic review and meta-analysis of randomized placebo-controlled trials". Annals of Clinical Psychiatry. 26 (1): 19–32. PMID 24501728.
- "Gender dysphoria – Treatment". NHS Gov.uk. May 21, 2012. Retrieved October 31, 2013.
- Traish AM, Saad F, Guay A (2009). "The dark side of testosterone deficiency: II. Type 2 diabetes and insulin resistance". Journal of Andrology. 30 (1): 23–32. doi:10.2164/jandrol.108.005751. PMID 18772488.
- Pike CJ, Rosario ER, Nguyen TV (Apr 2006). "Androgens, aging, and Alzheimer's disease". Endocrine. 29 (2): 233–41. doi:10.1385/ENDO:29:2:233. PMID 16785599.
- Rosario ER, Chang L, Stanczyk FZ, Pike CJ (Sep 2004). "Age-related testosterone depletion and the development of Alzheimer disease". JAMA. 292 (12): 1431–32. doi:10.1001/jama.292.12.1431-b. PMID 15383512.
- "S1. Anabolic Agents | List of Prohibited Substances and Methods". English. Retrieved 2016-06-06.
- "Anabolic Steroid Control Act" (PDF). United States Sentencing Commission. 1990.
- Karkazis K, Jordan-Young R (April 11, 2014). "The Trouble With Too Much T". New York Times. Retrieved April 12, 2014.
- Fagan, Kate (August 13, 2016). "Katie Ledecky is crushing records, so why are we still worried about Caster Semenya?". ESPN. Retrieved 2016-08-27.
- Padawer, Ruth (June 28, 2016). "The Humiliating Practice of Sex-Testing Female Athletes". The New York Times. ISSN 0362-4331. Retrieved 2016-08-27.
- Strahm E, Emery C, Saugy M, Dvorak J, Saudan C (Dec 2009). "Detection of testosterone administration based on the carbon isotope ratio profiling of endogenous steroids: international reference populations of professional soccer players". British Journal of Sports Medicine. 43 (13): 1041–44. doi:10.1136/bjsm.2009.058669. PMC . PMID 19549614.
- Kicman AT, Cowan DA (Jan 2009). "Subject-based profiling for the detection of testosterone administration in sport". Drug Testing and Analysis. 1 (1): 22–4. doi:10.1002/dta.14. PMID 20355155.
- Pozo OJ, Deventer K, Van Eenoo P, Rubens R, Delbeke FT (Aug 2009). "Quantification of testosterone undecanoate in human hair by liquid chromatography-tandem mass spectrometry". Biomedical Chromatography. 23 (8): 873–80. doi:10.1002/bmc.1199. PMID 19353724.
- Baselt RC (2008). Disposition of Toxic Drugs & Chemicals in Man (8th ed.). Foster City, Calif: Biomedical Publications. pp. 1501–04. ISBN 978-0-9626523-7-0.
- 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. Bibcode:2014PLoSO...985805F. doi:10.1371/journal.pone.0085805. PMC . PMID 24489673.
- 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 2013). "Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels". JAMA. 310 (17): 1829–36. doi:10.1001/jama.2013.280386. PMID 24193080.
- 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 (2010-07-08). "Adverse events associated with testosterone administration". The New England Journal of Medicine. 363 (2): 109–22. doi:10.1056/NEJMoa1000485. PMC . PMID 20592293.
- 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.
- Tavernise, Sabrina (September 17, 2014). "F.D.A. Panel Backs Limits on Testosterone Drugs". New York Times. Retrieved September 18, 2014.
- Staff (September 5, 2014). "FDA Panel To Review Testosterone Therapy Appropriateness and Safety". CNN News. Retrieved September 14, 2014.
- 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.
- Staff (June 19, 2014). "FDA adding general warning to testosterone products about potential for venous blood clots". FDA. Retrieved October 9, 2014.
- Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM (Jan 2007). "Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials". Mayo Clinic Proceedings. 82 (1): 29–39. doi:10.4065/82.1.29. PMID 17285783.
- 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 (Jun 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.
- "Testosterone Products: Drug Safety Communication – FDA Investigating Risk of Cardiovascular Events". FDA. January 31, 2014. Retrieved February 3, 2014.
- Rhoden EL, Averbeck MA (Nov 2009). "Testosterone therapy and prostate carcinoma". Current Urology Reports. 10 (6): 453–59. doi:10.1007/s11934-009-0072-1. PMID 19863857.
- Gaylis FD, Lin DW, Ignatoff JM, Amling CL, Tutrone RF, Cosgrove DJ (Aug 2005). "Prostate cancer in men using testosterone supplementation". The Journal of Urology. 174 (2): 534–38; discussion 538. doi:10.1097/01.ju.0000165166.36280.60. PMID 16006887.
