Ease Into Prep with a USMLE^® Step 2 CK Question of the Day

The correct answer is C. This patient has a pituitary mass, most likely a prolactinoma. An MRI will best evaluate the pituitary and nearby structures. Compression of the optic chiasm causes a bilateral temporal hemianopsia, and expansion of the sella is most likely the cause of the headaches. In men, hyperprolactinemia causes hypogonadotropic hypogonadism, which in this case has led to erectile dysfunction and gynecomastia. Men only rarely present with galactorrhea. In women, initial symptoms of a prolactinoma are typically amenorrhea and galactorrhea. Initial therapy is with a dopamine agonist to shrink the prolactinoma and relieve symptoms.

CT scan of the head (choice A) does not visualize the pituitary and the nearby optic chiasm as well as an MRI; therefore, it is not a good choice to investigate a suspected pituitary mass.

Serum insulin-like-growth factor-1 and ACTH + MRI of the head (choice B) can be useful for evaluating a suspected pituitary adenoma (somatotroph or corticotroph), but the most common pituitary adenoma is a prolactinoma and this patient's symptoms fit a lactotroph adenoma.

Serum TSH + MRI of the head (choice D) can be useful for evaluating a suspected pituitary thyrotroph adenoma, however, a lactotroph adenoma (prolactinoma) is much more likely.

Slit lamp examination of both eyes (choice E) is appropriate when a visual defect is suspected to be related to eye disease or abnormality. However, this patient's visual defect (bitemporal hemianopsia) is related to pressure on the optic chiasm not to any eye defect.