Direct effects indicate that FGF21 has a causal relationship with Type 2 diabetes (OR=0.787, 95%CI (0.646-0.960), P=0.0179) and Basal metabolic rate (OR=0.962, 95%CI(0.935-0.990), P=0.0091). Here, FGF21 is linked to type 2 diabetes mellitus.