Pituitary Disorders USMLE Step 1 Practice Question
A 33-year-old woman presents with hypertension (BP 158/96), tachycardia (HR 102), and progressive central obesity with proximal muscle weakness. Laboratory studies show elevated 24-hour urinary free cortisol at 285 mcg/day (normal <50) and ACTH 68 pg/mL, consistent with ACTH-dependent Cushing syndrome. Pituitary MRI shows no discrete adenoma. She denies recent weight loss or cough. Which test best distinguishes pituitary from ectopic ACTH secretion?
Answer choices
- AWater deprivation testing
- BInferior petrosal sinus samplingCorrect answer
- CUrine metanephrine measurement
- DCosyntropin stimulation testing
- ESerum calcitonin measurement
- FHigh-dose dexamethasone suppression test (8 mg overnight)
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