Comparison of zinc excretion and biochemical markers of bone remodelling in the assessment of the effects of alendronate and calcitonin on bone in postmenopausal osteoporosis

OBJECTIVES: The aim of this study was to determinate the clinical usefulness of urinary bone resorption markers, urinary zinc excretion, and other biochemical markers in postmenopausal women with osteoporosis. We also evaluated the effects of alendronate and calcitonin therapies on biochemical markers of bone remodeling and urinary zinc excretion over a 6-month period. SUBJECTS AND METHODS: The study design was a randomized placebo controlled study. The patients were randomly assigned to receive alendronate (10 mg/day; 45 patients) or calcitonin (200 IU/day; 45 patients) or placebo (45 patients) for 6 months. All patients received supplemental calcium (1000 mg/day). To assess bone resorption, we measured excretion of cross-linked N-telopeptides of Type I collagen (uNTx); urinary zinc concentrations and standard chemistry determinations were also measured; and osteocalcin (sOC) was measured as a marker of bone formation. All parameters were measured before therapy and again after 1, 3, and 6 months in all groups. RESULTS: A statistically significant decrease occurred in the levels of sOC, uZn, and uNTx after 3 and 6 months in patients receiving calcitonin therapy (P < 0.05). sOC, uZn, and uNTx levels in the calcitonin group were significantly lower after three and 6 months from both placebo and baseline values of calcitonin group. In the alendronate group, a statistically significant decrease was observed in the levels of uNTx and uZn after 1 month and in the sOC, uZn, and uNTx after 3 and 6 months from both placebo and baseline values of alendronate group (P < 0.05). uNTx, sOC, and uZn decreased about 44%, 36%, and 33%, respectively, in the calcitonin group and about 53%, 51%, and 38%, respectively, in the alendronate group below baseline values 6 months after initiating treatment. In the placebo group, there was no significant decrease in sOC, uZn, and uNTx during the course of the study. CONCLUSION: Our study suggests that in postmenopausal women with osteoporosis, both alendronate and calcitonin reduce the concentrations of uNTx, uZn, and sOC, the effect of the alendronate dose administered being significantly earlier and more pronounced. Measurement of uNTx, uZn, and sOC might be a useful biochemical method of observing the positive clinical effect following alendronate or calcitonin therapy in postmenopausal women.