Definition
A 70-residue hormone produced mainly in the liver in response to growth hormone; a key mediator of GH signalling.
Insulin-like growth factor 1 is a 70-amino-acid polypeptide, structurally related to insulin, produced mainly by the liver in response to growth hormone. It mediates many of growth hormone's downstream effects through the IGF-1 receptor, a receptor tyrosine kinase. Circulating IGF-1 is largely bound to IGF-binding proteins, which regulate its availability. Because it is more stable in circulation than pulsatile growth hormone, IGF-1 is the standard readout in secretagogue studies. Research analogues include IGF-1 LR3 and IGF-1 DES(1–3), engineered for reduced binding-protein affinity. Mecasermin, recombinant human IGF-1, is an approved prescription medicine.