Diagnostic Criteria and Classification of Diabetes

Diabetes mellitus is a heterogeneous group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Chronic hyperglycemia is associated with pathognomonic changes and failure of various organs, especially the eyes, kidneys, and nerves. Individuals with hyperglycemia are also subject to the accelerated cardiovascular disease that causes premature morbidity and mortality. Pathogenic processes involved in the development of diabetes range from autoimmune destruction of the β-cells of the pancreas with consequent insulin deficiency, to abnormalities in insulin signaling that result in resistance to insulin action. The vast majority of cases of diabetes fall into two broad etiopathogenetic groups. In one group (type 1 diabetes), the cause is an absolute deficiency of insulin secretion. Individuals at increased risk of developing this type of diabetes can often be identified by serological evidence of an autoimmune process of the pancreatic islets and by genetic markers. In the second and more prevalent group (type 2 diabetes), the cause is a combination of resistance to insulin action with inadequate compensatory insulin secretory response.