IGF-1
IGF-1 (insulin-like growth factor 1) is the hormone through which growth hormone drives body growth, and the signal whose reduction extends lifespan across species.
Function
IGF-1 is produced mainly by the liver in response to growth hormone from the pituitary and circulates bound to IGF-binding proteins. It signals through the IGF-1 receptor, a tyrosine kinase that activates the PI3K–AKT and RAS–MAPK pathways — the same routes growth-factor receptors use, but engaged systemically and continuously rather than locally and transiently. The result is growth: cell proliferation, skeletal growth, and anabolic metabolism. Its name records its structural kinship with insulin and its original discovery as a serum factor with insulin-like activity.
In aging and cancer
Reduced IGF-1 signaling is the most reproducible genetic longevity intervention known: growth hormone receptor knockouts, IGF-1 receptor heterozygotes, and hypopituitary dwarf lines live longer in mice, and orthologous reductions (daf-2 in worms, chico in flies) extend lifespan in invertebrates. The mechanism connects to the IGF aging axis: high IGF-1 drives growth and reproduction at a cost in maintenance. In cancer, IGF-1 is mitogenic and anti-apoptotic, serum IGF-1 levels correlate modestly with several cancer risks, and IGF-1R inhibitors have had limited clinical success.
Notes
- Human gene symbol: IGF1; UniProt P05019; 195 amino acids (precursor); insulin peptide family.