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ESSENTIALS OF DIAGNOSIS
Type 1 diabetes
Polyuria, polydipsia, and weight loss associated with random plasma glucose of 200 mg/dL (11.1 mmol/L) or more.
Plasma glucose of 126 mg/dL (7.0 mmol/L) or more after an overnight fast, documented on more than one occasion.
Ketonemia, ketonuria, or both.
Islet autoantibodies are frequently present.
Type 2 diabetes
Many patients are over 40 years of age and obese.
Polyuria and polydipsia. Ketonuria and weight loss 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 more after an overnight fast on more than one occasion. Two hours after 75 g oral glucose, diagnostic values are 200 mg/dL (11.1 mmol) or more.
HbA1c 6.5% or more.
Hypertension, dyslipidemia, and atherosclerosis are often associated.
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EPIDEMIOLOGIC CONSIDERATIONS
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An estimated 30.3 million people (9.4%) in the United States have diabetes mellitus, of which approximately 1.5 million have type 1 diabetes and most of the rest have type 2 diabetes. A third group designated as “other specific types” by the American Diabetes Association (ADA) (Table 27–1) number in the thousands. Among these are the monogenic defects of either B cell function or of insulin action, primary diseases of the exocrine pancreas, endocrinopathies, and medication-induced diabetes. Updated information about the prevalence of diabetes in the United States is available from the Centers for Disease Control and Prevention (http://www.cdc.gov/diabetes/pubs/estimates.htm#prev).
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CLASSIFICATION & PATHOGENESIS
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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 for the resistance.
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A. Type 1 Diabetes Mellitus
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This form of diabetes is due to pancreatic islet B cell destruction predominantly by an autoimmune process in over 95% of cases (type 1A) and idiopathic in less than 5% (type 1B). The rate of pancreatic B cell destruction is quite variable, being rapid in some individuals and slow in others. It occurs at any age but most commonly arises in children and young adults with a peak incidence before school age and ...