While hypoglycemia often affects people with diabetes, low blood sugar may also result from genetic conditions like congenital hyperinsulinism. Without treatment, this condition may cause seizures, coma, or death.

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Hypoglycemia is the medical term for low blood sugar. This condition is often related to type 1 or type 2 diabetes or other factors, like drinking alcohol or overheating. Hypoglycemia may also be caused by a genetic condition called congenital hyperinsulinism.

Here’s what you need to know about congenital hyperinsulinism, what causes it, and what treatments may help.

Learn more about hypoglycemia.

Congenital hyperinsulinism (CHI) is a genetic condition in which a person’s body pumps too much insulin into their blood.

Insulin is a hormone that turns food into energy and regulates blood sugar. Normal fasting blood sugar is between 70 mg/dL and 100 mg/dL. When there’s too much insulin, blood sugar may drop to dangerous levels below 70 mg/dL.

CHI is the most common cause of persistent and severe hypoglycemia in children. This rare condition affects between 1 in 25,000 to 50,000 births worldwide and is typically diagnosed within the first month after a baby is born.

Without early and aggressive treatment, children may experience brain injury — learning disabilities, seizures, blindness, or cerebral palsy. In some cases, it may be fatal.

What about diabetes?

Both type 1 and type 2 diabetes may cause hypoglycemia, and both have genetic components. However, according to the American Diabetes Association, you inherit a predisposition to these diseases and not the disease itself.

Symptoms of CHI are due to low blood sugar levels in the blood.

They include:

  • floppiness (weak muscle tone)
  • shakiness
  • sleepiness
  • lethargy
  • irritability
  • poor feeding
  • increased heart rate
  • excessive hunger

These symptoms may be difficult to spot in young babies, as some — like hunger and irritability — may not seem unusual. If blood sugar remains low without treatment, a person may experience more severe symptoms, like seizures or coma.

CHI is caused by beta cells, which make insulin, releasing too much insulin at all times instead of the appropriate amount when needed to regulate blood glucose, such as after eating. Too much insulin causes blood sugar to drop, resulting in the symptoms of hypoglycemia.

Transient HI occurs in situations like when a baby is born prematurely, is small for gestational age, or when a mother has uncontrolled diabetes in pregnancy. This type may last only a few days to a few months.

Persistent HI is caused by genetic issues inherited during conception. These issues may be inherited in either an autosomal recessive (inherits gene from both parents) or autosomal dominant (inherits gene from only one parent) pattern.

Types include:

  • KATP-HI Diffuse or Focal Disease: Low blood glucose due to calcium channel (KATP) issues where the beta-cells do not regulate insulin as they should. Diffuse means the whole pancreas is impacted. Focal means just a portion is impacted.
  • GDH-HI: Low blood glucose with fasting or protein consumption with high ammonia in the blood caused by a mutation in the enzyme glutamate dehydrogenase (GDH).
  • GK-HI: Beta-cells do not stop insulin production when blood sugar is already low.

Less common forms of persistent CHI include:

  • Exercise-induced HI (triggered by physical activity)
  • SCHAD-HI (caused by SCHAD enzyme changes — found in beta cells)
  • HNF4A and HNF1A HI (caused by mutations to the HNF4A and HNF1A genes)

The main risk factor for developing CHI is having a family history of CHI or a biological parent who carries a mutated gene. A person may not know they carry the gene without genetic testing.

Doctors use the following to diagnose CHI in a child:

  • symptoms
  • health history
  • blood test results
  • genetic testing

Around 60% of babies with this condition are diagnosed within the first month of life. Another 30% are diagnosed sometime within the first year, and the final 10% are diagnosed at some point later on.

Genetic testing is the most useful diagnostic test. For a genetic test, a blood sample is taken from the child and both biological parents to look for genetic mutations that cause CHI.

Additional blood testing during an episode of hypoglycemia may show:

  • low blood sugar
  • low ketones
  • low free fatty acids
  • increased insulin levels
  • increased ammonia levels
  • other markers of CHI

Your child’s doctor may also administer a glucagon stimulation test during an episode of hypoglycemia. An increase in blood sugar during this test may indicate CHI.

Some doctors use an 18-F-DOPA scan (a type of positron emission tomography or PET scan) to find focal lesions on the pancreas that occur in some forms of the disease.

Treatment of CHI aims at returning blood sugar levels to a normal range. In acute cases of hypoglycemia, this may involve giving a child a drink containing carbohydrates, administering intravenous (IV) glucose, or injecting glucagon.

Medical therapies for CHI include:

  • Diazoxide: an oral medication that prevents insulin secretion by acting on the KATP channel in the beta-cells
  • Octreotide: an injectable drug that blocks insulin secretion in the pancreas
  • Glucagon: an injectable treatment to address hypoglycemia by promoting glucose release in the liver

Surgical intervention may be necessary in the most severe cases:

  • Children who have diffuse KATP-HI may need up to 99% of their pancreas removed (pancreatectomy) to stop the excess insulin production.
  • Children who have focal KATP-HI may need surgery to remove a portion of the pancreas (focal lesion) that is affecting insulin production.

With treatment, CHI may become stable. CHI and the treatments to address it may also lead to long-term issues. However, with continued support, most people with CHI may lead relatively typical lives.

Children who experience brain injury may need academic support for learning difficulties. Those who were fed via an NG tube may need speech and language therapy to relearn how to eat and drink.

Children who had surgery to remove portions of the pancreas may need insulin treatment for diabetes and/or oral enzyme replacement therapy for pancreatic insufficiency.

Is hypoglycemia hereditary?

Hypoglycemia itself is not hereditary, as it occurs as the result of another disease. Some diseases that cause hypoglycemia, like CHI, can be hereditary, while others, like type 2 diabetes, are acquired.

What’s the lowest your blood sugar can be without dying?

Any blood sugar reading under 70 mg/dL is considered hypoglycemia. A reading under 54 mg/dL is considered a medical emergency and may lead to seizures, coma, or death.

Can a person without diabetes get hypoglycemia?

Yes. Things like drinking alcohol, being exposed to heat and humidity, being in puberty or menstruation, or being at high altitude may cause hypoglycemia in people who do not have diabetes.

CHI is a rare genetic disease that causes persistent hypoglycemia. Make an appointment with your pediatrician if you observe symptoms of low blood sugar in your child.

With early diagnosis and treatment, children with CHI may lead typical lives.