5-alpha-reductase deficiency history and symptoms

The condition affects only males (i.e. those with a Y chromosome) because DHT has no known role in female development. 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. Consequently they are often raised as girls and develop a female gender identity. Individuals with obvious undervirilisation at birth, eg. hypospadia, micropenis or complete ambiguous genitalia are currently raised as boys.

In individuals with feminised or ambiguous genitalia, there is a tendency towards an enlarged clitoris, or microphallus, and the urethra may attach to the phallus. This structure may be capable of erections as well as ejaculations. Individuals with 5-ARD are generally capable of producing viable sperm, however artificial insemination techniques or in-vitro fertilisation are necessary.

At puberty, individuals often have primary amenorrhoea, and may experience virilisation. This may include descending of the testes, hirsuitism and deepening of the voice. 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 by either 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.

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