Incidence and Pattern of Thyroid Dysfunction in Patients on Chronic Amiodarone Therapy: Experience at a Tertiary Care Centre in Oman

Objective: To determine the incidence and pattern of thyroid dysfunction (TD) in patients on chronic amiodarone therapy. Methods: A retrospective study which evaluated 59 patients who had received amiodarone therapy regularly for at least 12 months from a period of 3 years from October 2007 to October 2010. The patients were followed-up at the cardiac clinic at Sultan Qaboos University Hospital, Muscat, Oman. Results: The mean age of the cohort was 63 +/- 13 years ranging from 27 to 98 years. Fifty-one percent (n = 30) of the patients were female. There were 11 (19%) cases of thyroid dysfunction (TD). Seven (12%) patients were hypothyroid, 3 (5%) had hyperthyroidism and 1 (2%) patient had sub-clinical hypothyroidism; no cases of sub-clinical hyperthyroidism were noted. Female gender and presence of anti-thyroid peroxidase antibodies were significantly associated with amiodarone-induced hypothyroidism (p = 0.001) while age, amiodarone dose and duration of therapy were not correlated with the development of TD (all p-values > 0.05). Conclusion: Amiodarone-induced thyroid dysfunction is prevalent. Hypothyroidism was more frequent and seen more in female patients and those who had positive anti-thyroid peroxidase antibodies. Initial screening and periodic monitoring of thyroid function is mandatory for all patients on amiodarone therapy.