[Thyroid clinical dysfunction in patients chronically treated with amiodarone].

This is a prospective study of 132 patients, without previous thyroid dysfunction, chronically treated with amiodarone for cardiac arrhythmias, to determine the incidence of thyroid dysfunction. Age was 62 +/- 11 years (mean +/- SD); 54 were female and 78 male. The arrhythmia was supraventricular in 66%, ventricular in 26.5%, and both in 7.5%. Amiodarone dose was 2,390 +/- 65 mg/week, and follow-up 20 +/- 9 months (minimum 9 months). Thyroid status was evaluated at the onset and at regular intervals during follow-up by means of clinical indexes defined by Crooks et al and Billewicz et al. During follow-up 4 patients developed diagnostic indexes (two hyperthyroid and two hypothyroid) and seven more developed suggestive symptoms without reaching a diagnostic index. Biochemical serum determinations of thyroid function proved dysfunction in the four with diagnostic indexes, and were normal in the other seven. The prevalence of new thyroid dysfunction in patients chronically treated with amiodarone in our population is 3%, with equal incidence of hyper and hypofunction. This is the expected incidence for an area with adequate dietary iodine intake. The use of clinical indexes of thyroid dysfunction appear as a useful and economical means of following thyroid function in these patients, saving a large number of biochemical tests.