Epidermal Growth Factor,  a low-molecular-weight polypeptide, is the founding member of the EGF-family of proteins. It can be found in platelets, macrophages, urine, saliva, etc. EGF acts by binding with high affinity to the Epidermal Growth Factor Receptor (EGFR) and stimulating downstream protein tyrosine kinase activity. This signal transduction cascade results in increased intracellular calcium levels and increased rates of glycolysis and protein synthesis. EGF stimulates the growth of many epidermal and epithelial tissues. Pharmaceutical drugs designed to inhibit EGFR have been used to treat certain types of cancer.