Human IGF-I/IGF-1 DuoSet ELISA

IGF-1 is a growth hormone that plays a role in a variety of biological events. It 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. It binds two tyrosine kinase receptors, the IGF-1 receptor (IGF1R) and the insulin receptor, to initiate downstream events like the AKT and PI3K signal transduction pathways. This triggers cell proliferation and protects cells from apoptosis. IGF-1 also interacts with seven IGF-binding proteins (IGFBP-1 through IGFBP7), influencing IGF-1 binding to IGF1R and increasing IGF-1 half-life to closely regulate IGF-1 signaling. For example, 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. Proteases also facilitate IGF-1R binding by cleaving IGFBPs to modify their affinity for IGF or completely eliminate the IGFBP. 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. Its ability to inhibit apoptosis and stimulate cell growth and proliferation plays a significant role in prenatal development, growth to adulthood, and metabolic control. Serum levels of IGF-1 have been reported to increase from birth to puberty, followed by a slow decline through adulthood. IGF-1 also induces amino acid uptake, protein synthesis, and glucose utilization. In the brain, IGF-1 acts as a neurotrophic factor to promote neurogenesis and neuronal survival. Exercise increases levels of IGF-1 in blood serum, indicating it plays a role as a key mediator of exercise-induced neurogenesis.