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Diabetes Health Center

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The NIDDK on Hypoglycemia

Rare Causes of Hypoglycemia

Fasting hypoglycemia occurs when the stomach is empty. It usually develops in the early morning when a person awakens. As with other forms of hypoglycemia, the symptoms include headache, lack of energy, and an inability to concentrate. Fasting hypoglycemia may be caused by a variety of conditions such as hereditary enzyme or hormone deficiencies, liver disease, and insulin-producing tumors.

In hereditary fructose intolerance, a disorder usually seen in children, the body is unable to metabolize the natural sugar fructose. Attacks of hypoglycemia, marked by seizures, vomiting, and unconsciousness, are treated by giving glucose and eliminating fructose from the diet.

Galactosemia, a rare genetic disorder, hampers the body's ability to process the sugar galactose. An infant with this disorder may appear normal at birth, but after a few days or weeks of drinking milk (which contains galactose), the child may begin to vomit, lose weight, and develop cataracts. The liver may fail to release stored glycogen into the blood, triggering hypoglycemia. Removing milk from the diet is the usual treatment.

A deficiency of growth hormone causes increased sensitivity to insulin. This sensitivity occurs because growth hormone opposes the action of insulin on muscle and fat cells. For this reason, children with growth hormone deficiency sometimes suffer from hypoglycemia, which goes away after treatment.

People with insulin-producing tumors, which arise in the islet cells of the pancreas, suffer from severe episodes of hypoglycemia.

To diagnose these tumors, called insulinomas, a doctor will put the patient on a 24- to 72-hour fast while measuring blood levels of glucose, insulin, and proinsulin. High levels of insulin and proinsulin in the presence of low levels of glucose strongly suggest an insulin-producing tumor. These tumors are usually benign and can be surgically removed.

In rare cases, some cancers such as breast cancer and adrenal cancer may cause hypoglycemia through secretion of a hormone called insulin-like growth factor II. The treatment is removal of the tumor, if possible.


The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) was established by Congress in 1950 as one of the National Institutes of Health, the research arm of the Public Health Service under the U.S. Department of Health and Human Services.

The NIDDK conducts and supports research in diabetes, glucose metabolism, insulin action, and the hormonal controls of blood sugar. Current studies also focus on fasting hypoglycemia, obesity, and insulin resistance.

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