Hyperinsulinemia is an abnormally high level of insulin in the bloodstream. Chronic hyperinsulinemia is most often caused by insulin resistance, a condition in which the body cannot use insulin properly. Insulin is a hormone necessary to move glucose (blood sugar) from the bloodstream into the cells for use as energy. Insulin resistance is a feature of metabolic syndrome and type 2 diabetes.

Hyperinsulinemia may also be due to a tumor of the pancreas (insulinoma). Hyperinsulinemia in infants and children may be due to genetic defects or to diabetes in the mother during fetal development.

Other causes of and contributors to hyperinsulinemia include:

• Obesity
• Smoking
• Impaired liver function
• Pregnancy or breastfeeding
• Polycystic ovarian syndrome

Short-term hyperinsulinemia may be due to an overdosage of insulin medication, unusual physical exertion or a large carbohydrate load that requires extra insulin to process.

Hyperinsulinemia can cause hypoglycemia (low glucose) and insulin shock. It is especially dangerous because of its potential effects on the brain. Hypoglycemia that is related to hyperinsulinemia is more dangerous than most types of hypoglycemia. Severe hypoglycemia can lead to diabetic coma or death.

In other hypoglycemia-causing conditions, alternative sources of energy such as ketones help fuel the cells of the brain, although this does result in the buildup of potentially dangerous substances in the blood (diabetic ketoacidosis). Hyperinsulinemia may cause the production of such alternative sources to stop, leaving the brain without a source of energy. This can lead to brain damage.

Other complications of hyperinsulinemia and insulin resistance can include increased risk of:

• Heart attack and stroke
• Elevated blood pressure
• Excessive blood clotting
• Cancer
• Gout and kidney stones

Treatment first addresses any related hypoglycemia. Additionally, cases related to insulin resistance may be addressed with exercise, weight loss, diet and, if necessary, medication. Treatment of hyperinsulinemia in infancy may include intravenous glucose, medication or pancreatectomy. Hyperinsulinemia caused by insulinoma may be treated with surgery, chemotherapy or hormone therapy.