IGF1 (insulin-like growth factor 1), a hormone that promotes cell growth and cell division in both children and adults, is transported through the blood by a molecule called IGF-binding protein 3 (coded by the IGFBP3 gene). It regulates the activity of IGF1 by protecting it against breakdown and preventing it from binding to its receptor. Variations in this gene affect the levels of IGFBP-3 and IGF1 and may affect body composition.
Global population distribution:
Source: 1000 Genome Project. Global averages for both sexes
More about IGFBP3
THE IGFBP3 GENE
In blood, IGF proteins are mainly bound to insulin-like growth factor binding proteins (IGFBPs). IGFBP3 binds IGF’s and helps protect them from being broken down as well as helping regulate their activity.
The IGF1/IGFBP3 ratio in the blood has sometimes been used as a marker for the bioavailability of IGF in blood. However, this doesn’t take into account that IGF1 can bind to other IGFBP proteins and that IGF2 is even more abundant than IGF1 in adults and competes for binding to IGFBP3.
As well as binding and helping regulate IGF activity, IGFBP3 can also interact with cell receptors by itself and may be capable of inhibiting cell division as well as promoting repair of DNA.
Studies in twins indicate around 50% of the variation in circulating IGFBP3 levels is thought to be genetic.