Which cancer type is commonly associated with SIADH leading to hyponatremia?

Which cancer type is commonly associated with SIADH leading to hyponatremia?

• A. SMALL CELL LUNG CANCER
• B. RENAL CELL CARCINOMA
• C. SQUAMOUS CELL CARCINOMA
• D. HEPATOCELLULAR CARCINOMA

Answer: (C)

SIADH causes hyponatremia when tumor cells secrete ADH (vasopressin) inappropriately, leading to water retention, dilutional low sodium, low serum osmolality, and a euvolemic state with concentrated urine. The cancer most classically linked to this paraneoplastic ADH production is small cell lung cancer, which often behaves as a neuroendocrine tumor and can ectopically secrete ADH. That connection explains why hyponatremia occurs in these patients even if their total body sodium is normal. Other cancers have different paraneoplastic profiles. For example, squamous cell carcinoma of the lung commonly causes hypercalcemia via PTHrP, not SIADH; renal cell carcinoma and hepatocellular carcinoma have their own set of paraneoplastic effects but are not the classic sources of ectopic ADH. So the best answer reflects the well-known association between small cell lung cancer and SIADH-induced hyponatremia.

SIADH causes hyponatremia when tumor cells secrete ADH (vasopressin) inappropriately, leading to water retention, dilutional low sodium, low serum osmolality, and a euvolemic state with concentrated urine. The cancer most classically linked to this paraneoplastic ADH production is small cell lung cancer, which often behaves as a neuroendocrine tumor and can ectopically secrete ADH. That connection explains why hyponatremia occurs in these patients even if their total body sodium is normal.

Other cancers have different paraneoplastic profiles. For example, squamous cell carcinoma of the lung commonly causes hypercalcemia via PTHrP, not SIADH; renal cell carcinoma and hepatocellular carcinoma have their own set of paraneoplastic effects but are not the classic sources of ectopic ADH. So the best answer reflects the well-known association between small cell lung cancer and SIADH-induced hyponatremia.