Amiodarone and the thyroid.

Area of Science:

• Cardiology
• Endocrinology
• Pharmacology

Background:

• Amiodarone, an iodine-rich antiarrhythmic, frequently causes thyroid dysfunction (15-20%).
• This dysfunction manifests as amiodarone-induced hypothyroidism (AIH) or amiodarone-induced thyrotoxicosis (AIT).
• AIH is managed with L-thyroxine without drug cessation.

Purpose of the Study:

• To differentiate and outline management strategies for amiodarone-induced thyrotoxicosis (AIT).
• To discuss treatment options for different AIT types and mixed forms.
• To highlight the role of surgery in refractory AIT cases.

Main Methods:

• Classification of AIT into Type 1 (iodine-induced hyperthyroidism) and Type 2 (destructive thyroiditis).
• Assessment of underlying thyroid health (diseased vs. normal) for AIT type determination.
• Review of treatment modalities including thioamides, potassium perchlorate, glucocorticoids, radioiodine, and surgery.

Main Results:

• Type 1 AIT, common in diseased thyroids, responds variably to thioamides; perchlorate can enhance response.
• Type 2 AIT, occurring in normal thyroids, is best treated with glucocorticoids.
• Mixed/indefinite AIT forms may require combination therapy; radioiodine is often ineffective due to iodine load.

Conclusions:

• Effective management of AIT requires distinguishing between Type 1, Type 2, and mixed forms.
• Medical therapies (thioamides, perchlorate, steroids) are tailored to AIT type.
• Thyroidectomy is a valuable option for amiodarone-induced thyrotoxicosis resistant to medical treatment, especially in cardiac patients.