Amiodarone-induced thyrotoxicosis

Amiodarone-induced thyrotoxicosis requires specialist management. It can occur in patients with and without pre-existing thyroid disease. Amiodarone-induced thyrotoxicosis can be related to the high iodine content of amiodarone (type 1 amiodarone-induced thyrotoxicosis), but amiodarone can also directly damage thyroid cells (type 2 amiodarone-induced thyrotoxicosis). See also Overview of thyrotoxicosis  for details about the different types of amiodarone-induced thyrotoxicosis.

Amiodarone-induced thyrotoxicosis can develop during long-term amiodarone treatment, or some months after stopping treatment (because amiodarone has a long half-life). It has diverse presentations, and a poor correlation between biochemical and clinical severity. Extreme weight loss and myopathy can indicate life-threatening thyrotoxicosis. The decision to stop or continue the amiodarone should be made in consultation with the cardiologist. Stopping treatment may not reverse the thyrotoxicosis.

Distinguishing the subtype of amiodarone-induced thyrotoxicosis can be difficult. If the cause is clear, and the patient is stable, treat according to the disease type. Treat type 1 disease with antithyroid therapy, and treat type 2 disease with high-dose glucocorticoid therapy, tapering the dose based on clinical and biochemical responses. If a patient is severely unwell or has not responded to monotherapy, use empirical dual therapy with a high-dose glucocorticoid and a high-dose antithyroid drug, and seek urgent specialist review.

For a patient not responding to treatment at 4 to 6 weeks, thyroidectomy may be required. Seek specialist advice.