Radioiodine-Associated Exacerbation of Graves' Orbitopathy in the Japanese Population: Randomized Prospective Study.

CONTEXT: Exacerbation of Graves' orbitopathy (GO) after radioiodine (RAI) therapy has been examined in some populations but has not been fully described in Japanese populations.

OBJECTIVE: The purpose of this study was to clarify the characteristics of GO exacerbation after RAI therapy and the effectiveness of low-dose prophylactic corticosteroid (PCS).

DESIGN AND SETTING: This was a prospective randomized study in Tokyo, Japan.

PATIENTS: Between June 2011 and June 2012, 295 patients with Graves' disease with either inactive GO or no GO received RAI therapy. Of these, 147 received no PCS (PCS-Off group), whereas 148 received low-dose PCS (starting dose, 15 mg/day of prednisolone) for 6 weeks (PCS-On group). We used magnetic resonance imaging to thoroughly evaluate GO before and 1 year after RAI therapy.

MAIN OUTCOME MEASURES: Outcomes of GO 1 year after RAI therapy were determined.

RESULTS: GO exacerbation occurred in 29 patients (9.8%), and only 7 patients (2.4%) required ophthalmic treatment. No significant difference in the frequency of GO exacerbation was seen between the groups (PCS-On group: n = 18 [12.1%]; PCS-Off group: n = 11 [7.5%]; P = .17). Significant prognostic factors were identified as thyroid-stimulating antibody (by 100% linear increase: risk ratio, 1.15; 95% confidence interval, 1.07-1.24; P = .0003) and clinical activity score (≥1 vs 0: risk ratio, 6.40; 95% confidence interval, 2.17-19.7; P = .0009).

CONCLUSION: Exacerbation of GO after RAI therapy in the Japanese population appears less common than in other populations. Low-dose PCS did not produce a significant preventive effect and appeared insufficient. Patients presenting with risk factors would thus be recommended to receive higher-dose PCS.