A growth factor is, simply put, a substance that increases the rate at which cells grow and divide. The most important purpose of a growth factor is regulating the rate of cellular growth and other biological processes. Growth factors are important in the health sciences because they can be used to treat many different diseases, such as various forms of leukemia and anemia. They can also help increase the rate at which cells are regrown in bone marrow transplantation and in the treatment of some cardiovascular diseases.
Growth factors are grouped into many different families that have similar traits or purposes. One important growth factor family is the insulin-liked growth factors, or IFGs. IGFs interact with almost every cell in the human body and are structurally similar to insulin. Like insulin, IGFs moderate some metabolic and energy-management processes. They also play roles in cellular communication, DNA synthesis, cellular growth, and cellular development.
A growth factor may also be involved in wound healing. One type is referred to as the fibroblast growth factor or FGF. FGF is primarily involved in wound healing and angiogenesis, the production of new blood vessels. There are many different kinds of FGFs that have many different roles, ranging from limb development to neural development.
Structurally, a growth factor is a polypeptide, or a string of amino acids, usually in the form of a protein such as a steroid. Though they are not always specifically labeled as hormones, growth factors function in much the same way, and the distinction is typically only one of terminology. Like hormones, growth factors are extremely important in sending signals between cells.
Like other signaling mechanisms, growth factors bind to receptor molecules in order to transmit the signals necessary to initiate cell growth and other processes. Generally speaking, receptors are present in the plasma membranes of cells, allowing molecules such as growth factors to communicate with the cell from outside of the cell's membrane. Some receptors can only bind with one specific kind of signaling molecules while others can interact with several. Conversely, some signaling molecules can bind with many different receptors while others can only bind with one specific receptor.
It is not uncommon to use or to study a growth factor to better treat or understand certain types of cancer or other illnesses. In abundance, some growth factors can greatly increase the risk of some cancers. The regulatory properties of growth factors, on the other hand, can be used to treat some forms of cancer. Increased or decreased levels of a given growth factor can also be used as a diagnostic tool, as altered levels could indicate the presence of an illness.