Development of a Rat Model for Evaluating Thyroid-Stimulating Hormone Suppression after Total Thyroidectomy

Background: We developed an animal model for evaluating thyroid-stimulating hormone (TSH) suppression therapy after total thyroidectomy in rats. Methods: Sixty Wistar rats were randomly divided into 6 groups, including a sham-operated group (SO group), a total thyroidectomy group (TD group), and a L-thyroxine (L-T4) treatment I group (TS-I group), II group (TS-II group), III group (TS-III group), and IV group (TS-IV group) (in which rats were treated with 1.4, 1.6, 1.8, and 2.0 μg/100 g body weight, respectively) after total thyroidectomy. Results: HE staining in the TD group and all L-T4-treated rats showed that the resected tissue was normal thyroid gland. No residual thyroid tissue was found in neck tissue of the cross-section of the thyroid gland. Serum T3 levels in the TS-II group were not significantly different from those in the SO group, whereas serum T4 levels were slightly higher than those in the SO group, and serum TSH levels were slightly lower. Conclusions: Rats subcutaneously injected with L-T4 1.6 μg/100 g body weight for 15 days after total thyroidectomy were suitable as an animal model for TSH suppression therapy.