Diabetes, also known as diabetes mellitus, is a chronic health condition where the body is unable to produce enough insulin and properly break down sugar (glucose) in the blood. Glucose comes from food and is used by the cells for energy. Glucose is also made in the liver. Insulin is a hormone produced by the pancreas, a large gland behind the stomach. Insulin is needed to move sugar into the cells where it can be used for energy needed for body processes.
After digestion of food, glucose passes into the bloodstream. For glucose to get into cells, insulin must be present. Throughout the pancreas are clusters of cells called the islets of Langerhans. Islets are made up of several types of cells, including beta cells that make insulin. When normal individuals eat, beta cells in the pancreas automatically produce the right amount of insulin to move glucose from blood into the cells of the body. In individuals with diabetes, however, the pancreas either produces little or no insulin, or the cells do not respond appropriately to the insulin that is produced. Glucose builds up in the blood, overflows into the urine, and passes out of the body in the urine. Thus, the body loses its main source of fuel even though the blood contains large amounts of glucose. Glucose may also interact with cells, especially those in very narrow blood vessels. This process may lead to neuropathies and decreased immune function.
With Type 1 diabetes, the body does not make any insulin. With Type 2 diabetes, the more common type, the body does not make or use insulin properly. Without enough insulin, glucose stays in the blood and causes a condition called hyperglycemia, or high blood sugar levels.
Diabetes is associated with long-term complications that affect almost every part of the body. The disease often leads to blindness, heart and blood vessel disease, stroke, kidney failure, amputations, and nerve damage. Uncontrolled diabetes can complicate pregnancy, and birth defects are more common in babies born to women with diabetes. Pregnant women can temporarily develop gestational diabetes, a type of diabetes that begins late in pregnancy.
In 2007, an estimated 20.8 million children and adults in the United States, or 7% of the population, had diabetes mellitus. An estimated 14.6 million have been diagnosed with diabetes (both type 1 and type 2), while 6.2 million people (or nearly one-third) are unaware that they have type 2 diabetes.
Diabetes is widely recognized as one of the leading causes of death and disability in the United States. The U.S. Centers for Disease Control (CDC) recognizes diabetes as the 6th leading cause of death in the United States, with over 72,000 deaths in 2004.
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types and causes of diabetes
Pre-diabetes: Individuals with pre-diabetes have blood glucose levels that are higher than normal but not high enough for a diagnosis of diabetes. This condition raises the risk of developing type 2 diabetes, heart disease, and stroke.
Pre-diabetes is also called impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), depending on the test used to diagnose it. Some individuals have both IFG and IGT. In IFG, glucose levels are a little high when it has been several hours after eating. In IGT, glucose levels are a little higher than normal right after eating.
Pre-diabetes is becoming more common in the United States, according to estimates provided by the U.S. Department of Health and Human Services (DHHS). Many individuals with pre-diabetes go on to develop type 2 diabetes within 10 years.
Type 1 diabetes: Type 1 diabetes is an autoimmune disease. An autoimmune disease results when the body's immune system that fights infection begins to attack a part of the body. In diabetes, the immune system attacks and destroys the insulin-producing beta cells in the pancreas. The pancreas then produces no insulin. An individual with type 1 diabetes must take insulin daily for proper blood sugar control.
It is not known exactly what causes the body's immune system to attack the beta cells, but researchers believe that autoimmune, genetic, viral, and environmental factors may be involved. Type 1 diabetes accounts for about 5-10% of cases of diagnosed diabetes in the United States. Type 1 diabetes develops most often in children and young adults but can appear at any age.
Symptoms of type 1 diabetes usually develop over a short period, although beta cell destruction can begin years earlier. Symptoms may include increased thirst and urination, constant hunger, weight loss, blurred vision, and extreme fatigue. If not diagnosed and treated with insulin, a person with type 1 diabetes can develop a condition called diabetic ketoacidosis or a low blood pH due to the accumulation of ketones in the blood. Diabetic ketoacidosis may lead to a coma if not treated appropriately.
Type 2 diabetes: The most common form of diabetes is type 2 diabetes. About 90-95% of individuals with diabetes have type 2. This form of diabetes is most often associated with older age, obesity, family history of diabetes, previous history of gestational diabetes (diabetes developed during pregnancy), physical inactivity, and certain ethnicities. About 80% of individuals with type 2 diabetes are overweight.
Type 2 diabetes is increasingly being diagnosed in children and adolescents. When type 2 diabetes is diagnosed, the pancreas is usually producing enough insulin, but for unknown reasons the body cannot use the insulin effectively. This is a condition called insulin resistance. After several years of making extra insulin because the body cannot use it efficiently, insulin production decreases. The result is the same as for type 1 diabetes - glucose builds up in the blood and the body cannot make efficient use of its main source of fuel.
Insulin also normally shuts down the ability of the liver to produce glucose. In individuals with type 2 diabetes, however, insulin is unable to inhibit sugar production in the liver, either because the pancreas is not producing enough insulin or because insulin's signal cannot be detected.
