AN ENDOCRINOLOGISTS APPROACH TO THE GROWTH-HORMONE INSULIN-LIKE-GROWTH-FACTOR AXIS

Gene knockout studies in mice, and a recent case report, have demonstr ated that insulin-like growth factors (IGFs) are major mediators of pr e- and postnatal growth, whereas the growth-promoting role of growth h ormone (GH) appears to be confined largely to the postnatal period. Th e IGF axis is now known to consist of the growth factors themselves an d at least seven, and probably ten, IGF-binding proteins. These act ei ther by regulating the availability of IGFs to their receptors, or dir ectly on their target cells. Because of the difficulties associated wi th GH provocative testing, the central role of IGFs in pre- and postna tal growth, and the ease of assaying the various components of the IGF axis, it is suggested that the differential diagnosis of short statur e should be based on the concept of IGF deficiency rather than on GH s ecretory status.