Diabetes

August 23, 2011

Diabetes mellitus is a disease in which blood glucose (sugar) levels rise out of control. insulin is the hormone that regulates blood glucose levels by signaling cells to take glucose out of the bloodstream and by signaling the liver not to put more glucose into the bloodstream. insulin is made in the pancreas, an organ that lies in the upper abdomen, just below and behind the stomach. Diabetes occurs either because the pancreas fails to produce enough insulin (type 1 diabetes) or because cells do not respond normally to insulin (type 2 diabetes). Type 2 diabetes accounts for the vast majority of diabetes. Only about 5-10% of all diabetes is type 1.

Diabetes is the most common hormone disorder. About 17 million people in the United States have diabetes, accounting for 6.2% of the population. Another 6 million or so cases are undiagnosed. In 1999, diabetes was the sixth leading cause of death. In general, people with diabetes are twice as likely to die as those without diabetes. For women and young adults, diabetes increases the death rate by fourfold. According to the American Diabetes Association, in 1997, diabetes cost the United States $98 billion. Direct medical costs were $44 billion. Indirect costs related to disability, loss of work, and premature death were even higher, accounting for $54 billion.

Type 1 diabetes, in which the pancreas does not produce enough insulin, used to be called juvenileonset diabetes because it is usually diagnosed in children and young adults. However, type 1 diabetes can also develop later in life. Type 1 diabetes is an autoimmune disease in which the body’s immune system destroys insulin-producing cells in the pancreas, called beta cells. Usually a viral infection provokes this abnormal immune reaction. There seems to be an inherited predisposition to type 1 diabetes. If one identical twin has type 1 diabetes, the other twin has a 50% chance of developing it.

After type 1 diabetes starts, there may be a short period when insulin is not required, called the “honeymoon period.” However, when beta cell destruction is complete, patients must take insulin to stay alive. Glucose is the preferred fuel for organs and tissues. In the absence of insulin, cells cannot take in glucose for fuel, and blood glucose levels rise out of control. Instead, the body makes ketoacids as an alternate fuel. High levels of ketoacids in the blood can lead to acidification of the blood, which can be fatal.

Type 2 diabetes accounts for 90-95% of all diabetes. Insulin resistance is the hallmark of type 2 diabetes, although type 2 diabetes can also involve reduced insulin production. In insulin resistance, cells are insensitive to insulin, and do not take up glucose as fast as they should when exposed to insulin. Abdominal obesity seems to predispose people to insulin resistance. In turn, insulin resistance leads to elevated cholesterol and triglyeride levels, high blood pressure, clogged arteries (as in coronary artery disease), kidney stones, and polycystic ovary syndrome.

Risk factors for developing type 2 diabetes include increasing age, obesity, family history of type 2 diabetes, personal history of gestational diabetes, impaired glucose tolerance, and inactivity. There is a strong genetic basis for type 2 diabetes, likely due to multiple genes. If one identical twin is affected, the other has a 95% chance of developing type 2 diabetes. Certain ethnic groups are also at higher risk. These include African Americans, Hispanic Americans, American Indians, Asian Americans, and Pacific Islanders. Most patients develop type 2 diabetes after the age of 40; however, there are increasing numbers of younger type 2 diabetic patients. Glucose levels usually are high for 4-7 years before type 2 diabetes is diagnosed, because classic symptoms do not occur until glucose levels become extremely high.

Diagnosis of Diabetes

Classic symptoms of diabetes are increased urination, excessive thirst, and blurry vision as well as unusual weight loss, increased hunger, and fatigue. Usually, however, diabetes is diagnosed based on blood tests. Diabetes mellitus can be diagnosed by any of the following three criteria: (1) fasting glucose greater than 126 mg/dl on two or more occasions, (2) random blood glucose of 200 mg/dl or higher in the presence of symptoms (excessive urination, excessive thirst, weight loss), or (3) two glucose readings over 200 mg/dl during a 2-hr oral glucose tolerance test after drinking a solution containing 75 g of glucose. Gestational diabetes, or diabetes developing in pregnancy, is defined with slightly different cutoff values and is diagnosed with a 3-hr oral glucose tolerance test that uses a 100-g glucose load.

“Prediabetes” involves glucose levels that are above normal but not high enough to be called diabetes. Impaired fasting glucose (IFG) refers to fasting glucose between 100 and 125 mg/dl. Impaired glucose tolerance (IGT) is defined as glucose values between 140 and 200 mg/dl during a 2-hr glucose tolerance test, with normal fasting glucose levels. In either case, the diagnosis should be confirmed by repeat testing.

SEE ALSO: Cardiovascular disease, Cholesterol, Diet, Hypertension, Nutrition, Obesity

Suggested Reading

  • Brotman, D., & Girod, J. P. (2002). The metabolic syndrome: A tug-ofwar with no winner. Cleveland Clinic Journal of Medicine, 69, 990-994.
  • Haffner, S. (2002). Metabolic syndrome, diabetes and coronary heart disease. International Journal of Clinical Practice (Suppl. 132), 21-37.
  • Nathan, D. M., & Cagliero, E. (2001). Diabetes mellitus. In P. Felig & L. A. Frohman (Eds.), Endocrinology & metabolism (4th ed., pp. 827-926). New York: McGraw-Hill.

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