Regulation and Mechanism of Growth Hormone and Insulin-like Growth Factor-I Biosynthesis and Secretion

Abstract

This chapter illustrates the biosynthesis and regulation of Growth hormone (GH) and insulin-like growth factor-I (IGF-I). It focuses on GH biosynthesis and secretion in the pituitary and on IGF-I biosynthesis in the brain. The important factors and mechanism involved in these processes are described. Basic mechanisms regulating GH biosynthesis and secretion involve transcription factors and DNA methylation. Signaling mechanisms also plays an important role. GH secretion from somatotrophs is triggered by an elevation in the intracellular Ca 2+ concentration. This cytosolic Ca 2+ concentration elevation is brought about mainly by two signal transduction cascades namely, the adenylyl cyclase /protein kinase A pathway and the phospholipase C/protein kinase C pathway. The chapter attempts to understand the regulatory mechanisms of IGF-I expression in the brain have been made. Some physiological conditions such as fasting are found to control the expression of IGF-I in the CNS. Furthermore, the induction of IGF-I expression by GH and glucocorticoids, as well as during development and in brain injury, has been also discussed. © 2005 Elsevier Inc. All rights reserved.