Control of growth by the somatropic axis: growth hormone and the insulin-like growth factors have related and independent roles.
The traditionally accepted theory has been that most of the biological effects of growth hormone (GH) are mediated by circulating (endocrine) insulin-like growth factor-I (IGF-I). This dogma was modified when it was discovered that most tissues express IGF-I that can act via an autocrine/paracrine fashion. In addition, both GH and IGF-I had independent effects on various target tissues. Using tissue-specific gene deletion of IGF-I in the liver, it has been shown that circulating IGF-I is predominantly liver-derived but is not essential for normal postnatal growth. Therefore, it is proposed that non-hepatic tissue-derived IGF-I may be sufficient for growth and development. Thus the original somatomedin hypothesis has undergone further modifications.
Butler
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The Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland Oregon 97201-3098, USA. butlera@ohsu.edu
Le Roith
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D000818:Animals; D002455:Cell Division / Q000502:physiology; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout
D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone