Pituitary Disorders USMLE Step 1 Practice Question
A 38-year-old man presents with sudden-onset weakness, high fever (39.2°C), and altered consciousness. Vital signs show BP 108/70 mmHg, HR 102/min, RR 20/min, SpO2 98% on room air. Laboratory studies reveal hyponatremia (Na 118 mEq/L), serum osmolality 240 mOsm/kg, and urine osmolality 450 mOsm/kg. Head CT is unremarkable with no sellar mass. Chest X-ray shows infiltrates consistent with pneumonia. Which diagnosis best explains the inappropriate antidiuretic hormone secretion?
Answer choices
- APrimary hypothyroidism with impaired water excretion
- BPulmonary infection (pneumonia or tuberculosis)Correct answer
- CNephrotic syndrome with low plasma oncotic pressure
- DAdrenal insufficiency with cortisol replacement inadequacy
- EPsychogenic polydipsia from acute psychiatric illness
- FTraumatic brain injury with hypothalamic-pituitary disruption
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