Antidiuretic hormone (ADH) molecular model. The two primary functions of ADH are to retain water in the body and to constrict blood vessels. ADH plays an important role in homeostasis, by the regulation of water, glucose, and salts in the blood. ADH is synthesized in the hypothalamus and stored in vesicles at the posterior pituitary. Atoms are represented as spheres and are color-coded; hydrogen (white), nitrogen (blue), carbon (black), oxygen (red) and sulphur (yellow).