Why does excess thyroid hormone sometimes induce atrial fibrillation?

💡 Explanation

Excess thyroid hormone increases expression of sinoatrial node ion channels; this increases heart rate and automaticity because it enhances the funny current (If) and calcium handling in pacemaker cells, therefore promoting atrial fibrillation, rather than reducing nerve activity or altering cardiomyocyte ion concentrations in ways that directly trigger arrhythmia.

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