Influence of recombinant human parathyroid hormone [rhPTH(1-34)] and estrogen on bone metabolism in ovariectomized rats

Objective To investigate the effects of rhPTH(1-34) and estrogen on bone metabolism in ovarictomized rats. Methods Forty five female Sprague-Dawley rats, four months old, were divided randomly into 5 groups: Sham-operated (Sham, 8), ovariectomized group (OVX, 9), ovariectomized and treated with estrogen (OVX+E, 10), ovariectomized and treated with parathyroid hormone (OVX+PTH, 9), ovariectomized and treated with estrogen and parathyroid hormone (OVX+E+PTH, 9). After three and half months, all animals were sacrificed. Static and dynamic parameters of right tibias, biomechanics parameters and some related bone metabolic markers are evaluated. Results Both E_2 and PTH treatment increase bone mass. The parameters of formation and resorption decreased in E group while the bone formation rate increased in OVX+PTH group in comparison to OVX. Parameters of absorption of OVX+PTH group was higher than that of Sham group, but lower than OVX group. Parameters of bone mass and formation in rats treated with PTH+E revealed a significant increase not only compared with the OVX+E group, but also compared with OVX+PTH group. The parameters of bone turnover in OVX+PTH+E group between the PTH and E_2 individual treatment. The biomechanics parameters in E, PTH and E+PTH treated rats were slightly elevated compared to OVX rats, especially the OVX+E+PTH group. Conclusions Estrogen and PTH increases bone mass and biomechanics parameters effectively in ovariectomized rats. The combination treatment of PTH and Estrogen resulted in a marked overall increase of cancellous bone and exhibited synergistic effects.