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What Is Diabetes?

Diabetes refers to a group of chronic diseases that involve problems in the regulation of blood sugar. The two most common types of diabetes are, type 1 and type 2. Both forms result from the body's inability to either produce or respond adequately to insulin. (A third type, gestational diabetes, occurs only during pregnancy and may lead to type 2 diabetes.)

Insulin is the hormone that controls the movement of glucose from the blood into cells. Insulin is produced by the pancreas. Glucose--also called blood sugar--constantly moves through the bloodstream in order to supply the body with the energy needed for muscle contractions and metabolism.

The job of insulin is to make sure the glucose actually moves into the body's cells. Without insulin, the glucose builds up in the bloodstream. Over time, elevated glucose levels can damage the linings of blood vessels, leading to damage to the eyes, kidneys, and other sensitive tissues. This vascular damage can cause blindness (diabetic retinopathy), impotence, kidney failure (diabetic nephropathy and end-stage renal disease), increased risk for heart attack, and the deterioration of nerves or blood vessels. It also can cause insufficient blood flow to the arms and legs, resulting in amputation. Diabetes is the leading cause of new blindness in adults. It is also the most common condition leading to dialysis and kidney transplants, and the most common reason for below-the-knee amputations.

The process that causes type 1 diabetes, the less common form, directly affects the pancreas by destroying the organ's beta islet cells, the only cells in the body that produce insulin. Although type 1 diabetes can occur at any age, it is usually diagnosed in children and young adults. Genetic, autoimmune, and environmental factors are considered risk factors for type 1 diabetes. Currently, there is no known way to prevent type 1 diabetes.

Type 2 diabetes affects nine out of 10 people with diabetes. In the process that causes type 2 diabetes, the pancreas either does not produce enough insulin, or the body becomes less and less efficient at getting insulin to move glucose into the cells (insulin resistance). You can inherit the potential for type 2 diabetes, but whether you actually develop it may depend on a number of environmental factors, such as poor eating habits and lack of exercise. Other risk factors include older age and history of gestational diabetes. Race and ethnicity can also influence the occurrence of type 2 diabetes. African-Americans, Hispanic Americans, American Indians, and Native Hawaiians are at a particularly high risk of developing type 2 diabetes and its complications.