Diabetes mellitus is a condition where people don't produce enough insulin to meet their body's needs or their cells don't respond properly to insulin. Insulin is important because it moves glucose, a simple sugar, into the body's cells from the blood. It also has a number of other effects on metabolism.
The food people eat provides the body with glucose, which is used by the cells as a source of energy. If insulin isn't available or doesn't work correctly to move glucose from the blood into cells, glucose will stay in the blood. High blood glucose levels are toxic and cells that don't get glucose are lacking the fuel they need. These two problems cause the symptoms of diabetes.
There are two main kinds of diabetes: type 1 diabetes and type 2 diabetes. More than 90% of all people with diabetes have type 2. Overall, about 20 million people in North America have diabetes. Only about two-thirds of people with type 2 diabetes are aware of it and are receiving treatment because, for many people, early symptoms are not noticeable without testing.
Type 1 diabetes occurs when the pancreas cannot make insulin. Everyone with type 1 diabetes requires insulin injections. Type 1 diabetes occurs most commonly in people of northern European ancestry.
Type 2 diabetes occurs when the pancreas does not make enough insulin or the body does not use insulin properly. It usually occurs in adults, although in some cases children may be affected. People with type 2 diabetes usually have a family history of this condition and are most often overweight. People with type 2 diabetes may eventually need insulin injections. This condition occurs most commonly in people of American Indian descent, Hispanics, and North Americans of African descent.
Another less common form is gestational diabetes, a temporary condition that occurs during pregnancy. Gestational diabetes affects about 4% of pregnant women in the United States. The problem usually clears up after delivery, but women who have had gestational diabetes have a higher risk of developing type 2 diabetes later in life.
Type 1 diabetes is an autoimmune disorder. It's believed that a combination of genetic predisposition and additional (as yet unidentified) factors provoke the immune system into attacking and killing the insulin-producing cells in the pancreas.
Type 2 diabetes is mainly caused by insulin resistance. This means no matter how much or how little insulin is made, the body can't use it as well as it should. As a result, glucose can't be moved from the blood into cells. Over time, the excess sugar in the blood gradually poisons the pancreas causing it to make less insulin and making it even more difficult to keep blood glucose under control.
Obesity is a leading cause of insulin resistance - 90% of people with type 2 diabetes are overweight. There are probably genetic factors involved in the cause of type 2 diabetes as well. A family history of the disease has been shown to increase the chances of getting it.
Other risk factors for the development of type 2 diabetes include:
- a history of gestational diabetes
- being 40 years of age or older
- blood vessel disease
- American Indian, Hispanic, South Asian, Asian, or African descent
- giving birth to a large baby
- high blood pressure
- high cholesterol
- polycystic ovary syndrome
- prediabetes or impaired fasting glucose