FGF21 and metabolic dysfunction-associated steatotic liver disease: To date, the most promising proposed serum biomarkers (i.e.: cytokeratin-18 M30 fragment [8], fibroblast growth factor 21 [35], interleukin 1 receptor antagonist [36], pigment epithelium-derived factor [11], osteoprotegerin [37]), showed a potential in diagnosing NAFLD and NASH.