Monitoring thyroid function status in elderly patients on amiodarone

Objectives: To evaluate whether elderly patients on amiodarone were having their thyroid function status monitored as recommended in the literature and to identify the frequency and type of thyroid function test abnormalities noted. Methods: Patients on amiodarone were identified by examining the prescription charts and medical files of consecutive admissions into Zammit Clapp Hospital (ZCH) and residents at St Vincent de Paul Residence (SVPR). Data was obtained on whether thyroid function tests had been checked at the start of the medication and every six months; the results of such tests carried out over the previous year; the clinical indication to prescribe the medication; and the course of action followed when results were abnormal. Results: 1334 prescription charts were examined. 69 patients (5.2%) were on amiodarone. The most common clinical indication for the medication was atrial fibrillation (68.1%). As regards thyroid status, 39.1% of subjects had blood tests checked at the start of the medication but only 2.9% every 6 months. Although 75.4% had had their thyroid status checked over the previous year, 8.7% never had any thyroid function tests carried out whilst they were on the medication. In all 27.5% of subjects had thyroid gland dysfunction of which 13% had subclinical hypothyroidism, 11.6% clinical hypothyroidism and 2.9% clinical hyperthyroidism. All patients with abnormal results had been kept on amiodarone even when the arrhythmia had abated. Conclusions: Thyroid dysfunction is a common side effect of amiodarone medication. The regular measurement of thyroid function tests, as recommended, should be adhered to in a stricter manner.