IGF-I is required for normal embryonic growth in mice.

IGF-I is a plaiotropic hormone reported to affect linear growth, glucose metabolism, organ homeostasis, and the immune and neurologic systems. In contrast to IGF-II, IGF-I is expressed at low levels embryonically and has been thought to be more important for postnatal growth and developement. To investigate the role of IGF-I in normal development we generated mice with an inactive IGF-I gene by homologous recombinationin ES cells. heterozygous mice are healthy and fertile, but they are 10-20% smaller than wild-type litternates and have lower than normal levels of IGF-I