Small bone-building fragments of parathyroid hormone: new therapeutic agents for osteoporosis.

The brittle, fracture-prone bones of an osteoporotic postmenopausal woman are the products of an excessive uncompensated resorption of trabecular bone by osteoclasts. Osteoporosis is currently treated with the osteoclast suppressors calcitonin, bisphosphonates, or oestrogen, which stop further bone resorption without stimulating new bone growth. Here, James Whitfield and Paul Morley review the growing evidence that small adenylate cyclase-stimulating fragments of the parathyroid hormone are promising therapeutic agents for osteoporosis that potently stimulate osteoblasts to make mechanically strong or supranormally strong bone.