Predictors of a response to radioactive iodine therapy in hyperthyroidism – ablative dose concept: A 23-year single center 914-patient experience

Abstract

Objective

The three treatment modalities for patients with hyperthyroidism are antithyroid drugs (ATDs), surgery, and radioactive iodine (RAI) therapy. The study aims to determine the predictors of a response to RAI in patients with hyperthyroidism.

Materials and methods

We retrospectively assessed 914 patients who received RAI for the treatment of hyperthyroidism between January 2000 and December 2023, with a follow-up of at least 6 months after the first dose.

Results

Hypothyroidism was ultimately achieved in 62.9% of the patients. Multiple variables are possible predictors in univariable logistic regression analysis. However, only shorter duration of ATD therapy (odds ratio 0.996; 95% confidence interval [CI], 0.093–0.999; P = .003, multivariable logistic regression analysis) and a diagnosis of Graves’ disease (GD) (odds ratio 1.803; 95% confidence interval [CI], 1.042–3.141; P = .035, multivariable logistic regression analysis) are the independent predictors of post-treatment hypothyroidism, with decreasing age also being a late-response independent predictor of hypothyroidism 24 months after the treatment (odds ratio 0.983; 95% confidence interval [CI], 0.968–0.998; P = .028, multivariable logistic regression analysis). The median time to hypothyroidism was 10.0 ± 0.7 months (Kaplan-Meier method), with a statistically significant difference in hypothyroidism-free survival (HFS) between patients with GD on one side and solitary toxic adenoma (STA) and toxic multinodular goiter (TMG) on the other (P < .001, log-rank test).

Conclusions

GD and a shorter duration of previous ATD therapy are independent predictors of post-therapeutic hypothyroidism in patients treated for hyperthyroidism with RAI, with younger age also being an independent predictor of a late response.