[Syndrome of inappropriate ADH secretion (SIADH) in small-cell bronchus carcinoma].

Based upon the pertinent literature, the paraneoplastic syndrome of inappropriate antidiuretic hormone secretion (SIADH) in patients with small cell lung cancer is reviewed. Small cell lung cancer is a distinct tumor with neuroendocrine features capable of producing peptide hormones amongst which the antidiuretic hormone (ADH, arginine vasopressin) is one of the most frequent. Paraneoplastic SIADH may result from ectopic ADH production or from other tumor-related mechanisms leading to increased pituitary ADH secretion. The overt SIADH is characterized by neurological and psychiatric symptoms attributable to cerebral edema. Pooled published data suggest that the average incidence of clinically manifest SIADH in patients with newly diagnosed small cell lung cancer is 4%. Cases without clinical symptoms, detectable by laboratory tests only, are more frequent: hyponatremia, serum hypoosmolality and urine hyperosmolality are present in 14%, and an inappropriately elevated level of immunoreactive ADH in 38% of all patients respectively. Successful treatment of the underlying tumor, accompanied by a restricted fluid intake in severe cases, will usually result in prompt disappearance of the paraneoplastic SIADH. During and after the tumor treatment, plasma ADH may be useful as a tumor marker.