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?

1. A)Central diabetes insipidus
2. B)Hyperaldosteronism
3. C)Syndrome of inappropriate ADH secretionGABARITO
4. D)Adrenal crisis
5. E)Primary polydipsia