Syndrome of inappropriate antidiuretic hormone secretion: recognition and management.

Older persons are at greater risk for developing hyponatremia. Renal system changes which occur with aging cause alterations in the functional balance of fluid and electrolytes, and sodium regulation is not as effective. In one form of hyponatremia seen among the elderly, total body sodium content is normal, but water is retained because of increased antidiuretic hormone (ADH) secretion. This condition, called the syndrome of inappropriate antidiuretic hormone secretion (SIADH), has many causes including chronic illnesses and various medications. The physiology behind SIADH, its causes, diagnostics, and various treatment modalities are explored.