Pituitary Disorders USMLE Step 1 Practice Question
A 32-year-old woman presents with a 3-month history of amenorrhea, galactorrhea, and weight gain. Five months ago, she was started on clozapine 300 mg daily for schizophrenia. She has a known history of hypothyroidism but reports non-adherence with levothyroxine for the past 6 months. Vital signs are stable. Visual fields are intact to confrontation. Laboratory studies show: TSH 18.2 μU/mL (normal 0.4–4.0), free T4 0.6 ng/dL (normal 0.8–1.8), prolactin 92 ng/mL (normal <25), and LH/FSH are at the lower limit of normal. Pituitary MRI shows normal gland size with no focal lesion. Which of the following best explains her galactorrhea and menstrual disturbance?
Answer choices
- AClozapine-induced dopamine antagonism causing elevated prolactin
- BPrimary prolactinoma with incidental hypothyroidism
- CUntreated hypothyroidism causing TRH-mediated prolactin elevation and secondary hypogonadismCorrect answer
- DEctopic prolactin-secreting tumor in the adrenal gland
- EThyrotroph pituitary adenoma with co-secretion of prolactin
- FIdiopathic central hypogonadism with medication-related hyperprolactinemia
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.