Prediction of thyroidal 131I effective half-life in patients with Graves' disease

Purpose: Calculation of effective thyroidal half-life (Teff) of iodine-131(I-131) is cumbersome and tedious. The aim of this study was to investigate factors that could be used to predict Teff and to develop a Teff prediction model in Graves' disease patients. Methods: A total of 256 patients with GD were involved in this study. We investigated the influences of age, gender, disease duration, thyroid weight, antithyroid drugs, antithyroid drugs discontinuation period (ADP), thyroid function indexes, thyroid autoantibodies, thyroid-stimulating hormone receptor antibody (TRAb) level and radioactive iodine uptake (RAIU) values before I-131 therapy on Teff, applying univariate and multivariate analyses. Results: Teff correlated negatively with thyroid peroxidase antibody, TRAb and thyroid weight, as well as positively with 24-hour, 48-hour, and 72-hour RAIU. Additionally, a longer ADP (especially >= 14d) or without antithyroid drugs before I-131 therapy led to a longer Teff. Stepwise multiple linear regression analysis showed that 24-hour and 72-hour RAIU were statistically significant predictors of Teff (P<0.001). The relationship was: predictive Teff = 5.277+0.295x72-hour RAIU-0.217x24-hour RAIU (r = 0.865, P < 0.001). Conclusion: The present results indicate that prediction of Teff from 24-hour and 72-hour RAIU is feasible in patients with Graves' disease, with high prediction accuracy.