Melatonin prevents possible radiotherapy-induced thyroid injury

Purpose: We aimed to investigate the protective effect of melatonin in radiotherapy-induced thyroid gland injury in an experimental rat model.Materials and methods: Thirty-two rats were divided into four groups: the control group, melatonin treatment group, radiotherapy group and melatonin plus radiotherapy group. The neck region of each rat was defined by simulation and radiated with 2 Gray (Gy) per min with 6-MV photon beams, for a total dose of 18Gy. Melatonin was administered at a dose of 50mg/kg through intraperitoneal injection, 15min prior to radiation exposure. Thirty days after the beginning of the study, rats were decapitated and analyses of blood and thyroid tissue were performed.Results: Tumor necrosis factor- (TNF-), interleukin-1 beta (IL-1), thiobarbituric acid reactive substances (TBARS) and nitric oxide (NO) levels in the radiotherapy group were significantly higher than those in the melatonin plus radiotherapy group (p<.05), whereas interleukin-10 (IL-10) and glutathione (GSH) values were higher in the melatonin plus radiotherapy group (p<.05). The infiltration of inflammatory cells and percentage of apoptosis in the radiotherapy group were significantly higher than those in the melatonin plus radiotherapy group (p<.05).Conclusions: Melatonin helped protect thyroid gland structure against the undesired cytotoxic effects of radiotherapy in rats.