Insulin-Like Growth Factor I — An Important Intrauterine Growth Factor

The importance of insulin-like growth factor I (IGF-I) in regulating the effects of growth hormone on postnatal growth and development is well established, but its role during the prenatal period is not. Postnatally, the synthesis and release of IGF-I and its carriers — the IGF-binding proteins — are induced by the binding of growth hormone to its receptors in the liver. IGF-II, on the other hand, is not dependent on growth hormone. IGF-I acts by means of receptors for IGF-I and perhaps insulin, and IGF-II acts by means of a mannose-6-phosphate receptor. An understanding of how the system functions prenatally . . .