Congenital Hyperinsulinism is the most common cause of low blood sugar (hypoglycemia) in infants and children.Infants who are born with this problem have low blood sugar, which can cause seizures or brain damage.

We are doing this study to see if the patterns of abnormalities in controlling insulin in children and adults with hyperinsulinism are related to any underlying genetic cause and to identify possible new genetic causes.This will be done by standard clinical tests of insulin control: a glucose tolerance test, a protein tolerance test, and a fasting test.