Treatment of Graves' Hyperthyroidism With Selenium Plus Methimazole

30 untreated GD hyperthyroid patients will be randomized into two groups (A and B). Group A patients will be treated with an anti-thyroid drug (methimazole) at the dose aimed to control hyperthyroidism. Group B patients will be treated with methimazole plus selenium (160 mg daily). Patients will be evaluated at time 0, 45 and 90 days for symptoms of hyperthyroidism (by a specific questionnaire), clinical status (weight, heart rate), laboratory (thyroid function tests, TSHR autoantibodies, serum selenium, index of oxidative stress-MDA, cholesterol, SHBG) and EKG. The aim of the study is to evaluate if the combined treatment (methimazole plus selenium) is more effective than methimazole alone in controlling GD hyperthyroidism.