GCH1 and hyperinsulinemic hypoglycemia, familial, 4: To investigate the role of inducing maternal endothelial Gch1 deletion and BH4 deficiency in pregnancy, virgin female Gch1fl/flVE-Cad-Cre and WT (Gch1fl/fl) mice (aged 10–16 years weeks) received tamoxifen and were then mated with male Gch1fl/fl mice 2 weeks later (Figure 5A).