Diabetes Mellitus USMLE Step 1 Practice Question
A 66-year-old man with newly diagnosed small cell lung carcinoma presents with confusion and nausea. Vital signs show BP 128/76 mmHg, HR 88/min, RR 16/min, temperature 37.2°C, and SpO2 98% on room air. Physical examination reveals euvolemia with no edema or jugular venous distension. Serum sodium is 118 mEq/L with inappropriately elevated urine osmolality of 650 mOsm/kg and low serum osmolality of 265 mOsm/kg. Which of the following is the most likely diagnosis?
Answer choices
- ACentral diabetes insipidus
- BHyperaldosteronism
- CSyndrome of inappropriate ADH secretionCorrect answer
- DAdrenal crisis
- EPrimary polydipsia
- FNephrogenic diabetes insipidus
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.