A 32-year-old man with no previous medical history complains of frontal headache for 3 months, unintentional weight gain of 10 pounds, and cold intolerance. On examination, his blood pressure is 120/60 mm Hg and his pulse is 60 beats/minute. His thyroid is not enlarged. His thyroid-stimulating hormone (TSH) level is 464 mIU/L (normal range, 2.5-4.0 mIU/L), free thyroxine (T4) is 0.1 ng/dL (normal range, 0.7-1.9 ng/dlL), and free triiodothyronine (T3) is 75 pg/dL (normal range, 230-619 pg/dL).
Magnetic resonance imaging of the brain shows a sellar mass extending into the suprasellar cistern with mild compression of the optic chiasm (see Figure).
Figure. Reproduced from Franceschi R, Rozzanigo U, Failo R, Bellizzi M, Di Palma A. Pituitary hyperplasia secondary to acquired hypothyroidism: case report. Ital J Pediatr. 2011;37:15.
What is the likely cause of this patient’s sellar mass?
This question appears in Med-Challenger Internal Medicine Exam Review with CME
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