From the Guidelines
Amiodarone can cause hypothyroidism, with hypothyroidism being two to four times more common than hyperthyroidism in patients receiving long-term amiodarone therapy. Amiodarone is an antiarrhythmic medication used to treat various heart rhythm disorders, but it has a significant side effect of thyroid dysfunction. Approximately, the exact percentage of patients developing hypothyroidism is not specified in the most recent and highest quality study, but it is acknowledged as a common side effect 1. This occurs because amiodarone contains high amounts of iodine, which can disrupt normal thyroid function. Additionally, amiodarone can directly damage thyroid cells and interfere with thyroid hormone production and metabolism.
Key Points to Consider
- The risk of developing hypothyroidism is higher in patients with pre-existing thyroid autoimmunity and in those living in iodine-sufficient areas.
- Hypothyroidism typically develops within the first 1-2 years of treatment but can occur at any time during therapy.
- Patients taking amiodarone should have their thyroid function monitored regularly with TSH and free T4 tests, typically every 3-6 months, as recommended by the ESC Guidelines 1.
- If hypothyroidism develops, it can be managed with levothyroxine supplementation while continuing amiodarone if the medication remains necessary for cardiac management 1.
Monitoring and Management
- Regular monitoring of lung, liver, and thyroid function is needed when administering amiodarone, due to the potential for complex drug interactions and extracardiac side effects 1.
- The longer the therapy and the higher the dose of amiodarone, the greater the likelihood that adverse side effects will require discontinuation of the drug.
From the FDA Drug Label
Amiodarone can cause either hypothyroidism or hyperthyroidism. Hypothyroidism has been reported in 2 to 4% of patients in most series, but in 8 to 10% in some series Hypothyroidism is best managed by amiodarone dose reduction and/or thyroid hormone supplement
Yes, Amio can cause hypothyroidism, as reported in 2 to 4% of patients in most series, but in 8 to 10% in some series 2.
- Hypothyroidism may be identified by relevant clinical symptoms and particularly by elevated serum TSH levels.
- Management of hypothyroidism includes amiodarone dose reduction and/or thyroid hormone supplement.
From the Research
Amiodarone and Hypothyroidism
- Amiodarone is known to cause thyroid dysfunction in a significant proportion of patients, with both hypothyroidism and hyperthyroidism being common side effects 3, 4, 5, 6, 7.
- Amiodarone-induced hypothyroidism (AIH) is diagnosed and managed in the same way as a usual case of hypothyroidism, with supplementary levothyroxine therapy being the basis of treatment 3, 5, 7.
- The incidence of AIH has been reported to be around 11.5% in a nationwide retrospective cohort study, with a higher incidence in areas with sufficient iodine intake 6.
- Risk factors for AIH include female sex, diabetes, chronic kidney disease, and Hashimoto's thyroiditis 6.
Mechanism and Treatment
- The high iodine content and prolonged biological half-life of amiodarone can result in thyroid dysfunction, including hypothyroidism 3, 5.
- AIH is more common in patients with previously diagnosed Hashimoto's thyroiditis, and treatment with levothyroxine does not usually require discontinuation of amiodarone therapy 5, 7.
- Regular monitoring of thyroid function is recommended for patients treated with amiodarone, including laboratory testing and clinical examinations, to early detect any deviations in thyroid function 4, 5, 6.