The most severe forms of congenital hyperinsulinemic hypoglycemia are due to molecular defects in the genes ABCC8 and KCNJ11. Milder forms of hyperinsulinemic hypoglycemia may occur due to molecular defects in several other genes, which play a key role in the regulation of insulin secretion. This evidence concerns the gene KCNJ11 and hyperinsulinemic hypoglycemia.