- Pastuszak AW, Pearlman AM, Lai WS, Godoy G, Sathyamoorthy K, Liu JS, Miles BJ, Lipshultz LI, Khera M (Aug 2013). "Testosterone replacement therapy in patients with prostate cancer after radical prostatectomy". The Journal of Urology. 190 (2): 639–44. doi:10.1016/j.juro.2013.02.002. PMC . PMID 23395803.
- Calistro Alvarado L (2010). "Population differences in the testosterone levels of young men are associated with prostate cancer disparities in older men". American Journal of Human Biology. 22 (4): 449–55. doi:10.1002/ajhb.21016. PMID 20087895.
- Bostwick DG, Burke HB, Djakiew D, Euling S, Ho SM, Landolph J, Morrison H, Sonawane B, Shifflett T, Waters DJ, Timms B (Nov 2004). "Human prostate cancer risk factors". Cancer. 101 (10 Suppl): 2371–490. doi:10.1002/cncr.20408. PMID 15495199. Lay summary – Mercer University School of Medicine.
- Grech A, Breck J, Heidelbaugh J (October 2014). "Adverse effects of testosterone replacement therapy: an update on the evidence and controversy". Therapeutic Advances in Drug Safety. 5 (5): 190–200. doi:10.1177/2042098614548680. PMC . PMID 25360240 – via PubMed Central.
- "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.
- Rhoden EL, Morgentaler A (February 2004). "Treatment of testosterone-induced gynecomastia with the aromatase inhibitor, anastrozole". International Journal of Impotence Research. 16 (1): 95–7. doi:10.1038/sj.ijir.3901154. PMID 14963480.
- "Testosterone Pregnancy and Breastfeeding Warnings". Retrieved February 1, 2014.
- Swaab DF, Garcia-Falgueras A (2009). "Sexual differentiation of the human brain in relation to gender identity and sexual orientation". Functional Neurology. 24 (1): 17–28. PMID 19403051.
- Browne KR (2002). Biology at work: rethinking sexual equality. New Brunswick, N.J: Rutgers University Press. p. 112. ISBN 0-8135-3053-9.
- Forest MG, Cathiard AM, Bertrand JA (Jul 1973). "Evidence of testicular activity in early infancy". The Journal of Clinical Endocrinology and Metabolism. 37 (1): 148–51. doi:10.1210/jcem-37-1-148. PMID 4715291.
- Corbier P, Edwards DA, Roffi J (1992). "The neonatal testosterone surge: a comparative study". Archives Internationales de Physiologie, de Biochimie et de Biophysique. 100 (2): 127–31. doi:10.3109/13813459209035274. PMID 1379488.
- 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". The European Journal of Neuroscience. 27 (9): 2473–80. doi:10.1111/j.1460-9568.2008.06216.x. PMID 18445234.
- Kalat JW (2009). "Reproductive behaviors". Biological psychology. Belmont, Calif: Wadsworth, Cengage Learning. p. 321. ISBN 0-495-60300-7.
- Ganong (2012). Ganong's Review of Medical Physiology (24 ed.). TATA McGRAW Hill. pp. 423–25. ISBN 978-1-25-902753-6.
- "Cellular and Molecular Mechanisms of Bone Remodeling". The Journal of Biological Chemistry.
- Kelsey, Thomas W.; Li, Lucy Q.; Mitchell, Rod T.; Whelan, Ashley; Anderson, Richard A.; Wallace, W. Hamish B. (October 8, 2014). "A Validated Age-Related Normative Model for Male Total Testosterone Shows Increasing Variance but No Decline after Age 40 Years". PLoS One. 9 (10): e109346. Bibcode:2014PLoSO...9j9346K. doi:10.1371/journal.pone.0109346. PMC . PMID 25295520 – via PubMed Central.
- Mehta PH, Jones AC, Josephs RA (Jun 2008). "The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat" (PDF). Journal of Personality and Social Psychology. 94 (6): 1078–93. doi:10.1037/0022-35188.8.131.528. PMID 18505319.
- 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.
- Ajayi AA, Mathur R, Halushka PV (Jun 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.
- Van Anders SM, Watson NV (2006). "Menstrual cycle irregularities are associated with testosterone levels in healthy premenopausal women". American Journal of Human Biology. 18 (6): 841–44. doi:10.1002/ajhb.20555. PMID 17039468.
- Morgentaler A, Schulman C (2009). "Testosterone and prostate safety". Frontiers of Hormone Research. Frontiers of Hormone Research. 37: 197–203. doi:10.1159/000176054. ISBN 978-3-8055-8622-1. PMID 19011298.
- Rhoden EL, Averbeck MA, Teloken PE (Sep 2008). "Androgen replacement in men undergoing treatment for prostate cancer". The Journal of Sexual Medicine. 5 (9): 2202–08. doi:10.1111/j.1743-6109.2008.00925.x. PMID 18638000.
