Endocrine Abstracts

Introduction: Amiodarone is a well-established class III antiarrhythmic drug used in the treatment of arrhythmias and atrial fibrillation.

Case report: History

A 68 year old gentleman who has background history of persistent Atrial fibrillation, dilated cardiomyopathy, took digoxin 125 mg, bisoprolol 2.5 mg and warfarin 2 mg, simvastatin 40 mg, Ramipril 10 mg. Digoxin was discontinued due to the nocturnal pauses, bradycardia on 24 hour holter and Aamiodarone 200 mg was started on April 2015. Following four months commencement of Amiodarone, he developed nausea, palpitation, fatigue, unintentional weight loss and found to have thyrotoxicosis. No iodine-containing contrast agents had been recently administered and family history was negative for thyroid disorders.

Diagnosis

Amiodarone induced thyroiditis [AIT] was made. TSH < 0.01 [0.35–5.50 mu/l], Free T4–30 [10–19.8 pmol/l], TSH receptor Antibody –negative, TPO antibody negative. Routine blood tests are unremarkable.

Treatment and Follow up

Amiodarone was stopped and carbimazole was started. His thyroid function test back to baseline, clinically and biochemically euthyroid after two years of treatement.

Discussion: A diagnosis of AIT can be considered at any time in a patient who develops clinical signs of thyrotoxicosis after taking amiodarone. The main mechanism is iodine-induced hyperthyroidism (type 1 AIT), a form of Jod Basedow, or destructive thyroiditis (type 2 AIT), caused by amiodarone itself and its high iodine content. The risk of hyperthyroidism also increases with increased dosage. The effects of amiodarone on the thyroid can be seen as early as a few weeks after startingtreatment and or up to several months after its discontinuation as Amiodarone is lipophilic and has a long half-life in the body.

Conclusion: Patients with cardiac disease receiving amiodarone treatment should be monitored for signs of thyroid dysfunction, which often manifest as a reappearance of the underlying cardiac disease state. Because thyroid dysfunction is relatively common in amiodarone therapy,all patients should have free thyroxine and thyroid-stimulating hormone (TSH) levels measured before starting therapy, at three- month intervals during treatment and for at least one year after the amiodarone is discontinued.