RESUMEN
Several studies have shown that vitamin D (Vit. D) deficiency in elderly people enhances bone mass loss. Most of these studies have been carried out in areas of low solar irradiation. In order to establish Vit. D circulating levels in elderly people in our community (34 degrees S) and their relationship with bone metabolism, 34 men and 33 women were studied at the end of the summer. These subjects, all residents of nursing homes, had a mean age of 81.9 + 8.1 years (range 69-99). Calcemia, parathyroid hormone (PTH and 25-hydroxyvitamin D (25(HO)D) were measured in serum and bone markers in serum and urine. Bone densitometry (BMD) of cortical and trabecular bone in the forearm (distal third of the radius (R33%) and ultradistal (RUD), respectively) were performed using X-ray absorptiometry. We found: 1) Low serum 25(HO)D (14.4 + 1.7 ng/ml) at summer's end. 40.5% showed levels < 10 ng/ml. 2) Secondary hyperparathyroidism (PTH: 169.4 + 30.9 pg/ml), 3) Hypocalcemia was observed in 34.5% of elderly people, 4) increased bone turnover in the subpopulation with hypovitaminosis D. 5) The serum levels of 25(HO)D correlated with BMD R33% (r = 0.55, n = 54, P < 0.001), with BMD RUD (r = 0.50, n = 54, P < 0.001) and with PTH (r = -0.44, n = 42, P < 0.01). A deficiency of Vit.D was found in our population of elderly people, probably due to diminished epidermic production of its precursors and/or to scant exposure to sunlight in the elderly. The decrease is associated to age. The positive correlation of 25(HO)D with bone mass (cortical and trabecular bone) underscores its importance for the preservation of bone mass. Hyperparathyroidism, triggered by Vit. D deficit, enhances bone loss.