Diabetes

Classification

There are four clinical classifications of diabetes: (1) Type 1 diabetes, (2) Type 2 diabetes, (3) “other specific types,” and (4) gestational diabetes mellitus (GDM). In addition, there are two categories of abnormal glucose tolerance: (1) impaired glucose tolerance (IGT) and (2) impaired fasting glucose (IFG). Type 1 and Type 2 diabetes are the most common forms of diabetes, representing approximately 10% and 90% of the diabetes population, respectively. Gestational diabetes mellitus, a form of diabetes diagnosed during pregnancy, affects 4% of all pregnancies. “Other specific types” of diabetes may result from a variety of factors, including genetic conditions, surgery, drugs, malnutrition, and infections. IFG is characterized by elevated (though nondiabetic) fasting blood glucose levels, while IGT is characterized by elevated postmeal blood glucose levels. Individuals with IGT and IFG have a substantially increased risk of developing Type 2 diabetes.

Diabetes Complications

A variety of acute and chronic complications are associated with diabetes. The acute complications are medical emergencies and include diabetic ketoacidoisis (DKA), hyperosmolar hyperglycemic syndrome (HHS), and hypoglycemia. The chronic complications include disorders associated with microvascular (small vessel) changes in the eyes, nerves, and kidneys, along with macrovascular (large vessel) changes in the heart, veins, and arteries. These changes result in retinopathy (eye disease, e.g., blindness); neuropathy (nerve disease, e.g., nerve damage affecting sensation and pain pathways in the hands and feet, nerve damage affecting the ability to digest food); nephropathy (kidney disease, e.g., end-stage renal disease requiring dialysis or renal transplantation); and premature and accelerated development of coronary heart disease (CHD), cerebrovascular disease, and peripheral vascular disease (PVD). In particular, heart disease and stroke account for 65% of deaths in people with diabetes. Diabetes-related complications are associated with excessive morbidity and mortality from heart disease, blindness, kidney failure, extremity amputations, and other chronic conditions.

Risk Factors

The development of Type 1 diabetes is associated primarily with an autoimmune destruction of the insulin-producing cells of the pancreas and is characterized by a nearly complete loss of insulin secretion. In contrast, Type 2 diabetes is characterized by insulin resistance and decreased insulin secretion. The development of both Type 1 and Type 2 diabetes is initiated by the interplay between genetics and the environment. Type 1 diabetes results when an environmental insult, in an individual genetically predisposed to the disorder, initiates [Page 294]autoimmune destruction of the insulin-producing cells. The environmental factor initiating this destruction is not known and is an area of intense investigation.

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