SIADH is diagnosed when blood osmolality is <275 mOsm/kg, blood sodium is ≤130 mmol/l, urine osmolality is greater than blood osmolality, urine sodium is high (usually >40 to 60 mmol/l), and cardiac, hepatic, renal, thyroid or adrenal failure, effects of pituitary surgery, diuretic therapy, or medications known to stimulate AVP have been excluded (15). The gene discussed is AVP; the disease is inappropriate ADH syndrome.