FGF21 and diabetes mellitus: However, despite its favorable metabolic effects, elevated serum FGF-21 levels have been consistently observed in obese individuals with metabolic syndrome (MS) compared to healthy individuals [19,20] These levels tend to rise progressively as glycemic control worsens, transitioning from normal glucose tolerance to prediabetes and type 2 diabetes mellitus, and are notably elevated in various cardiometabolic conditions, including obesity, MetS, T2DM, coronary artery disease, and non-alcoholic fatty liver disease (NAFLD) [21].