Predictors of Hypothyroidism Following Empirical Dose Radioiodine Treatment In Patients with Toxic Adenoma and Toxic Multinodular Goitre: Real-Life Experience

We aimed to determine the factors predicting hypothyroidism after the radioactive iodine (RAI) treatment in patients with toxic adenoma (TA) and toxic multinodular goiter (TMNG).We collected the retrospective data of 237 patients with TMNG/TA who consecutively received RAI treatment between 2014 and 2020 at two medical centers. Patients who received the second RAI treatment and whose medical records could not be accessed were excluded from the study. Finally, 133 patients have included in the study. RAI was administered as an empirical dose of 15 or 20 mCi.The median age of the 133 participants was 69 (interquartile range [IQR],62-75) years, and 64.7% of the participants were women. While 42.1% of the patients had TA, 57.9% had TMNG. The median follow-up was 24 (IQR,11-38) months. During the follow-up, 61.7% of patients developed euthyroid, 30.8% developed hypothyroid, and 7.5% remained hyperthyroid. The median month of hypothyroidism onset was 4 (IQR, 2-9) months. Regression analysis revealed two factors that could predict hypothyroidism: thyroid-stimulating hormone (TSH) (odds ratio [OR] = 2.548; 95% confidence interval [CI]: 1.042-6.231; p=0.04) and thyroid volume (OR=0.930; 95%CI: 0.885-0.978; p=0.005).Overall, 30.8% of the cases developed hypothyroidism after the RAI treatment. Approximately 78% of hypothyroidism developed within the first 10 months. The risk of hypothyroidism was higher in patients with a higher TSH and smaller thyroid volume.