Effects of hypothyroidism on bone repair in adult rats

Thyroid hormones are major regulators of bone development and remodeling. In this experimental study, we evaluated the relationship between hypothyroidism and repair of tibial bone in female rats. 60 adult female rats aged 4-6 weeks were randomly assigned into two groups, the first group were rendered hypothyroid by adminstration of methimazole in the drinking water, second group were normal controls. The parameters studied in each group were body weight, number of osteoblasts and osteoclasts, length and diameter of tibia and thickness of periosteum. Our results show that, the number of osteoblasts were decreased in hypothyroid rats, while in this group of rats the number of osteoclasts were increased. The thickness of periosteum and body weight in hypothyroid rats decreased. Longitodinal growth of tibia in control rats was increased as compared with hypothyroid rats. The findings suggest that hypothyroidization delays the process of bone repair.