Alterations in the serum thyroid hormone levels are associated with significant pathophysiologic changes in various organ systems, including the cardiovascular system.[1] These include arrhythmias, atrial fibrillation (Afib), thromboembolism, heart failure, cardiomyopathies, valvular heart disease, and pulmonary hypertension (PHTN).[2] Although the association of PHTN with thyroid disorders is known, the mechanism and dynamics of the association remain largely unexplored. This evidence concerns the gene TG and atrial fibrillation.