Diabetes Mellitus and Glucose Tolerance Teset

The name "diabetes mellitus" means "sweet urine." It stems from ancient times, when physicians would taste a patient's urine as a part of diagnosis.

A Glucose Tolerance Test is a diagnostic test for diabetes. After fasting overnight, you are given a concentrated sugar solution (50 to 100 grams of glucose) to drink, and your blood is sampled periodically over the next several hours to test its glucose levels. Normally, blood glucose does not rise very much and returns to normal within two to three hours. In a diabetic, the blood glucose is usually higher after fasting, rises more after the glucose solution and takes from four to six hours to come down.

Diabetes

Now that you know how your body handles glucose with insulin and glucagon, you are ready to understand diabetes. Diabetes is classified into three types: Type 1, Type 2 and gestational diabetes.

Type 1 (also called juvenile diabetes or insulin-dependent diabetes) is caused by a lack of insulin. This type is found in five percent to 10 percent of diabetics and usually occurs in children or adolescents. Type 1 diabetics have an abnormal glucose-tolerance test and little or no insulin in their blood. In Type 1 diabetics, the beta cells of the pancreatic islets are destroyed, possibly by the person's own immune system, genetic or environmental factors.

Type 2 (also called adult-onset diabetes or non-insulin-dependent diabetes) occurs when the body does not respond or can't use its own insulin (insulin resistance). Type 2 occurs in 90 percent to 95 percent of diabetics and usually occurs in adults over the age of 40, most often between the ages of 50 and 60. Type 2 diabetics have an abnormal glucose-tolerance test and higher than normal levels of insulin in their blood. In Type 2 diabetics, the insulin resistance is linked to obesity, but we do not know exactly how this occurs. Some studies suggest that the number of insulin receptors on liver, fat and muscle cells is reduced, while others suggest that the intracellular pathways activated by insulin in these cells are altered.

Gestational diabetes can occur in some pregnant women and is similar to Type 2 diabetes. Gestational diabetics have an abnormal glucose-tolerance test and slightly higher levels of insulin. During pregnancy, several hormones partially block the actions of insulin, thereby making the woman less sensitive to her own insulin. She develops a diabetes that can be managed by special diets and/or supplemental injections of insulin. It usually goes away after the baby is delivered.

Regardless of the type of diabetes, diabetics exhibit several (but not necessarily all) of the following symptoms:

  • Excessive thirst (polydipsia)
  • Frequent urination (polyuria)
  • Extreme hunger or constant eating (polyphagia)
  • Unexplained weight loss
  • Presence of glucose in the urine (glycosuria)
  • Tiredness or fatigue
  • Changes in vision
  • Numbness or tingling in the extremities (hands, feet)
  • Slow-healing wounds or sores
  • Abnormally high frequency of infection

These symptoms can be understood when we see how insulin deficiency or insulin resistance affects the body's physiology.