Endocrine Abstracts

This single-centre retrospective analysis evaluated the effectiveness of a fixed-dose protocol for first-dose radioactive iodine (RAI) therapy in benign hyperthyroidism, including Graves’ disease (DTG), toxic multinodular goitre (TMNG) and toxic uninodular goitre (TUNG). We assessed biochemical outcomes up to 12 months post-treatment and compared results with European Association of Nuclear Medicine (EANM) targets. All patients receiving first-dose RAI between 2019 and 2024 were included. The institutional protocol specified a fixed dose of 300 MBq for DTG and 500 MBq for TMNG/TUNG. A total of 150 patients were analysed (83.3% female; median age 55 (44–73) years). In the DTG group (n = 85), outcome data were available for 72 (84.7%) patients. Of these, 51 (70.8%) became hypothyroid, 9 (12.5%) euthyroid, and 12 (16.7%) remained hyperthyroid. The mean time to hypothyroidism was 3.5 months, and 60 (83.3%) patients met the EANM target (≥90%). For the TMNG/TUNG group (n = 65), outcome data were available for 52 (80%) patients. Here, 15 (28.8%) became hypothyroid, 28 (53.8%) euthyroid, and 9 (17.3%) remained hyperthyroid. The mean time to hypothyroidism was 5.3 months, and 43 (82.7%) patients met the EANM target (≥80%). Correlation between administered dose and favourable outcomes was weakly positive (r = 0.129 for DTG and r = 0.095 for TMNG/TUNG), while the correlation between pre-treatment 24-hour iodine-131 uptake and favourable outcomes was negligible in DTG (r = 0.0), and weakly negative in TMNG/TUNG (r = -0.38). Our fixed-dose RAI protocol met EANM targets for TMNG/TUNG. However, DTG outcomes were below the target, which may be attributed to the absence of individualised dosimetic planning.