WEBWATCH - Types of Diabetes

The two major forms of diabetes are Type 1 (previously called insulin-dependent diabetes mellitus (IDDM) or juvenile-onset diabetes), and Type 2 (previously called noninsulin-dependent diabetes mellitus (NIDDM) or maturity-onset diabetes). They share a central feature: elevated blood sugar levels due to absolute or relative insufficiencies of insulin, a hormone produced by the pancreas. Insulin is a key regulator of the body's metabolism. After meals, food is digested in the stomach and intestines; carbohydrates are broken down into sugar molecules, of which glucose is one, and proteins are broken down into amino acids. Glucose and amino acids are absorbed directly into the bloodstream, and blood glucose levels rise. Normally, the rise in blood glucose levels signals important cells in the pancreas -- called beta cells -- to secrete insulin, which pours into the bloodstream. Insulin, in turn, enables glucose and amino acids to enter cells in the body --importantly, those in the muscles where, along with other hormones, it directs whether these nutrients will be burned for energy or stored for future use. As blood sugar falls to pre-meal levels, the pancreas reduces the production of insulin, and the body uses its stored energy until the next meal provides additional nutrients.

Type 2 diabetes is by far the more common form of diabetes -- accounting for 90% of cases. About 16 million Americans have Type 2 diabetes and half are unaware they have it.

Most Type 2 diabetics produce variable -- even normal -- amounts of insulin, but they have abnormalities in liver and muscle cells that resist its actions. Insulin attaches to the receptors of cells, but glucose does not get inside a condition known as insulin resistance. Because many Type 2 diabetics seem to be incapable of secreting enough insulin to overcome insulin resistance, it is likely that in such cases an additional defect exists in the beta cells that impairs insulin secretion. Other factors may also play a role in Type 2 diabetes.

Maturity-Onset Diabetes in Youth. Maturity-onset diabetes in youth (MODY) is a rare genetic form of Type 2 diabetes that usually develops in thin teenagers; it accounts for 2% to 5% of Type 2 cases. A variant has also been reported in Florida among African Americans. In about half of these families an abnormality in a liver enzyme is most likely responsible for this condition. Gestational Diabetes. About 0.5% of pregnant women develop a form of Type 2 diabetes in their third trimester called gestational diabetes. After delivery, blood glucose levels generally return to normal, although one-third to one-half of these women develop Type 2 diabetes within 10 years.

Type 1 Diabetes In Type 1 diabetes, the beta cells in the pancreas that produce insulin are gradually destroyed; eventually insulin deficiency is absolute. Without insulin to move glucose into cells, blood glucose levels become excessively high, a condition known as hyperglycemia. Because the body cannot utilize the sugar, it spills over into the urine and is lost. Weakness, weight loss, and excessive hunger and thirst are among the consequences of this "starvation in the midst of plenty". Patients become dependent on administered insulin for survival.

Diabetes Secondary To Other Conditions Conditions that damage or destroy the pancreas, such as pancreatitis, pancreatic surgery, or certain industrial chemicals can cause diabetes. Certain drugs can also cause temporary diabetes, including corticosteroids, beta blockers, and phenytoin. Rare genetic disorders (Klinefelter's syndrome, Huntington's chorea, Wolfram's syndrome, leprechauns, Rabson-Mendenhall syndrome, lipotropic diabetes, and others) and hormonal disorders (Acromegaly, Cushing's syndrome, pheochromocytoma, hyperthyroidism, somatostatinoma, aldosteronoma) also increase the risk for diabetes.

What Causes Type 2 Diabetes? Causes of Insulin Resistance: Elevated levels of three factors are believed to be involved in development of obesity and insulin resistance leading to Type 2 diabetes. They are: free fatty acids (acids in the blood produced by breakdown of fat); leptin (a protein produced by fat cells); and tumor-necrosis factor, or TNF (a component of the immune system). How each of these factors produce contributes to Type 2 diabetes is under investigation.

Diabetes, particularly Type 2, is reaching epidemic proportions through the world as more and more cultures adopt Western dietary habits. Currently an estimated 100 million people have diabetes and experts predict that by 2010 this number will double. In the U.S. alone, it is estimated that 16 million people have diabetes and that about half are unaware they have it.