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Congenital hyperinsulinism is a condition characterized by having too much insulin in the body. There are several different forms of this genetic disorder, but the most common include diffuse KATP HI, GHD HI, focal KATP HI, and GK HI. Understanding the genetics of congenital hyperinsulinism helps healthcare providers treat this condition, as well as recognize it and understand how it occurs and affects the body.
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What is Congenital Hyperinsulinism?
This genetic disorder occurs when the beta cells (insulin cells of the pancreas) put out too much insulin at the wrong time. This excess insulin then causes blood sugar levels to drop. Under normal circumstances, the beta cells put out just the right amount of insulin to keep blood sugar levels normal. With congenital hyperinsulinism, insulin secretion is not regulated properly, resulting in excess insulin production which causes low blood sugar.
Blood sugar levels ranging between 70 and 100 mg/dL are considered normal. When they drop below 60 mg/dL, they are considered low. Once they drop below 50 mg/dL, the severe symptoms associated with hypoglycemia are likely to occur. Permanent brain damage and seizures can occur when blood sugar levels are severely low or low for a prolonged period of time.
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What are the Symptoms of Congenital Hyperinsulinism?
The common symptoms that can occur when blood sugar levels are low include:
- Clammy skin
Additional symptoms can occur when the brain is deprived of glucose for an extended period of time and these include:
- Difficulty in thinking
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How Common is Congenital Hyperinsulinism?
This genetic disorder affects about every one in 50,000 live births. In countries in which marriage among family members is common, the incidence rate is about one in 2,500 live births.
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Genetics of Congenital Hyperinsulinism
The most common form of this disorder is the diffuse form, in which all beta cells put out too much insulin. In the focal form on this disorder, only some of the beta cells put out too much insulin. ABCC8 gene mutations are the most common cause of congenital hyperinsulinism, accounting for approximately 40 percent of all cases. The diffuse form of this condition has an autosomal recessive inheritance pattern in most cases, however, some diffuse cases have an autosomal dominant inheritance pattern.
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Diagnosing Congenital Hyperinsulinism
Patient and family medical history, a physical exam, and some laboratory testing are the main methods in diagnosing this genetic disorder. In some cases, genetic testing is done. In order to distinguish between the diffuse form and the focal form, special radiologic testing, an F-DOPA PET scan is thought to be helpful, but has yet to be approved by the FDA.
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How is Congenital Hyperinsulinism Treated?
In order to prevent low blood sugar levels, those with this condition may need to consume specific amounts of sugar on a routine schedule. Tube feeding of formula or dextrose water into the stomach may be used for babies who cannot consume enough sugar with regular feedings.
Because feeding is often not sufficient in helping to control low blood sugar levels, medications are often prescribed as well. These medications help to block and/or prevent the release and secretion of insulin. These medications can include diazoxide (oral), octreotide (injection), and glucagon (injection).
When medications are not effective, surgery to remove a portion of the pancreas may done.
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The Children's Hospital of Philadelphia. (2010). About Congenital Hyperinsulinism. Retrieved on June 25, 2010 from The Children's Hospital of Philadelphia: http://www.chop.edu/service/congenital-hyperinsulinism-center/about-congenital-hyperinsulinism/
Genetics Home Reference. (2010). Familial Hyperinsulinism. Retrieved on June 25, 2010 from Genetics Home Reference: http://ghr.nlm.nih.gov/condition/familial-hyperinsulinism