The use of intermittent human parathyroid hormone as a treatment for osteoporosis

Parathyroid hormone (PTH), given intermittently, is an anabolic agent. PTH has been demonstrated to increase bone mass and reduce vertebral and nonvertebral fractures, and has been approved for use in the US and Europe. PTH is a genetically engineered 34 amino acid protein with the designation teriparatide (recombinant DNA origin) or recombinant human PTH 1-34. A recombinant DNA preparation with all 84 amino acids of the native PTH molecule is in clinical trials. These PTH preparations are self-administered daily injections, and it is approved for women and men at high risk for fractures, including patients with prevalent fractures, low bone mass, and multiple risk factors. PTH is likely to be used most frequently in patients who fracture on therapy, but can be used in high-risk treatment-naïve patients. Previous treatment with alendronate appears to impair the anabolic response of PTH preparations. Patients who have Paget's disease, prior radiation therapy to the skeleton, as well as children and young adults with open epiphyses, are at higher risk for osteosarcoma and should not be given PTH. Patients with hypercalcemia and hyperparathyroidism also should not receive the drug.