A protein hormone that is produced by the body’s bone cells (when those bone cells have been stimulated by parathyroid hormone and/or estrogen), which is a promoter of bone formation and follicle development (in ovaries). Another function of IGF- 1 is to facilitate the transport of amino acids into cells, and further inhibit protein breakdown in cells. If the body is injured, IGF-1 works with platelet-derived growth factor (PDGF) to stimulate fibroblast and collagen cell division/metabolism to cause healing of wounds and bones. IGF- 1 also occurs naturally in cow’s milk.
A group of related peptides, synthesized by the liver as a result of human growth hormone secretion. The IGF family of polypeptides is structurally similar to insulin in that it is composed of two subunits that are short polypeptides. IGF- 1 and IGF-2, for example, each contain about 70 amino acids. They have a wide variety of functions, including the stimulation of cell growth and proliferation (e.g., in the developing embryo and neonate), DNA synthesis, bone growth, and the replication of cancer cells. Drugs that block insulin-like growth factor have been tested for use in cancer chemotherapy.