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NBME 18 Answers

nbme18/Block 2/Question#30 (18.3 difficulty score)
35 yo man, 4 weeks of severe midline back pain
ACTH🔍
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nnp  even prolactin causes reduced bone density +1  
jmangels  I was thinking the same thing about the prolactin, but the weight gain made me lean toward ACTH +  



Even though TSH producing adenomas mat also produce compression fractures they are far less common than ACTH producing tumors

spow  But if you had a TSH secreting adenoma, you would NOT have had weight gain (hyperthyroid = weight loss) +4  



 +0  upvote downvote
submitted by usmile1(75),

This pt clearly has a pituitary adenoma given the bitemporal hemianopsia. The most common functioning pituitary adenoma is a Prolactinoma, so you want to be very sure before not picking prolactin. However, according to FA, "Prolactinoma classically presents as galactorrhea, amenorrhea, and decreased bone density due to suppression of estrogen in women and as decreased  libido, infertility in MEN. No decrease in bone density in men. Thus, given the compression fractures in a male and weight gain, the answer has to be ACTH.




 +0  upvote downvote
submitted by hello(251),

Pt has a pituitary adenoma + weight gain + compression fractures.

Prolactinoma = most common pituitary adenoma. However this male patient lacks appropriate symtoms, e.g. decreased libido + infertility. Eliminate choice A.

**Eliminate choice C because this patient does not have signs on increased testosterone.

Eliminate choice E because this pt has weight gain, whereas a TSH-secreting adenoma would cause weight loss.

You are now left with choices A and B.

ACTH-secreting tumors are associated with weight gain + bone fractures. This is because increased ACTH causes hypercortisolism, which has an AE of osteoporosis. This is choice A.

hello  Also, choice B is incorrect because a GH-secreting tumor would result acromegaly (enlarged hands, feet, head), which this pt does not have. +