Hypouricemia, inappropriate secretion of antidiuretic hormone, and small cell carcinoma of the lung.

The hospital records of 106 patients with small cell carcinoma of the lung were reviewed to determine if hypouricemia accompanied hyponatremia (less than 130 mmole/L) and if coexistent hypouricemia and hyponatremia were predictive of the presence of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Thirty-seven patients were excluded because of insufficient data or factors that would affect the uric acid level. Six of eight patients with SIADH had hypouricemia. The coexistence of hypouricemia and hyponatremia predicted SIADH reliably (6/6 patients), but hypouricemia alone had a low predictive value (46%) since it was seen in seven of 61 patients without SIADH.