RESEARCH DESIGN AND METHODS - We will include patients who have benign thyroid tumors diagnosed with fine needle aspiration cytology and have normal thyroid function into our study. After informed consent, patients will be randomly assigned into two groups. Patients in the first group will take thyroxin one hour before breakfast until thyrotropin level stabilized between 0.5 and 1.0 mU/L for 3 months. Then thyroxin will be discontinued. Patients will restart thyroxin therapy three months later but after breakfast. Patients in another group will take thyroxin postprandial, discontinue thyroxin and then one hour before breakfast. Questionnaire interviews about diet and life style, blood samples and fine needle aspiration cytology samples will be obtained. Changes of thyroid nodules will be evaluated with thyroid echo.