Various conditions have been associated with hyponatremia, including chronic heart failure, chronic kidney disease, liver cirrhosis, hypovolemia, and the syndrome of inappropriate antidiuresis (SIAD), in which antidiuretic hormone (ADH)/arginine vasopressin (AVP) secretion occurs in the absence of an osmotic or hemodynamic abnormality (1, 2). The gene discussed is AVP; the disease is congestive heart failure.