Hyperthyroidism in elderly patients with atrial fibrillation and normal thyroid hormone measurements.

The results of a study to investigate possible underdiagnosis of hyperthyroidism in the elderly are reported. Four out of 24 patients with atrial fibrillation for which there was no obvious cause and who had normal thyroid hormone measurements were found to have subnormal thyrotropin responses to thyrotropin-releasing hormone and abnormal thyroid scans. The implications of this finding are discussed.