NBME 19 Testosterone (NBME Answers)

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Retired NBME 19 Answers

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A newborn delivered at term to a ...
Testosterone 🔍 / 📺 / 🌳 / 📖
tags: repro

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submitted by ∗iceberglettuce(15)

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Complete Androgen Insensitivity Syndrome (CAIS):

Mutated androgen receptor (AR) in 46 XY (male fetus)
Y chromosome is present, so SRY gene will code for testis determining factor, and therefore Leydig and Sertoli cells are present.
Leydig cells are producing testosterone, but lack of functioning AR means no male external/internal structures. External genitalia "defaults" to female.
Sertoli cells produce Mullerian Inhibitory Hormone (MIH), which inhibits female internal structures. --> The absence of any internal genitalia means MIH is working, so choice D is wrong.

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unknown001 excellent physio recap +

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submitted by ∗mannan(18)

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Why would it not be answer C) Lutenizing hormone?

My thought process was this:

Leydig cells make testosterone (internal genitalia) that also gets converted to DHT (external genitalia)

Without the leydig cells working you don't have internal genitalia (patient in stem) and you dont have male external (patient in stem)

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solidshake Androgen insensitivity is the better answer because it is more specific for the findings given. A deficiency of LH secretion would point to a problem with Gonadotropic cells in the anterior pituitary which would present with problems with LH and FSH, but the sertoli cells are working here. If you say its because of LH insensitivity, i suppose this is plausible, but Androgen insensitivity is a well known condition that gives this presentation. +1

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