A Case of Sexual Ambiguity- Repeated USMLE Question

Q- A 12-year-old female is evaluated for enlarged phallus at puberty. Examination reveals no breast development, a blind vaginal pouch and no uterus. Laboratory tests show normal levels of testosterone and estrogen and very low levels of dihydrotestosterone (DHT). What is the most likely diagnosis?

A- Female pseudohermaphrodite

B- Male pseudohermaphrodite

C- True hermaphrodite

D- Turner’s syndrome

B- Male pseudohermaphrodite- This condition is due to deficiency of the enzyme responsible for conversion of testosterone into dihydrotestosterone which is essential in the fetus for development of the prostate and external genitalia. True hermaphrodite would reveal the presence of both male and female genital organs.

Q- Which of the following is the enzyme responsible for conversion of testosterone into dihydrotestosterone (DHT)?

A- 17 alpha-hydroxylase

B- 3-beta-hydroxylase

C- 5-alpha-reductase

D- Aromatase

C- 5-alpha-reductase- Is the enzyme responsible for the conversion of testosterone into dihydrotestosterone. Other enzymes assists in synthesis of testosterone in different stages.

Q- Which one of the following medications inhibits the conversion of testosterone into dihydrotestosterone?

A- Aldosterone

B- Finasteride

C- Leuprolide

D- Spironolactone

B- Finasteride- It is the only one on the list that is 5α-Reductase inhibitor, the enzyme responsible for converting testosterone into dihydrotestosterone. It is used in cases of senile enlarged prostate.

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