MARKERS OF BONE REMODELING IN THE ELDERLY SUBJECT - EFFECTS OF VITAMIN-D INSUFFICIENCY AND ITS CORRECTION

The elderly subject is prone to both vitamin D insufficiency and calci um insufficiency due to a low calcium intake and calcium malabsorption , These two alterations may lead to secondary hyperparathyroidism, and thus to increased bone loss, We investigated 72 elderly subjects (16 men and 56 women) with vitamin D insufficiency and 25 healthy elderly women,vith normal vitamin D status, with respect to their indices of c alcium metabolism and of bone remodeling: serum total alkaline phospha tases (AP), bone AP (BAP), osteocalcin (BGP), tartrate-resistant acid phosphatase (TRAP), urine hydroxyproline (HYP), and the 3-OH-pyridiniu m derivatives pyridinoline (PYD) and deoxypyridinoline (DPD), which ar e new markers of bone resorption, We then studied the modifications of these markers in the patients with vitamin D insufficiency at 3 month s and 6 months after onset of a daily vitamin D and calcium supplement ation. When compared with elderly subjects with normal vitamin D statu s, patients with vitamin D insufficiency had increased intact parathyr oid hormone (iPTH) levels (60.1 +/- 10.2 vs 30.2 +/- 4.5, p < 0.001) a nd a high bone turnover as reflected by increased values of most serum and urine markers of bone remodeling. PYD and DPD levels were signifi cantly correlated,vith all indices of bone turnover, unlike HYP, which showed no correlation with bone formation markers (AP, BAP, and BGP), A daily supplement of 800 IU vitamin D-3 and 1 g of elemental calcium increased 25(OH)D levels and induced a dramatic decrease of iPTH leve ls; at 3 and 6 months, the mean iPTH level decreased by 50% (p < 0.000 1), reaching the mean value of healthy vitamin D sufficient elderly wo men, All markers of bone turnover, except TRAP, decreased significantl y at 3 and 6 months, The PYD/DPD ratio increased significantly at 3 an d 6 months, The decrease of bone markers was more marked in patients w ith more severe hyperparathyroidism, the greatest variations being obt ained with BAP (45%, p = 0.006) and DPD (43%, p = 0.036) levels, Most markers of bone remodeling are increased in elderly subjects with vita min D insufficiency and vary with its correction, However, BAP and DPD are the most sensitive indicators of increased bone turnover due to s econdary hyperparathyroidism.