Type 2 diabetes was previously referred to as non-insulin-dependent diabetes or adult-onset diabetes. The cause of type 2 diabetes is more complicated. The hyperglycemia can result from insulin resistance, insulin deficiency, or a defect in insulin secretion. Although the specific etiologies may not be known, autoimmune destruction of beta cells does not usually occur, and patients do not have any of the other known causes of diabetes. Most, but not all, patients with type 2 diabetes are obese. Obesity itself causes some degree of insulin resistance. Patients who are not obese by traditional weight criteria may have an increased percentage of body fat distributed predominantly in the abdominal region.
Type 2 diabetes is often association with a strong genetic predisposition, more so than type 1 diabetes. However, the genetics of type 2 is poorly understood.
Insulin resistance is probably the primary dysfunction. The insulin is present; however, due to other metabolic processes, it is unable to act on peripheral cells and tissue. The pancreas is unable to increase insulin production to compensate for the resistance and therefore, insulin activity is deficient. At least initially, and often throughout their lifetime, individuals with type 2 diabetes may not need insulin treatment to survive.
The insulin resistance and deficiency result from a combination of genetic and environmental factors. Common among these are obesity, family history, and distribution of body fat. Truncal obesity is associated with insulin resistance. Increased calorie intake, weight gain, duration of obesity, and decreased physical activity are other factors contributing to type 2 diabetes onset. Type 2 diabetes accounts for approximately 90% of all diabetes.
With type 2 diabetes, ketoacidosis seldom occurs spontaneously and when it does occur, it usually arises in association with the stress or another illness (eg, infection). Frequently, type 2 diabetes may go undiagnosed for several years because hyperglycemia tends to develop gradually and, in the early stage, the hyperglycemia may not be severe enough for symptoms to appear.
Note: The testing and diagnosis of type 2 diabetes will be discussed later in this course.