Human Free IGF-I/IGF-1 ELISA Kit

While IGF-1 has very complex functions, it appears largely to mediate the actions of growth hormone. Thus, IGF-1 is important in prenatal development, growth to adulthood and metabolic control. It induces amino acid uptake, protein synthesis and glucose utilization. It is an important mitogen and regulator of the cell cycle and apoptosis. IGF-1 is produced primarily by hepatocytes, serving an endocrine function. It is also produced by many other cells, where it may act in an autocrine or paracrine manner. Serum levels of IGF-1 have been reported to increase from birth to puberty, followed by a slow decline through adulthood. 

There are two receptors for the IGFs; type I IGF receptor, which signals through a tyrosine kinase, and type II IGF receptor, which is identical to the mannose-6-phosphate receptor and may not signal. The action of IGF on its receptors is very complex, with control by at least six IGF-binding proteins (IGFBP-1 through IGFBP-6). IGFBP-3 binds over 90% of the total IGF in serum in a complex of IGF, IGFBP and an acid-labile subunit. This ternary complex greatly stabilizes IGF in the circulation, changing the half life from minutes to hours. In addition, IGFBPs modulate the action of IGF on the membrane receptors. Adding to the complexity is a family of proteases that act on IGFBPs, modifying their affinity for IGF or completely eliminating the IGFBPs. The interactions of IGF, IGFBP, IGFBP proteases, and IGF receptors are referred to as the IGF axis. The IGF axis affects many primary physiological and pathological processes, including development, growth, metabolic regulation, tumorigenesis, atherosclerosis and angiogenesis.