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 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.
Type 3 diabetes mellitus
All other specific forms of diabetes, accounting for up to 5% of all diagnosed cases of diabetes, are termed Type 3:
Type 3A: genetic defect in beta cells.
Type 3B: genetically related insulin resistance.
Type 3C: diseases of the pancreas.
Type 3D: caused by hormonal defects.
Type 3E: caused by chemicals or drugs.
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Gestational diabetes mellitushttp://en.wikipedia.org/wiki/Diabetes#Type_2_diabetes_mellitus