Effects of 8 Weeks of Aerobic Exercise and Different Diets on Hormonal Level and Histopathological Changes of Thyroid Tissue in Obese Male Rats

Obesity is a well-known public health problem that affects people of all ages. It has myriad effects on several body tissues, including the thyroid, in both human and animal models. Some treatments, such as dietary modification and physical activity, may be effective or ineffective in reducing obesity. Accordingly, the present research investigated the effects of obesity on thyroid tissue and the impact of diet modification and aerobic exercises on histopathological and hormonal changes in the thyroid tissue of obese male rats.

In this experimental study, for obesity induction, 50 three-week-old male Wistar rats were exposed to a high-fat diet (including 40% fat, 40% protein, and 20% carbohydrate) for 12 weeks. Then, 25 rats were randomly divided into 5 groups: healthy control, obese + high-fat diet, obese + normal diet, obese + high-fat diet + aerobic, obese + normal diet + aerobic. After the induction of obesity, 2 groups were given a standard diet (including 20% fat, 10% protein, and 70% carbohydrates). Aerobic exercises for 8 weeks included 30 minutes per day, 8 m/min, and 5 days per week. After anesthesia, an autopsy was performed, and the thyroid tissue was sent to the laboratory for histopathological studies. Also, 5 cc of blood was taken to study TSH, T3, and T4 using a radioimmunoassay kit.

The serum levels of TSH hormone increased slightly in the high-fat diet groups compared to the control group and the normal diet with/without aerobic activity group. Also, the amount of T3 hormone in the group receiving a normal diet along with aerobic activity was significantly lower than in the control, high-fat diet, and high-fat diet along with aerobic activity groups (P<0.05). The T4 hormone increased significantly in all obesity groups compared to the control group (P<0.05), and these values were at the level of the control group (P<0.05) only in the group receiving the normal diet along with aerobic activity. Regarding the histopathological results, many changes were found in the follicular, parafollicular, and follicle cells of the thyroid tissue in the obesity group continuing the high-fat diet; these changes were significantly reduced in the groups for which the diet was changed to the normal diet alone and with aerobic activity.

Induction of obesity causes significant structural and biochemical changes in the thyroid, and the combination of diet modification and aerobic activity is more effective in alleviating these changes.