1. The GHRH/GH/IGF-1 system
The GHRH/GH/IGF-1 system. The effects of growth hormone (GH) on growth are partly due to its direct anabolic effects in the muscle, liver, and bone. In addition, GH stimulates many tissues to produce insulin-like growth factor 1 (IGF-1) locally, which stimulates the growth of the tissue itself (paracrine effect of IGF-1). The action of GH on the liver results in the secretion of IGF-1 (circulating IGF-1), which stimulates growth in other tissues (endocrine effect of IGF-1). The action of growth hormone on the liver also enhances the secretion of IGF-binding protein 3 (IGFBP-3) and acid-labile subunit (ALS), which form a high-molecular-weight complex with IGF-1. The function of this complex is to transport IGF-1 to its target tissues, but the complex also serves as a reservoir and possible inhibitor of IGF-1 action. In various chronic illnesses, the direct metabolic effects of GH are inhibited; the secretion of IGF-1 in response to GH is blunted, and in some cases IGFBP-3 synthesis is enhanced, resulting in marked inhibition in the growth of the child. GHRH, growth hormone–releasing hormone.
Source: Endocrine Disorders, CURRENT Diagnosis & Treatment Pediatrics, 23e
Citation: Hay WW, Jr., Levin MJ, Deterding RR, Abzug MJ. CURRENT Diagnosis & Treatment Pediatrics, 23e; 2016 Available at: Accessed: December 25, 2017
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