Vasopressin is a hormone produced by the pituitary gland. It assists with the regulation of the volume of water, glucose and salts in the body. Its primary action is suppressing kidney function and the production of urine, resulting in the body retaining water, salt and glucose. It also constricts blood vessels. Vasopressin also appears to have a role in brain function, but this is less well understood. It appears to regulate memory, sleep, blood pressure, body temperature and even pain relief.