Endocrine Abstracts

Background: Amiodarone is frequently associated with thyroid dysfunction. Identifying predictors for amiodarone-associated thyroid dysfunction and assessing treatment outcome may aid clinicians in daily practice.

Patients and methods: In our retrospective study, we included 303 consecutive patients with amiodarone therapy for cardiac arrhythmias (260 with atrial fibrillation and 43 with ventricular arrhythmias). Thyroid function tests were performed every 6 months.

Results: Mean age was 63±12 years and 66% was male. After median follow-up of 3.3 (0.1–24) years, 23 (8%) patients developed amiodarone-associated thyrotoxicosis (incidence rate 1.9 per 100 person years) and 18 (6%) hypothyroidism (incidence rate 1.1 per 100 person years). The only predictor for amiodarone-associated thyrotoxicosis was age <62 years (HR=2.4 (95% CI 1.0–5.7), P=0.05). Predictors for amiodarone-associated hypothyroidism were thyroid stimulating hormone >1.4 mU/l at baseline (HR=5.1 (95% CI 1.1–22.4), P=0.03), left ventricular ejection fraction < 45% (HR=3.8 (95% CI 1.1–13.3), P=0.04) and diabetes mellitus at baseline (HR=3.3 (95% CI 1.1–10.3), P=0.04). Gender was not a predictor for amiodarone-associated thyroid dysfunction. Five out of 23 (22%) patients with thyrotoxicosis exhibited spontaneous normalization of thyroid function on continuation of amiodarone therapy. Mean time to normalization in the total group was 6.2±3.3 months, with no difference between continuing or discontinuing amiodarone (6.6±3.8 versus 5.8±2.8 months, P=0.5).

Conclusions: During median follow-up of 3.3 years, the incidence of amiodarone-associated thyrotoxicosis was higher compared to hypothyroidism. Only general predictors for amiodarone-associated thyroid dysfunction were observed. Discontinuation of amiodarone did not influence treatment outcome.