MedGen

Congenital hyperinsulinism is a condition that causes individuals to have abnormally high levels of insulin. Insulin is a hormone that helps control levels of blood glucose, also called blood sugar. People with this condition have frequent episodes of low blood glucose (hypoglycemia). In infants and young children, these episodes are characterized by a lack of energy (lethargy), irritability, or difficulty feeding. Repeated episodes of low blood glucose increase the risk for serious complications such as breathing difficulties, seizures, intellectual disability, vision loss, brain damage, and coma.

The severity of congenital hyperinsulinism varies widely among affected individuals, even among members of the same family. About 60 percent of infants with this condition experience a hypoglycemic episode within the first month of life. Other affected children develop hypoglycemia by early childhood. Unlike typical episodes of hypoglycemia, which occur most often after periods without food (fasting) or after exercising, episodes of hypoglycemia in people with congenital hyperinsulinism can also occur after eating. [from MedlinePlus Genetics]

An abnormality of the islet of Langerhans, i.e., of the regions of the pancreas that contain its endocrine cells. These are the alpha cells, which produce glucagon, the beta cells, which produce insulin and amylin, the delta cells, which produce somatostatin, the PP cells, which produce pancreatic polypeptide, and the epsilon cells, which produce ghrelin. [from HPO]