Paradoxical exacerbation of preexisting Graves' disease induced by insufficient radioiodine treatment: a report of five patients

Objective This study reports on early and paradoxical aggravation of hyperthyroidism, which needs long-term treatment, in patients with Graves' disease after radioactive iodine (RAI) treatment. Immediate and long-term treatments with antithyroid medications or second dose of RAI treatment were required in all the patients to control persistent hyperthyroidism. Methods Five patients (0.4%) out of 1333 consecutive patients with Graves' disease who underwent RAI treatment by using an empirical fixed dose of 131 1 between January 2000 and March 2006 revisited the emergency center because of early and markedly aggravated thyrotoxic manifestations, which seemed to differ from those for radiation-induced thyroiditis. The clinical features, changes in the laboratory, and scintigraphic findings before and after RAI treatment, and long-term follow-up of these patients were reviewed retrospectively. Results The mean interval between the RAI treatment and paradoxical exacerbation of hyperthyroidism was 47.8 days (range: 28-69 days). In all five patients, the serum levels of thyroid hormones were markedly increased compared with those before the RAI treatment. The patients also exhibited an increased uptake of radioiodine or technetium-99m pertechnetate on the scintigraphy after RAI treatment. The serum levels of thyrotropin receptor antibodies were increased compared with those before the RAI treatment. Conclusion The early and paradoxical exacerbation of preexisting Graves' disease, as distinct from radiation-induced thyroiditis, can occur after insufficient dose of RAI treatment for Graves' disease. Nucl Med Commun 30:275-280 (C) 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins.