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Diabetes mellitus is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. All types of diabetes mellitus share similar symptoms and complications at advanced stages. Hyperglycemia itself can lead to dehydration and ketoacidosis. Longer-term complications include cardiovascular disease (doubled risk), chronic renal failure (it is the main cause for dialysis), retinal damage with eventual blindness, nerve damage and eventual gangrene with risk of amputation of toes, feet, and even legs.

The most important forms of diabetes are due to decreased production of insulin (diabetes mellitus type 1, the first recognized form), or decreased sensitivity of body tissues to insulin (diabetes mellitus type 2, the more common form). The former requires insulin injections, while the latter is generally managed with oral medication and only requires insulin if the tablets are ineffective.

Patient understanding and participation is vital as blood glucose levels change continuously, while successfully keeping blood sugar within normal limits has been compellingly shown to reduce or prevent development of some of the complications of diabetes. Other risk factors that can require addressing to reduce complications are: cessation of smoking, optimizing cholesterol levels, maintaining a stable body weight, controlling high blood pressure and engaging in regular exercise.

Diabetes Statistics

In 2004, according to the World Health Organization, more than 150 million people worldwide suffer from diabetes. Its incidence is increasing rapidly, and it is estimated that by the year 2025 this number will double. Diabetes mellitus occurs throughout the world, but is more common (especially type 2) in the more developed countries. The greatest increase in prevalence rate is, however, expected to occur in Asia and Africa, where most of the diabetic patients will be seen by 2025. The increase in incidence of diabetes in the developing countries follows the trend of urbanisation and life style changes. Diabetes is in the top 10, and perhaps the top 5, of the most significant diseases in the developed world, and is gaining in significance (see big killers).

For at least 20 years, diabetes rates in North America have been increasing substantially. In 2002 there were about 18.2 million diabetics in the United States alone. The Centers for Disease Control has termed the change an epidemic. The National Diabetes Information Clearinghouse estimates that diabetes costs $132 billion in the United States alone every year.

Causes and types of Diabetes

Mechanism of insulin release in normal pancreatic beta cells (ie, glucose dependence). Insulin production doesn't depend on blood glucose levels; insulin is stored pending release

Since insulin is the principal hormone that regulates uptake of glucose into cells (primarily muscle and fat cells) from the blood, deficiency of insulin or its action plays a central role in all forms of diabetes.

Most of the carbohydrates in food are rapidly digested to glucose, the principal sugar in blood. Insulin is produced by beta cells in the pancreas in response to rising levels of glucose in the blood, as occurs after a meal. Insulin makes it possible for most body tissues to remove glucose from the blood for use as fuel, for conversion to other needed molecules, or for storage. Insulin is also the principal control signal for conversion of glucose (the basic sugar unit) to glycogen for storage in liver and muscle cells. Lowered insulin levels result in the reverse conversion of glycogen to glucose when glucose levels fall -- though only in the liver not muscle tissue. Higher insulin level increase many anabolic ("building up") processes such as cell growth, cellular protein synthesis, and fat storage. Insulin is the principal signal in converting many of the bidirectional processes of metabolism from a catabolic to an anabolic direction.

If the amount of insulin produced is insufficient, if cells respond poorly to the effects of insulin (insulin insensitivity or resistance), or if the insulin itself is defective, glucose is not handled properly by body cells (about 2/3 require it) nor stored appropriately in the liver and muscles. The net effect is persistent high levels of blood glucose, poor protein synthesis, and other metabolic derangements.

Type 1 diabetes mellitus

Type 1 diabetes is most commonly diagnosed in children and adolescents, but can occur in adults as well. It is an autoimmune disorder, in which the body's own immune system attacks the beta cells in the Islets of Langerhans of the pancreas, destroying them or damaging them sufficiently to reduce insulin production. The autoimmune attack may be triggered by reaction to an infection, for example by one of the viruses of the Coxsackie virus family. A subtype of type 1 (identifiable by the presence of antibodies against beta cells) develops slowly and so is often confused with Type 2. In addition, a small proportion of type 1 cases has the hereditary condition maturity onset diabetes of the young (MODY).

