Background: Radiation thyroiditis caused by 131I therapy for Graves' hyperthyroidism is asymptomatic in most patients and is rarely associated with pain or fever. Currently, there are few reports on the ultrasonographic findings of radiation thyroiditis after 131I therapy for Graves' hyperthyroidism.
Case report: We herein report 5 cases with painful radiation thyroiditis (including 2 febrile cases) after 131I therapy for Graves' hyperthyroidism. The cases included 4 women, aged 49, 50, 76, and 81 years, and 1 man, aged 60 years. Anterior neck pain developed 0-10 days after 131I administration (fixed dose of 481 MBq). Each patient visited our clinic 0-4 days after the development of anterior neck pain. The thyroid glands were noticeably enlarged (increasing from 18 g at 131I administration to 35 g after the development of anterior neck pain in 1 patient, and from 20 to 33 g, 21 to 39 g, 21 to 51 g, and 40 to 51 g in the other patients) and tender. The echogenicity of the thyroid parenchyma was increased, and the parenchyma was more heterogeneous. Granular hyperechoic lesions were scattered throughout the thyroid gland in the most severe case. The border between the thyroid gland and the surrounding tissue was blurred, and the surrounding tissue was hyperechoic.
Conclusion: Painful radiation thyroiditis should be reacknowledged as one of the complications of 131I therapy for Graves' hyperthyroidism. Ultrasonography demonstrated the characteristic changes caused by 131I-induced radiation thyroiditis.
Keywords: Graves’ disease; Hyperthyroidism; Radiation thyroiditis; Radioactive iodine.