Tomografic and Tensiometric Assessment on Femurs from Oophorectomized Rats Subjected to Hormone Replacement Therapy

OBJECTIVE To analyze the biomechanical and tomographic effects of hormone replacement therapy (HRT) on femurs from rats subjected to induced menopause. METHODS Forty-five adult Wistar rats were divided equally into three groups. The first and second groups consisted of rats subjected to oophorectomy, and the third was the control group, consisting of nonoophorectomized rates. After verifying that hormone failure had occurred (exfoliative cytological test), only the first group received HRT, over a two-month period. After this period, the femurs were disarticulated and subjected to biomechanical tests in a universal testing machine to evaluate their strength, and were subjected to tomographic evaluation to determine the bone mineral density. RESULTS The exfoliative cytological test showed that hormone failure was induced in all the oophorectomized animals. A significant difference (p = 0.030) in maximum strength measurements was observed between the groups (higher in the group with HRT). Greater bone fragility was observed in the oophorectomized animals without HRT than in those with HRT (p = 0.010), in relation to the control group (p = 0.0107). There was greater bone strength in the oophorectomized rats with HRT than in those without HRT, and these values were similar to those of the control group (p = 0.179). In the tomographic evaluation, no significant differences were found between the groups (p = 0.625). CONCLUSION A significant increase in bone strength was observed with the use of HRT. However, treatment with HRT did not show any significant change in bone mineral density.