Association between Serum Amiodarone and N-Desethylamiodarone Concentrations and Development of Thyroid Dysfunction

This retrospective cohort study was performed to examine the association between serum amiodarone (AMD) and N-desethylamiodarone (DEA) concentrations and the development of thyroid dysfunction.

Patients treated with AMD from January 2012 to April 2016 were identified from the computerized hospital information system database at the National Cerebral and Cardiovascular Center. Only patients whose serum AMD and DEA concentrations had been determined at least once were included in the study.

A total of 377 patients were enrolled. Consequently, 54 (14.3%) and 60 (15.9%) patients who developed AMD-induced thyrotoxicosis and hypothyroidism were included. The mean DEA/AMD ratio during the pre-index period in the thyrotoxicosis group (0.86 ± 0.24) was significantly higher than in the hypothyroidism (0.68 ± 0.27) and euthyroidism (0.78 ± 0.30; p < 0.0001) groups. In addition, the mean DEA/AMD ratio during the post-index period in the thyrotoxicosis group (1.05 ± 0.40) was significantly higher than in the hypothyroidism (0.81 ± 0.24) and euthyroidism (0.88 ± 0.22; p < 0.0001) groups. A persistently higher DEA/AMD ratio was observed throughout the study period in the thyrotoxicosis group. In addition, good correlations between the DEA/AMD ratio and the levels of free thyroxine, free triiodothyronine levels, and log (thyroid-stimulating hormone) were observed in the thyrotoxicosis and euthyroidism groups.

Patients with AMD-induced thyrotoxicosis had an increased DEA/AMD ratio and patients with AMD-induced hypothyroidism had a decreased DEA/AMD ratio before the development of thyroid dysfunction. The DEA/AMD ratio may be a predictive marker for AMD-induced thyroid dysfunction.