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The effects of amiodarone on the thyroid
E Martino1, L Bartalena, F Bogazzi
1Dipartimento di Endocrinologia e Metabolismo, University of Pisa, Ospedale de Cisanello, via Paradisa, 2, 56124 Pisa, Italy. e.martino@endoc.med.unipi.it
Endocrine Reviews
|April 11, 2001
Summary
Amiodarone, a drug for heart rhythm disorders, can cause thyroid dysfunction in 14-18% of patients. This includes amiodarone-induced thyrotoxicosis (AIT) and amiodarone-induced hypothyroidism (AIH), requiring specific treatments based on the type.
Area of Science:
- Endocrinology
- Cardiology
- Pharmacology
Background:
- Amiodarone is a widely used antiarrhythmic drug containing iodine.
- It frequently alters thyroid function tests by inhibiting deiodinase activity.
- Overt thyroid dysfunction, amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH), occurs in 14-18% of patients.
Purpose of the Study:
- To review the mechanisms of amiodarone-induced thyroid dysfunction.
- To outline the clinical presentation and risk factors for AIT and AIH.
- To discuss current treatment strategies for amiodarone-induced thyroid disorders.
Main Methods:
- Review of existing literature on amiodarone and thyroid dysfunction.
- Analysis of the pathogenesis of iodine-induced thyroid abnormalities.
- Synthesis of treatment approaches for AIT and AIH.
Main Results:
- Amiodarone's iodine content and enzyme inhibition lead to altered thyroid hormone levels.
- Preexisting Hashimoto's thyroiditis increases the risk of amiodarone-induced hypothyroidism (AIH).
- AIT is classified into Type I (excess synthesis) and Type II (destructive), with mixed forms common.
- AIH treatment involves L-T(4) replacement or amiodarone withdrawal.
- Type I AIT is treated with thionamides and potassium perchlorate; Type II AIT with glucocorticoids; mixed forms with combinations.
Conclusions:
- Amiodarone frequently causes thyroid dysfunction through various mechanisms.
- Accurate diagnosis and tailored treatment are crucial for managing AIT and AIH.
- Understanding the specific type of amiodarone-induced thyroid dysfunction guides therapeutic decisions.