Thyroid Doppler blood flow – the proportion of colored pixels is a new activity parameter in Graves´disease (GD)

Purpose : Graves' disease (GD) is characterized by autoimmune stimulation of the thyroid via thyrotropin receptor antibodies (TRAb), leading to hyperthyroidism and increased thyroid vascularity. While TRAb is the gold standard biomarker for disease activity, imaging correlates are underutilized in clinical practice. This study aimed to evaluate a Doppler-based method for quantifying thyroid blood flow as a marker of disease activity during antithyroid drug (ATD) treatment. Methods : In a prospective study, 43 newly diagnosed GD patients underwent serial evaluations, including TRAb, TSH, and free T4 (fT4), at baseline, 3–9 months, and 9–12 months after starting ATD. Color Doppler ultrasound images were captured at each time point, and thyroid blood flow was quantified as the percentage of colored pixels within a defined region of interest. Blood flow was compared with TRAb levels over time, and statistical correlations were assessed using Pearson and Wilcoxon tests. Results : Blood flow significantly decreased over time, paralleling reductions in TRAb levels (p < 0.05). Thyroid vascularity remained elevated after normalization of fT4 and even TRAb in some cases, indicating persistent intrathyroidal autoimmune activity. Correlations between blood flow and TRAb reduction were found at both group and individual levels (r = 0.4, p < 0.05). The method was rapid, reproducible, and easy to implement using standard ultrasound equipment. Conclusions : Doppler-based quantification of thyroid blood flow offers a simple tool to monitor disease activity in GD. Persistent blood flow despite biochemical remission may identify patients at risk for relapse, potentially guiding individualized treatment duration and follow-up.