Diabetes Mellitus USMLE Step 1 Practice Question
A 46,XY newborn presents with ambiguous external genitalia and cryptorchidism. At age 13, he develops progressive virilization with increased muscle mass, deepening voice, and facial hair. Vital signs: BP 118/76, HR 88, RR 16, temp 37.2°C, SpO2 98%. Laboratory studies show testosterone 650 ng/dL (normal for Tanner stage IV). Pelvic ultrasound reveals normal internal reproductive structures. He denies exogenous androgen exposure. Which of the following enzyme defects most likely explains his presentation?
Answer choices
- AMutation causing absent GnRH secretion
- BDeficient conversion of testosterone to dihydrotestosteroneCorrect answer
- CFailure of Müllerian inhibiting factor production
- DLoss of gonadal Sertoli cells in utero
- EInability to respond to estrogen
- FPartial androgen insensitivity syndrome (PAIS)
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