Amiodarone and thyroid dysfunction

Amiodarone and thyroid dysfunction Brief Review Amiodarone is one of the most widely used anti arrhythmic drug. It is well known that amiodarone can induce both hypothyroidism and hyperthyroidism due to the iodine content of the drug. 200 milligrams of amiodarone daily would deliver twenty to forty times the usual daily iodine intake. Amiodarone reduces 5-deiodinase activity and thereby the monodeiodination of T4 to T3. There is decreased generation of T3 and reduced clearance of rT3 (reverse T3), which accumulates. Destructive thyroiditis is due to the direct toxic effect of amiodarone and its metabolite on the thyroid follicular cells.1 It has been mentioned that during amiodarone treatment, hypothyroidism occurs in iodine sufficient areas and hyperthyroidism occurs in iodine deficient areas.2 Screening for pre-existing thyroid disease and thyroid function prior to initiating amiodarone are ideal in cases where the drug is being started on an elective basis. Thyroid scan results may not be interpretable once a significant dose of iodine in the form of amiodarone has been delivered into the system, especially after an initial intravenous initiation of therapy in life threatening situations. Periodic follow up with thyroid function tests are also recommended while on long term amiodarone therapy. Thyroid stimulating hormone (TSH) level is one of the earliest to rise with amiodarone and can occur as early as 48 hours, reaching nearly three times the normal levels by 10th day....
Source: Cardiophile MD - Category: Cardiology Authors: Tags: General Cardiology Source Type: blogs