Type 1 diabetes is much less common than type 2 diabetes and typically arises in children. Type 1 diabetes (T1D) usually begins before 40 years of age, although occasionally people have been people diagnosed at an older age. In the United States, the peak age at diagnosis is most often around 14 years old.
Type 1 diabetes is associated with a deficiency or lack of insulin. It is not known why, but the pancreatic islet cells stop producing insulin in the quantities needed to maintain a normal blood glucose level. Without sufficient insulin, the blood glucose level rises, causing some of the common signs and symptoms of hyperglycemia.
When this happens, the person experiencing high blood sugar (hyperglycemia) must get medical help. One of the first signs of high blood sugar is unexpected and unexplained weight loss that occurs over several days and is associated with the onset of their diabetes. The appearance of these first symptoms of type 1 diabetes may be fairly abrupt or can occur more gradually.
To learn more about type 1 diabetes basics, see our type 1 diabetes slideshow.
It has been estimated that the yearly incidence of type 1 diabetes developing is 3.7 to 20 per 100,000. More than 700,000 Americans have this type of diabetes. This is about 10% of all Americans diagnosed with diabetes; the other 90% have type 2 diabetes.
In the case of type 1 diabetes, the islet cells of the pancreas that produce insulin are seen as the "enemy" by mistake. The body then creates antibodies to fight the "foreign" tissue and destroys the islet cells' ability to produce insulin.
The lack of sufficient insulin thereby results in diabetes. It is unknown why this autoimmune diabetes develops. Most often it is a genetic tendency. Sometimes it follows a viral infection such as mumps, rubella, cytomegalovirus, measles, influenza, encephalitis, polio, or Epstein-Barr virus.
Certain people are more genetically prone to this happening although why this occurs is not know. In some cases, family members of those with type 1 diabetes also have a family history of autoimmine conditions. Thus, 2 people may be infected with the same virus and only one of them who is genetically prone will go on to develop diabetes.
Other less common (very rare) causes of type 1 diabetes include injury to the pancreas from toxins, trauma, or after the surgical removal of the majority (or all) of the pancreas.
Type 1 diabetes tends to have less tendency to have other family members affected with diabetes than type 2 diabetes. In the first large family study of diabetes, less than 4% of parents and 6% of siblings of a person with diabetes also had diabetes.
In studies with identical twins, less than 50% of the siblings of a person with diabetes also had diabetes versus almost 100% of siblings of people with type 2 diabetes. Children of fathers with type 1 diabetes are more likely to develop type 1 diabetes than children of mothers with type 1 diabetes.
Type 1 diabetes must be treated with insulin. This involves injecting insulin under the skin—in the fat—for it to get absorbed into the bloodstream where it can then access all the cells of the body that require it. Insulin cannot be taken as a pill because the juices in the stomach would destroy the insulin before it could work. Remember, insulin is a hormone, and like all other hormones, insulin is a protein and therefore it has a very important 3-dimensional structure which is destroyed by the acid in the stomach.
See the section on treatments for a comprehensive summary of the types of insulin available.
Even if insulin did make it through the stomach, the digestive enzymes secreted by the pancreas would breakdown the insulin protein molecule so it could no longer do its job. Scientists are looking for new ways to give insulin such as an inhaled version; It is typically given with meals, and long-acting insulin is still needed by anyone with type 1 diabetes.
Still, injections are the most widely used method but pens now make it much easier to give yourself the right dose quickly. Insulin pumps are becoming more popular. Since more insurance companies are covering some or all of the cost, this method of insulin delivery is gaining in use. There is now an implantable insulin device that lasts for 90 days, and is expected to gain approval for twice that long. And, the concept of an artificial pancreas is advancing.