Iodide‐induced thyrotoxicosis in a thyroidectomized patient with metastatic thyroid carcinoma

Abstract

An unusual case of iodide‐induced thyrotoxicosis is documented in this article. The patient was a 64‐year‐old euthyroid man with acromegaly. He also had multiple follicular and papillary thyroid carcinomas with a metastatic lesion in the lumbar vertebrae. After a total thyroidectomy, he became slightly hypothyroid, and the lumbar lesion began to incorporate 131I by scintigraphy. When an iodine‐containing contrast medium happened to be injected, a transient increase of serum thyroid hormone level was observed. After complete thyroid ablation with 83 mCi of 131I, the oral administration of 100 mg of potassium iodide for 7 days induced a prominent increase of serum thyroid hormone level. These findings indicated that the metastatic thyroid carcinoma could produce excess thyroid hormone insofar as a sufficient amount of iodide was given. Although this is the first report of such a case, iodide‐induced thyrotoxicosis may not be rare in patients with thyroid carcinomas because the Wolff‐Chaikoff effect is thought to be lost, and the organic iodinating activity and lysosomal protease activity are well‐preserved. Copyright © 1988 American Cancer Society