[Influence of aging on vitamin D metabolism].

Aging is associated both with calcium deficiency, due to low dietary intake and decreased intestinal absorption, and with vitamin D deficiency, secondary to depletion of body stores resulting from inadequate exposure to sunlight. Hepatic hydroxylation of vitamin D remains normal in elderly individuals. Recent data suggest that renal hydroxylation of vitamin D, previously believed to decrease with advancing age, also remains virtually normal even when creatinine clearance declines, as is very often the case in elderly patients. The combined deficiency in calcium and vitamin D stimulates the secretion of parathyroid hormone which tends to normalize serum calcium levels and causes the bone disorders of senile osteoporosis.