The effect of PTH(1–84) or strontium ranelate on bone formation markers in postmenopausal women with primary osteoporosis: results of a randomized, open-label clinical trial

Summary We explored the effects of PTH(1–84) compared with strontium ranelate on bone remodeling as measured by bone remodeling markers in postmenopausal women with osteoporosis. Biochemical markers of bone formation were significantly increased after treatment with PTH(1–84) but not strontium ranelate, indicating a different mechanism of action between these agents. Introduction PTH(1–84) and strontium ranelate (SR) are both known to reduce fracture risk in osteoporosis. Measuring changes in biochemical markers of bone turnover induced by these agents can help in characterizing the action of PTH(1–84) and SR on bone remodeling. Methods A 24-week, randomized, open-label, parallel group, phase IVtrial was conducted in 81 postmenopausal womenwith primary osteoporosis (≥50 years of age, lumbar spine, or total hip T-score ≤−2.5 SD) to assess the effect of SR as compared to PTH(1–84) on bone formation markers P1NP and BSAP. The bone resorption marker CTX was also measured. Subjects were randomly assigned to receive daily either 100 μg PTH(1–84) (n=41) (subcutaneous injection) or oral 2 g SR (n=40) for 24 weeks with daily supplements of 800 IU vitamin D3 and 1,000 mg calcium. Patient-reported outcomes were collected to investigate the effect of treatment on quality of life (QoL). Results Percentage changes frombaseline in P1NP and BSAP were significantly increased for PTH(1–84) by week 24 compared with SR (p<0.0001). Significant changes from baseline in P1NP and BSAP were noted for PTH(1–84) from week 4 onwards; no significant changes were noted for SR. A trend towards a positive impact on QoL was seen with PTH(1–84) treatment. Safety profiles concur with previous analyses. Conclusions PTH(1–84) had a more rapid and higher effect on bone formation markers compared to SR, indicating that SR has a different mode of action on bone remodeling than the bone building agent PTH(1–84) in postmenopausal women with osteoporosis.