Intrauterine Growth Retardation and Postnatal Growth Failure Associated with Deletion of the Insulin-Like Growth Factor I Gene

Insulin-like growth factor I (IGF-I) mediates the majority of the growth-promoting effects of growth hormone (GH) after birth.1 In the prenatal period, GH does not appear to have a major influence on fetal growth, whereas IGF-I does. Infants with congenital GH deficiency and defects in the GH-receptor gene have only mild retardation of growth at birth,2–4 whereas transgenic mice with a homozygous defect of the IGF-I gene (IGF-I knockout mice) have profound embryonic and postnatal growth retardation.5–7 Although there is no direct evidence that IGF-I has a prominent role in human fetal growth, fetal tissues express IGF-I from . . .