- Morgentaler A, Traish AM (Feb 2009). "Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth". European Urology. 55 (2): 310–20. doi:10.1016/j.eururo.2008.09.024. PMID 18838208.
- Jones TH, Saad F (Dec 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.
- Stanworth RD, Jones TH (2008). "Testosterone for the aging male; current evidence and recommended practice". Clinical Interventions in Aging. 3 (1): 25–44. PMC . PMID 18488876.
- Marazziti D, Canale D (Aug 2004). "Hormonal changes when falling in love". Psychoneuroendocrinology. 29 (7): 931–36. doi:10.1016/j.psyneuen.2003.08.006. PMID 15177709.
- van Anders SM, Watson NV (Jul 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.
- Booth A, Dabbs JM (1993). "Testosterone and Men's Marriages". Social Forces. 72 (2): 463–77. doi:10.1093/sf/72.2.463.
- Mazur A, Michalek J (1998). "Marriage, Divorce, and Male Testosterone". Social Forces. 77 (1): 315–30. doi:10.1093/sf/77.1.315.
- Gray PB, Chapman JF, Burnham TC, McIntyre MH, Lipson SF, Ellison PT (Jun 2004). "Human male pair bonding and testosterone". Human Nature. 15 (2): 119–31. doi:10.1007/s12110-004-1016-6. PMID 26190409.
- Gray PB, Campbell BC, Marlowe FW, Lipson SF, Ellison PT (Oct 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.
- van Anders SM, Watson NV (Feb 2007). "Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships". Hormones and Behavior. 51 (2): 286–91. doi:10.1016/j.yhbeh.2006.11.005. PMID 17196592.
- Berg SJ, Wynne-Edwards KE (Jun 2001). "Changes in testosterone, cortisol, and estradiol levels in men becoming fathers". Mayo Clinic Proceedings. 76 (6): 582–92. doi:10.4065/76.6.582. PMID 11393496.
- "Parenting Skills Influenced by Testosterone Levels, Empathy". Psych Central.com. Retrieved 2015-11-02.
- Fox CA, Ismail AA, Love DN, Kirkham KE, Loraine JA (Jan 1972). "Studies on the relationship between plasma testosterone levels and human sexual activity". The Journal of Endocrinology. 52 (1): 51–8. doi:10.1677/joe.0.0520051. PMID 5061159.
- van Anders SM, Dunn EJ (Aug 2009). "Are gonadal steroids linked with orgasm perceptions and sexual assertiveness in women and men?". Hormones and Behavior. 56 (2): 206–13. doi:10.1016/j.yhbeh.2009.04.007. PMID 19409392.
- Exton MS, Bindert A, Krüger T, Scheller F, Hartmann U, Schedlowski M (1999). "Cardiovascular and endocrine alterations after masturbation-induced orgasm in women". Psychosomatic Medicine. 61 (3): 280–89. doi:10.1097/00006842-199905000-00005. PMID 10367606.
- Purvis K, Landgren BM, Cekan Z, Diczfalusy E (Sep 1976). "Endocrine effects of masturbation in men". The Journal of Endocrinology. 70 (3): 439–44. doi:10.1677/joe.0.0700439. PMID 135817.
- Harding SM, Velotta JP (May 2011). "Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats". Hormones and Behavior. 59 (5): 666–73. doi:10.1016/j.yhbeh.2010.09.009. PMID 20920505.
- James PJ, Nyby JG, Saviolakis GA (Sep 2006). "Sexually stimulated testosterone release in male mice (Mus musculus): roles of genotype and sexual arousal". Hormones and Behavior. 50 (3): 424–31. doi:10.1016/j.yhbeh.2006.05.004. PMID 16828762.
- Wallen K (Sep 2001). "Sex and context: hormones and primate sexual motivation". Hormones and Behavior. 40 (2): 339–57. doi:10.1006/hbeh.2001.1696. PMID 11534996.
- Kraemer HC, Becker HB, Brodie HK, Doering CH, Moos RH, Hamburg DA (Mar 1976). "Orgasmic frequency and plasma testosterone levels in normal human males". Archives of Sexual Behavior. 5 (2): 125–32. doi:10.1007/BF01541869. PMID 1275688.
- Pirke KM, Kockott G, Dittmar F (Nov 1974). "Psychosexual stimulation and plasma testosterone in man". Archives of Sexual Behavior. 3 (6): 577–84. doi:10.1007/BF01541140. PMID 4429441.
- 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.
- 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.
- Roney JR, Mahler SV, Maestripieri D (2003). "Behavioral and hormonal responses of men to brief interactions with women". Evolution and Human Behavior. 24 (6): 365–75. doi:10.1016/S1090-5138(03)00053-9.
