SIADH, AKA [[Schwartz-Bartter syndrome]], was first described with [[bronchogenic cancer]] which is one cause of [[SIAD]]. SIADH is the release of [[antidiuretic hormone]] ([[ADH]]), AKA [[arginine vasopressin]] (AVP), in the absence of physiologic (osmotic) stimuli. Result: elevated [[urine osmolality]], and expansion of the [[extracellular fluid volume]] leading to dilutional [[hyponatremia]] which can produce fluid overload ([[hypervolemia]]), but SIADH may also occur with [[euvolemia]]. For unclear reasons, [[edema]] does not occur.
The hyponatremia of SIADH must be differentiated from that due to [[cerebral salt wasting]] (CSW) due to differences in [[hyponatremia treatment]] recommendations.