SIADH is characterized by reduced water excretion, resulting in hyponatremia, euvolemia, plasma hypoosmolality, and inappropriately concentrated urine, with increased urinary osmolality, increased natriuresis, and increased AVP circulating levels, in cases of normal kidney, heart, liver, adrenal, and thyroid function [40, 41]. The gene discussed is AVP; the disease is inappropriate ADH syndrome.