FGF21 is a secreted growth factor of the FGF family, classified as an FGF19 subfamily member. Proteins of the FGF family are known to play a central role with respect to both prenatal and postnatal growth and development, and regeneration of a variety of tissues by promoting cellular proliferation and differentiation. In the presence of beta Klotho (protein cofactor), FGF21 signals via the FGFR receptors to stimulate insulin independent glucose uptake by adipocytes.