Introduction:Thyroid hormones are major regulators of bone metabolism and development. In hyperthyroidism, bone resorption is increased, however, the mechanism by which thyroid hormones increase osteoclasts activity and its growth remains unknown. This research was designed to study the effect of hypothyroidism on the bone repair.
Materials and Methods:Sixty mature female rats were randomly divided into two groups: control and methimalole treated groups. In the methimazole treated group, hypothyroidism was induced. Medial surfaces of right tibia of control and methimazole treated groups were drilled; all the rats were killed after three weeks by choloroform inhalation. Bone samples were obtained from defected regions and were subjected to histomorphometric study.
Results:The weight, length and periosteum thickness of tibia of the rats were significantly decreased in methimazole treated group as compared to the controls. There was significant decrease in osteoblast numbers (19.23.6 vs 34.13.1, p<0.001) and increase in the numbers of osteoclasts (5.9 1.6 vs 2.31.1, p<0.001) of the methimazole treated group compared to the control group.
Conclusion:This study demonstrates that hypothyroidism delays bone remodeling and repair in rat.
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