Iodide excess exerts oxidative stress in some target tissues of the thyroid hormones.

Environmental iodine deficiency continues to be a significant public health problem worldwide. On the other hand, iodide excess results principally from the use of iodine-containing medicinal preparations or radiographic contrast media. For this reason we intended to explore iodide excess impairment on prooxidant/antioxidant balance of the thyroid gland, hepatic tissue and in blood and the effect of selenium administration on oxidative stress markers under the same circumstances. Experiments were performed for 10 days with white, male, Wistar rats, as follows: group 1: control-normal iodine supply group; 2: high iodine diet, group; 3: high iodine diet and selenium; group 4: high iodine diet and Carbimasole. Oxidative stress markers such as lipid peroxides were determined in thyroid gland, hepatic tissue and in blood. Measuring H+ donor ability of the sera and catalase activity in thyroid gland and in hepatic tissue assessed antioxidant defense. Iodide excess had prooxidant effects, leading to an increased lipid peroxides level and catalase activity in target tissues and in blood and to a decreased H+ donor ability of the sera. Selenium supplementation had opposite effects. Present data allow us to conclude that the alterations due to iodide excess in thyroid gland, hepatic tissue and in blood are mediated through oxidative stress.