How amiodarone affects thyroid function

Learn how amiodarone affects thyroid hormones and how to monitor them long-term.

Tracy Tylee, MD
Tracy Tylee, MD
14th Mar 2018 • 2m read

Patients using amiodarone can exhibit symptoms of thyroid dysfunction years after commencing therapy. In this video, you'll find out how amiodarone affects thyroid function, when this effect stabilizes, and how often you should monitor the lab results of patients using amiodarone.

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Video Transcript

[00:00:00] Amiodarone can have a number of different effects on thyroid function including on thyroid hormone production and thyroid hormone action. Some of these effects can alter the results of our thyroid labs. Amiodarone blocks the conversion of T4 to T3, which results in low T3 levels and slightly higher T4 levels. This leads to a decrease in inhibition at the pituitary due to the low levels of T3, which leads to an increase in TSH levels. So, initial labs for

[00:00:30] patients starting on amiodarone therapy will show an elevation in TSH, with a low T3, and a slightly elevated T4. Over time, the increased TSH leads to increase in T4 production. The higher levels of T4 are able to overcome that blockade of amiodarone and convert to adequate levels of T3. This increases inhibition at the level of the pituitary and TSH levels return to normal. So, after several months of amiodarone therapy, patient's labs will show a normal

[00:01:00] TSH, with a high T4 but a T3 that's at the low end of normal. In addition to the changes in thyroid labs, amiodarone can have a number of different effects on thyroid function. While many patients will maintain normal thyroid function on amiodarone, some patients will develop thyroid dysfunction months or years into therapy. Thus, it is important that patients who are on amiodarone therapy are appropriately monitored for thyroid function. At baseline, all patients should have a TSH and free thyroid hormone levels measured, and this should be repeated at three months.

[00:01:30] While patients are on amiodarone therapy, they should have a TSH checked every six months, to ensure that their thyroid function remains normal while on therapy.

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