Some poisons (e.g. certain rat poisons) work by selectively destroying certain types of cells, including pancreatic beta cells, thus producing "artificial" type 1 diabetes. Other pancreatic problems including trauma, pancreatitis or tumors (either malignant or benign) can also lead to loss of insulin production.

Currently, type 1 is treated with insulin injections, lifestyle adjustments, and careful monitoring of blood glucose levels using blood test kits. Insulin delivery is also available by an insulin pump, which allows the infusion of insulin 24 hours a day at preset levels, and the ability to program push doses (bolus) of insulin as needed at meal times. The treatment must be continued indefinitely. Experimental replacement of beta cells (by transplant) is being investigated in several research programs and may become clinically available in the future.

About 5-10% of all North American cases of diabetes are Type 1 diabetics. The fraction of type 1 diabetics in other parts of the world differs; this is likely due to both differences in the rate of type 1 and differences in the rate of other types, most prominently type 2. Most of this difference is not currently understood.

Formerly, type 1 diabetes was called "childhood" or "juvenile" diabetes or "insulin dependent" diabetes. Each term is a misnomer, especially since the obesity epidemic in recent years has led to increased incidence of type 2 diabetes in children and adolescents in the USA, and insulin is used in some type 2 cases.

Type 2 diabetes mellitus

Type 2 diabetes is characterized by "insulin resistance" as body cells do not respond appropriately when insulin is present. This is a more complex problem than type 1, but is sometimes easier to treat, since insulin is still produced, especially in the initial years. Type 2 may go unnoticed for years in a patient before diagnosis, since the symptoms are typically milder (no ketoacidosis) and can be sporadic. However, severe complications can result from unnoticed type 2 diabetes, including renal failure, and coronary artery disease.

Type 2 diabetes was formerly known by a variety of partially misleading names, including "adult-onset diabetes", "obesity-related diabetes", "insulin-resistant diabetes", or "non-insulin-dependent diabetes" (NIDDM). It may be caused by a number of diseases, such as hemochromatosis and polycystic ovary syndrome, and can also be caused by certain types of medications (e.g. long-term steroid use). About 90-95% of all North American cases of diabetes are type 2, and about 20% of the population over the age of 65 is a type 2 diabetic. The fraction of type 2 diabetics in other parts of the world varies substantially, almost certainly for environmental and lifestyle reasons. There is also a strong inheritable genetic connection in type 2 diabetes: having relatives (especially first degree) with type 2 is a considerable risk factor for developing type 2 diabetes. The majority of patients with type 2 diabetes mellitus are obese - chronic obesity leads to increased insulin resistance that can develop into diabetes, most likely because adipose tissue is a (recently identified) source of chemical signals (hormones and cytokines). Other research shows that type 2 diabetes causes obesity.

Type 2 is initially treated by changes in diet and through weight loss. This can restore insulin sensitivity, even when the weight lost is modest e.g. around 5 kg (10 to 15 lb). The next step, if necessary, is treatment with oral antidiabetic drugs: the sulphonylureas, metformin, or (if these are insufficient) thiazolidinediones. When these have failed, insulin therapy may be necessary to maintain normal glucose levels.

Signs and symptoms of Diabetes

Type 2 diabetes almost always has a slow onset (often years), but in type 1, particularly in children, onset may be quite fast (weeks or months). Early symptoms of type 1 diabetes are often polyuria (frequent urination) and polydipsia (increased thirst, and consequent increased fluid intake). There may also be weight loss (despite normal or increased eating), increased appetite, and irreduceable fatigue. These symptoms may also manifest in Type 2 diabetes in patients who present with frank poorly controlled diabetes. Binary file (standard input) matches