OBJECTIVES: This study aimed to evaluate the impact of Radioactive iodine 131 (RAI 131) therapy on the quality of life (QoL) of patients with hyperthyroidism using the Thyroid Patient-Reported Outcome (ThyPRO) questionnaire and to quantify the extent of these improvements. METHODS: This two-year, prospective, single-center study was conducted at the University Medical Faculty Hospital. Eighty-four patients (39 males and 45 females) diagnosed with hyperthyroidism due to Graves' disease, toxic multinodular goiter, or toxic adenoma received RAI 131 therapy at doses of 10, 15, 20, or 30 mCi. The ThyPRO questionnaire, consisting of 84 questions across 12 domains, was administered before treatment and six months post-treatment to assess QoL. The primary outcome was the change in ThyPRO scores. RESULTS: Significant improvements in all post-treatment QoL measures were observed in both males and females (p<
0.001). The average age of the patients was 58.33±12.45 years. QoL improvements were consistent across all age groups (<
50, 50-60, >
60 years) and at all levels of hyperthyroidism severity (mild, moderate, and severe). All RAI 131 dose groups (10, 15, 20, and 30mCi) showed significant improvements in QoL, with no significant differences between dose groups. The correlation analysis revealed that age had a weak negative correlation with QoL improvement (r=-0.20, p=0.05), whereas thyroid hormone levels were significantly correlated with QoL improvement. Multiple regression analysis identified initial ThyPRO score and age as significant predictors of QoL improvement, whereas sex and RAI 131 dose were not significant predictors. CONCLUSION: RAI therapy significantly enhanced the QoL of hyperthyroid patients according to demographic and disease severity. These findings support the use of RAI 131 as a primary treatment for hyperthyroidism, highlighting the importance of personalized treatment approaches for optimizing patient outcomes. Future research should focus on long-term QoL outcomes and refine therapeutic strategies.