Measurement of thyroid blood flow area is useful for diagnosing the cause of thyrotoxicosis

We have utilized color Doppler ultrasonography (CDU) to evaluate the thyroid blood flow area (TBFA) quantitatively, and we propose criteria to differentiate Graves' disease (GD) and destruction-induced thyrotoxicosis (DT) in patients with thyrotoxicosis. We studied 32 patients with diffuse toxic goiter, 21 with GD in the euthyroid state, 12 with chronic thyrolditis in the euthyroid state, and 31 normal individuals. TBFA was calculated as (thyroid blood flow area/thyroid area) X 100%. CDU showed high sensitivity (84%) and specificity (90%) in distinguishing GD from DT when TBFA was between 7.7% and 8.8%. Using CDU to diagnose GD in cases with TBFA >= 8% or positive serum anti-thyrotropin receptor antibody (TRAb), the sensitivity was 95% and the specificity was 90%, which are similar results to those obtained when GD was diagnosed by radioactive iodine uptake (sensitivity 100%, specificity 90%). Therefore, CDU is a more useful and economical method of distinguishing GD patients with TBFA of 8% or above from DT than measurement of TRAb or radioactive iodine uptake.