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Hyperthyroidism is a hypermetabolic state accompanied by increased oxygen utilization, increased production of reactive oxygen species and consequentially measurable changes in antioxidative factors. Therefore, the activities of whole blood glutathione peroxidase (GPx) and erythrocyte superoxide dismutase (SOD), total antioxidant status (TAS) in serum and erythrocytes, and serum urate and transferrrin concentrations were determined in 70 women: 14 with newly diagnosed Graves' disease (group A); 28 with hyperthyroidism on therapy with methimazole (group B, divided into two subgroups, B1 and B2) and 28 healthy women (group C). In comparison with control group C, GPx activity was significantly decreased in all patient groups (p < 0.05), whereas SOD activity was significantly decreased in group A (p < 0.01) and significantly increased in group B (p < 0.01). In comparison with the control group, serum TAS activity was significantly decreased in group A, and erythrocyte TAS activity in all patient groups. Study results suggest that the impaired antioxidative factor balance leads to the development and presence of oxidative stress in women with hyperthyroidism. The severity of these alterations, considered contradictory by some authors, appears to depend on the use of therapy.

Graves' disease is an autoimmune disorder and the most common cause of hyperthyroidism. Graves' disease occurs more often in women with a female/male ratio of 5:1 and a population prevalence of 1 to 2 %. The disease is associated with circulating immunoglobulins that bind to and stimulate thyrotropin, the thyroid stimulating hormone (TSH) receptor, resulting in sustained thyroid overactivity (1). Through its hormones, The effect of supplementation with a fixed combination of antioxidants (beta-carotene, selenium, vitamins C and E) on serum lipids was monitored in patients with newly detected Graves' disease. Measurements were made prior to the commencement of therapy and after 30 and 60 days. Patients were randomized into two groups. Test group comprised patients who received antioxidant supplementation in addition to methimazole, while patients treated with methimazole only were in the control group. The concentration of total and HDL-cholesterol increased significantly in test and control groups (p < 0.05) but these groups did not differ significantly. Concentration of LDL-cholesterol increased significantly in the test group only (p < 0.005) and was significantly different from the control group 60 days after the commencement of therapy (p < 0.005). Significant increase in the LDL-cholesterol concentration in the test group requires further investigations.

The effects of supplementation with a fixed combination of antioxidants (vitamins C and E, beta-carotene and selenium) on superoxide dismutase activity, copper and zinc concentrations, and total antioxidant status were monitored in erythrocytes derived from a group of patients with Graves' disease treated with methimazole, with respect to the rate of achieving euthyroidism. Thyroid-stimulating hormone (TSH), thyroid hormones and the above-mentioned parameters were measured before therapy, and on days 30 and 60 after therapy initiation. The patients receiving antioxidant supplementation along with methimazole therapy (group A, n = 27) achieved euthyroidism at a faster rate than those treated with methimazole alone (group B, n = 28). The activity of superoxide dismutase decreased significantly in both patient groups during the treatment; however, there was no significant difference between the groups. There was no significant change in the erythrocyte concentration of copper, whereas the zinc concentration and total antioxidant status showed significant between-group differences. The study results clearly show that antioxidant supplementation in the treatment of Graves' disease is justified, while zinc and total antioxidant status in erythrocytes seem to be sensitive indicators of the efficacy of supplemental therapy.