THYROID VASCULARIZATION BY COLOR DOPPLER ULTRASONOGRAPHY IN GRAVES-DISEASE - CHANGES RELATED TO DIFFERENT PHASES AND TO THE LONG-TERM OUTCOME OF THE DISEASE

To investigate possible correlations between thyroid vascularization a nd activity of Graves' disease, we measured blood flow (TBF) at the in ferior thyroid artery and intraparenchymal vascularization (number of vessels per square centimeter) by color Doppler ultrasonography (CDU) on Graves' patients at different phases of the disease. We studied 88 patients cross sectionally: 22 untreated; 17 euthyroid after 6 months of methimazole; 49 euthyroid at drug withdrawal after 12 to 24 months of treatment. The patients of the latter group were followed up for 29 .1 +/- 6.3 months after discontinuation of treatment. On the day of CD U examination, free triiodothyronine (FT3), free thyroxine (FT4), thyr otropin (TSH), antiperoxidase and anti-TSH receptor (TRAb) antibodies were measured. Vascularization indices were significantly higher in th e Graves' patients than in controls. In the patients euthyroid under t reatment, vascularization was not significantly lower than in the untr eated group, but TBF and vessel number both appeared clearly reduced i n the patients tested at drug withdrawal. The vascularization indices at drug withdrawal were significantly higher in the patients who relap sed than in those in stable remission: TBF (mL/min) 50.6 +/- 36.8 vs. 23.8 +/- 17.5, p = 0.001; vessel number/cm(2) 1.8 +/- 0.8 vs. 0.8 +/- 0.5, p = 0.002. A multivariate analysis, evaluating the predictive val ue of vascularization, hormonal and immunological parameters for relap se, demonstrated a significant predictive value for TRAb (RR 8.2; p = 0.001) and a weak predictive value for TBF (RR 1.1; p = 0.02). In conc lusion, CDU examination confirms that thyroid hypervascularization in Graves' disease is not related to thyroid hormone circulating levels. The association of increased TBF and high levels of TRAb in the relaps ing forms of disease suggests that thyroid hypervascularization is pro bably related to the activity of the underlying autoimmune processes.