A 58-year-old man with small cell lung carcinoma develops hyponatremia and inappropriately concentrated urine. The paraneoplastic syndrome is caused by ectopic secretion of which substance?
- A Antidiuretic hormone (ADH/AVP) ✓
- B Parathyroid hormone-related protein (PTHrP)
- C Adrenocorticotropic hormone (ACTH)
- D Erythropoietin
Correct answer: A. Antidiuretic hormone (ADH/AVP)
Explanation
Small cell lung carcinoma classically produces ectopic ADH causing SIADH, manifesting as hyponatremia with inappropriately concentrated urine. PTHrP causes hypercalcemia (squamous cell carcinoma). Ectopic ACTH from SCLC causes Cushing syndrome but not hyponatremia. Erythropoietin excess causes polycythemia.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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