Effects of amiodarone on thyroid function.

PURPOSE

To review the literature on the effects of amiodarone on thyroid physiology and management of amiodarone-induced thyroid disease.

DATA SOURCES

English-language articles identified through a MEDLINE search (for 1975 to 1995, using the terms amiodarone and thyroid) and selected cross-referenced articles.

STUDY SELECTION

Articles on the effects of amiodarone on thyroid physiology and function tests and occurrence, recognition, and management of amiodarone-induced thyroid disease.

DATA EXTRACTION

Data were manually extracted from selected studies and reports; emphasis was placed on information relevant to the practicing clinician.

DATA SYNTHESIS

Amiodarone can have many effects on thyroid function test results, even in the absence of hyperthyroidism or hypothyroidism. It may cause an increase in serum levels of thyroxine, reverse triiodothyronine, and thyroid-stimulating hormone and a decrease in serum triiodothyronine levels. Thyrotoxicosis occurs in some patients and is related to several pathogenetic mechanisms. It often present dramatically with obvious clinical manifestations and further changes in thyroid function test results. Medical options include therapy with thionamides, perchlorate, and prednisone. Radioactive iodine is of little use. Thyroidectomy is effective and is the only measure that consistently allows continued use of amiodarone. Unlike thyrotoxicosis, hypothyroidism is related to a persistent Wolff-Chaikoff effect and often has a vague presentation. The goal of treatment of amiodarone-induced hypothyroidism is to bring serum thyroxine levels to the upper end of the normal range, as often seen in euthyroid patients who are receiving amiodarone.

CONCLUSIONS

Thyroid dysfunction commonly occurs with amiodarone therapy. It may be difficult to recognize the dysfunction because of the many changes in thyroid function test results that occur in euthyroid patients who are receiving amiodarone. Effective strategies exist for the management of hyperthyroidism and hypothyroidism; these should be tailored to the needs of the individual patient.