IL6 and atrial fibrillation: FGF-23 is an early marker of impaired kidney function involved in renal phosphate homeostasis and vitamin D metabolism, and is associated with myocardial fibrosis.43 Similar to IL-6, we found that FGF-23 was significantly lower in those with spontaneous conversion to SR compared to those undergoing ECV, with a non-significant trend toward higher FGF-23 values in the individuals with AF recurrence.