antidiuretic hormone (ănˌtēdĪyōrĕtˈĭk) [key], polypeptide hormone secreted by the posterior pituitary gland. Its principal action is to regulate the amount of water excreted by the kidneys. Antidiuretic hormone (ADH), known also as vasopressin, causes the kidneys to resorb water directly from the renal tubules, thus concentrating the salts and waste products in the liquid, which will eventually become urine. ADH secretion by the pituitary is regulated by neural connections from the hypothalamus, which is believed to monitor either the volume of blood passing through it or the concentration of water in the blood. Dehydration or body stress will raise ADH secretion and water will be retained. Alcohol inhibits ADH secretion. Failure of the pituitary to produce ADH results in diabetes insipidus. In pharmacological doses ADH acts as a vasoconstrictor. The structure and chemical synthesis of ADH was announced (1953) by Nobel laureate Vincent Du Vigneaud and others.