A disorder where too much insulin causes low blood sugar in infants. Prompt treatment is needed to avoid the brain being damaged by repeated periods of low blood sugar. The various types of familial hyperinsulinemic hypoglycemia are distinguished by their genetic origin. HHF3 is due to a mutation in the gene for glucokinase on chromosome 7p15-p13. See also Hyperinsulinemic hypoglycemia, familial, 3