A 74-year-old male with a PMH significant for 50-pack-year c…
A 74-year-old male with a PMH significant for 50-pack-year cigarette use, presents for evaluation of worsening cough and one episode of hemoptysis. Other than nicotine stains present on his left index and middle fingers, his physical examination is unremarkable. CXR reveals a 4 cm. right lung mass. Serum sodium is 125 mEq/L (↓), BUN 12 mg/dL, creatinine 1.1mg/dL. Serum osmolality is 260 mOsm/L (↓), and urine sodium is 50 mEq/L (↑). The patient’s mucous membranes are moist, skin turgor is normal, and he does not demonstrate orthostatic change in BP. He currently takes no prescription or OTC medications or supplements. TSH level is normal. Based on this information, which of the following conditions is the most likely etiology of this patient’s hyponatremia?
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