Anabolic effects of parathyroid hormone on bone.

Parathyroid hormone (PTH) is classically considered to be a bone catabolic agent; however, when delivered intermittently at low doses, PTH potently stimulates cortical and/or trabecular bone growth in animal and clinical studies. Understanding the mechanism of PTH's osteopenic actions has led to the making of small, novel, and possibly noninjectable PTH analogues that can build biomechanically normal bone in osteopenic rats and are promising candidates for treating osteoporosis in humans.