The symptoms of type 2 diabetes develop gradually. Their onset is not as sudden as in type 1 diabetes. Symptoms may include fatigue, frequent urination, increased thirst and hunger, weight loss, blurred vision, and slow healing of wounds or sores. Some individuals have no symptoms.
Type 2 diabetes can be treated with diet,exercise, and oral prescription medications but may requireinsulin shots.
Hyperinsulinemia: Hyperinsulinemia is when an individual has too much insulin in the blood. Hyperinsulinemia is not diabetes, but may lead to type 2 diabetes if not managed appropriately. Hyperinsulinemia is a sign of an underlying problem that is causing the pancreas to secrete excessive amounts of insulin. The most common cause of hyperinsulinemia is insulin resistance, a condition in which the body is resistant to the effects of insulin and the pancreas tries to compensate by making more insulin. Rarely, hyperinsulinemia is caused by a tumor of the insulin-producing cells of the pancreas (insulinoma) or excessive numbers of insulin-producing cells in the pancreas (nesidioblastosis). Hyperinsulinemia may not have signs or symptoms unless it causes low blood sugar (hypoglycemia).
Metabolic syndrome: Metabolic syndrome, also known as syndrome X or insulin resistance syndrome (IRS), is a set of abnormalities in which type 2 diabetes (insulin resistant) or hyperinsulinemia is almost always present. Insulin resistance causes the tissues to stop responding to insulin. If an individual has insulin resistance, the body will make more and more insulin, but because the tissues do not respond to it, the body will not be able to use glucose (sugar) properly. Insulin resistance often occurs with other health problems, such as diabetes, high cholesterol, high blood pressure and heart attack. When a person has many of these problems together, doctors call it insulin resistance syndrome. Metabolic syndrome includes hypertension (high blood pressure), hyperlipidemia (high cholesterol), large waist size, an increase in cortisol (stress hormone), abnormalities in blood clotting, and an increase in inflammatory responses. A high rate of cardiovascular disease is associated with the metabolic syndrome.
Diabetes insipidus: Diabetes insipidus (DI) is a rare disease, not widely diagnosed, in which the kidneys produce abnormally large volumes of dilute urine. DI is caused by a deficiency of the antidiuretic hormone (ADH), also known as vasopressin. DI can also be caused by insensitivity of the kidneys to ADH. DI is different from diabetes mellitus (DM), which involves insulin problems and high blood sugar. The symptoms can be similar, such as extreme thirst and frequent urination. However, DI is related to how the kidneys handle fluids. Urine and blood tests can determine which is present.
Gestational diabetes: Some women develop gestational diabetes late in pregnancy. Although this form of diabetes usually disappears after the birth of the baby, women who have had gestational diabetes have a 20-50% chance of developing type 2 diabetes within 5-10 years. Maintaining a reasonable body weight and being physically active may help prevent development of gestational diabetes turning into type 2 diabetes.
As with type 2 diabetes, gestational diabetes occurs more often in some ethnic groups and among women with a family history of diabetes. Gestational diabetes is caused by the hormones of pregnancy or a shortage of insulin. Women with gestational diabetes may not experience any symptoms. When a woman has diabetes and her blood sugar is poorly controlled and too high, excess amounts of sugar are transported to the baby. Since the baby does not have diabetes, the fetus is able to increase the production of insulin substantially in order to use this extra sugar. This abnormal cycle of events can result in several complications including macrosomia (large baby, over 8.8 pounds), neonatal hypoglycemia (low blood sugar), stillbirth, and birth defects (such as brain, spinal cord, or heart conditions).
The only treatment for gestational diabetes is insulin, as oral anti-diabetic medications can not be used in pregnancy due to the possible risks.
Maturity-onset diabetes of the young (MODY): Maturity-onset diabetes of the young (MODY) is a type of diabetes that is caused by genetic mutations. MODY may occur during childhood or adolescence, but may be misdiagnosed as Type 1 or Type 2 diabetes, or may be unidentified until the patient is an adult. Research indicates that the genetic mutations responsible for MODY interfere with normal pancreatic secretion of insulin. Currently, six gene mutations have been identified as causative factors for MODY, each of which produce several different forms of MODY, named MODY 1-MODY 6. Each type of MODY has different signs and symptoms, clinical manifestations, complications, and treatments.
It has been estimated that 1- 5% of diabetes cases in the United States are MODY. MODY typically presents during a patients 20s, usually before the age of 25. Patients at risk for MODY have a strong family history of diabetes, and/or have developed diabetes before middle age. In contrast to clinical manifestations in other forms of diabetes, MODY patients are typically not overweight, and are sometimes able to be treated with meal planning, oral diabetes medications, or low doses of insulin. It is recommended for the patient to work closely with their healthcare provider to determine the best treatment, based on the specific type of MODY diagnosed.