Context: Although some of endocrine surgeons administer Lugol's solution to decrease thyroid gland vascularity, there is still no agreement on its effectiveness. Objective: The aims of this clinical trial are to evaluate thyroid blood flow and microvessel density in the patients with Graves' disease according to the Lugol's solution treatment preoperatively.

Design: Retrospective clinical trial. Setting: A tertiary referral center. Method: Thirty-six patients were randomly assigned to preoperative medication with Lugol's solution. Patients in group 1 (n=17) received Lugol's solution for 10 days before surgical intervention, whereas patients in group 2 (n=19) didn't receive it. Main Outcome Measures: Blood flow through the thyroid arteries of patients with Graves' disease was measured by color flow Doppler ultrasonography. The microvessel density (MVD) was assessed immunohistochemically and Western blot analysis using the level of expression of CD-34 in thyroid tissue. The thyroid gland's weight and blood loss were measured in all patients.