A 55-year-old man with small-cell lung carcinoma presents with hyponatremia and concentrated urine. The paraneoplastic syndrome responsible involves ectopic secretion of which molecule?
- A Parathyroid hormone-related peptide (PTHrP)
- B ACTH
- C Antidiuretic hormone (ADH/AVP) ✓
- D Erythropoietin
Correct answer: C. Antidiuretic hormone (ADH/AVP)
Explanation
Small-cell lung carcinoma commonly causes SIADH via ectopic secretion of ADH/AVP, resulting in euvolemic hyponatremia with inappropriately concentrated urine. PTHrP causes hypercalcemia (typically squamous cell carcinoma), ACTH causes Cushing syndrome, and erythropoietin causes polycythemia (renal cell carcinoma).
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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