Pituitary Disorders USMLE Step 1 Practice Question
A 19-year-old man with Marfan syndrome presents with acute-onset polyuria (10 L/day) and polydipsia. Vital signs: BP 118/76, HR 88, RR 16, temp 37°C, SpO2 98%. Labs show serum osmolality 310 mOsm/kg, serum glucose 95 mg/dL, and urine osmolality 150 mOsm/kg. No recent head trauma or infection history. Desmopressin administration increases urine osmolality to 600 mOsm/kg. Which diagnosis best explains these findings?
Answer choices
- ANephrogenic diabetes insipidus
- BPsychogenic polydipsia
- CPrimary hyperaldosteronism
- DUncontrolled diabetes mellitus
- ECentral diabetes insipidusCorrect answer
- FSyndrome of inappropriate antidiuretic hormone secretion (SIADH)
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