Master the board step 3

Master the Boards: USMLE Step 3
Cholesterol
ACTH
Pregnenolone
17α-OH-pregnenolone
DHA
Progesterone
21-hydroxylase
17α-OH-progesterone
2
4-adione
Deoxycorticosterone
11-Deoxycortisol
Corticosterone
Cortisol
11β-hydroxylase
21-deoxycortisol
18-OH-corticosterone
Aldosterone
Steroidogenesis in 21-Hydroxylase Deficiency
In 21-hydroxylase deficiency, the patient cannot convert progesterone to deoxycorticosterone,
leading to a deficiency in corticosterone. The patient also cannot
convert 17 alpha-hydroxyprogesterone into 11-deoxycortisol, leading to a low
cortisol level that stimulates the ACTH to produce more. The result is a buildup
of progesterone and androgens, causing masculinization of the genitalia.
CAH presents in an infant with the following signs:
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Vomiting
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Dehydration
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Hyponatremia (salt losing)
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Hypoglycemia
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Hyperkalemia
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Females have ambiguous genitalia at birth.
Diagnostic Testing
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Best initial test: Increased 17-OH progesterone (Also find low cortisol levels,
increased renin, and decreased aldosterone.)
· · Definitive diagnostic test: 17-OH progesterone before and after an intravenous
bolus of ACTH.
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