Biological effects of supplementation with vitamin D and calcium in postmenopausal women with low bone mass receiving alendronate

Objective: To investigate the biological effects of supplementation with vitamin D and calcium versus supplementation with calcium alone during the first 3 months of treatment with alendronate in postmenopausal women with a risk of fracture and with vitamin D and calcium insufficiency. Design: Randomised, double-blind trial. Subjects: The study randomised 48 osteopenic and osteoporotic women, mean age 70 6 years and at least 5 years after menopause, who were living at home. Inclusion criteria were low bone mineral density (more than 1 SD below reference value), serum 25-hydroxy-vitamin D-3 (25-OHD), calcifediol) <12 mug/L and dietary calcium intake <1 g/day. Methods: The women were divided into two groups. The first group (n = 23) received alendronate 10mg once daily supplemented with calcium and vitamin D (elemental calcium 500mg, colecalciferol [vitamin D-3] 4001U) twice daily for 3 months. The second group (n = 25) received the same dosage of alendronate and a placebo with calcium alone (500 mg/day). Blood, serum and urine samples were obtained for measurement of calcaemia, intact parathyroid hormone (i-PTH) and markers of bone remodelling such as the N- and C-terminal telopeptides of type I collagen (NTX and CTX). Results: Supplementation with calcium and vitamin D caused a rapid increase of 25-OHD levels without changes in calcaemia or i-PTH levels. In the two groups, serum and urinary CTX and urinary NTX were dramatically and significantly decreased after as little as 15 days of treatment and remained decreased throughout the course of treatment. No significant difference between the two treatments was observed, but the combined treatment resulted in a more pronounced effect as assessed by the Hodge-Lehman test, particularly after I month for the bone resorption markers serum CTX (p = 0.064) and urinary NTX (p = 0.076). Conclusion: Supplementation with calcium and vitamin D could be appropriate in elderly women with calcium and vitamin D insufficiencies being treated with alendronate in order to achieve rapid reduction of bone remodelling.