- Miller SL, Maner JK (Feb 2010). "Scent of a woman: men's testosterone responses to olfactory ovulation cues". Psychological Science. 21 (2): 276–83. doi:10.1177/0956797609357733. PMID 20424057.
- Gangestead SW, Thornhill R, Garver-Apgar CE (2005). "Adaptations to Ovulation: Implications for Sexual and Social Behavior". Current Directions in Psychological Science. 14 (6): 312–16. doi:10.1111/j.0963-7214.2005.00388.x.
- Alexander GM, Sherwin BB (Sep 1991). "The association between testosterone, sexual arousal, and selective attention for erotic stimuli in men". Hormones and Behavior. 25 (3): 367–81. doi:10.1016/0018-506X(91)90008-6. PMID 1937428.
- Hart BL (Dec 1983). "Role of testosterone secretion and penile reflexes in sexual behavior and sperm competition in male rats: a theoretical contribution". Physiology & Behavior. 31 (6): 823–27. doi:10.1016/0031-9384(83)90279-2. PMID 6665072.
- Traish AM, Kim N, Min K, Munarriz R, Goldstein I (Apr 2002). "Role of androgens in female genital sexual arousal: receptor expression, structure, and function". Fertility and Sterility. 77 Suppl 4: S11–8. doi:10.1016/s0015-0282(02)02978-3. PMID 12007897.
- van Anders SM, Hamilton LD, Schmidt N, Watson NV (Apr 2007). "Associations between testosterone secretion and sexual activity in women". Hormones and Behavior. 51 (4): 477–82. doi:10.1016/j.yhbeh.2007.01.003. PMID 17320881.
- Tuiten A, Van Honk J, Koppeschaar H, Bernaards C, Thijssen J, Verbaten R (Feb 2000). "Time course of effects of testosterone administration on sexual arousal in women". Archives of General Psychiatry. 57 (2): 149–53; discussion 155–6. doi:10.1001/archpsyc.57.2.149. PMID 10665617.
- Goldey KL, van Anders SM (May 2011). "Sexy thoughts: effects of sexual cognitions on testosterone, cortisol, and arousal in women". Hormones and Behavior. 59 (5): 754–64. doi:10.1016/j.yhbeh.2010.12.005. PMID 21185838.
- Bolour S, Braunstein G (2005). "Testosterone therapy in women: a review". International Journal of Impotence Research. 17 (5): 399–408. doi:10.1038/sj.ijir.3901334. PMID 15889125.
- Sapienza P, Zingales L, Maestripieri D (Sep 2009). "Gender differences in financial risk aversion and career choices are affected by testosterone". Proceedings of the National Academy of Sciences of the United States of America. 106 (36): 15268–73. Bibcode:2009PNAS..10615268S. doi:10.1073/pnas.0907352106. PMC . PMID 19706398.
- 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): 384–90. doi:10.1016/j.evolhumbehav.2008.07.001.
- Wilson JD (Sep 2001). "Androgens, androgen receptors, and male gender role behavior". Hormones and Behavior. 40 (2): 358–66. doi:10.1006/hbeh.2001.1684. PMID 11534997.
- Cosgrove KP, Mazure CM, Staley JK (Oct 2007). "Evolving knowledge of sex differences in brain structure, function, and chemistry". Biological Psychiatry. 62 (8): 847–55. doi:10.1016/j.biopsych.2007.03.001. PMC . PMID 17544382.
- Marner L, Nyengaard JR, Tang Y, Pakkenberg B (Jul 2003). "Marked loss of myelinated nerve fibers in the human brain with age". The Journal of Comparative Neurology. 462 (2): 144–52. doi:10.1002/cne.10714. PMID 12794739.
- Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, Bunnell TJ, Tricker R, Shirazi A, Casaburi R (Jul 1996). "The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men". The New England Journal of Medicine. 335 (1): 1–7. doi:10.1056/NEJM199607043350101. PMID 8637535.
- "Testosterone Affects Some Women's Career Choices". NPR. August 28, 2009.
- Hogervorst E, Bandelow S, Combrinck M, Smith AD (2004). "Low free testosterone is an independent risk factor for Alzheimer's disease". Experimental Gerontology. 39 (11–12): 1633–39. doi:10.1016/j.exger.2004.06.019. PMID 15582279.
- Moffat SD, Zonderman AB, Metter EJ, Kawas C, Blackman MR, Harman SM, Resnick SM (Jan 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.
- Moffat SD, Hampson E (Apr 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.
- Wright J, Ellis L, Beaver K (2009). Handbook of crime correlates. San Diego: Academic Press. pp. 208–10. ISBN 0-12-373612-9.
- 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.
- Coccaro E (1996). "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. 794: 82–89. Bibcode:1996NYASA.794...82C. doi:10.1111/j.1749-6632.1996.tb32511.x. PMID 8853594.
