Causes of Type 1 Diabetes
Type 1 diabetes usually is diagnosed in children and teenagers. For this reason, it used to be called juvenile diabetes. It also is often diagnosed in people in their 20s. Diagnosis after age 30 is much less common.
In the United States, 1 out of every 400 to 600 children and teenagers has type 1 diabetes. The International Diabetes Federation estimates that around the world, close to 430,000 children have this condition. Both genes and environment seem to be involved in causing this disease. Environment includes what you are exposed to and what happens to you in your life.
Type 1 diabetes is not inherited directly in the way that some other diseases are. However, it does seem to be related to genetic (inherited) factors. People who have a first-degree relative with type 1 diabetes are more likely to develop diabetes than the general population. A first-degree relative is a parent, brother, sister or child.
No specific "diabetes gene" has been found. But many genes have been linked to type 1 diabetes. The best-studied is a cluster of genes known as the HLA complex. Genes contain the blueprints for making proteins. Proteins from the HLA group affect how the immune system responds to foreign substances.
Certain combinations of HLA gene types are more common in people with type 1 diabetes. We still don't know why this is the case. And HLA gene types are clearly not the whole story. Many people who have HLA patterns associated with type 1 diabetes never develop the disease.
The patterns of this disease in families show that more than genes must be involved. Most people with type 1 diabetes don't have a first-degree relative with the disease. Also, when one identical twin has type 1 diabetes, the other twin, with identical genes, has less than a 50% chance of developing the disease.
In a person who is at risk because of HLA gene types, life experience or exposures may determine whether type 1 diabetes will develop. Researchers are still researching to better understand triggers.
Experts believe some viruses may trigger diabetes. Exposure to a virus in the womb or early infancy can influence the way that the immune system develops. This can "program" later events. For example, exposure in the womb to the rubella virus (German measles) is linked with a high rate of type 1 diabetes later in childhood. In this case, the virus infection occurs in pregnancy. The baby that is born develops diabetes much later (5 to 20 years after the infection exposure). The measles, mumps and rubella vaccine is an important way that we can prevent rubella in the womb). Early-age stresses other than viruses, such as nutrition problems in infancy, might also play a role. Researchers are looking at whether childhood viruses such as the diarrhea-causing enterovirus or coxsackievirus may also activate the immune system in a way that promotes type 1 diabetes.
Most people with type 1 diabetes have antibodies that are known to promote diabetes. For most people, it is not possible to say what virus or other exposure triggered these antibodies to be produced.
The most common antibodies formed in people who go on to develop type 1 diabetes are islet cell antibodies. They damage cells in the pancreas that make insulin. Some children with diabetes make a second type of antibodies, which can damage cells in the thyroid gland. Children who are newly diagnosed with diabetes should have a blood test to check for thyroid problems, too.
Any medical illness that is severe enough to destroy most or all of the cells in the pancreas can result in type 1 diabetes. The most common cause is inflammation in the pancreas. This is called pancreatitis. Pancreatitis can result from alcohol abuse, gallstones, high levels of triglyceride-type cholesterol, certain drugs or traumatic injury.
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