By: Dr. Sunir Kumar
Endocrinology is an essential part of the Internal Medicine Medical Clerkship and ABIM Board
exam. According to the ABIM exam blueprint, questions testing endocrinology topics comprise
~8% of the exam. Approximately ~5-10% of the NBME Clerkship exam is composed of
endocrinology questions.
Pearl #1: Don’t let thyroid nodules intimidate you.
This systematic approach will help you workup a thyroid nodule.
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K N O W M E D G E
Pearl # 2: Workup of hirsutism is not as difficult as it seems. Follow this approach and
you will be able to diagnose the cause of hirsutism.
Hirsutism is caused by either excessive testosterone or excessive 17-OH steroids
(DHEA-S) production.
Excessive Testosterone production is seen in ovarian cancer or polycystic ovarian
syndrome (PCOS)
o Ovarian cancer: worked up with trans-vaginal ultrasound to look for adnexal
mass. In addition, CA-125 marker is usually elevated in ovarian cancer.
o PCOS: Amenorrhea, insulin resistance, and LH:FSH ratio of greater than equal
to 3:1
Excessive DHEA-S production is seen in congenital adrenal hyperplasia (CAH),
Cushing’s disease, or adrenal carcinoma
CAH: Usual cause is 21 beta hydroxylase deficiency, which is used to convert 17-OH
progesterone to cortisol. Since this enzyme is deficient, 17-OH progesterone levels
remain elevated. Decreased cortisol levels will cause an elevated ACTH level through
a negative feedback mechanism. With increased ACTH, hyperpigmentation will also
occur.
Cushing’s disease: Defect in anterior pituitary causes increased ACTH, which
increases cortisol. MRI of pituitary is ordered to work up Cushing’s. If suspicion is high
for Cushing’s disease despite negative MRI of the pituitary, perform inferior petrosal
sinus sampling.
Adrenal carcinoma: Problem occurs in the adrenal gland, which will lead to elevated
cortisol levels. The elevated cortisol level will suppress the ACTH level. Since ACTH is
suppressed, hyperpigmentation will not occur.
Pearl # 3: Workup of an adrenal mass and management depends on the size and the