Evaluation of the Efficacy of Potassium Iodide Preparation for Radioactive Iodine Therapy in Graves’ Disease: A Retrospective Chart Review

Abstract

Background: Pretreatment by antithyroid drugs (ATDs) before radioactive iodine therapy (RAIT) for Graves’ disease (GD) is often performed to avoid aggravation of thyroid function including thyroid storm. However, in patients suffering from adverse effects of ATDs, potassium iodide (KI) is often selected to treat hyperthyroidism before RAIT in Japan. The aim of this study was to evaluate the efficacy of KI preparation for RAIT in GD and whether a short-term discontinuation of KI before RAIT is a safe and useful method in GD patients showing adverse effects from ATDs. Methods: This is a retrospective chart review. The 24 patients enrolled in this study were divided into two groups. Patients who had large goiter and/or underwent previous RAIT were excluded. Before RAIT, 11 patients were administered KI and were referred to as the KI group. The remaining 13 patients were administered methimazole (MMI) and referred to as the MMI group. Between these two groups, the following factors were compared; radioactive iodine uptake (RAIU) before RAIT, thyroid gland weight, dose of administered 131-I, dose of 131-I based on thyroid gland weight, free thyroxine (FT4) at RAIT, difference in FT4 between before and 4 days after discontinuation of drugs, and thyroid function and thyroid gland weight 1 year after RAIT. Results: RAIU before RAIT (P = 0.0018), dose of 131-I (P = 0.0037), FT4 at RAIT (P = 0.0034), and thyroid gland weight 1 year after RAIT (P = 0.0065) showed significant differences. Thyroid gland weight, dose of 131-I based on thyroid gland weight, difference in FT4 between before drug discontinuation and at RAIT, and thyroid function at 1 year after RAIT did not show any significant differences. Conclusion: These results suggest that most patients without large goiter and/or highly aggressive disease may be safely and efficiently treated with RAIT and KI pretreatment until 4 days before therapy. J Endocrinol Metab. 2017;7(1):25-30 doi: https://doi.org/10.14740/jem394w