The growth hormone/insulin-like growth factor-I system: implications for organ growth and development |
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| Authors: | S. Yakar J.-L. Liu D. Le Roith |
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| Affiliation: | (1) Section on Molecular and Cellular Physiology, Clinical Endocrinology Branch, National Institute of Diabetes, Digestive and Kidney Diseases, NIH, Bethesda MD 20892-1758, USA, US;(2) Clinical Endocrinology Branch, Room 8D12, Building 10, NIH MSC 1758, Bethesda MD 20892-1758, USA e-mail: derek@helix.nih.gov Tel.: +1-301-4968090, Fax: +1-301-4804386, US |
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| Abstract: | Growth hormone (GH) and insulin-like growth factors (IGFs) are essential for normal growth and development during embryonic stages as well as postnatally. While GH has little effect on these processes prenatally, the IGFs are important during these stages. On the other hand the GH-IGF-I axis is important for pubertal growth. To determine whether postnatal growth and development are dependent on circulating or locally produced IGF-I, we deleted the IGF-I gene in the liver using the cre/LoxP system used for tissue-specific gene deletion. These animals demonstrated approximately 75%–80% reduction in circulating IGF-I and an approximate fourfold increase in circulating GH. Despite the marked reductions in circulating IGF-I, growth and development was apparently normal. Thus the original somatomedin hypothesis needs to be re-evaluated in the light of these new findings. Received: 5 September 1999 / Revised: 11 December 1999 / Accepted: 18 December 1999 |
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| Keywords: | Growth hormone Insulin-like growth factor-I Growth Development Knock-out mice |
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