FGF21 and obesity due to melanocortin 4 receptor deficiency: Fibroblast growth factor-21, a hepatokine crucial for glucose and lipid metabolism regulation, increases in response to metabolic stress in MASLD, with higher levels correlating with obesity, insulin resistance, and disease severity.4 Cytokeratin-18, a hepatocyte cytoskeletal protein, is released into the bloodstream during apoptosis, particularly as caspase-cleaved CK-18 (ccCK-18).