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Reviewed January 2014
What is congenital hyperinsulinism?
Congenital hyperinsulinism is a condition that causes individuals to have abnormally high levels of insulin, which is a hormone that helps control blood sugar levels. People with this condition have frequent episodes of low blood sugar (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 sugar 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.
How common is congenital hyperinsulinism?
Congenital hyperinsulinism affects approximately 1 in 50,000 newborns. This condition is more common in certain populations, affecting up to 1 in 2,500 newborns.
What genes are related to congenital hyperinsulinism?
Congenital hyperinsulinism is caused by mutations in genes that regulate the release (secretion) of insulin, which is produced by beta cells in the pancreas. Insulin clears excess sugar (in the form of glucose) from the bloodstream by passing glucose into cells to be used as energy.
Gene mutations that cause congenital hyperinsulinism lead to over-secretion of insulin from beta cells. Normally, insulin is secreted in response to the amount of glucose in the bloodstream: when glucose levels rise, so does insulin secretion. However, in people with congenital hyperinsulinism, insulin is secreted from beta cells regardless of the amount of glucose present in the blood. This excessive secretion of insulin results in glucose being rapidly removed from the bloodstream and passed into tissues such as muscle, liver, and fat. A lack of glucose in the blood results in frequent states of hypoglycemia in people with congenital hyperinsulinism. Insufficient blood glucose also deprives the brain of its primary source of fuel.
Mutations in at least nine genes have been found to cause congenital hyperinsulinism. Mutations in the ABCC8 gene are the most common known cause of the disorder. They account for this condition in approximately 40 percent of affected individuals. Less frequently, mutations in the KCNJ11 gene have been found in people with congenital hyperinsulinism. Mutations in each of the other genes associated with this condition account for only a small percentage of cases.
In approximately half of people with congenital hyperinsulinism, the cause is unknown.
See a list of genes associated with congenital hyperinsulinism.
How do people inherit congenital hyperinsulinism?
Congenital hyperinsulinism can have different inheritance patterns, usually depending on the form of the condition. At least two forms of the condition have been identified. The most common form is the diffuse form, which occurs when all of the beta cells in the pancreas secrete too much insulin. The focal form of congenital hyperinsulinism occurs when only some of the beta cells over-secrete insulin.
Most often, the diffuse form of congenital hyperinsulinism is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Less frequently, the diffuse form is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
The inheritance of the focal form of congenital hyperinsulinism is more complex. For most genes, both copies are turned on (active) in all cells, but for a small subset of genes, one of the two copies is turned off (inactive). Most people with the focal form of this condition inherit one copy of the mutated, inactive gene from their unaffected father. During embryonic development, a mutation occurs in the other, active copy of the gene. This second mutation is found within only some cells in the pancreas. As a result, some pancreatic beta cells have abnormal insulin secretion, while other beta cells function normally.
Where can I find information about diagnosis or management of congenital hyperinsulinism?
These resources address the diagnosis or management of congenital hyperinsulinism and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about congenital hyperinsulinism?
You may find the following resources about congenital hyperinsulinism helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for congenital hyperinsulinism?
What if I still have specific questions about congenital hyperinsulinism?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding congenital hyperinsulinism?
autosomal ; autosomal dominant ; autosomal recessive ; cell ; coma ; congenital ; embryonic ; fasting ; gene ; glucose ; hormone ; hyperinsulinemia ; hyperinsulinism ; hypoglycemia ; inheritance ; insulin ; lethargy ; mutation ; neonatal ; pancreas ; pancreatic ; recessive ; secretion
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (8 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.