FGF-21 is a secreted growth factor of the FGF family, classified as an FGF-19 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), FGF-21 signals via the FGFR receptors to stimulate insulin independent glucose uptake by adipocytes.