However, gains with PTH were modest, and side effects were common.
In a previous study, recombinant human parathyroid hormone (PTH; teriparatide, or Forteo) increased bone-mineral density (BMD) and reduced the incidence of new vertebral fractures among postmenopausal women with prior vertebral fractures (Journal Watch May 18 2001). In this new multinational trial, researchers examined the effect of PTH on the incidence of fracture in 2679 postmenopausal women with osteoporosis (mean T-score, –3.0 at lumbar spine), 81% of whom had no prior vertebral fracture. Women were randomized to receive 100 µg of PTH subcutaneously or placebo daily for 18 months; 1701 completed the trial. The drug maker funded the study and performed the statistical analyses, and the authors reported numerous possible financial conflicts of interest.
At 18 months, BMD in the PTH group increased at the lumbar spine and hip but decreased at the distal radius, compared with BMD in the placebo group. Significantly fewer women in the PTH group than in the placebo group had a new or worsened vertebral fracture (1.4% vs. 3.4%). When study dropouts were assumed to have the same fracture rate as placebo subjects, however, the difference was no longer significant. The study groups did not differ significantly in rates of nonvertebral fractures. Hypercalciuria, hypercalcemia, and nausea were significantly more common in the PTH group.
Comment: Although the results suggest PTH can prevent fractures, the effects were modest, side effects were common, and the outcome of the study was sensitive to assumptions about those who dropped out. The authors describe PTH as a therapeutic option for women with osteoporosis without fracture, but the subcutaneous administration and high cost (more than US$9000 yearly) make it unlikely to become a first-line treatment.
— Richard Saitz, MD, MPH, FACP, FASAM
Published in Journal Watch General Medicine March 22, 2007