Color Flow Doppler Sonography (CFDS) has become in the last years an increasing procedure to assess the thyroid blood flow. Previous studies showed specific changes of thyroid blood flow in hyperthyroidism, Hashimoto's thyroiditis and thyroid nodules when investigated by CFDS. Subclinical hyperthyroidism and hypothyroidism are common laboratory findings, defined by normal thyroid hormones concentrations along with ,respectively,decreased or increase Thyroid stimulating hormone (TSH) level. We purpose to investigate thyroid vascularity by CFDS in patients with subclinical hyperthyroidism or hypothyroidism and compared them with euthyroid patients.