Hyperinsulinism in a newborn is a condition characterized by the overproduction of insulin by the pancreas. Insulin is a hormone that helps regulate blood sugar, and an excess can cause blood sugar levels to drop dangerously low, a state known as hypoglycemia. This condition is the most prevalent cause of persistent hypoglycemia in infants, affecting approximately 1 in 25,000 to 50,000 newborns.
High insulin levels prevent the body from using alternative energy sources. When blood sugar is low, the body normally breaks down stored fats into ketones to fuel the brain. Excess insulin blocks this process, leaving the brain entirely dependent on a dwindling glucose supply. This makes the hypoglycemia caused by hyperinsulinism particularly damaging.
Causes of Newborn Hyperinsulinism
Newborn hyperinsulinism is categorized as either transient or persistent. Transient hyperinsulinism is a temporary form that resolves on its own and is often associated with perinatal stress. Factors like birth asphyxia (a lack of oxygen during delivery), intrauterine growth restriction, and maternal diabetes can lead to this temporary state of excessive insulin production. This form appears within the first day of life and may last for a few weeks.
Persistent hyperinsulinism, or congenital hyperinsulinism (CHI), is a long-term condition from genetic mutations. These changes cause the pancreas’s beta cells to release insulin inappropriately. Unlike the transient form, this condition requires ongoing medical management. There are at least 10 known gene mutations that can cause CHI by disrupting the normal regulation of insulin release.
The persistent form manifests in two ways: diffuse or focal. In the diffuse form, all beta cells in the pancreas are abnormal. The focal form involves a small cluster of abnormal cells within an otherwise healthy pancreas. This distinction influences the treatment strategy, and genetic testing can help identify the specific type.
Symptoms and Diagnostic Process
The symptoms of hyperinsulinism are a direct result of hypoglycemia and can be subtle. Common signs include:
- Jitteriness or shakiness
- Irritability
- Excessive hunger
- Lethargy or sleepiness
- A weak cry
- A rapid heart rate
In severe cases, extremely low blood sugar can cause seizures, which may lead to brain damage if not addressed quickly.
Confirming a diagnosis of hyperinsulinism involves specific medical testing. While a blood test can show low blood sugar, it doesn’t confirm the cause. Doctors must obtain a “critical sample,” which is a blood sample taken during an episode of hypoglycemia. This sample is analyzed to measure the levels of insulin and other substances, which will show an inappropriately high insulin level for the low level of glucose, confirming hyperinsulinism.
Once hyperinsulinism is confirmed, further investigations determine the underlying cause. Imaging studies, such as a specialized scan, may be used to locate a focal lesion within the pancreas.
Treatment Approaches
The immediate goal is to stabilize blood sugar levels and prevent hypoglycemia. This is first managed with frequent feedings to provide a steady supply of glucose. If feedings are insufficient, an intravenous (IV) glucose infusion is started to deliver sugar directly into the bloodstream. The objective is to maintain blood glucose levels above 70 mg/dL.
Once blood sugar is stable, medical therapy may be initiated. The most common medication is diazoxide, which inhibits insulin release from the pancreatic beta cells, and about half of children respond well. If diazoxide is ineffective, another medication called octreotide may be used, which decreases insulin secretion through a different mechanism.
Surgery may be required for severe cases that do not respond to medical treatment. For the focal form, a surgeon can remove the small, affected portion of the pancreas, curing the condition in over 96% of cases. For diffuse disease that is unresponsive to medication, a near-total pancreatectomy (removal of most of the pancreas) may be necessary to control the life-threatening hypoglycemia.
Long-Term Outlook and Care
The long-term outlook depends on the type and severity of the condition. For newborns with the transient form, the prognosis is positive as it resolves within a few weeks. With careful blood sugar management during this time, these infants experience no lasting effects and require no long-term treatment.
Children with persistent hyperinsulinism require ongoing medical management from a pediatric endocrinologist. The goal of long-term care is controlling blood sugar levels to prevent hypoglycemia and protect the brain. This often involves a combination of medications, a specific diet, and frequent blood sugar monitoring.
With prompt diagnosis and consistent management, the risk of long-term neurological complications like learning disabilities or seizure disorders is significantly reduced. This comprehensive approach helps ensure children with persistent hyperinsulinism can develop normally and lead healthy lives.