Congenital Hyperinsulinism

What is congenital hyperinsulinism (HI)?

Congenital hyperinsulinism (HI) is a genetic disorder in which the insulin cells of the pancreas, called beta cells, secrete too much insulin. Excess insulin causes low blood sugar (hypoglycemia).

Ordinarily, beta cells secrete just enough insulin to keep the blood sugar in the normal range. In children with HI, the secretion of insulin is not properly regulated, causing excess insulin secretion and low blood sugar.

Low blood sugar can be very dangerous, because the brain needs a constant source of sugar. If the brain doesn't get the sugar it needs, it can lead to seizures, brain damage, and possibly death.

Congenital HI is a rare disease, affecting 1 in 25,000 to 50,000 babies. Since most children’s hospitals encounter only one or two cases a year, it is important to receive medical care from an experienced treatment center, such as the Congenital Hyperinsulinism Center at CHOP.

There are several forms of HI:

Causes

Congenital hyperinsulinism is caused by genetic mutations that result in inappropriate and excess insulin secretion from the beta cells of the pancreas. It is not related to anything that the mother did during pregnancy. Genetic testing can help to identify the cause of HI.

Symptoms

Congenital hyperinsulinism causes low blood sugar (hypoglycemia).The symptoms of hypoglycemia in infants are often difficult to identify, as they can be similar to normal infant activities.

Common symptoms of hypoglycemia include:

  • irritability
  • sleepiness
  • lethargy
  • excessive hunger
  • rapid heart rate 

More severe symptoms, such as seizures and coma, can occur with a prolonged low blood sugar or an extremely low blood sugar. Common symptoms of hypoglycemia in older children include feelings of shakiness, weakness, tiredness, confusion, and rapid heart rate.

We consider a normal blood sugar to be >70 mg/dL. Anything less than 60 mg/dL is low, although severe symptoms due to hypoglycemia are not likely unless the blood sugar is less than 50 mg/dL. Prolonged or severe low blood sugar can cause seizures and permanent brain damage. 

Diagnosis

The diagnosis of congenital hyperinsulinism is based on history, laboratory findings, and genetic testing. Prompt diagnosis and establishment of effective treatment are essential to avoid neurologic damage. The diagnosis is made by evaluating the child's medical history, and the result of laboratory and genetic tests.

History

The history of the child is an important piece of the puzzle. This includes information such as when the low blood sugars started, the timing of the low blood sugars, whether the baby was born large for gestational age (LGA), any family history of low blood sugar or unexplained infant deaths.

Laboratory findings

Blood tests drawn when the blood sugar is less than 50 mg/dL are essential to the diagnosis of HI. In congenital HI, with a blood sugar <50, you will see suppressed ketones and free fatty acids, an elevated insulin level (although this may not always be captured), and a glycemic response to glucagon, with the blood sugar rising more than 30 mg/dL when glucagon is administered.

It is important that these samples at the time of a critically low blood sugar be obtained in an experienced, controlled environment, as we do not want a child to be kept with a critically low blood sugar longer than is absolutely necessary to make the diagnosis.

Genetic testing

The DNA from a blood sample from the child with congenital HI and each parent can be analyzed to screen for the mutations that cause the most common types of HI. This can be done at commercial laboratories and should be considered in any child suspected to have congenital HI. Contact us for more information on where to have this testing performed.

Treatment

Because congenital HI causes dangerously low blood sugars as a result of excess insulin, the treatment for this condition is to try and maintain blood sugars greater than 70 mg/dL. There are two options for treatment of congenital HI, medical therapy and surgical intervention. About 50 percent of children respond to medical therapy, while the other half require surgery for a partial or near total pancreatectomy.

Long-term outcomes

We are now tracking and compiling data on the long-term outlook for children with congenital hyperinsulinism. We know that with rapid diagnosis and appropriate treatment, keeping blood sugars >70 mg/dL, it is less likely that children with congenital HI will have long-term effects of hypoglycemia. With focal hyperinsulinism, 94 percent of children are cured with surgery.

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