AVP is released in response to sexual stimulation, uterine dilatation, stress, and dehydration. AVP acts principally on renal collecting tubules to increase water reabsorption. Diabetes insidious, characterized by the inability to appropriately concentrate urine, is mainly caused by decreased AVP production and renal response to AVP. Inappropriate AVP secretion happens in certain situations, particularly in elderly patients, as well as with central nervous system pathology, such as head injury, stroke, or cerebral tumor, or as a side effect of central acting drugs that interfere with hypothalamic regulation. AVP released directly into the brain may play an important role in social behavior, sexual motivation and pair bonding, as well as maternal responses to stress.