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Assessment of thyroid blood flow in hyperthyroidism
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A study in the January/February 2009 issue of Endocrine Practice reports the use of thyroid blood flow assessment by color flow Doppler ultrasonography in differentiating Graves’ disease from destructive thyroiditis.
A total of 65 patients participated. Thyroid blood flow as assessed by the peak systolic velocity of the inferior thyroid artery was significantly higher in individuals with Graves’ disease compared with thyroiditis (57.6 ± 13.1 cm/s vs. 22.4 ± 5.4 cm/s; P<.05). Limitations of the study were the small number of participants, the fact that nuclear imaging was not available for all patients, and that thyroid receptor antibody testing was not performed to assist in the confirmation of Graves’ disease.
Ultrasonographic color flow assessment to differentiate between causes of hyperthyroidism has been suggested for some time. Vitti et al classified thyroid vascularity by color flow Doppler sonography of non-nodular thyroid disease into patterns 0, I, II and III. Other authors have suggested similar classifications. Measurement of the peak systolic velocity of the intrathyroidal arteries or the inferior thyroid artery is another, perhaps more objective, method of quantifying thyroid vascularity.
In my own practice, color flow assessment of thyroid vascularity has been useful in certain clinical situations. In a pregnant woman with hyperthyroidism, nuclear imaging is contraindicated. Color flow assessment combined with other studies such as thyroid-stimulating antibodies helps in making a diagnosis of Graves’ disease.
It can be challenging to differentiate between type 1 and type 2 amiodarone-induced thyrotoxicosis. Distinguishing between types of amiodarone-induced thyrotoxicosis permits initiation of the most appropriate therapy. Amiodarone-induced thyrotoxicosis type 1 has detectable flow; either a Vitti pattern I, II or III. Amiodarone-induced thyrotoxicosis type 2 has limited or no vascularity.
In a patient with severe thyrotoxicosis whom I desire to treat immediately and not wait until the results of nuclear imaging are available, color flow provides immediate assessment. The information often allows diagnosis on the spot. A Vitti pattern III or “thyroid inferno” is classic for Graves’ disease. Minimal flow suggests thyroiditis.
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