- Finkelstein JW, Susman EJ, Chinchilli VM, Kunselman SJ, D'Arcangelo MR, Schwab J, Demers LM, Liben LS, Lookingbill G, Kulin HE (1997). "Estrogen or testosterone increases self-reported aggressive behaviors in hypogonadal adolescents". Journal of Clinical Endocrinology and Metabolism. 82 (8): 2433–38. doi:10.1210/jcem.82.8.4165. PMID 9253313.
- Delville Y, Mansour KM, Ferris CF (July 1996). "Testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus". Physiology & Behavior. 60 (1): 25–9. doi:10.1016/0031-9384(95)02246-5. PMID 8804638.
- Eisenegger C, Naef M, Snozzi R, Heinrichs M, Fehr E (2010). "Prejudice and truth about the effect of testosterone on human bargaining behaviour". Nature. 463 (7279): 356–59. Bibcode:2010Natur.463..356E. doi:10.1038/nature08711. PMID 19997098.
- van Honk J, Montoya ER, Bos PA, van Vugt M, Terburg D (May 2012). "New evidence on testosterone and cooperation". Nature. 485 (7399): E4–5; discussion E5–6. Bibcode:2012Natur.485E...4V. doi:10.1038/nature11136. PMID 22622587.
- Eisenegger C, Naef M, Snozzi R, Heinrichs M, Fehr E (2012). "Eisenegger et al. reply". Nature. 485 (7399): E5–E6. Bibcode:2012Natur.485E...5E. doi:10.1038/nature11137.
- Zak PJ, Kurzban R, Ahmadi S, Swerdloff RS, Park J, Efremidze L, Redwine K, Morgan K, Matzner W (2009-01-01). "Testosterone administration decreases generosity in the ultimatum game". PLoS ONE. 4 (12): e8330. Bibcode:2009PLoSO...4.8330Z. doi:10.1371/journal.pone.0008330. PMC . PMID 20016825.
- McGinnis MY (Dec 2004). "Anabolic androgenic steroids and aggression: studies using animal models". Annals of the New York Academy of Sciences. 1036: 399–415. Bibcode:2004NYASA1036..399M. doi:10.1196/annals.1330.024. PMID 15817752.
- von der PB, Sarkola T, Seppa K, Eriksson CJ (Sep 2002). "Testosterone, 5 alpha-dihydrotestosterone and cortisol in men with and without alcohol-related aggression". Journal of Studies on Alcohol. 63 (5): 518–26. doi:10.15288/jsa.2002.63.518. PMID 12380846.
- Archer J (2006). "Testosterone and human aggression: an evaluation of the challenge hypothesis" (PDF). Neuroscience and Biobehavioral Reviews. 30 (3): 319–45. doi:10.1016/j.neubiorev.2004.12.007. PMID 16483890.
- Ellis, Lee; Hoskin, Anthony W. (2015). "The evolutionary neuroandrogenic theory of criminal behavior expanded". Aggression and Violent Behavior. 24: 61–74. doi:10.1016/j.avb.2015.05.002.
- Hoskin, Anthony W.; Ellis, Lee (2015). "FETAL TESTOSTERONE AND CRIMINALITY: TEST OF EVOLUTIONARY NEUROANDROGENIC THEORY". Criminology. 53 (1): 54–73. doi:10.1111/1745-9125.12056.
- Ellis, Lee; Hoskin, Anthony W. (2015). "The evolutionary neuroandrogenic theory of criminal behavior expanded". Aggression and Violent Behavior. 24: 61–74. doi:10.1016/j.avb.2015.05.002.
- Perciavalle V, Di Corrado D, Petralia MC, Gurrisi L, Massimino S, Coco M (Jun 2013). "The second-to-fourth digit ratio correlates with aggressive behavior in professional soccer players". Molecular Medicine Reports. 7 (6): 1733–38. doi:10.3892/mmr.2013.1426. PMC . PMID 23588344.
- Bailey AA, Hurd PL (Mar 2005). "Finger length ratio (2D:4D) correlates with physical aggression in men but not in women". Biological Psychology. 68 (3): 215–22. doi:10.1016/j.biopsycho.2004.05.001. PMID 15620791. Lay summary – LiveScience (2 March 2005).
- Benderlioglu Z, Nelson RJ (Dec 2004). "Digit length ratios predict reactive aggression in women, but not in men". Hormones and Behavior. 46 (5): 558–64. doi:10.1016/j.yhbeh.2004.06.004. PMID 15555497.
- Liu J, Portnoy J, Raine A (Aug 2012). "Association between a marker for prenatal testosterone exposure and externalizing behavior problems in children". Development and Psychopathology. 24 (3): 771–82. doi:10.1017/S0954579412000363. PMC . PMID 22781854.
