The Use of ^99m Tc‐Methoxy‐isobutyl‐isonitrile (sestaMIBI) Uptake on Scintigraphy ( ^99m ‐STS) in Amiodarone‐Induced Thyrotoxicosis: Case Series and Review of the Literature

Abstract

Amiodarone is a class III antiarrhythmic drug, used by cardiologists to treat arrhythmia including atrial fibrillation (A fib) and ventricular fibrillation. However, amiodarone is associated with endocrine dysfunction including both hypo‐ and hyperthyroidism. In the literature, two types of amiodarone‐induced thyrotoxicosis (AIT) were described: AIT‐1 and AIT‐2. Mixed AIT also called AIT type 3 (AIT‐3) has been described in the literature when the cases do not have a typical presentation. In order to differentiate different types of AIT, various clinical, biochemical, and radiological tools have been proposed. The use of 99m Tc‐methoxy‐isobutyl‐isonitrile (sestaMIBI) uptake on scintigraphy ( 99m ‐STS) has been suggested in the literature in only few studies (no large retrospective or prospective studies have been established in the United States). We present a case series describing 5 patients presenting to the University of Arizona with AIT where we used 99m ‐STS to assess in diagnosis and treatment of different types of AIT followed by a review of the literature.