Physiology of Vasopressin Secretion

Vasopressin (AVP) represents the key endocrine regulator of water balance. It is synthesized in the hypothalamic supraoptic and paraventricular nuclei and then transported to the neurohypophysis, where it is released in the bloodstream. Alterations in plasma osmolality represent the main input affecting AVP secretion, yet many other physiological and pathophysiological conditions can intervene in modulating its levels, as hypovolemia and hypotension. AVP primarily controls plasma osmolality and fluid volume by inducing synthesis and insertion of essential water transport proteins in the kidneys, thus reabsorbing water into blood circulation and reducing diuresis. Moreover, AVP exerts vascular and platelet control and intervenes in several metabolic pathways, including glycogenolysis and gluconeogenesis. Furthermore, AVP stimulates the release of adrenocorticotropic hormone (ACTH). AVP exerts its multiple effects by binding to its receptors, classified in different subtypes depending on tissue expression, function, and second messengers. Disorders in AVP synthesis or action can lead to clinical syndromes characterized by water and electrolyte imbalance.