Pituitary Disorders USMLE Step 1 Practice Question
A 72-year-old man with hypertension and diabetes presents with progressive memory loss, confusion, and polyuria over 6 months. Serum sodium is 118 mEq/L (normal 135-145). Urine osmolality is 285 mOsm/kg (low), and serum osmolality is 237 mOsm/kg (low). TSH and cortisol are normal. Chest X-ray shows a small lung nodule. Which of the following is the most likely diagnosis?
Answer choices
- ACentral diabetes insipidus from pituitary mass
- BSyndrome of inappropriate antidiuretic hormone secretion from lung cancerCorrect answer
- CHypothyroidism
- DNephrotic syndrome
- EPrimary adrenal insufficiency
- FPsychogenic polydipsia with secondary hyponatremia
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