FGF-21, also known as fibroblast growth factor-21 and FGFL, is a secreted growth factor belonging to theheparin-binding growth factor family. It is produced by hepatocytes in response to fatty acid stimulation. FGF-21 couples with its co-factor beta-Klotho to signal through FGFR1c and FGFR4. Signal transduction results in insulin-independent uptake of glucose by adipocytes. Clinical administration of FGF-21 induces energy expenditure, fat utilization and lipid excretion.