Osteoprotective effect of hormone therapy on bone microarchitecture before impaired bone mineral density in ovariectomized rats

Abstract

Objective: We aimed to determine the effect of hormone replacement therapy on bone microarchitecture in ovariectomized rats. Material and Methods: In the Animal Ethics Committee approvedstudy, the effect of treatment with 17 β-estradiol 50 μg/kg and medroxyprogesterone 2.5 mg/kg on bone architecture and bone mineral density in rats versus ovariectomized control rats over the course of 20 days were evaluated. Femoral and lumbar bone mineral density levels and morphometric measurements were performed. Results: There were no significant differences in the femoral and lumbar bone mineral density levels between the groups. In the intact control group, the trabecular structures were significantly superior to those in the other groups. Additionally, the osteoblast count was significantly higher while the osteoclast count was significantly lower than in all other groups. Two parameters reflecting trabecular bone microarchitecture, which include the trabecular count and the trabecular area, demonstrated significant improvement in the hormone replacement group when compared to the ovariectomized control group. In the hormone replacement groups, the osteoblast count was significantly higher while the osteoclast count was significantly lower than in the ovariectomized control group. Conclusion: We suggest that offering estrogen alone or in combination with progestogen can be a beneficial approach in preventing early postmenopausal bone loss regardless of bone mineral density. ©Copyright 2012 by the Turkish-German Gynecological Education and Research Foundation.