Epidermal growth factor (EGF) is an acid- and heat-stable 53 amino acid protein of 6 kDa originally found in rodents and humans. EGF has been shown to be a potent mitogen for a variety of cell types both in vivo and in vitro. It binds to the 170 kDa EGF receptor on the surface of cells and mediates intrinsic phos phoryl ation of the receptor on tyrosine residues. EGF has been detected in nearly all body fluids such as urine (urogastrone), saliva, milk and platelet-rich plasma. EGF, TGFalpha and vaccinia virus growth factor exhibit 30-40 % amino acid homology. Several additional members of the EGF/TGF family have been described, these include Cripto, Amphiregulin and the heparin-binding EGF-like growth factor, each of which, except Cripto, binds to the EGF receptor.Synonyms: Epidermal growth factor, HOMG4, Pro-epidermal growth factor, URG, Urogastrone