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 μg 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.