Long-term follow-up of Graves' orbitopathy after treatment with short-term or long-term methimazole or radioactive iodine.

OBJECTIVE: The aim of this study was to compare long-term outcomes in terms of new onset or worsening of GO in patients with Graves' disease treated with different therapeutic modalities for hyperthyroidism.

METHODS: A total of 1163 patients with Graves' disease entered this study; 263 patients were treated with radioiodine and 808 patients received MMI therapy for a median of 18 months of whom, 178 patients continued MMI for a total of 96 months (long-term MMI). Thyroid hormonal status and GO were evaluated regularly for a median of 159 months since enrollment.

RESULTS: Rates of relapse, euthyroidism and hypothyroidism at the end of the follow-up were: radioiodine treatment: 16%, 22% and 62%, short-term MMI group: 59%, 36% and 5% and long-term MMI group: 18%, 80% and 2%, respectively. In the first 18 months of therapy, worsening of GO (11.5% vs 5.7%), and de novo development of GO (12.5% vs 9.8%) were significantly more frequent after radioiodine, p<0.004. The overall worsening and de novo development of GO from>18-234 months was 26(9.9%) in radioiodine and 8(4.5%) in LT-MMI groups, p<0.037. No case of worsening or new onset of GO was observed in patients treated with long-term MMI from>60-234 months of follow-up.

CONCLUSION: Progression and development of GO were associated more with radioiodine than MMI treatment; GO may appear de novo or worsen years after radioiodine but not after long-term MMI therapy.