oa Journal of Endocrinology, Metabolism and Diabetes in South Africa - Amiodarone-induced thyroid dysfunction
<i>Background.</i> Little is known about the frequency of thyroid dysfunction (TD) associated with amiodarone therapy in southern Africa. <br><i>Objectives.</i> To determine the incidence of TD in a cohort of patients initiated on amiodarone therapy at a cardiac clinic in Cape Town, South Africa, believed to be an iodine-replete area. <br><i>Patients.</i> Pharmacy records were used to obtain the names of patients who received amiodarone between November 1999 and December 2002. <br><i>Results.</i> The sample size was 194, but data analysis was limited to the 163 patients for whom there were complete data. The mean age ± standard deviation (SD) was 59.0 ± 15.0 years (range 22 - 89 years). There were 67 female and 96 male patients. The indications for amiodarone therapy were supraventricular tachycardias (N = 102, 62.6%), ventricular tachycardia (N = 55, 33.7%), and prophylaxis against tachycardias (N = 3, 1.8%). The indication was uncertain in 3 patients (1.8%). The median duration of amiodarone treatment was 679.0 days (quartile deviation (QD) 1 172 days, range 3 - 6 425 days) in the whole cohort. The median duration of amiodarone therapy until new TD was 943 days (QD 1 185 days), significantly longer than in patients who remained euthyroid (547 days, QD 1 135 days) (P = 0.05). There were 45 new TD cases (27.6%): 11 patients (6.7%) were thyrotoxic, 1(0.6%) transient thyrotoxicosis, 1 (0.6%) subclinical hyperthyroidism, 13 (8.0%) had subclinical hypothyroidism, 12 (7.4%) hypothyroidism and 7 (4.3%) had minor changes in thyroid function. <br><i>Conclusions.</i> We found a high incidence of new-onset TD, similar to the highest rates reported internationally. Local factors responsible for this need to be investigated.
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