Hormonal aspects of fluid and sodium balance in the elderly.

Normal aging is accompanied by many changes in the hormonal systems involved in control of sodium and water balance. These alterations, together with age-associated changes in renal function, diminish the capacity of the elderly person to withstand the challenges of illness, drugs, and physiologic stresses. Thus, the aging individual is at increased risk of developing clinically significant alterations in sodium and water balance, which are commonly expressed as hyperatremia and hypoatremia. Awareness of the limitations of homeostatic ability allow the physician to anticipate the impact of illness and drugs on volume and electrolyte status and lead to prevention or to a rational approach to therapeutic intervention and management.