Variants in at least ten genes have now been linked to congenital hyperinsulinism, including genes that encode the KATP channel subunits (ABCC8 and KCNJ11), glucokinase (GCK), glutamate dehydrogenase (GLUD1), the mitochondrial enzyme 3-hydroxyacyl-CoA dehydrogenase (HADH), proton-linked monocarboxylate transporter (SLC16A1), mitochondrial uncoupling protein 2 (UCP2), hepatocyte nuclear factor 1 alpha (HNF1A) and 4 alpha (HNF4A), and hexokinase 1 (HK-1) (15). Here, GCK is linked to congenital isolated hyperinsulinism.