More than 600 mutations of human glucokinase gene have been identified in patients with glucokinase linked hyperinsulinemic hypoglycemia (PHHI-GK), glucokinase-linked permanent neonatal diabetes (PDNM-GK) and glucokinase-linked maturity-onset diabetes of the young (MODY-GK, also called MODY-2). The gene discussed is GCK; the disease is hyperinsulinemic hypoglycemia.