Endocrine Abstracts

Background: Over two-thirds of patients treated with radioactive iodine (RAI) for benign thyroid disease develop hypothyroidism within one year¹ and timely detection and treatment is essential to prevent morbidity². NICE³ and British Thyroid Foundation (BTF) guidelines¹ therefore recommend thyroid function testing (TFTs) 4-6 weeks post-RAI. We wanted to assess the average time to hypothyroidism in our population and whether thyroid pathology and type and dose of antithyroid drug (ATD) treatment pre-RAI influences time to hypothyroidism.

Aims: Primary – Analyse the timeframe to hypothyroidism and assess our trust’s compliance with post-RAI follow-up guidelines. Secondary – Assess correlation between thyroid pathology and type and dose of ATD treatment pre-RAI with time to hypothyroidism.

Methods: A retrospective analysis was undertaken of adults aged > 16 years who received fixed-dose (555 MBq) RAI for benign thyroid disease at London Northwest Healthcare NHS Trust between 2021-2024. Patients with incomplete/inaccessible records and those lost to follow-up were excluded. Data was collected from electronic patient records and analysed with Microsoft Excel and SciPy software.

Results: 127 patients were included in the study (67 patients excluded). 62.3% (n = 79) became hypothyroid, 11.8% (n = 15) became euthyroid and 25.9% (n = 33) remained hyperthyroid (17.3%, n = 22 had recent RAI <1 year). The median time to hypothyroidism and levothyroxine initiation was 97 and 104 days respectively. There was no difference in time to hypothyroidism between different thyroid pathologies and type and dose of ATD. Only 20.3% of patients had follow-up 4-6 weeks post-RAI as recommended, whilst the majority (67.1%) had delayed follow-up (median 48 days).

Conclusions: Our trust was not compliant with follow-up guidelines post-RAI and this study prompted a trust-wide change in clinical practice; all patients now have TFTs and follow-up booked 6 weeks post-RAI with our endocrine nurse, with a departmental target for a second follow-up to be arranged within 97 days post-RAI.