Effect of 1,25(OH)(2) vitamin D-3 on circulating insulin-like growth factor-I and beta(2) microglobulin in patients with osteoporosis

To test the hypothesis that growth factors mediate the stimulatory effect of 1,25(OH)(2) vitamin D-3 [1,25(OH)(2)D-3] on bone remodeling in osteoporosis, the authors studied the effect of the secosteroid administration in two doses (1 mu g/day and 2 mu g/day) for 14 days on circulating insulin-like growth factor-I (IGF-I), beta(2) microglobulin, and osteocalcin in 18 osteoporotic women. The biological effectiveness of the treatment was controlled by a decline of serum intact parathyroid hormone. Compared with the values before treatment, 1,25(OH)(2)D-3 increased means of plasma IGF-I, beta(2) microglobulin, and serum osteocalcin significantly; however, the effects were only apparent after the higher dose of the drug (169 +/- 26 versus 134 +/- 28 ng/ml, P < 0.01; 2.08 +/- 0.1 versus 1.92 +/- 0.1 mu g/ml, P < 0.05; and 8.5 +/- 1.3 versus 5.3 +/- 1.1 ng/ml, P < 0.01, respectively). The authors conclude that exogenous 1,25(OH)(2)D-3, promotes the production of IGF-I and beta(2) microglobulin in osteoporotic patients in parallel to the marker of osteoblastic function, osteocalcin, which supports the tested hypothesis.