Inappropriate antidiuretic hormone secretion in oat-cell carcinoma of bronchus. Aggravation of hyponatraemia by intravenous cyclophosphamide.

Hyponatraemia associated with bronchial carcinoma was first described by Winkler and Crankshaw (1938). Schwartz, Bennett, Curelop, and Bartter (1957) suggested that the hyponatraemia was due to 'inappropriate' secretion of antidiuretic hormone (ADH) by the tumour itself. Confirmation of this was provided by Lee, Jones, and Barraclough (1964) when a substance with an action resembling that of ADH was isolated from tumour tissue. The syndrome appears to be associated exclusively with the oat-cell type of carcinoma, but Azzopardi, Freeman, and Poole (1970) described a case which may have been due to a squamous carcinoma. Because oat-cell carcinoma tends to disseminate early, by either blood or lymphatic spread, most patients with inappropriate secretion of ADH are first seen at a stage when surgical resection of the tumour or curative treatment with deep x rays is impossible. Linton and Hutton (1965) reported a case in which treatment with nitrogen mustard was followed by reversal of the electrolyte disturbances and suggested that cytotoxic drug therapy might be a useful form of palliative treatment in this condition. In the case reported here, hyponatraemia was intensified by treatment with cyclophosphamide given in intermittent high doses.