Effect of Chronic Regular Swimming Exercise on Thyroid Function in Ovariectomized Rats

Abstract
Background: Thyroid dysfunction may occur in women in menopausal period or after ovariectomy. Effect of exercise on thyroid function remains controversial and need more investigations.
Aim of Study: This study was done to investigate the effect of chronic regular swimming exercise on thyroid function in ovariectomized rats.
Material and Methods: Rats were divided into 6 groups (7 rats per each); Sham-operated sedentary (sham-S) group, (2) Sham-operated with swimming exercise training (sham + Ex) group, (3) Ovariectomized sedentary (OVX-S) group, (4) OVX-group with swimming exercise training (OVX + Ex), (5) OVX-group injected with 17-b  estradiol (OVX + E), (6) OVX-group with swimming exercise training and injected with 17-R estradiol (OVX + Ex + E). 3 months after the surgery, rats were exposed to the exercise protocol for another 3 months. BMI was calculated. At the end experimental period, the serum levels of T3, T4, TSH, estradiol and interleukin-6 (IL-6) were determined. The thyroid glands were weighed. The histopathological examination of thyroid tissue was done for determination of epithelial cell height, follicular and colloidal areas.
Results: In OVX-S group, final BMI was significantly increased, serum levels of T3 and T4 were significantly decreased with significant increase of serum TSH level as compared with Sham-S group. While, as compared to OVX-S group, final BMI was significantly decreased, T3 and T4 levels were significantly increased with decrease of TSH level in OVX-treated groups. Estradiol level was significantly decreased in OVX-S group compared to sham-S group. While, in comparison with OVX-S group, its level significantly increased in OVX-treated groups. Serum IL-6 was insignificant changed between Sham-S, OVX-S and OVX + E groups. But, it significantly increased in Sham-Ex, OVX + Ex and OVX + Ex + E groups as compared to Sham-S, OVX-S and OVX + E groups. Histopathological examination showed significant decrease of the thyroid gland weight and height of epithelial cells, with significant increase in the follicular and colloidal areas in the OVX-S group as compared to sham-S group. These histopathological changes were improved in OVX-treated groups.
Conclusion: We concluded that regular swimming exercise in OVX-rats ameliorated the thyroid hypofunction which may be related to its ability to increase estradiol level in these rats.