A Case of Thyrotoxicosis and Excess Iodine Due to Habitual Use of Polyvinylpyrrolidone Iodine while Gargling in an Iodine-sufficient Area

Abstract

Excess iodine can influence the pathophysiology of the thyroid gland and results of various thyroid-related examinations. We herein report a 60-year-old Japanese man with thyrotoxicosis and excess iodine due to habitual use of polyvinylpyrrolidone iodine (PVP-I) to gargle for 20 years. Initial laboratory and imaging findings were suggestive of painless thyroiditis. However, after cessation of PVP-I use for gargling, these results changed to findings suggestive of Graves' disease, with worsening thyrotoxicosis. A detailed questionnaire regarding excess iodine is important for the accurate diagnosis of thyrotoxicosis, even in patients living in iodine-sufficient areas where iodine-induced thyrotoxicosis is rare.