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 99mTc-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.
Highlights
Amiodarone is a class III antiarrhythmic drug, used by cardiologists to treat arrhythmia including atrial fibrillation (A fib) and ventricular fibrillation
There is a direct toxic effect on the thyroid follicular cells, resulting in a destructive thyroiditis referred to amiodarone-induced thyrotoxicosis type 2 (AIT-2). e iodine content in amiodarone mediates amiodarone-induced thyrotoxicosis type 1 (AIT-1) and amiodarone-induced hypothyroidism (AIH)
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
Summary
Amiodarone is a class III antiarrhythmic drug, used by cardiologists to treat arrhythmia including atrial fibrillation (A fib) and ventricular fibrillation. Is dysfunction is explained by the high iodine content (containing 75 mg of iodine per 200 mg tablet) and its direct toxic effect on the thyroid [1]. Amiodarone principle metabolite is desethylamiodarone (DEA), which accumulates in different tissues including the lung, the adipose tissues, and the thyroid. E intrinsic properties of the drug explain the effect of amiodarone on thyroid hormone. It inhibits the outer ring 5'-monodeiodination of thyroxine (T4). There is a direct toxic effect on the thyroid follicular cells, resulting in a destructive thyroiditis referred to amiodarone-induced thyrotoxicosis type 2 (AIT-2). AIT-1 has underlying abnormal thyroid gland (nodular goiter and latent Graves’ disease) with positive
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