Predicting outcomes and complications following radioiodine therapy in Graves' thyrotoxicosis.

Abstract

Radioiodine (RAI) is an effective treatment for Graves' thyrotoxicosis but is associated with a failure rate of 15% and may be a risk factor for thyroid eye disease (TED) and weight gain. We sought to examine predictors of RAI failure, weight gain, TED and patient satisfaction. Retrospective cohort study. A total of 655 episodes of RAI in Graves' thyrotoxicosis patients (2006-2015). Biochemical assessment, including TFTs and thyrotropin receptor antibodies (TRAb), clinical features (eg, TED, weight and thionamide use) and patient questionnaire. The treatment failure rate was 17%. Failure was greater with higher fT4 (P=0.002) and higher TRAb (P=0.004). Failure rate was 42.2% when TRAb >40U/L. Median weight gain was 3.2kg in those with normal fT4 prior to RAI and 5.8kg when fT4 was elevated (P<0.001). New TED developed in 7.6% but was not associated with post-RAI dysthyroidism. Treatment satisfaction was generally high (median response 8/10). Treatment failure after RAI occurs in predictable groups and this should be reflected in the information provided to patients. Weight gain is common and may not entirely be explained by a return to pre-thyrotoxic baseline. We were unable to detect any significant impact of post-RAI dysthyroidism on weight gain, TED or thyroid symptoms in this large cohort.