Radioiodine-induced oxidative stress in patients with differentiated thyroid carcinoma and effect of supplementation with vitamins C and E and selenium (antioxidants)

OBJECTIVE: : The objective of this study, in addition to confirming that therapy with (131)I causes oxidative stress, was to evaluate the effect of supplementation with vitamins C and E and selenium on this phenomenon by measuring plasma 8-epi-PGF2a, a marker of lipid peroxidation. SUBJECTS AND METHODS: : Forty patients with thyroid cancer submitted to thyroidectomy, who received 3.7 GBq (131)I after levothyroxine withdrawal, were selected; 20 patients did not receive (control group) and 20 patients received (intervention group) daily supplementation consisting of 2000 mg vitamin C, 1000 mg vitamin E and 400 µg selenium for 21 days before (131)I. Plasma 8-epi-PGF2a was measured immediately before and 2 and 7 days after (131)I. RESULTS: : A significant increase in plasma 8-epi-PGF2a after (131)I was observed in the two groups. The concentrations of 8-epi-PGF2α were significantly higher in the control group before and 2 and 7 days after (131)I. The percentage of patients with elevated 8-epi-PGF2α was also significantly higher in the control group before and after (131)I. Furthermore, the increase (percent) in 8-epi-PGF2α was significantly greater in the control group (average of 112.3% versus 56.3%). Only two patients (10%) reported side effects during supplementation. CONCLUSIONS: : Ablation with (131)I causes oxidative stress which can be minimized by the use of antioxidants.