Antidiuretic hormone excess.

Known physiologic mechanisms explain the elevated blood ADH levels observed in most patients with the syndrome of inappropriate ADH. Therefore the word "inappropriate" is a misnomer. It implies that the mechanisms that regulate ADH release are not functioning normally--which is not true. The term misleads the physician who, ideally, should determine why a patient has an excessive blood ADH level and initiate appropriate treatment. Patients with ectopic production of ADH and hyponatremia should be so labeled: "Hyponatremia due to ectopic ADH production." The term SIADH, if used at all, should be reserved for the rare patient with CNS injury or disease that causes increased ADH release and in which the hypothalamic center does not respond normally to afferent peripheral stimuli.