FGF21 and ischemia: Moreover, in patients with liver transplantation, serum FGF21 levels rise sharply and reach the peak as early as two hours after reperfusion, whereas the peak of serum ALT levels appears at 24 hours after reperfusion, suggesting a superior sensitivity of serum FGF21 compared to the currently used biomarkers for detection of hepatic ischemia/reperfusion injury11.