Assesment of oxidative status and its association with thyroid autoantibodies in patients with euthyroid autoimmune thyroiditis

Oxidative stress results from either overproduction of free radicals or insufficiency of several antioxidant defense systems. It leads to oxidation of main cellular macromolecules and a resultant molecular dysfunction. Thyroid hormones regulate oxidative metabolism and, thus, play a role in free radical production. Studies evaluating oxidative stress in patients with hypothyroidism and hyperthyroidism have been encountered in recent years; however, oxidative status in patients with euthyroid autoimmune thyroiditis (AIT) was not investigated previously. Thirty-five subjects with euthyroid AIT and 35 healthy controls were enrolled in the study. Serum oxidative status was determined by the measurement of total anti-oxidant status (TAS), total oxidant status (TOS), ischemia-modified albumin (IMA), and oxidized-low density lipoprotein (ox-LDL) levels. Serum TAS levels were significantly lower (p < 0.001), while serum TOS levels and IMA levels were significantly higher (p < 0.001 and p = 0.020, respectively) in patients compared to controls. In both groups, ox-LDL levels were similar (p = 0.608). Serum TAS levels were negatively correlated with antithyroid peroxidase and anti-thyroglobulin (anti-TG) levels (rho = -0.415, p = 0.001 and rho = -0.484, p < 0.001, respectively). Serum TOS was positively correlated with anti-TG levels (rho = 0.547, p < 0.001). Further, TAS was positively correlated with free T4 levels (r = 0.279, p = 0.043). No correlation was observed between thyrotropin, free T3 levels, and TOS and TAS levels. These results suggest that oxidants are increased, and anti-oxidants are decreased in patients with euthyroid AIT, and oxidative/anti-oxidative balance is shifted to the oxidative side. Increased oxidative stress might have a role in thyroid autoimmunity.