Aims: To investigate radiation-induced oxidative damage in erythrocytes after administration of radioiodine-131 (131I) in patients with hyperthyroidism. Materials and Methods: Twenty patients with hyperthyroidism (11 F, 9 M) treated with 131I were included into the study. Blood samples were taken from patients just before, 1 hour after and 3 hours after applying radioiodine. Malondialdehyde (MDA) and levels of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) were measured to evaluate the radiation-induced oxidative damage. Results: We found that enzyme activities of SOD, GPX and CAT were decreased 1 hour and 3 hours after radioiodine treatment (P < 0.05), while MDA levels were increased 1 hour and 3 hours after the radioiodine treatment (P < 0.05). Conclusions: Ionizing radiation causes harmful effects through the generation of free radicals. We found that radiation caused an oxidative damage in erythrocytes after administration of 131I in patients with hyperthyroidism. In conclusion, although the population of the study was too small, these results indicate that exposure of hyperthyroid patients to 131I decreased the erythrocyte antioxidant levels and increased MDA levels.

Aims: To investigate radiation-induced oxidative damage in erythrocytes after administration of radioiodine-131 (131I) in patients with hyperthyroidism. Materials and Methods: Twenty patients with hyperthyroidism (11 F, 9 M) treated with 131I were included into the study. Blood samples were taken from patients just before, 1 hour after and 3 hours after applying radioiodine. Malondialdehyde (MDA) and levels of antioxidant enzymes such as glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) were measured to evaluate the radiation-induced oxidative damage. Results: We found that enzyme activities of SOD, GPX and CAT were decreased 1 hour and 3 hours after radioiodine treatment (P < 0.05), while MDA levels were increased 1 hour and 3 hours after the radioiodine treatment (P < 0.05). Conclusions: Ionizing radiation causes harmful effects through the generation of free radicals. We found that radiation caused an oxidative damage in erythrocytes after administration of 131I in patients with hyperthyroidism. In conclusion, although the population of the study was too small, these results indicate that exposure of hyperthyroid patients to 131I decreased the erythrocyte antioxidant levels and increased MDA levels.