The role of melatonin on acute thyroid damage induced by high dose rate X-ray in head and neck radiotherapy

Abstract

The purpose of the present study was to investigate the acute period radioprotective effect of melatonin (Mel) against radiation-iömnduced tissue damage in thyroid gland of rats using thyroid gland scintigraphy imaging.Forty-eight Sprague Dawley female rats were divided into six groups; the control group, melatonin treatment group, low dose rate (LDR-RT), high dose rate (HDR-RT) only radiotherapy groups and radiotherapy plus melatonin groups, (LDR-RT) + Mel and (HDR-RT) + Mel. The head and neck region of each rat was irradiated with single dose of 16 Gy at 6 MV X-ray in FF and FFF beam mode. Melatonin was administered at a single dose of 10 mg/kg through intraperitoneal injection, 15 min prior to radiation exposure. Functional evaluation of the thyroid glands were made using scintigraphy imaging before and after radiotherapy.Statistically significant difference was not observed in thyroid gland to background ratio (T/B) for all experimental rat groups before exposure (p = 0.379). However, when acute effects of irradiation are considered after radiotherapy T/B ratio showed a significant difference (p < 0.001). In the radiotherapy only groups, for both FF and FFF modes, statistically significant difference was not observed in the T/B ratio of LDR-RT group compared to HDR-RT group (p = 0.946). In the radiotherapy plus melatonin groups, both FF and FFF modes, statistically significant difference was also observed in the T/B ratio of LDR-RT group compared to HDR-RT group (p < 0.05).We showed that melatonin administered before radiotherapy provided significant protective effect against acute rat thyroid gland dysfunction caused by single dose LDR-RT and HDR-RT.