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Causes

By Mayo Clinic staff

The exact cause of type 1 diabetes is unknown. Scientists do know that in most people with type 1 diabetes, their body's own immune system — which normally fights harmful bacteria and viruses — mistakenly destroys the insulin-producing (islet) cells in the pancreas. Genetics may play a role in this process, and exposure to certain viruses may trigger the disease.

Whatever the cause, once the islet cells are destroyed, you'll produce little or no insulin. Normally, the hormone insulin helps glucose enter your cells to provide energy to your muscles and tissues. Insulin comes from the pancreas, a gland located just behind the stomach. When everything is working properly, once you eat, the pancreas secretes insulin into the bloodstream. As insulin circulates, it acts like a key by unlocking microscopic doors that allow sugar to enter the body's cells. Insulin lowers the amount of sugar in the bloodstream, and as the blood sugar level drops, so does the secretion of insulin from the pancreas.

The liver acts as a glucose storage and manufacturing center. When insulin levels are low — when you haven't eaten in a while, for example — the liver converts stored glycogen back to glucose to keep your blood glucose level within a normal range.

In type 1 diabetes, none of this occurs because there's no insulin to let glucose into the cells. So instead of being transported into your cells, sugar builds up in your bloodstream, where it can cause life-threatening complications.

The cause of type 1 diabetes is different from the cause of the more familiar type 2 diabetes. In type 2 diabetes, the islet cells are still functioning, but the body becomes resistant to insulin or the pancreas doesn't produce enough insulin.

Risk factors Symptoms
References
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June 13, 2009

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