An Analysis for Aggravation of Thyroid Function After Discontinuing Potassium Iodine in Graves Patients Treated With Methimazole and Potassium Iodine

Abstract

Background: The efficacy of methimazole (MMI) combined with potassium iodine (KI) therapy as an initial treatment of Graves disease (GD) is reported in an area of excessive iodine intake. However, transient aggravation of thyroid function after cessation of KI is often observed. Therefore, we evaluated the factors related with transient aggravation after cessation of KI in GD patients treated with MMI and KI therapy.

Methods: This was a retrospective chart review. Seventy-three GD patients were enrolled in this study. Subjects were divided into two groups. Subjects with transient aggravation were group A, and those without transient aggravation were group B. Between two groups, possible factors were evaluated. Standardized assays were used to measure TSH, free T4 (FT4), free T3 (FT3) and thyrotropin-binding inhibitor immunoglobulin (TRAb). Ultrasonography was used to estimate thyroid volume.

Results: Fishers exact test or Mann-Whitney U test revealed that firstly adjusted drugs, the duration of FT4 normalization from initiation of medication to correction of FT4 to normal range and adoption of simultaneous reduction of both MMI and KI are significant factors. In addition, the latter two factors stayed significant even by multiple logistic regression analysis.

Conclusion: Our study suggested that the methods of drugs adjustment and the duration from initiation of medication to normalization of thyroid hormone may be significant factors of transient aggravation after cessation of KI. It may be better not to reduce both drugs simultaneously, especially in patients who show the relatively shorter duration of normalization of thyroid function.




J Endocrinol Metab. 2013;3(6):132-137
doi: http://dx.doi.org/10.4021/jem204w