Amiodarone and the thyroid.
Amiodarone, a benzofuranic iodine-rich antiarrhythmic drug, causes thyroid dysfunction in 15-20% of cases. Amiodarone can cause both hypothyroidism (AIH, amiodarone-induced hypothyroidism) and thyrotoxicosis (AIT, amiodarone-induced thyrotoxicosis). AIH is treated by L-thyroxin replacement and does not need amiodarone discontinuation. There are two main forms of AIT: type 1, a form of true iodine-induced hyperthyroidism; and type 2, a drug-induced destructive thyroiditis. However, mixed/indefinite forms exist, contributed to by both pathogenic mechanisms. Type 1 AIT usually occurs in diseased thyroid glands, whereas type 2 AIT develops in substantially normal thyroid glands. Thioamides represent the first-line treatment for type 1 AIT, but iodine-replete glands are poorly responsive; sodium/potassium perchlorate, by inhibiting thyroidal iodine uptake, may increase the response to thioamides. Type 2 AIT is best treated by oral glucocorticoids. Response depends on thyroid volume and severity of thyrotoxicosis. Mixed/indefinite forms may require a combination of thioamides, potassium perchlorate, and steroids. Radioiodine treatment is usually not feasible because amiodarone-related iodine load decreases thyroidal radioiodine uptake. Thyroidectomy represents an important and helpful option in cases resistant to medical therapy. Surgery performed by a skilled surgeon may represent an emergent treatment in patients who have severe cardiac dysfunction.
Department of Endocrinology, Jagiellonian University, Medical College, Krakow, Poland. ajabrocka@op.pl.
Agata
A
Jabrocka-Hybel
Tomasz
T
Bednarczuk
Luigi
L
Bartalena
Dorota
D
Pach
Marek
M
Ruchała
Grzegorz
G
Kamiński
Marta
M
Kostecka-Matyja
Alicja
A
Hubalewska-Dydejczyk
D000368:Aged; D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced* / Q000188:drug therapy / Q000601:surgery; D008297:Male; D008875:Middle Aged; D013854:Thioamides / Q000627:therapeutic use; D013961:Thyroid Gland / Q000187:drug effects*; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000188:drug therapy / Q000601:surgery; D013974:Thyroxine / Q000627:therapeutic use
D000889:Anti-Arrhythmia Agents; D005938:Glucocorticoids; D013854:Thioamides; D000638:Amiodarone; D013974:Thyroxine