Insulin-like growth factors somatomedins

Han YKM, D Ercole AJ, Lund PK. Cellular localization of somatomedin (insulin-like growth factor) messenger RNA in the human fetus. Science 1987 236 193-197. 

The anabolic effects of somatropin are mediated by somatomedins or insulin-like growth factors. Somatropin is a synthetic polypeptide identical to the natural occurring growth hormone which stimulates longitudinal growth. Only preparations made with recombinant DNA technology are used nowadays. They can consist of 191 amino acids as growth hormone itself or 192 amino acids with one extra methionine. Somatropin is employed in the treatment... 

Growth hormone-releasing hormone (GHRH) (+) Somatotropin release-inhibiting hormone (SRIH, somatostatin) (-) Growth hormone (somatotropin, GH) Liver Insulin-like growth factors (IGF, somatomedins)... 

Growth hormone is a peptide hormone produced by the anterior pituitary. It produces growth at open epiphyses via stimulation of insulin-like growth factor I (IGF-I, somatomedin C). It also causes lipolysis in adipose tissue and growth of skeletal muscle. 

In addition to these various actions on rather general metabolic functions, GH also has some very specific effects. It has a general stimulatory effect on protein synthesis but also stimulates synthesis of some proteins selectively. Predominant among these is somatomedin C/insulin-like growth factor I (Sm-C/IGF-I), production of which is stimulated markedly in many tissues, especially the liver [13,16]. 

Insulin-like growth factors (IGFs) or somatomedins are in a family of polypeptides with growth-promoting activities and which can also modulate some of the shortterm metabolism effects of insulin [47,48]. 

Growth hormone requires mediation by somatomedins for many of its actions. These are chiefly formed in the liver, including the important somatomedin C (= insulin-like growth factor 1, IGF-1). Pegvisomant is a newly developed antagonist at the GH receptor and inhibits the production of IGF-1. 

The anterior pituitary releases GH in 6 to 8 pulsatile bursts over a 24 h period the major portion is released just prior to deep sleep. Its secretion is controlled by hypothalamic peptides GH-releasing hormone stimulates GH secretion, while somatostatin inhibits it. GH stimulates the synthesis of insulin-like growth factor-1 (IGF-1 somatomedin C) mainly, but not solely, in the liver. GH and IGF-1 receptors are widely scattered throughout the body, and both hormones exert important metabolic actions in various tissues, especially muscle and bone. 

R2. Ravenna, L., Lubrano, C., Di Silverio, F., Vacca, A., Felli, M. P., etal., Androgenic and antian-drogenic control on epidermal growth factor, epidermal growth factor receptor, and androgen receptor expression in human prostate cancer cell line LNCaP. Prostate 26, 290—298 (1995). R3. Rechler, M. M., and Nissley, S. P., Insulin-like growth factor (IGF)/somatomedin receptor subtypes structure, function and relationships to insulin receptors and IGF carrier proteins. Horm. Res. 24, 152-159 (1986). 

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