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5α-Reductase 2 deficiency

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5α-Reductase 2 deficiency
SpecialtyMedical genetics Edit this on Wikidata

5-Alpha-reductase deficiency (5-ARD) is an autosomal recessive intersex condition caused by a mutation of the 5-alpha reductase type 2 gene.[1]

Normal function

5-Alpha-reductase is an enzyme that converts testosterone to dihydrotestosterone (DHT) in peripheral tissues. 5-Alpha-reductase deficiency-2 is biochemically characterized by low to low-normal levels of testosterone and decreased levels of 5α-DHT, creating a higher testosterone/DHT ratio.

Biochemical effects of 5-alpha-reductase deficiency-2 in testosterone biosynthesis. Levels of testosterone are elevated, while levels of DHT are significantly decreased, leading to male undervirilization.

DHT is a potent androgen, necessary for the development of male external genitalia in utero.

Signs

The condition affects only genetic males (that is, those with a Y chromosome) because DHT has no known role in female development.[2]

Individuals with 5-ARD can have normal male external genitalia, ambiguous genitalia, or normal female genitalia. They are born with male gonads, including testicles and Wolffian structures, but usually appear to have female primary sex characteristics. As a consequence, they are often raised as girls, but usually have a male gender identity.[3][4]

In general, individuals with 5-ARD are capable of producing viable sperm. In individuals with feminized or ambiguous genitalia, there is a tendency towards a macroclitoris or microphallus, and the urethra may attach to the phallus. This structure may be capable of ejaculations as well as erections, but may be insufficient for intercourse.

At puberty, individuals often have primary amenorrhoea, and may experience virilization. This may include descending of the testes, hirsutism (facial/body hair considered normal in males - not to be confused with hypertrichosis), deepening of the voice, and enlargement of the clitoris. In adulthood, individuals do not experience male-pattern baldness.[1] As DHT is a far more potent androgen than testosterone alone, virilisation in those lacking DHT may be absent or reduced compared to males with functional 5-alpha reductase. It is hypothesized that rising testosterone levels at the start of puberty (around age twelve) are able to generate sufficient levels of DHT either by the action of 5-alpha-reductase type 1 (active in the adult liver, non-genital skin and some brain areas) or through the expression of low levels of 5-alpha-reductase type 2 in the testes.

Complications

With 5-ARD, there is a risk of gender identity disorder as well as infertility, due to underdevelopment of seminal vesicles and prostate.

Infertility

There is an increased risk of cryptorchidism in 5-ARD, causing infertility, but also a higher risk of testicular cancer. Fertility is further compromised by the underdevelopment of seminal vesicles and prostate.

On the other hand, fertility depending on the female characteristics is impossible; although the external genitalia appear female, the "pseudovagina" consists only of the lower two-thirds of a normal vagina, creating a blind-ending vaginal pouch. Due to the normal action of Müllerian inhibiting factor produced by the testis in utero, individuals with 5-ARD lack a uterus and Fallopian tubes. Thus, individuals with 5-ARD are not able to carry a pregnancy, and, since they have testes and not ovaries, they are unable to create ova, which precludes such infertility treatments as surrogate motherhood.

Prevalence

The number of people with this condition varies relative to geographic location, depending on how much of a given population is interrelated. In 1974, Jullianne Imperato-McGinley has estimated an incidence of 1:90 males in the Dominican Republic. This can be seen in that certain regions have evolved terminology for the condition.

Local names

The term Guevedoche or Guevedoces is Spanish slang for the condition. It originated in the Dominican Republic, where more than three dozen cases have occurred in the small village of Salinas, all descended from a single individual named Altagracia Carrasco. It stands for the colloquial expression huevo a los doce, which translates literally as "eggs at twelve" ("eggs" being a common slang term for "testicles"). It is also known locally as Machihembras (literally "malefemale").

A similar cluster of cases among the Simbari of the Eastern Highlands of Papua New Guinea has the local name Kwolu-aatmwol ("female thing transforming into male thing").

  • Jeffrey Eugenides won a Pulitzer Prize for his 2002 novel Middlesex, which explores this deficiency.
  • Documentaries on the condition include "Guevote: The Way I Feel Is How I Am" ("Guevote: So wie ich mich fuehle, bin ich"), 1996, by filmmaker Rolando Sánchez,[5] and "The Fight to be Male", 1979, British Broadcasting Company.

See also

References

  1. ^ a b "5-alpha reductase deficiency". GPnotebook.
  2. ^ eMedicine article on 5-ARD
  3. ^ "Gender identity of children and young adults with 5alpha-reductase deficiency". J Pediatr Endocrinol Metab. 21 (2 ed.): 173–9. February 2008. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ "Androgens and the Evolution of Male-Gender Identity among Male Pseudohermaphrodites with 5α-Reductase Deficiency". New England Journal of Medicine. 300: 1233–1237. May 31, 1979. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  5. ^ Guevote - The Way I Feel Is How I Am (Guevote - So wie ich mich fühle, bin ich)

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