Chronic administration of amiodarone and thyroid function: a follow-up study.

Area of Science:

• Endocrinology
• Pharmacology

Background:

• Amiodarone is an effective antiarrhythmic drug.
• Its use is associated with various adverse effects, including thyroid dysfunction.

Purpose of the Study:

• To evaluate the effects of chronic amiodarone treatment on thyroid function.
• To assess the prevalence of thyroid dysfunction and thyrotropin-releasing hormone (TRH) stimulation abnormalities in patients on long-term amiodarone therapy.

Main Methods:

• Prospective study of 43 patients on chronic amiodarone treatment (mean duration >9 months).
• Thyroid function tests (T3, T4, rT3, TSH) and TRH stimulation tests were performed at baseline and 12-18 months later.

Main Results:

• At baseline, 5 patients (11.6%) had overt thyroid dysfunction (hypothyroidism or hyperthyroidism).
• Mean T4 and rT3 levels were elevated, while T3 levels were decreased in the remaining patients.
• Thirteen patients (30%) showed hyperresponsiveness to TRH.
• Over 12-18 months, 2 new cases of hypothyroidism developed, and T3 levels decreased further.
• TSH levels and TRH-stimulated TSH increased significantly, with 5 new hyperresponders to TRH.

Conclusions:

• Chronic amiodarone administration is associated with a progressive increase in thyroid dysfunction.
• A high prevalence of hyperresponsiveness to TRH stimulation is observed.
• Long-term amiodarone therapy carries a significant risk of developing thyroid dysfunction.