(Science: biochemistry) a complex family of polypeptide hormones or biological factors that are produced by the body to control growth, division and maturation of blood cells by the bone marrow. They regulate the division and proliferation of cells and influence the growth rate of some cancers. These factors occur naturally but some can be synthesised using molecular biology techniques and are used clinically to stimulate normal white Cell production following chemotherapy or bone marrow transplantation.
Examples include epidermal growth factor, platelet-derived growth factor, fibroblast growth factor. Insulin and somatomedin are also growth factors, the status of nerve growth factor is more uncertain. Perturbation of growth factor production or of the response to growth factor is important in neoplastic transformation.