Hyponatremia in a smoker most commonly reflects SIADH due to which tumor?

Hyponatremia in a smoker most commonly reflects SIADH due to which tumor?

• A. Squamous cell carcinoma
• B. Small cell carcinoma of the lung
• C. Adenocarcinoma
• D. Large cell carcinoma

Answer: (B)

Hyponatremia in this setting is most commonly due to SIADH from ectopic ADH production by a small cell lung cancer. Small cell carcinoma is a neuroendocrine tumor strongly linked to smoking and known for secreting hormones like ADH that cause water retention, diluting serum sodium and producing euvolemic hyponatremia. Other lung cancers (squamous, adenocarcinoma, large cell) have different paraneoplastic profiles—squamous cell often causes hypercalcemia via PTHrP, while adenocarcinoma and large cell are less typically associated with SIADH. Therefore, the scenario points to small cell carcinoma as the tumor most likely driving the hyponatremia.

Hyponatremia in this setting is most commonly due to SIADH from ectopic ADH production by a small cell lung cancer. Small cell carcinoma is a neuroendocrine tumor strongly linked to smoking and known for secreting hormones like ADH that cause water retention, diluting serum sodium and producing euvolemic hyponatremia. Other lung cancers (squamous, adenocarcinoma, large cell) have different paraneoplastic profiles—squamous cell often causes hypercalcemia via PTHrP, while adenocarcinoma and large cell are less typically associated with SIADH. Therefore, the scenario points to small cell carcinoma as the tumor most likely driving the hyponatremia.