First, we demonstrate that Slc7a7Lbu/Lbu mice exhibited severe postnatal growth failure and reduced plasma IGF-1 concentrations compared to those of WT embryos, whereas Slc7a7Lbu/Lbu embryos exhibited mild intrauterine growth restriction (IUGR) and similar plasma IGF-1 concentrations to those of WT embryos. Here, IGF1 is linked to fetal growth restriction.