ESSENTIALS OF DIAGNOSIS
Type 1 diabetes
Polyuria, polydipsia, and weight loss with random plasma glucose of ≥ 200 mg/dL (11.1 mmol/L).
Plasma glucose of ≥ 126 mg/dL (7.0 mmol/L) 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 have obesity.
Polyuria and polydipsia. Ketonuria and weight loss are uncommon at time of diagnosis. Candidal vaginitis may be an initial manifestation.
Plasma glucose of ≥ 126 mg/dL 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).
HbA1c ≥ 6.5%.
Hypertension, dyslipidemia, and atherosclerosis are often associated.
An estimated 34.2 million people (10.5%) in the United States have diabetes mellitus, of whom approximately 5–10% 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. Current statistics about diabetes in the United States are available from the CDC (https://www.cdc.gov/diabetes/data/statistics/statistics-report.html).
Table 27–1.Other specific types of diabetes mellitus. ||Download (.pdf) Table 27–1. Other specific types of diabetes mellitus.
Genetic defects of pancreatic B cell function
MODY 1 (HNF-4alpha); rare
MODY 2 (glucokinase); less rare
MODY 3 (HNF-1alpha); accounts for two-thirds of all MODY
MODY 4 (PDX1); very rare
MODY 5 (HNF-1beta); very rare
MODY 6 (neuroD1); very rare
Genetic defects in insulin action
Type A insulin resistance
Diseases of the exocrine pancreas
Drug- or chemical-induced diabetes
Other genetic syndromes (Down, Klinefelter, Turner, others) sometimes associated with diabetes
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 for the resistance.
A. Type 1 Diabetes Mellitus
This form of diabetes is due to autoimmune destruction of pancreatic islet B cell. The rate of pancreatic B cell destruction is 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 at age 10–14 years. It is a catabolic disorder in which circulating insulin is virtually absent, plasma glucagon is elevated, and the pancreatic B cells fail to respond to all insulinogenic stimuli. Type 1 diabetes is usually associated with ketosis in its untreated state. Exogenous insulin is therefore required to reverse the catabolic state, prevent ketosis, reduce ...