Imaging evaluation of amiodarone-induced thyroid dysfunction: ultrasonographic and radionuclide findings with clinical correlation.

Background: Amiodarone is a commonly used antiarrhythmic drug in clinical practice, and amiodarone often causes thyroid dysfunction. The mechanism by which amiodarone causes thyroid dysfunction is mainly due to high iodine exposure, which can lead to hypothyroidism and two different types of thyroid toxicity. Due to the vastly different treatment options, it is particularly important to distinguish between the two types of thyroid toxicity induced by amiodarone. This study aims to examine the clinical and radiological characteristics of thyroid disorders induced by amiodarone, a medication commonly used for arrhythmias, and to elucidate its association with thyroid function. Methods: The study included 628 patients undergoing amiodarone treatment for arrhythmia and a control group of 80 individuals without pre-existing thyroid conditions who visited the hospital during the same period. Serum thyroid function was monitored in both groups (3 months to 6 years). Ultrasound examinations were performed on all participants, and thyroid radionuclide imaging was conducted on the study group regardless of the results of thyroid function test (TFT). The radionuclide imaging findings were analyzed in relation to changes in thyroid function. Results: Among the 628 patients, 476 (75.80%) maintained normal thyroid function, while 152 (24.20%) exhibited thyroid dysfunction. Radionuclide imaging showed increased thyroid uptake in 21 cases (3.34%) and decreased uptake in 14 cases (2.23%). No significant correlation was found between the development of amiodarone-induced thyroid disorders and the age or gender of the patients. However, the presence of positive initial thyroglobulin antibodies (Tgabs) and thyroid peroxidase antibodies (TPOabs) was associated with a higher likelihood of developing amiodarone-induced thyroid disorders. Conclusions: Amiodarone therapy can result in thyroid dysfunction, highlighting the need for regular monitoring of thyroid function. A combination of radionuclide imaging and ultrasound is recommended for accurately determining the type of thyrotoxicosis. Early diagnosis and precise classification are essential for timely and appropriate treatment.