Fibroblast Growth Factor 21（FGF-21） is a member of the fibroblast growth factor （FGF） family and it is involved in the modulation of cell proliferation, growth, and differentiation as well as cell metabolism. This protein is a secreted endocrine factor that functions as a major metabolic regulator, and stimulates the uptake of glucose in adipose tissue. FGF21 binds to FGFR1c complexed with β-Klotho expressed in adipocytes to activate the canonical FGF signaling pathway （ERK1/2） and the AMPK/PGC1α pathway. Therefore, FGF-21 is being pursued as a therapeutic target for diabetes and obesity.