Predictive factors for early hypothyroidism following the radioactive iodine therapy in Graves' disease patients

Background Radioactive iodine (RAI) therapy is an important treatment option for Graves' disease (GD), the main side effect of RAI treatment is hypothyroidism, and the factors resulting in hypothyroidism are still controversial. The purpose of this retrospective study was to clarify the possible risk factors of early hypothyroidism after RAI therapy in Graves' disease. Methods We reviewed 312 GD patients treated with RAI between January 2017 to December 2018, collected the potential risk factors, and analyzed the relationship between these variables and early hypothyroidism. Results After 6 months' follow-up, 218 (69.87%) patients were evaluated as early hypothyroid. Male gender, shorter duration of disease, smaller thyroid weight, lower 2-h radioactive iodine uptake (RAIU), 6-h RAIU, 24-h RAIU and 6/24-h uptake ratio, lower administered dosages were significantly associated with early hypothyroidism. Logistics regression analysis showed that male gender, smaller thyroid weight and lower 6-h RAIU were associated with early hypothyroidism. Multi-factors combined ROC curve analysis suggested that the predictive power of male gender, smaller thyroid weight and lower 6-h RAIU for early hypothyroidism was 0.711. Conclusions Our results show that RAI is an effective therapy for GD and most of the cured patients became to hypothyroid within 6 months. Male gender, smaller thyroid weight and lower 6-h RAIU are the main risk factors for early hypothyroidism.