Epidermal growth factor (EGF) is a growth factor that stimulates cell growth, proliferation, and differentiation by binding to its receptor EGFR. Human EGF is a 6045-Da protein[2] with 53 amino acid residues and three intramolecular disulfide bonds. EGF was originally described independently as a secreted peptide found in the submaxillary glands of mice and in human urine. Initially, human EGF was known as urogastrone.

Epidermal growth factor can be found in urine, saliva, milk, and plasma. The production of epidermal growth factor has been found to be stimulated by testosterone. EGF acts by binding with high affinity to epidermal growth factor receptor (EGFR) on the cell surface. This stimulates ligand-induced dimerization,[8] activating the intrinsic protein-tyrosine kinase activity of the receptor.