- Butovskaya M, Burkova V, Karelin D, Fink B (2015-10-01). "Digit ratio (2D:4D), aggression, and dominance in the Hadza and the Datoga of Tanzania". American Journal of Human Biology. 27 (5): 620–27. doi:10.1002/ajhb.22718. PMID 25824265.
- Joyce CW, Kelly JC, Chan JC, Colgan G, O'Briain D, Mc Cabe JP, Curtin W (Nov 2013). "Second to fourth digit ratio confirms aggressive tendencies in patients with boxers fractures". Injury. 44 (11): 1636–39. doi:10.1016/j.injury.2013.07.018. PMID 23972912.
- Carré JM, Olmstead NA (Feb 2015). "Social neuroendocrinology of human aggression: examining the role of competition-induced testosterone dynamics" (PDF). Neuroscience. 286: 171–86. doi:10.1016/j.neuroscience.2014.11.029. PMID 25463514.
- Klinesmith J, Kasser T, McAndrew FT (Jul 2006). "Guns, testosterone, and aggression: an experimental test of a mediational hypothesis". Psychological Science. 17 (7): 568–71. doi:10.1111/j.1467-9280.2006.01745.x. PMID 16866740.
- Mcandrew FT (2009). "The Interacting Roles of Testosterone and Challenges to Status in Human Male Aggression" (PDF). Aggressive and Violent Behavior. 14 (5): 330–335. doi:10.1016/j.avb.2009.04.006.
- Batrinos ML (2012-01-01). "Testosterone and aggressive behavior in man". International Journal of Endocrinology and Metabolism. 10 (3): 563–68. doi:10.5812/ijem.3661. PMC . PMID 23843821.
- Weierstall R, Moran J, Giebel G, Elbert T (2014-05-01). "Testosterone reactivity and identification with a perpetrator or a victim in a story are associated with attraction to violence-related cues". International Journal of Law and Psychiatry. 37 (3): 304–12. doi:10.1016/j.ijlp.2013.11.016. PMID 24367977.
- Nguyen TV, McCracken JT, Albaugh MD, Botteron KN, Hudziak JJ, Ducharme S (Jan 2016). "A testosterone-related structural brain phenotype predicts aggressive behavior from childhood to adulthood". Psychoneuroendocrinology. 63: 109–18. doi:10.1016/j.psyneuen.2015.09.021. PMC . PMID 26431805.
- Soma KK, Scotti MA, Newman AE, Charlier TD, Demas GE (Oct 2008). "Novel mechanisms for neuroendocrine regulation of aggression". Frontiers in Neuroendocrinology. 29 (4): 476–89. doi:10.1016/j.yfrne.2007.12.003. PMID 18280561.
- 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". Journal of Comparative Physiology A. 186 (7–8): 759–69. doi:10.1007/s003590000129. PMID 11016791.
- McGinnis MY, Lumia AR, Breuer ME, Possidente B (Feb 2002). "Physical provocation potentiates aggression in male rats receiving anabolic androgenic steroids". Hormones and Behavior. 41 (1): 101–10. doi:10.1006/hbeh.2001.1742. PMID 11863388.
- Waterman MR, Keeney DS (1992). "Genes involved in androgen biosynthesis and the male phenotype". Hormone Research. 38 (5–6): 217–21. doi:10.1159/000182546. PMID 1307739.
- Zuber MX, Simpson ER, Waterman MR (Dec 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.
- Mooradian AD, Morley JE, Korenman SG (Feb 1987). "Biological actions of androgens". Endocrine Reviews. 8 (1): 1–28. doi:10.1210/edrv-8-1-1. PMID 3549275.
- Zouboulis CC, Degitz K (2004). "Androgen action on human skin -- from basic research to clinical significance". Experimental Dermatology. 13 Suppl 4 (s4): 5–10. doi:10.1111/j.1600-0625.2004.00255.x. PMID 15507105.
- Brooks RV (Nov 1975). "Androgens". Clinics in Endocrinology and Metabolism. 4 (3): 503–20. doi:10.1016/S0300-595X(75)80045-4. PMID 58744.
- Payne AH, O'Shaughnessy P (1996). "Structure, function, and regulation of steroidogenic enzymes in the Leydig cell". In Payne AH, Hardy MP, Russell LD. Leydig Cell. Vienna [Il]: Cache River Press. pp. 260–85. ISBN 0-9627422-7-9.
- Swerdloff RS, Wang C, Bhasin S (Apr 1992). "Developments in the control of testicular function". Baillière's Clinical Endocrinology and Metabolism. 6 (2): 451–83. doi:10.1016/S0950-351X(05)80158-2. PMID 1377467.
- 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". Reproductive Health. 8 (1): 24. doi:10.1186/1742-4755-8-24. PMC . PMID 21849026.
- Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A (Mar 2011). "Effect of vitamin D supplementation on testosterone levels in men". Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones et Métabolisme. 43 (3): 223–25. doi:10.1055/s-0030-1269854. PMID 21154195.
- Prasad AS, Mantzoros CS, Beck FW, Hess JW, Brewer GJ (May 1996). "Zinc status and serum testosterone levels of healthy adults". Nutrition. 12 (5): 344–48. doi:10.1016/S0899-9007(96)80058-X. PMID 8875519.
- Koehler K, Parr MK, Geyer H, Mester J, Schänzer W (Jan 2009). "Serum testosterone and urinary excretion of steroid hormone metabolites after administration of a high-dose zinc supplement". European Journal of Clinical Nutrition. 63 (1): 65–70. doi:10.1038/sj.ejcn.1602899. PMID 17882141.
- Livera G, Rouiller-Fabre V, Pairault C, Levacher C, Habert R (Aug 2002). "Regulation and perturbation of testicular functions by vitamin A". Reproduction. 124 (2): 173–80. doi:10.1530/rep.0.1240173. PMID 12141930.
- Schultheiss OC, Campbell KL, McClelland DC (Dec 1999). "Implicit power motivation moderates men's testosterone responses to imagined and real dominance success". Hormones and Behavior. 36 (3): 234–41. doi:10.1006/hbeh.1999.1542. PMID 10603287.
- Liu PY, Pincus SM, Takahashi PY, Roebuck PD, Iranmanesh A, Keenan DM, Veldhuis JD (Jan 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". American Journal of Physiology. Endocrinology and Metabolism. 290 (1): E34–41. doi:10.1152/ajpendo.00227.2005. PMID 16339924.
- Andersen ML, Tufik S (Oct 2008). "The effects of testosterone on sleep and sleep-disordered breathing in men: its bidirectional interaction with erectile function" (PDF). Sleep Medicine Reviews. 12 (5): 365–79. doi:10.1016/j.smrv.2007.12.003. PMID 18519168.
- 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.
- 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". The Journal of Steroid Biochemistry and Molecular Biology. 110 (1–2): 130–37. doi:10.1016/j.jsbmb.2008.03.030. PMID 18455389.
- Armanini D, Fiore C, Mattarello MJ, Bielenberg J, Palermo M (Sep 2002). "History of the endocrine effects of licorice". Experimental and Clinical Endocrinology & Diabetes. 110 (6): 257–61. doi:10.1055/s-2002-34587. PMID 12373628.
- 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". Phytotherapy Research. 21 (5): 444–47. doi:10.1002/ptr.2074. PMID 17310494.
- Kumar V, Kural MR, Pereira BM, Roy P (Dec 2008). "Spearmint induced hypothalamic oxidative stress and testicular anti-androgenicity in male rats - altered levels of gene expression, enzymes and hormones". Food and Chemical Toxicology. 46 (12): 3563–70. doi:10.1016/j.fct.2008.08.027. PMID 18804513.
- Grant P (Feb 2010). "Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial". Phytotherapy Research. 24 (2): 186–88. doi:10.1002/ptr.2900. PMID 19585478.
- Carney DR, Cuddy AJ, Yap AJ (Oct 2010). "Power posing: brief nonverbal displays affect neuroendocrine levels and risk tolerance". Psychological Science. 21 (10): 1363–66. doi:10.1177/0956797610383437. PMID 20855902.
- Randall VA (Apr 1994). "Role of 5 alpha-reductase in health and disease". Baillière's Clinical Endocrinology and Metabolism. 8 (2): 405–31. doi:10.1016/S0950-351X(05)80259-9. PMID 8092979.
- Meinhardt U, Mullis PE (Aug 2002). "The essential role of the aromatase/p450arom". Seminars in Reproductive Medicine. 20 (3): 277–84. doi:10.1055/s-2002-35374. PMID 12428207.
- Trager L (1977). Steroidhormone: Biosynthese, Stoffwechsel, Wirkung (in German). Springer-Verlag. p. 349. ISBN 0-387-08012-0.
- Hiipakka RA, Liao S (Oct 1998). "Molecular mechanism of androgen action". Trends in Endocrinology and Metabolism. 9 (8): 317–24. doi:10.1016/S1043-2760(98)00081-2. PMID 18406296.
- McPhaul MJ, Young M (Sep 2001). "Complexities of androgen action". Journal of the American Academy of Dermatology. 45 (3 Suppl): S87–94. doi:10.1067/mjd.2001.117429. PMID 11511858.
- Bennett NC, Gardiner RA, Hooper JD, Johnson DW, Gobe GC (2010). "Molecular cell biology of androgen receptor signalling". Int. J. Biochem. Cell Biol. 42 (6): 813–27. doi:10.1016/j.biocel.2009.11.013. PMID 19931639.
