Ectopic functioning thyroid tissue in the thyroglossal duct detected by radionuclide imaging.

A 49-year-old man with a clinical diagnosis of Graves' disease was referred for a thyroid scan and radioactive ablation of the gland. Tc-99m pertechnetate scan revealed a diffuse toxic goiter and radiotracer concentration in the thyroglossal duct. He was given 10 mCi of I-131 orally as treatment of thyrotoxicosis. Repeat scanning of the anterior neck 2 days later revealed concentration of radioiodine in the diffusely enlarged gland and the thyroglossal duct as found on the Tc-99m pertechnetate scan, thus confirming the presence of functioning thyroid tissue in the thyroglossal duct.