To stimulate postnatal body growth in a coordinated fashion, growth hormone (GH) acts directly or indirectly on virtually every tissue in the body. Furthermore, GH has metabolic actions that are important in many species long after major statural growth has been accomplished. Although the actions of GH were long thought to be mediated entirely via the generation of hepatic insulin-like growth factor-1 (IGF-1), it is now clear that GH
From: Human Growth Hormone: Basic and Clinical Research Edited by: R. G. Smith and M. O. Thorner © Humana Press Inc., Totowa, NJ
also has direct effects in many tissues acting in concert with locally generated IGF-1 (and probably many other growth factors) in addition to IGF-1 from the circulation. Although the brain is not usually considered an obvious target tissue for GH there is increasing circumstantial and direct evidence to support this idea. In this short chapter the authors address three principle questions:
1. Are there specific functional receptors for GH in the central nervous system (CNS)?
2. How does GH reach these receptors in adequate amounts? and
3. Do these receptors mediate physiological effects of GH within the CNS?
Some data from new experimental approaches that have recently been used to address some of these issues will be reviewed.
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