Amiodarone and thyroid dysfunction.
Amiodarone is a potent antiarrhythmic drug associated with thyroid dysfunction. Its high iodine content causes inhibition of 5'-deiodinase activity. Most patients remain euthyroid. Amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH) may occur depending on the iodine status of individuals and prior thyroid disease. AIT is caused by excess iodine-induced thyroid hormone synthesis (type I AIT) or by destructive thyroiditis (type II AIT). If the medical condition allows it, discontinuation of the drug is recommended in type I AIT. Otherwise, large doses of thioamides are required. Type II AIT is treated with corticosteroids. Mixed cases require a combination of both drugs. Potassium perchlorate has been used to treat resistant cases of type I AIT but use is limited by toxicity. Thyroidectomy, plasmapheresis, lithium, and radioiodine are used in select cases of AIT. AIH is successfully treated with levothyroxine. Screening for thyroid disease before starting amiodarone and periodic monitoring of thyroid function tests are advocated.
Padmanabhan
Hema
H
Department of Medicine, Endocrine Section, Veterans Affairs Medical Center, 1970 Roanoke Boulevard, Salem, VA 24153, USA. ramayana48@hotmail
D000638:Amiodarone / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D013956:Antithyroid Agents / Q000627:therapeutic use; D003266:Continuity of Patient Care; D005938:Glucocorticoids / Q000627:therapeutic use; D020249:Hormone Replacement Therapy; D006801:Humans; D007037:Hypothyroidism / Q000139:chemically induced* / Q000175:diagnosis / Q000628:therapy; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008713:Methimazole / Q000627:therapeutic use; D010472:Perchlorates / Q000008:administration & dosage; D010956:Plasmapheresis; D012307:Risk Factors; D013961:Thyroid Gland / Q000000981:diagnostic imaging; D013963:Thyroid Hormones / Q000097:blood; D013965:Thyroidectomy; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000145:classification / Q000175:diagnosis / Q000628:therapy; D013974:Thyroxine / Q000627:therapeutic use; D014463:Ultrasonography
D000889:Anti-Arrhythmia Agents; D013956:Antithyroid Agents; D005938:Glucocorticoids; D007457:Iodine Radioisotopes; D010472:Perchlorates; D013963:Thyroid Hormones; D008713:Methimazole; D000638:Amiodarone; D013974:Thyroxine; C494474:perchlorate