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Andrew A. Butler, Derek LeRoith, Minireview: Tissue-Specific Versus Generalized Gene Targeting of the igf1 and igf1r Genes and Their Roles in Insulin-Like Growth Factor Physiology, Endocrinology, Volume 142, Issue 5, 1 May 2001, Pages 1685–1688, https://doi.org/10.1210/endo.142.5.8148
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Abstract
The insulin-like growth factors (IGF-I and IGF-II) and the IGF-I receptor are critically important for normal growth and development of the organism. Gene-deletion of these elements has demonstrated that IGF-I is important for both prenatal and postnatal development, whereas IGF-II is important during prenatal stages only. The IGF-I receptor gene-deleted mouse dies at birth apparently as a result of poor muscular development. Utilizing the conditional gene-deletion approach, we have demonstrated that mice lacking the liver IGF-I gene have an approximately 80% reduction in circulating total IGF-I levels. Despite this marked reduction, postnatal growth and development was normal, suggesting that liver IGF-I is not essential for this function. Local tissue IGF-I production was unaffected and may compensate for the lack of the liver IGF-I. Further studies are ongoing to establish the role of the endocrine vs. the autocrine/paracrine IGF-I.