Early thyrotoxic thyroiditis after radiotherapy for tonsillar carcinoma

Thyroiditis with hyperthyroidism is a recognized early complication of intrathyroidal irridiation by orally ingested radiolabeled iodine I 131, but has seldom been described following external delivery of radiotherapy to the thyroid bed. We treated a man who was initially seen with a clinical picture suggestive of hyperthyroidism after receiving a course of radiotherapy for tonsillar carcinoma. Laboratory studies and thyroidal radioiodine uptake confirmed the diagnosis of thyrotoxic thyroiditis, having onset within 2 weeks of completion of the course of radiotherapy. The literature concerning thyroiditis and thyroid function following external beam radiotherapy is reviewed. Because several of the clinical features of thyrotoxic thyroiditis may resemble those resulting from the cancer under treatment or complications of its therapy, we recommend evaluation of thyroid function at the conclusion of the course of radiotherapy and 2 weeks thereafter to exclude this self-limited and treatable cause of weight loss.