Amiodarone is a class III anti-arrhythmic for tachyarrhythmias
Although most patients remain euthyroid on amiodarone, 4-18% develop thyroid disease months to years after exposure.
Amiodarone-induced thyroid disease occurs because amiodarone is structurally similar to triiodothyronine and thyroxine and each 200mg tablet contains 75 mg of iodine.
Two types of amiodarone-induced thyroid disease:
Amiodarone-induced hypothyroidism (AIH)
Amiodarone-inducedthyrotoxicosis (AIT)
Amiodarone-induced hypothyroidism (AIH)
Presents with subtle to overt hypothyroidism
Treat by discontinuing amiodarone; thyroid recovers within 3 months
If amiodarone cannot be discontinued, start levothyroxine
Amiodarone-inducedthyrotoxicosis (AIT)
Sudden symptom onset months to years following exposure; mean 2-47 months post-exposure
Can be a life-threatening presentation (similar to thyroid storm) with severe cardiac manifestations and hemodynamic instability
