AVP and heart failure: Even though the most important cause of hyponatremia in the elderly is syndrome of inappropriate secretion of anti-diuretic hormone (SIADH)2, hyponatremia is frequently multifactorial2–7 and entails several causative factors such as medication (thiazide and loop diuretics, proton pump inhibitors, non-steroidal anti-inflammatory agents), cardiac failure, chronic kidney disease, chronic liver disease, respiratory infections, volume overloaded and dehydration3,7 (Fig. 2-3).