Amiodarone

Question 1

General findings

Answer 1

Amiodarone is a class III antiarrhythmic drug used in the treatment of recurrent severe ventricular arrhythmias, paroxysmal atrial tachycardia, atrial fibrillation and maintenance of sinus rhythm after cardioversion of atrial fibrillation (1). Amiodarone-induced thyrotoxicosis (AIT) develops in 3% of amiodarone-treated patients in North America. For those living in iodine-depleted areas, the incidence is higher (10%) (2). This risk also increases with increased dosage

Amiodarone-induced thyrotoxicosis (AIT) develops in 3% of amiodarone-treated patients in North America. AIT is classified as type 1 or type 2. Type 1 AIT occurs in patients with underlying thyroid pathology such as autonomous nodular goiter or Graves’ disease. Type 2 AIT is a result of amiodarone causing a subacute thyroiditis with release of preformed thyroid hormones into the circulation.

Question 2

Signs and symptoms of amiodarone-induced thyrotoxicosis

Answer 2

Sinus tachycardia
Atrial fibrillation
Ventricular tachycardia
Angina
Heart failure

Total and free T4 levels increased
Total and free T3 levels increased
Thyroid-stimulating hormone dramatically decreased

Question 3

Type 1

Normal IL-6 levels

Answer 3

AIT occurs in patients with an underlying thyroid pathology such as autonomous nodular goiter or Graves’ disease. In these patients, there is accelerated thyroid hormone synthesis secondary to the iodide load from the amiodarone therapy (the Jod-Basedow phenomenon) 💥

The uptake is typically normal or high in type 1 AIT

Treatment: antitiroidei!

Question 4

Type 2

Elevated IL-6 levels!

Answer 4

In type 2 AIT, the thyrotoxicosis is a destructive thyroiditis that results in excess release of preformed T4 and T3 into the circulation (11). It typically occurs in patients without underlying thyroid disease, and is caused by a direct toxic effect of amiodarone on thyroid follicular cells. The thyrotoxic phase may last several weeks to several months, and it is often followed by a hypothyroid phase with eventual recovery in most patients.

There is very little or no uptake of the iodine due to destruction or damage to the thyroid tissue

Treatment: steroids!