Endocrine Abstracts

Background: Thyroid eye disease (TED) is common among patients with Graves’ disease (GD), with an estimated prevalence of 25-58%. While radioactive iodine (RAI) therapy is effective in managing GD, there are concerns regarding the risk of TED after RAI. Therefore, studying the effects of RAI on TED is essential for improving clinical decision-making.

Aim: To determine the incidence of the development or exacerbation of TED in patients undergoing RAI for GD in our service and to identify the risk factors that are associated with this outcome.

Method: Data from 204 GD patients treated with RAI in 2022 at the Christie were collected from the Electronic Patient Record. The follow-up period was 6-16 months. Baseline and post-RAI thyroid function, smoking status, and patients’ medical background were recorded. Fisher’s exact test and Student’s t-test were used.

Result: Follow-up data were available for 143 patients (70.1%). Among them, 4 individuals (2.8%) developed or experienced worsening TED after RAI, with 3 having pre-existing TED. Two of these patients required immunomodulatory treatment for TED. Uncontrolled thyrotoxicosis before RAI (OR 8.3, P=0.045) and early fluctuations in thyroxine levels (hypothyroidism within 4-8 weeks post-RAI [OR 11.29, P=0.012]), were significant risk factors for TED development. Active smoking status (OR 1.87, P=0.593) and known TED (OR 3.23, P=0.299) did not demonstrate statistical significance. However, 94.1% of patients (16/17) with pre-existing TED and 67.9% (19/28) of active cigarette smokers received prophylactic steroids. Female gender, co-existing autoimmune disorders, and type 2 diabetes were not associated with an elevated risk.

Conclusion: Well-controlled thyrotoxicosis before RAI and prophylactic steroids in high-risk patients may reduce the risk of TED development post-RAI. An emphasis on regular and early (<6 weeks) clinical and biochemical follow-up after RAI may reduce this risk. Larger studies and meta-analyses are needed to further elucidate the relationship between RAI and TED.