What is Type 1 Diabetes?



Type 1 Diabetes at the Islet Level

A healthy islet. Click to see a larger image.

An islet under attack. Click to see a larger image.

This graph illustrates the progression of islet mass loss that leads to overt type 1 diabetes. Click to see a larger image.

According to research by Dr. David Harlan of the NIH/NIDDK, some people with long standing type 1 diabetes have measurable c-peptide production, which may help reduce their risk of complications and could indicate that the body continues to generate new islets even in the face of the autoimmune attack of type 1 diabetes.
Islet images courtesy of the Diabetes Research Institute.
Type 1 diabetes is an autoimmune disease in which the body destroys insulin-producing beta cells in the pancreas. Insulin is required by the body to use glucose, the simple sugar that most foods are broken down into by our digestive system. Without insulin, the body starves to death.

It's important to note that everyone is insulin-dependent. People without diabetes make insulin in their pancreas. People with Type 1 diabetes must inject insulin.

According to the National Institutes of Health, an estimated 850,000 to 1.7 million Americans have Type 1 diabetes. Of those, about 125,000 are kids 19 and under. An additional 30,000 Americans develop Type 1 diabetes every year, 13,000 of whom are children. Type 2 diabetes is much more prevalent, with an estimated 16 million Americans having Type 2. Millions of people with type 2 diabetes have not yet been diagnosed.

Diabetes Develops Gradually

The process of developing diabetes is gradual. Studies performed by the Joslin Clinic1 have shown changes as much as nine years before the actual presentation of diabetes symptoms. The development of Type 1 diabetes can be broken down into five stages:

  1. Genetic predisposition
  2. Environmental trigger
  3. Active autoimmunity
  4. Progressive beta-cell destruction
  5. Presentation of the symptoms of Type 1 diabetes

People with Type 1 diabetes have a genetic pre-disposition to the disease, but one or more environmental insults is required to trigger disease. This fact can be derived from studies of identical twins with Type 1 diabetes. When one twin has Type 1 diabetes, the other twin gets diabetes only half the time. If the cause of Type 1 diabetes were purely genetic, both identical twins would always have Type 1 diabetes.

One environmental trigger is thought to be the Coxsackie B virus. Researchers at UCLA found that a small segment of GAD is structurally similar to a segment of a Coxsackie B protein. GAD is found on the surface of insulin-producing beta cells. The implication is that the body's immune system, after warding off the Coxsackie B virus, continues to attack beta cells because of the similarity of GAD to the virus.2

The environmental trigger results in the production of autoantibodies. People with Type 1 diabetes have antibodies in their blood that indicate an "allergy to self," or an autoimmune condition. One autoantibody found in people with Type 1 diabetes is the islet cell antibody. This antibody is often present months or years before the diabetes presents. Other antibodies include the GAD (or 64-K) antibody and the ICA 512 antibody. The presence of these antibodies is a sign that the body is attacking its own beta cells.

Symptoms of Diabetes

Once over 90% of the beta cells are destroyed, the body is no longer able to regulate blood sugar levels and the patient develops some or all of the classic symptoms of diabetes:

While the symptoms appear abruptly, the development of the disease actually occurs over a much longer period of time.

If you suspect that you or your child has diabetes, contact your doctor immediately. Untreated type 1 diabetes can lead to a very serious condition called diabetic ketoacidosis, which can be fatal.


Type 1 diabetes is treated with daily injections of insulin. Oral diabetes medications are not effective. Many patients with Type 1 diabetes, after beginning insulin injections, experience a period of reduced insulin need called the honeymoon period. During the honeymoon period, the remaining beta cells continue to produce insulin. It is very important to continue insulin therapy during the honeymoon period, because even low doses of insulin appear to help prolong the duration of the honeymoon.

For More Information

Historical Information About Diabetes


  1. Understanding Insulin-Dependent Diabetes by H. Peter Chase, M.D.
  2. Management of Diabetes Mellitus: Perspectives of Care Across the Life Span edited by Debra Haire-Joshu, MSEd, MSN, PhD, RN.


  1. Srikanta S and others: "Islet-cell antibodies and beta-cell function in monozygotic triplets and twins initially discordant for type I diabetes," New England Journal of Medicine, 308:322-325, 1983.
  2. Common Class of Viruses Implicated as Cause of Type 1 Diabetes and Getting the Goods on GAD


  1. Type 1 diabetes and latent autoimmune diabetes in adults (LADA): one end of the rainbow. Free full text available in PDF format.


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Last Updated: Sun Feb 19 13:11:50 2006
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