Endocrine Abstracts

Background: Radioactive iodine (RAI) is a safe and effective treatment for management of hyperthyroidism caused by Graves’ disease and multinodular goitres. However, patient engagement with this therapy is limited by concerns regarding significant weight gain following treatment. We therefore aimed to audit weight changes in individuals receiving RAI within our service and identify factors that may influence this outcome.

Methods: We audited all patients who underwent RAI therapy at Forth Valley Royal Hospital between January and November 2021. Weights were obtained at the time of administering RAI, and follow up weights were either self reported or obtained via electronic records. Biochemistry at presentation, antithyroid drug regimen, and post-treatment thyroid stimulating hormone and levothyroxine usage was also obtained.

Results: Twenty-seven individuals (59.3% female) received RAI during the audit period with a median follow up of 13 months. No significant difference in participants weight before and after the use of RAI (median weight change: 0.5 kg; 95% CI -10, 19) was observed. There was no difference between individuals who received carbimazole dose titration (44%; -0.5 Kg; 95% CI -10, 11.3) verses a block and replace regimen (56%; 0.5 Kg; 95% CI -1.6, 19) prior to RAI. A trend was observed in males experiencing higher weight gain than females (median increase 10kg; P=0.051) following RAI.

Conclusion: This audit identified no significant change in the weight of individuals that received RAI treatment. Our results indicated that males may be at higher risk of weight gain. Research relating to weight gain in RAI suggests the risk is high. However, these studies are largely retrospective, uncontrolled pre-post analyses with limited sample size. Prospective analyses comparing RAI to long-term antithyroid drug usage are required to compare this risk and inform the potential advantages and disadvantages of RAI in this patient group