Congenital hyperinsulinism (HI) is a rare genetic disorder that causes seriously low blood sugar in babies and children. It happens when cells in the pancreas, called beta cells, make too much insulin. Insulin is the hormone that converts glucose, a type of sugar in your blood, into energy for your cells.
HI affects about 1 out of every 25,000 to 50,000 newborns, both males and females. It's important to diagnose and treat it quickly to prevent the brain damage that very low blood sugar can cause.
What Are the Symptoms of Congenital Hyperinsulinism?
HI-related low blood sugar symptoms are hard to identify, especially in infants and newborns. That's because it's easy to confuse many of them with typical newborn behavior.
Common signs of hypoglycemia include:
- Excessive hunger
- Irritability
- Lethargy
- Sleepiness
- Rapid heart rate
In older children, symptoms may also include:
- Shakiness
- Weakness
- Confusion
If your child has very low blood sugar or has had it for a long time, it can cause more serious symptoms such as:
- Seizures
- Coma
This can lead to permanent brain damage.
Doctors consider blood sugar levels above 70 milligrams per deciliter (mg/dL) to be normal. Anything below 60 mg/dL is low. Blood sugar below 50 mg/dL may cause serious symptoms.
What Causes Congenital Hyperinsulinism?
Congenital hyperinsulinism can be inherited. In this case, it results from a change, or mutation, in any of the 10 genes that control the release of insulin from your beta cells. The genetic types of HI don't go away on their own, but they may get easier to treat as the child grows.
Other things that can cause HI include:
Perinatal stress: This type of HI usually affects newborns. It happens due to stressors during labor and right after birth, such as problems with the placenta or with the baby getting enough oxygen. This is a temporary form of HI.
Other syndromes. Among the disorders that can cause low blood sugar are:
- Beckwith-Wiedemann syndrome
- Kabuki syndrome
- Sotos syndrome
- Turner syndrome
Types of Hyperinsulinism
There are several types of HI. They include:
Diazoxide-responsive and diffuse KATP HI. Our beta cells have potassium channels known as KATP channels. They help control the release of insulin. If you have one of these types of HI, these channels don’t work properly.
Focal KATP HI. If you have this, an isolated (focal) area of your pancreas is abnormal. The rest of your pancreas works properly.
GDH-HI. Insulin overproduction causes your blood sugar levels to dip when you don't eat, or when you eat protein.
Glucokinase HI. With this type, all the beta cells in your pancreas are affected. They're unable to turn off insulin production when your blood sugar levels run low.
HNF1a and 4a defects. These are rare forms of HI that progress to diabetes during adolescence or in adulthood.
MCT-1 HI. Exercise can trigger this rare type of HI.
SCHAD-HI. This type is caused by a very rare disorder that affects your body's metabolism of fatty acids. It affects all the beta cells in your pancreas.
UCP-2 HI. This is a rare type of congenital HI that will go away over time.
How Is HI Diagnosed?
Doctors can't always diagnose HI with just a blood test, since blood sugar levels may change several times during the day. About 60% of babies with congenital HI are diagnosed before they're a month old. About 30% are diagnosed later in their first year, and the rest sometime after that.
If your doctor thinks your child may have HI, they may:
Take a detailed history. Your doctor may ask you questions about symptoms, when they started, the child's weight at birth, and family history related to low blood sugar, seizures, or sudden infant death.
Perform lab tests. They may do blood tests to check for insulin levels and fasting blood sugar. It’s usually drawn when your levels are below 50 mg/dL.
Order genetic testing. DNA tests are done using a blood sample from the baby and both parents to check if HI is genetic. The parents are also screened for mutations that cause the most common types of HI.
What Are the Treatment Options?
The goal of HI treatment is to keep blood sugar levels within the normal range. The treatment options include prescription medication and surgery.
Medications to control HI include:
Diazoxide. You take this pill by mouth two to three times per day. It works by stopping the pancreas from overproducing insulin.
Octreotide. It’s usually given as an injection through a vein. You can also get it through an insulin pump under your skin. Like diazoxide, it prevents insulin overproduction.
Glucagon. You get this through an IV or an injection under the skin or into a muscle. It’s designed to stimulate your liver to release glucose, especially if your blood sugar levels get very low.
Around half of children with HI respond well to medication. The others may need surgery.
If you need surgery, depending on the type of HI you have, your doctor might opt for a partial or full pancreatectomy. That's surgery to remove the pancreas.
Surgery is effective for about 97% of children with the focal type of hyperinsulinism. Some children with HI may need more than one surgery.
Outlook for Hyperinsulinism
Quick diagnosis and proper treatment make children less likely to have long-term issues with hypoglycemia. This can help them avoid neurological delays such as epilepsy, impaired movement, or learning difficulties.