Type 1 diabetes:
Polyuria, polydipsia, and weight loss associated with random plasma glucose 200 mg/dL.
Plasma glucose of 126 mg/dL or higher after an overnight fast, documented on more than one occasion.
Ketonemia, ketonuria, or both.
Islet autoantibodies are frequently present.
Type 2 diabetes:
Most patients are over 40 years of age and obese.
Polyuria and polydipsia. Ketonuria and weight loss generally are uncommon at time of diagnosis. Candidal vaginitis in women may be an initial manifestation. Many patients have few or no symptoms.
Plasma glucose of 126 mg/dL or higher after an overnight fast on more than one occasion. After 75 g oral glucose, diagnostic values are 200 mg/dL or more 2 hours after the oral glucose.
Hypertension, dyslipidemia, and atherosclerosis are often associated.
In 2002, an estimated 18.2 million people in the United States had diabetes mellitus, of which approximately 1 million have type 1 diabetes and the rest mostly have type 2 diabetes. A third group that was designated as “other specific types” by the American Diabetes Association (ADA) (Table 27–1) number only in the thousands. Among these are the rare monogenic defects of either B cell function or of insulin action, primary diseases of the exocrine pancreas, endocrinopathies, and drug-induced diabetes. Updated information about the prevalence of diabetes in the United States is available from the Centers for Disease Control and Prevention.
Classification & Pathogenesis
Diabetes mellitus is a syndrome with disordered metabolism and inappropriate hyperglycemia due to either a deficiency of insulin secretion or to a combination of insulin resistance and inadequate insulin secretion to compensate. Type 1 diabetes is due to pancreatic islet B cell destruction predominantly by an autoimmune process, and these patients are prone to ketoacidosis. Type 2 diabetes is the more prevalent form and results from insulin resistance with a defect in compensatory insulin secretion.