Congenital hyperinsulinism is a meical term referring to a variety of congenital disorders in which hypoglycemia is caused by excessive insulin secretion. Congenital forms of hyperinsulinemic hypoglycemia can be transient or persistent, mild or severe. These conditions are present at birth and most become apparent in early infancy. The severe forms can cause obvious problems in the first hour of life, but milder forms may not be detected until adult years.