ABSTRACT

We aimed to determine the effect of hormone replacement therapy on bone microarchitecture in ovariectomized rats.

In the Animal Ethics Committee approved-study, 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.

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.

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.

Keywords: Hormone replacement therapy, bone density, ovariectomy, menopause, bone microarchitecture