Conditions
Type 1 diabetes is a disorder of sugar metabolism in which the pancreas is no longer able to produce insulin.
Summary
- Type 1 diabetes is a disorder of sugar metabolism in which the pancreas is no longer able to produce insulin.
- This is due to destruction of the insulin-producing beta cells of the pancreas by an autoimmune process.
- Type 1 diabetes commonly develops before the age of 40, with a peak incidence around 14. Those with a strong family history of diabetes are at risk of developing the disease.
- The symptoms of diabetes are excessive thirst and urination and weight loss, which can occur abruptly over a few days. Type 1 diabetes can also present as diabetic ketoacidotic coma.
- Type 1 diabetes is treated with insulin and careful attention to diet and lifestyle.
- The long-term complications of Type 1 diabetes can be well controlled by using a "tight control" regime in which blood glucose is measured several times each day and the insulin dose adjusted accordingly.
Alternative names
Insulin-dependent diabetes - now seldom used.
What is Type 1 diabetes?
Diabetes, correctly called diabetes mellitus, is a disorder of carbohydrate metabolism. In Type 1 diabetes, the pancreas is no longer able to produce the hormone insulin. Insulin is produced by the beta cells of the pancreas; it is secreted in response to an increased concentration of glucose in the blood, and is vital in controlling blood glucose levels. A person with diabetes cannot control their blood glucose and they become hyperglycaemic - meaning that they have abnormally high levels of glucose in the blood.
What causes Type 1 diabetes?
By the time a person with Type 1 diabetes experiences symptoms, almost all the beta cells in the pancreas have been destroyed. This destruction is almost certainly as a result of an automimmune process in which the body produces antibodies to its own cells. However, the details of the process are obscure.
It seems that there must initially be a genetic tendency for the disease, which is then triggered by an environmental event such as a viral infection. The third step in the process is an inflammation of the pancreas called insulitis. The fourth step is an alteration in the surface of the beta cell so that it is no longer recognised as "self" - part of the body - but is perceived by the immune system to be a foreign cell or "non-self". The fifth step is the development of an immune response.
The end result is the destruction of the beta cell and the development of diabetes.
Who gets Type 1 diabetes and who is at risk of the disease?
The percentage of the population with diabetes is highly variable among geographical regions and populations, so estimates are often inaccurate. A recent figure is 110 million people around the world with diabetes, but most of them have Type 2 diabetes. Type 1 diabetes probably comprises between 10 and 15% of all cases of diabetes.
Type 1 diabetes usually begins before the age of 40, the peak incidence being around 14.
A strong family history is a definite risk factor for Type 1 diabetes, although the way in which the disease is inherited is not clear. There is a strong association between Type 1 diabetes and the HLA-D complex on the sixth chromosome.
What are the symptoms and signs of Type 1 diabetes?
The characteristic symptoms of diabetes are:
- Excessive thirst
- Weight loss
- Excessive urination
- Tiredness
These symptoms may be abrupt, developing over a period of a few days.
However, the first sign of Type 1 diabetes can also be acidote coma, or near coma, as a result of an event called diabetic ketoacidosis in which the levels of glucose in the blood are so high that this life-threatening state occurs. Due to a lack of insulin the glucose in the blood cannot enter the cells where it is desperately needed.
To prevent starvation and cell death, lipids are metabolized to ketones. Ketones can be used as food by the cells, for example cells in the brain, even in the absence of insulin. However, the ketones are not only good. They are acidic in nature and cause an acidosis. The condition is called ketoacidosis and is the result of insulin deficiency in type 1 diabetics. As a consequence of this condition, the blood and the tissues are more acidic than normal and this in turn may lead to malfunctioning of organs such as the heart. Initially, a person with ketoacidosis compensates by breathing deeply (called Kussmual