Risk factors and outcomes of Graves' orbitopathy after radioactive iodine therapy

Graves' orbitopathy (GO) is a common extrathyroidal manifestation of Graves' disease (GD) and can be triggered by radioactive iodine (RAI) treatment. However, the incidence or factors influencing GO development after RAI remain unclear. We aimed to investigate the incidence, risk factors, and clinical outcomes of GO following RAI treatment in GD patients.

A retrospective cohort study using data from Korea's National Health Information System (2008-2020) included GD patients treated with RAI from 2008-2018, followed until 2020. GO was identified via diagnostic codes, and risk factors were assessed using Cox proportional hazards models. Clinical outcomes were compared between patients with GO who did and did not undergo RAI.

Among 12,819 GD patients treated with RAI, 453 (3.5%) developed GO, compared to 4007 (0.3%) of 1,529,386 GD patients without RAI. The median time to GO onset post-RAI was 18.7 months. Younger age, shorter time from GD diagnosis to RAI, and smoking were significant risk factors, while post-RAI levothyroxine use reduced risk. Patients with GO after RAI required more intensive treatments, such as intravenous steroids and orbital radiotherapy, compared to those with GO not receiving RAI.

GO risk after RAI treatment was higher in younger patients, smokers, and those receiving earlier RAI. Levothyroxine treatment appeared protective. These findings emphasize the importance of patient selection, smoking cessation, timely hormone replacement, and close monitoring to mitigate GO risk and improve outcomes.