Tayal B, et al. – In this cross-sectional study that involved 132,707 primary healthcare patients in Copenhagen, Denmark, who had a thyroid function test and an ECG filed within 7 days of each other between 2001 and 2011, researchers examined associations of both overt and subclinical thyroid dysfunction with common ECG parameters. A significant association of hyperthyroidism with higher heart rate and prolonged QTc interval with significant interaction with age and sex was observed. For patients with older age, these associations were less obvious. Subclinical hyperthyroidism was linked to higher heart rate among females—a trend that was similarly observed among males. However, slower heart rate and shorter QTc were associated with hypothyroidism—but only among women. In patients with both subclinical and overt hypothyroidism, longer P-wave duration, longer PR interval, and low voltage were evident. However, the presence of low voltage was less obvious with higher age. In all, overt and subclinical thyroid disorders were linked with significant alterations in important ECG parameters. Further, a significant impact of age and sex on the association of thyroid dysfunction, particularly on heart rate and QTc interval, was also observed.