Of the MODY genes described to date, only hepatocyte nuclear factor-4-alpha (<i>HNF4A</i>; MODY1) and hepatocyte nuclear factor-1-alpha <i>(HNF1A</i>; MODY3) mutations may result in a biphasic phenotype of hypoglycemia in early life and hyperglycemia in later life. Here, HNF1A is linked to Hypoglycemia.