The Role of Melatonin in Thyroid Function in Adult Rats

Background: The thyroid gland, a vital endocrine organ, the thyroid gland synthesizes and secretes hormones, such as triiodothyronine (T۳), thyroxine (T۴), and calcitonin. The pineal gland produces and releases melatonin, which is stimulated in the dark and suppressed in the presence of light. Objectives: This study aimed to assess how melatonin influences adult male rats’ thyroid performance.Methods: Eighteen adults male Wistar albino rats (Rattus norvegicus) (approximately ۱۲-۱۴ weeks old and weighing ۲۲۰±۱۰ g) were randomly divided into three groups, each containing six rats, and were treated for ۳۰ days as follows: The control group (A) received distilled water (DW). The A۱ group received ۱۰ mg/kg body weight (B.W.) of melatonin orally daily, and the A۲ group received ۲۰ mg/kg B.W. of melatonin orally daily for ۳۰ days. At the end of the study, blood was drawn by cardiac puncture, and serum was collected to assess thyroid hormone levels: T۳, T۴, thyroid stimulating hormone (TSH), and total antioxidant capacity (TAC).Results: T۳ levels increased dramatically in the A۲ group, whereas T۴ and TSH levels remained constant. On the other hand, there was a significant increase in TAC in the A۱ groups compared with the control and A۲-treated groups. The histological section of the thyroid glands revealed the normal histological structure of the thyroid in the A۱ group compared to the A۲ group. Besides, the figures of the thyroid gland in the A۲ group showed severe vascular degeneration and necrosis of thyroid follicles. Conclusion: Treatment with melatonin at higher doses may influence thyroid hormone regulation, highlighting its potential physiological effects, while melatonin at a dose of ۱۰ mg/kg plays a key role in regulating thyroid functions and enhancing antioxidant status.

کلیدواژه ها:

Hormonal regulation ، oxidative stress ، Pineal Gland ، Triiodothyronine (T۳) ، Thyroxine (T۴)