Intermittent administration of the circulating form of human parathyroid hormone (hPTH-1-37) prevents bone loss in ovariectomized rats.

The circulating hormonal form of human parathyroid hormone (hPTH-1-37) has been assessed in vitro as well as in vivo in the ovariectomized rat, a model for postmenopausal osteoporosis. In vitro, hPTH-1-37 induces a dose-dependent cAMP formation and increases vitality as well as alkaline phosphatase activity in UMR106 osteosarcoma cells. Differentiation and proliferation of osteoclasts in rat bone marrow-derived stem cell preparations are decreased. Daily hPTH-1-37 s.c. administration in ovariectomized rats for 60 days results in augmented formation of new bone, in amplified femural bone density, and in thickening of the calvaria.