Predicting outcomes and complications following radioiodine therapy in Graves' thyrotoxicosis

OBJECTIVE: 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.

DESIGN: Retrospective cohort study.

PATIENTS: 655 episodes of RAI in Graves' thyrotoxicosis patients (2006 - 2015).

MEASUREMENTS: Biochemical assessment, including TFTs and thyrotropin receptor antibodies (TRAb), clinical features (e.g. TED, weight, thionamide use) and patient questionnaire.

RESULTS: 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).

CONCLUSIONS: 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 dysthryoidism on weight gain, TED or thyroid symptoms in this large cohort. This article is protected by copyright. All rights reserved.