How frequently would you check thyroid function in a patient who has been on amiodarone for more than one year with no prior thyroid disease and consistently normal thyroid function tests?

Amiodarone-induced thyroid dysfunction occurs in approximately 2–24% of cases. Hypothyroidism is more common than hyperthyroidism. Hypothyroidism can occur within 3 months of the beginning of Amiodarone in 10–20% of cases or may develop up to 1 year in 5–10% of cases. In some studies, the median time for the onset of hypothyroidism was about 183 days and for the onset of hyperthyroidism was as long as 720 days.

However, because of the frequency of Amiodarone-induced thyroid dysfunction, it is advisable to check thyroid function approximately every 3 months. This should be continued for at least one year even after Amiodarone has been discontinued.

Ylli et al., PMID 33159436