MON-607 Monitoring Thyroid Function in Patients on Amiodarone: A Review of Practice Patterns and Adherence to the Recommended Guidelines in a Health Care System

Amiodarone is a commonly prescribed medication that has complex effects on the thyroid, including thyroid dysfunction in 15-20% of patients. Amiodarone-induced hypothyroidism (AIH) and amiodarone-induced thyrotoxicosis (AIT) are important clinical concerns. The American Thyroid Association and North American Society of Pacing recommend use of thyroid function tests (TFTs) before starting amiodarone and monitoring of thyroid function at regular intervals thereafter. We hypothesized that thyroid function in these patients is not being evaluated and monitored per recommendations in our health care system. We retrospectively reviewed charts of patients who were on amiodarone with ICD 9/10 codes associated with the diagnosis of atrial and/or ventricular tachyarrhythmias seen in outpatient clinics in our multicenter system from January 2012 through December 2017. Of the 1218 patients identified, 867 (71.18%) did not have a baseline TSH before starting amiodarone. A total of 137 patients (11.24%) had a baseline TSH and 214 (17.5%) had an unknown amiodarone start date; therefore, we were unable to determine whether baseline TSH was done. Of the 137 patients who had a baseline TSH, 21(15.3%) had appropriate 3-month follow-up TSH evaluation and 23 (16.8%) had repeat TSH at 6 months. Of the 1218 patients, 484 had at least one TSH performed while on amiodarone, and 152 of those patients had abnormal TFTs after starting amiodarone therapy. Of these 152 patients, 52 (34.21%) developed mild thyroid function abnormalities on amiodarone with normalization in 6 months to 1 year. Twenty (13.15%) were determined to have preexisting hypothyroidism. Fifty-four (35.5 %) developed AIH, 10 (6.57%) developed AIT and nine (21%) developed subclinical hypothyroidism. Of the 1218 patients, 93% were followed by a cardiologist and 6.6% were followed by other providers (endocrinologist, internist, family medicine specialist). These findings reveal that the majority of patients were not appropriately evaluated before starting amiodarone therapy and were not followed subsequently with TFTs as recommended in the guidelines. Further study is needed to understand the reasons behind the lack of appropriate evaluation and education of providers regarding the guidelines may be helpful.