Head-to-head comparison of risedronate vs. teriparatide on bone turnover markers in women with postmenopausal osteoporosis: a randomised trial

Aims: We aimed to compare the effect of risedronate (RIS) and teriparatide (TPTD) (recombinant human parathyroid hormone 1-34) on bone turnover markers in women with postmenopausal osteoporosis. Methods: Forty-four Caucasian women (age 65.1 +/- 1.6 years) with postmenopausal osteoporosis were randomly assigned to receive either RIS 35 mg once weekly (n = 22) or TPTD 20 mu g once daily (n = 22) for 12 months. Serum N-terminal propeptide of type 1 collagen (P1NP), C-terminal telopeptide of type 1 collagen (CTx), total alkaline phosphatase (ALP) and intact parathyroid hormone (iPTH) were obtained from all women before, 3 and 6 months after treatment initiation. Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry before and 12 months after treatment initiation. Results: P1NP, CTx and total ALP levels decreased in RIS group (p < 0.001) and increased in TPTD group (p < 0.001) throughout the treatment. iPTH increased significantly in RIS group (p < 0.05) and decreased in TPTD group (p < 0.001). Finally, lumbar spine BMD increased significantly in both RIS (p = 0.003) and TPTD groups (p < 0.001) without significant differences between them. Conclusions: Our data suggest that both serum P1NP and CTx are reliable markers of RIS and TPTD action in women with postmenopausal osteoporosis. In a similar way, serum total ALP can be used as an alternative marker for monitoring both RIS and TPTD action, while iPTH can be used only for TPTD-treated women. The increase in P1NP and CTx after 3 months of treatment with RIS or TPTD can predict the increase in BMD after 12 months of treatment.