Physiology of ADH secretion.

The past decade has witnessed continuing advances in our understanding of the physiology of vasopressin secretion. Despite some empirical and theoretical objections, linear regression analysis of the relationship between plasma vasopressin and plasma osmolality or sodium continues to provide a simple and useful way to describe the major functional properties of the osmoregulatory system. Recent studies employing this approach have shown that the sensitivity and "set" of the system can be altered independently, indicating that they have different bases and control mechanisms. All factors known to alter the sensitivity of the system also produce a reciprocal change in sensitivity to the antidiuretic action of vasopressin. This association suggests that the existence of some as yet unrecognized feedback signal that links the regulation of vasopressin secretion and action. The "set" of the osmoregulatory system appears subject to modification by a large number of physiologic and pathological variables, some of which may act directly or indirectly by endogenous opioids. Even the solute specificity of the osmoreceptor is subject to change since insulin deficiency significantly increases the stimulatory potency of hyperglycemia. A fuller understanding of the variables and mechanisms that alter the various properties of the osmoregulatory system will enhance management of clinical disorders of water balance and other diseases in which abnormalities in vasopressin secretion may play a role.