Thyroid steal syndrome?

A 57-year-old woman with hyperthyroidism had a loud to-and-fro bruit which persisted when the patient was inadvertently rendered hypothyroid with antithyroid drugs. Symptoms suggestive of transient cerebral ischemia prompted an angiographic study which demonstrated both normal cerebral circulation and an enormous increase in the size of thyroid vasculature. The possibility that the enhanced blood supply to the thyroid had compromised cerebral circulation (thyroid steal syndrome) was considered. The angiographic presentation of hyperthyroidism is reviewed, and the lack of specificity of thyroid bruits as a marker of hyperthyroidism in patients on antithyroid drugs is stressed.