Roles of insulin-like growth factor (IGF) binding proteins in regulating IGF actions

Gen Comp Endocrinol. 2005 May 15;142(1-2):44-52. doi: 10.1016/j.ygcen.2004.12.022. Epub 2005 Feb 5.


The insulin-like growth factor (IGF) system is an evolutionarily conserved signaling pathway that is composed of two IGF ligands, two IGF receptors, and six IGF binding proteins. Studies in a variety of species suggest that the IGF signaling system plays a fundamental role in regulating embryonic growth and differentiation as well as in maintaining homeostasis in the adults. In extracellular fluids, IGFs are present in a complex with an IGF-binding protein (IGFBP). These IGFBPs are traditionally thought to function as carrier proteins and regulate circulating IGF turnover, transport, and distribution. Locally expressed IGFBPs can also inhibit and/or potentiate IGF activities. Recent studies have shown that some IGFBPs, in particular IGFBP-3 and -5, possess intrinsic biological activities and can act through IGF-independent mechanisms. In this article, we provide a brief overview of our current understanding of the IGF signaling system with particular reference to IGFBPs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Fishes
  • Humans
  • Insulin-Like Growth Factor Binding Proteins / pharmacology
  • Insulin-Like Growth Factor Binding Proteins / physiology*
  • Somatomedins / physiology*


  • Insulin-Like Growth Factor Binding Proteins
  • Somatomedins