Evaluating the incidence of hypothyroidism and its associated factors within one-year post radioactive iodine (RAI) therapy for benign thyroid disease; a single centre experience

Khan Huma Humayun; Aparna Pal; Turner Helen E; May Christine JH

doi:10.1530/endoabs.109.P344

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Endocrine Abstracts (2025) 109 P344 | DOI: 10.1530/endoabs.109.P344

SFEBES2025 Poster Presentations Late Breaking (68 abstracts)

Evaluating the incidence of hypothyroidism and its associated factors within one-year post radioactive iodine (RAI) therapy for benign thyroid disease; a single centre experience

Huma Humayun Khan , Aparna Pal , Helen E Turner & Christine JH May

Author affiliations

Oxford Centre for Diabetes, Endocrinology and Metabolism, Oxford, United Kingdom

RAI is a definitive treatment option for benign thyroid disease aiming for euthyroidism. In practice, incidence of subsequent hypothyroidism is 5–50%, with potential for significant symptoms and exacerbation of thyroid eye disease (TED). NICE guidance recommends close monitoring of thyroid function (TFT) following RAI therapy with prompt initiation of levothyroxine; however, practice varies and there is no consensus RAI dosage algorithm.

Aims: 1. Assess effectiveness of centre doses (400 MBq -Graves’ disease (GD)/ multinodular goitre, 200 MBq -toxic adenoma). 2. Evaluate frequency of abnormal TFT post RAI and adherence to NICE guideline, following implementation of automated EPR requesting for 6 weekly TFT monitoring at point of RAI consent.

Method: Retrospective data analysis (OUHFT registered audit) of patients undergoing RAI (April 2021-April 2022).

Results: Of 84 patients identified, 40 were excluded as followed-up by referring centre. The majority of patients received RAI for relapsed GD (80%). Outcome: 25 patients (57%) hypothyroid, 10 euthyroid (23%) and 6 remained hyperthyroid; mean time to hypothyroidism 3 months. 79% of 400 MBq dose patients were rendered euthyroid/ hypothyroid and 5 patients had treatment failure. Elevated TRAB was associated with treatment failure. 3 patients received prophylactic steroid; no patient developed/worsened TED. Adherence to NICE guidelines was 93% at 6 months, 78% at 12 months.

Discussion: Lower than national average RAI dose led to comparable outcomes for euthyroidism (23%) and hypothyroidism (57%). The lower doses allow reduced radiation protection precautions which is of practical benefits to patients’ day-to-day life post-treatment. We find that hypothyroidism within 6 months of RAI is captured by the NICE monitoring regime. Using prophylactic steroid/avoidance of RAI in those with active TED led to no worsening of TED. Adherence to NICE guidelines was encouraging and demonstrated the electronic change to arranging this works effectively. Realistic consent for hypothyroidism is important.