The parathyroid hormones: bone-forming agents for treatment of osteoporosis.

This is a 3-part article. Part 1 is an overview of bone formation and resorption and the consequences of estrogen loss on bone. Part 2 comprehensively reviews the most current data on the ability of a family of potent osteoblast-stimulating bone-builders, the native 84-amino-acid parathyroid hormone (PTH), and certain of its 31- to 38- amino-acid fragments to stimulate the growth of animal and human bones. These PTHs are currently in, or about to enter, clinical trial as treatment for postmenopausal osteoporosis. Part 3 provides a detailed consideration of how these PTHs might stimulate bone growth via PTH receptor signaling.