New aspects of the physiology of the GH-IGF-1 axis

Growth hormone (GH) secretion from the pituitary is regulated by a complex network of CNS and peripheral inputs. Circulating GH binds to its receptor and initiates a cascade of signaling events which involve the JAK2-STAT pathway, the PI3K/Akt pathway and the RAS/MAPK pathway, leading to the transcription of several genes, including insulin-like growth factor 1 (IGF-1), IGFBP3, ALS, and others. Recent findings indicate that nutrition plays an important role in GH secretion and action. Furthermore, data are emerging which suggest that the RAS-MAPK pathway as well as epigenetic regulation of transcription may be important in determining both circulating and locally produced IGF-1.