Neuroendocrine mechanisms and cardiovascular homeostasis in the elderly.

Reduced homeostatic capacity is typical of the aging process and is particularly apparent in changes in the neuroendocrine control of cardiovascular homeostasis. Not only is there reduced beta-adrenoceptor responsiveness, but reduced baroreflex function also occurs with age. These result in increased sensitivity to the therapeutic and postural hypotensive effects of diuretics and vasodilators. Increased total body sodium and reduced activity of the renin-angiotensin-aldosterone system may also contribute to the therapeutic effect of diuretics and salt restriction in elderly hypertensives. In addition, atrial natriuretic peptide levels are increased in the elderly and may in part be responsible for the suppressed renin and aldosterone levels found in older groups. Vasopressin secretion and thirst are also disturbed with age, and may act in concert with declining renal function to predispose the elderly to disturbances of water balance. An understanding of these neuroendocrine changes with age is important to maximize therapeutic benefit and to minimize adverse effects in the treatment of hypertension in the elderly.