Diabetes mellitus

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 which can lead to blindness, nerve damage which can lead to erectile dysfunction (impotence), gangrene with risk of amputation of toes, feet, and even legs. The more serious complications are all more common in those with poor glycemic control.

Causes and types

The role of insulin

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.

Related Topics:
Insulin - Hormone - Glucose

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Most of the carbohydrates in food are rapidly converted 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 levels 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.

Related Topics:
Carbohydrate - Glucose - Sugar - Insulin - Beta cell - Pancreas - Glycogen - Protein - Fat

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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.

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Type 1 diabetes mellitus

Main Article diabetes mellitus type 1

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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.

Related Topics:
Autoimmune disorder - Immune system - Islets of Langerhans - Pancreas

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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.

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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.

Related Topics:
Obesity - Epidemic

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Type 2 diabetes mellitus

Main Article diabetes mellitus type 2

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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.

Related Topics:
Insulin resistance - Ketoacidosis - Renal failure - Coronary artery disease

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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. If these fail, insulin therapy may be necessary to maintain normal glucose levels.

Related Topics:
Weight loss - Antidiabetic drug - Sulphonylurea - Metformin - Thiazolidinedione

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Type 3 diabetes mellitus

One classification system called all other forms of diabetes that do not fit into type 1 or type 2 or gestational diabetes as type 3 diabetes. This nomenclature is rarely used.

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• 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.

Gestational diabetes mellitus

Main article: Gestational diabetes mellitus

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Gestational diabetes mellitus appears in about 2-5% of all pregnancies. It is temporary and fully treatable, but if untreated it may cause problems with the pregnancy, including macrosomia (high birth weight) of the child. It requires careful medical supervision during the pregnancy. In addition, about 20-50% of these women go on to develop type 2 diabetes.

Related Topics:
Pregnancies - Macrosomia

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Genetics

Both type 1 and type 2 diabetes are at least partly inherited. Type 1 diabetes appears to be triggered by infection, stress, or environmental factors (e.g. exposure to a causative agent). There is a genetic element in the susceptibility of individuals to some of these triggers which has been traced to particular HLA genotypes (i.e. genetic "self" identifiers used by the immune system). However, even in those who have inherited the susceptibility, type 1 diabetes mellitus seems to require an environmental trigger. A small proportion of type 1 diabetics carry a mutation that causes maturity onset diabetes of the young (MODY).

Related Topics:
HLA - Genotype - Mutation - Maturity onset diabetes of the young

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There is an even stronger inheritance pattern for Type 2 diabetes; those with type 2 ancestors or relatives have very much higher chances of developing Type 2. Concordance among monozygotic twins is close to 100%, and 25% of those with the disease have a family history of diabetes. It is also often connected to obesity, which is found in approximately 85% of (North American) patients diagnosed with that form of the disease, so inheriting a tendency toward obesity seems also to contribute. Age is also thought to be a contributing factor, as most type 2 patients in the past were older. The exact reasons for these connections are unknown.

Related Topics:
Concordance - Monozygotic twins

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