Effect of Parathyroid Hormone (1-34) on Fractures and Bone Mineral Density in Postmenopausal Women With Osteoporosis

Background Once-daily injections of parathyroid hormone or its amino-terminal fragments increase bone formation and bone mass without causing hypercalcemia, but their effects on fractures are unknown. Methods We randomly assigned 1637 postmenopausal women with prior vertebral fractures to receive 20 or 40 μg of parathyroid hormone (1-34) or placebo, administered subcutaneously by the women daily. We obtained vertebral radiographs at base line and at the end of the study (median duration of observation, 21 months) and performed serial measurements of bone mass by dual-energy x-ray absorptiometry. Results New vertebral fractures occurred in 14 percent of the women in the placebo group and in 5 percent and 4 percent, respectively, of the women in the 20-μg and 40-μg parathyroid hormone groups; the respective relative risks of fracture in the 20-μg and 40-μg groups, as compared with the placebo group, were 0.35 and 0.31 (95 percent confidence intervals, 0.22 to 0.55 and 0.19 to 0.50). New nonvertebral fragili...