Nephrogenic syndrome of inappropriate antidiuresis (NSIAD): a paradigm for activating mutations causing endocrine dysfunction.

Mutations of G protein-coupled receptors are responsible for a wide range of diseases. With respect to water balance and vasopressin signaling, more than 180 different inactivating mutations have been previously described in the V2 vasopressin receptor (V2R), resulting in nephrogenic diabetes insipidus. In contrast, we have recently described the first known patients with V2R activating mutations. Patients with these novel gain-of-function V2R mutations have a disorder which we have termed "nephrogenic syndrome of inappropriate antidiuresis" (NSIAD): a clinical presentation consistent with the syndrome of inappropriate antidiuretic hormone secretion but with undetectable levels of arginine vasopressin (antidiuretic hormone). The mechanisms by which these mutations constitutively activate the V2R are currently being investigated.