Predictive factors of radioactive iodine therapy failure in hyperthyroidism: a retrospective study of 171 patients.

Introduction: radioiodine therapy with iodine-131 is a standard treatment for hyperthyroidism. Nevertheless, the variability in individual response underscores the need to identify reliable predictors of treatment failure. The study aimed to determine the clinical and biological factors associated with the failure of the first course of radioactive iodine therapy in hyperthyroid patients. Methods: this was a retrospective cohort study conducted between 2012 and 2018, including 171 patients treated for hyperthyroidism with radioiodine therapy at the Salah Azaiez Institute. Demographic, clinical, biological, and therapeutic data were collected and analysed. Results: the median age was 49 years, with a female predominance (sex ratio: 0.41). Graves' disease accounted for 73.7% of cases, and resistance to antithyroid drugs was the main indication for radioiodine therapy (68%). A fixed dose of iodine-131 was administered (mean: 14 ± 2.6 mCi). Treatment failure after the first course occurred in 22.2% of patients (n=38). Failure was significantly associated with higher administered doses (p=0.007), TSH receptor antibody positivity (p=0.005), and the presence of ophthalmopathy (p=0.013). Conclusion: failure after radioiodine therapy appears to be influenced by biological markers (TSH receptor antibodies) and specific clinical factors (ophthalmopathy). These results support individualised dosing strategies and highlight the need for multicenter studies to standardise treatment protocols in nuclear medicine centers in Tunisia.