- Wang C, Liu Y, Cao JM (2014). "G protein-coupled receptors: extranuclear mediators for the non-genomic actions of steroids". Int J Mol Sci. 15 (9): 15412–25. doi:10.3390/ijms150915412. PMC . PMID 25257522.
- Lang F, Alevizopoulos K, Stournaras C (2013). "Targeting membrane androgen receptors in tumors". Expert Opin. Ther. Targets. 17 (8): 951–63. doi:10.1517/14728222.2013.806491. PMID 23746222.
- Breiner M, Romalo G, Schweikert HU (Aug 1986). "Inhibition of androgen receptor binding by natural and synthetic steroids in cultured human genital skin fibroblasts". Klinische Wochenschrift. 64 (16): 732–37. doi:10.1007/BF01734339. PMID 3762019.
- Kelly MJ, Qiu J, Rønnekleiv OK (2005-01-01). "Estrogen signaling in the hypothalamus". Vitamins and Hormones. 71: 123–45. doi:10.1016/S0083-6729(05)71005-0. PMID 16112267.
- 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". Current Medicinal Chemistry. 12 (8): 927–43. doi:10.2174/0929867053507306. PMID 15853706.
- Engel JB, Schally AV (Feb 2007). "Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone". Nature Clinical Practice. Endocrinology & Metabolism. 3 (2): 157–67. doi:10.1038/ncpendmet0399. PMID 17237842.
- "Testosterone Information". Drugs.com.
- "Striant Official FDA information, side effects and uses". Drugs.com.
- "AndroGel Official FDA information, side effects and uses". Drugs.com.
- "Testim (patches and gel) medical facts". Drugs.com.
- "Testopel Pellets". www.slatepharma.com.
- Berthold AA (1849). "Transplantation der Hoden" [Transplantation of testis]. Arch. Anat. Physiol. Wiss. (in German). 16: 42–6.
- Brown-Sequard CE (1889). "The effects produced on man by subcutaneous injections of liquid obtained from the testicles of animals". Lancet. 2 (3438): 105–07. doi:10.1016/S0140-6736(00)64118-1.
- Gallagher TF, Koch FC (November 1929). "The testicular hormone". J. Biol. Chem. 84 (2): 495–500.
- David KG, Dingemanse E, Freud JL (May 1935). "Über krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron" [On crystalline male hormone from testicles (testosterone) effective as from urine or from cholesterol]. Hoppe Seylers Z Physiol Chem (in German). 233 (5–6): 281–83. doi:10.1515/bchm2.1935.233.5-6.281.
- Butenandt A, Hanisch G (1935). "Umwandlung des Dehydroandrosterons in Androstendiol und Testosterone; ein Weg zur Darstellung des Testosterons aus Cholestrin" [About Testosterone. Conversion of Dehydro-androsterons into androstendiol and testosterone; a way for the structure assignment of testosterone from cholestrol]. Hoppe Seylers Z Physiol Chem (in German). 237 (2): 89–97. doi:10.1515/bchm2.1935.237.1-3.89.
- Freeman ER, Bloom DA, McGuire EJ (Feb 2001). "A brief history of testosterone". The Journal of Urology. 165 (2): 371–73. doi:10.1097/00005392-200102000-00004. PMID 11176375.
- 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 (9): 1859–62. doi:10.1002/cber.19350680937.
- 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: 1264–75. doi:10.1002/hlca.193501801176.
- Hoberman JM, Yesalis CE (Feb 1995). "The history of synthetic testosterone". Scientific American. 272 (2): 76–81. doi:10.1038/scientificamerican0295-76. PMID 7817189.
- 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.
- Schwarz S, Onken D, Schubert A (Jul 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.
- de Kruif P (1945). The Male Hormone. New York: Harcourt, Brace.
- Harris A. "Abbott Labs Sued by Five Men Claiming Androgel Injuries". Bloomberg.com. Bloomberg, L.P. Retrieved June 16, 2014.
- Kicman AT (June 2008). "Pharmacology of anabolic steroids". British Journal of Pharmacology. 154 (3): 502–21. doi:10.1038/bjp.2008.165. PMC . PMID 18500378.
- Becker KL (2001). Principles and Practice of Endocrinology and Metabolism. Lippincott Williams & Wilkins. p. 1183. ISBN 978-0-7817-1750-2.
- Nelson RF (2005). An introduction to behavioral endocrinology. Sunderland, Mass: Sinauer Associates. p. 143. ISBN 0-87893-617-3.
- 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.
- Mechoulam R, Brueggemeier RW, Denlinger DL (September 1984). "Estrogens in insects". Journal Cellular and Molecular Life Sciences. 40 (9): 942–44. doi:10.1007/BF01946450.