Significance of thyroid blood flow as a predictor of methimazole sensitivity in untreated hyperthyroid patients with Gravesʹ disease

Objective The peak systolic velocity (PSV) of the inferior thyroid artery (ITA) is increased in untreated hyperthyroid patients with Gravesʹ disease (GD). We investigated the clinical significance of the ITA-PSV and its determinants in hyperthyroid GD patients. Patients and methods ITA-PSV, together with thyroid volume, was measured by ultrasonography in untreated hyperthyroid GD patients (n = 49) and healthy subjects (n = 22). Established markers of GD activity such as TSH receptor antibody (TRAb), thyroid stimulating antibody (TSAb), vascular endothelial growth factor (VEGF) and immunoglobulin E (IgE) were simultaneously determined. Results ITA-PSV, thyroid volume, VEGF and IgE were significantly higher in hyperthyroid GD patients than in normal subjects. ITA-PSV in hyperthyroid GD patients was correlated positively with serum levels of FT3, FT4 and IgE, smoking index and thyroid volume, and negatively with total, HDL- and LDL-cholesterols, but did not correlate significantly with age, triglyceride, TRAb, TSAb or VEGF. In stepwise regression analysis, ITA-PSV showed significant positive and negative associations with IgE and LDL-cholesterol, respectively, in hyperthyroid GD patients. In the pre-treatment hyperthyroid state, FT4 and ITA-PSV, but not IgE, were found to be significantly and positively associated with the maintenance dose of methimazole (MMI) required to keep serum TSH within normal range for at least 12 months. Conclusion These results suggest that ITA-PSV in untreated hyperthyroid GD patients may reflect GD activity and thus MMI sensitivity.