Causes of female pseudohermaphrodism ?
**Core Concept**
Female pseudohermaphroditism, also known as female pseudohermaphroditism of adrenal origin, is a condition where an individual is genetically female (46, XX) but has internal reproductive organs with virilized external genitalia, often resembling those of a male. This condition is caused by an excess of androgens, typically due to an enzymatic defect in the adrenal glands.
**Why the Correct Answer is Right**
The most common cause of female pseudohermaphroditism is congenital adrenal hyperplasia (CAH), specifically the 21-hydroxylase deficiency. This enzyme deficiency leads to an accumulation of 17-hydroxyprogesterone (17-OHP) and subsequent overproduction of androgens, such as testosterone and dihydroepiandrosterone sulfate (DHEA-S). The excess androgens stimulate the growth of male genitalia, resulting in virilization of the external genitalia. The internal reproductive organs, however, remain female.
**Why Each Wrong Option is Incorrect**
**Option A:** Androgen insensitivity syndrome is a condition where an individual with a Y chromosome has a mutation in the androgen receptor gene, making them resistant to the effects of androgens. This results in a female phenotype despite the presence of testes and internal male genitalia.
**Option B:** Turner syndrome is a chromosomal abnormality characterized by the absence of one X chromosome (45, X). Individuals with Turner syndrome have a short stature, infertility, and gonadal dysgenesis, but are not typically virilized.
**Option C:** Swyer syndrome is a rare chromosomal disorder where an individual with a Y chromosome has a deletion or mutation of the SRY gene, leading to gonadal dysgenesis and a female phenotype. However, the individual may have a male karyotype and may be resistant to androgens.
**Clinical Pearl / High-Yield Fact**
In cases of suspected female pseudohermaphroditism, it's essential to perform a karyotype analysis to determine the genetic sex and to assess the levels of androgens and corticosteroids to diagnose congenital adrenal hyperplasia.
**Correct Answer: D. 21-hydroxylase deficiency**