TG and atrial fibrillation: <h4>Background</h4>The relationship between thyroid hormone sensitivity and atrial fibrillation (AF) progression remains unclear.<h4>Objective</h4>This study aimed to investigate the relationship between impaired thyroid hormone sensitivity and the progression of AF in individuals with normal thyroid function.<h4>Methods</h4>This retrospective cross-sectional study included 1,190 consecutive patients with AF, who were classified into paroxysmal AF (<i>n</i> = 623) and persistent AF (<i>n</i> = 567) groups.