Inappropriate secretion of antidiuretic hormone. An overview of the syndrome.

The syndrome of inappropriate secretion of antidiuretic hormone is characterized by production of less than maximally dilute urine in the presence of hypotonic plasma. It may be secondary to malignant disease, central nervous system disorders, or pulmonary disease, among other conditions, or it may be idiopathic. Manifestations are those of water intoxication, eg, confusion, fatigue, nausea, headache, and neurologic signs. The pathogenesis is not completely understood. Restriction of fluid intake to obtain a negative water balance is effective treatment.