Anabolic and catabolic bone effects of human parathyroid hormone (1-34) are predicted by duration of hormone exposure.

Parathyroid hormone (PTH)(1-34), given once daily, increases bone mass in a variety of animal models and humans with osteoporosis. However, continuous PTH infusion has been shown to cause bone loss. To determine the pharmacokinetic profile of PTH(1-34) associated with anabolic and catabolic bone responses, PTH(1-34) pharmacokinetic and serum biochemical profiles were evaluated in young male rats using dosing regimens that resulted in either gain or loss of bone mass.