Treatment Selection Criteria for Patients with Drug-resistant Graves’Disease : Radioactive Iodine Therapy vs. Surgery

Objective : To identify the characteristics of patients with drug-resistant Graves’ disease (GD) suitable for radioactive iodine (RI) therapy and surgery. Methods : We retrospectively analyzed 373 patients with GD treated at Shinshu University Hospital between April 2015 and September 2023. Remission was defined as the absence of treatment for at least six months after discontinuation of antithyroid drugs (ATDs), RI therapy, or surgery. Clinical characteristics, including thyroid hormone levels, free triiodothyronine (FT3)/free thyroxine (FT4) ratio, thyroid antibodies, and the prevalence of T3-predominant GD, were compared among patients who achieved remission with ATDs (Drug group), RI therapy (RI group), or surgery (Surgery group). Results : Of the 373 patients, 141 achieved remission : 73 in the Drug group, 23 in the RI group, and 45 in the Surgery group. The FT3/FT4 ratio differed significantly among the groups and was highest in the Surgery group (median 5.90) compared with the Drug group (2.99) and RI group (3.18) (p＜0.001). Anti-thyroid stimulating hormone receptor antibodies (TRAb) levels were also significantly higher in the Surgery group (39.56 IU/L) than in the Drug (5.92 IU/L) and RI (18.67 IU/L) groups (p＜0.001). T3-predominant GD was more frequent in the Surgery group (71.4 ％) than in the Drug (8.2 ％) and RI (11.1 ％) groups. No significant differences were observed between the Drug and RI groups. Conclusion : Higher FT3/FT4 ratios and TRAb levels were associated with patients achieving remission through surgery. The FT3/FT4 ratio may serve as a practical indicator for selecting surgical treatment in GD management. Shinshu Med J 74 : 261 ―270, 2026