Recombinant parathyroid hormone in the management of osteoporosis

Intermittent administration of PTH and its peptides by subcutaneous injection results in anabolic effects in cancellous and cortical bone. Recombinant human PTH 1-34 (teriparatide) reduces vertebral and nonvertebral fracture riskin postmenopausal women with osteoporosis and also has beneficial effects on BMD in men with osteoporosis, similar to those observed in postmenopausal women. The safety and tolerability profile of teriparatide in clinical trials is good although long-term administration of high doses of teriparatide in rats was associated with the development of osteosarcoma, existing evidence in humans is reassuring in this respect. There is evidence that antiresorptive therapy, if given concomitantly with PTH, blunts its anabolic action and prior antiresorptive therapy may also have a similar effect. However, antiresorptive therapy after PTH administration may maintain or even increase the benefits achieved for BMD. Finally, after discontinuation of PTH, BMD appears to decrease within the first 18 months off treatment and, in one study, biochemical markers had returned to baseline values by 6 months after treatment withdrawal. However, in all of these areas further studies are required. Although teriparatide compares favorably with other interventions in terms of antifracture efficacy at vertebral and nonvertebral sites, it is more expensive and its use in clinical practice is likely to be restricted mainly to postmenopausal women with severe osteoporosis who are unable to tolerate or respond to other treatments. In clinical practice, this constitutes an important, albeit relatively small, population. © 2005 Springer Science+Business Media, Inc.