Diabetes mellitus , often referred to simply as diabetes, is a syndrome characterized by disordered metabolism and abnormally high blood sugar (hyperglycaemia) resulting from low levels of the hormone insulin with or without abnormal resistance to insulin's effects. The characteristic symptoms are excessive urine production (polyuria), excessive thirst and increased fluid intake (polydipsia), blurred vision, unexplained weight loss and lethargy. These symptoms are likely to be absent if the blood sugar is only mildly elevated.
The World Health Organization recognizes three main forms of diabetes mellitus: type 1, type 2, and gestational diabetes (occurring during pregnancy), which have different causes and population distributions. While, ultimately, all forms are due to the beta cells of the pancreas being unable to produce sufficient insulin to prevent hyperglycemia, the causes are different. Type 1 diabetes is usually due to autoimmune destruction of the pancreatic beta cells. Type 2 diabetes is characterized by insulin resistance in target tissues. This causes a need for abnormally high amounts of insulin and diabetes develops when the beta cells cannot meet this demand. Gestational diabetes is similar to type 2 diabetes in that it involves insulin resistance; the hormones of pregnancy can cause insulin resistance in women genetically predisposed to developing this condition.
Gestational diabetes typically resolves with delivery of the child, however types 1 and 2 diabetes are chronic conditions. All types have been treatable since insulin became medically available in 1921. Type 1 diabetes, in which insulin is not secreted by the pancreas, is directly treatable only with injected insulin, although dietary and other lifestyle adjustments are part of management. Type 2 may be managed with a combination of dietary treatment, tablets and injections and, frequently, insulin supplementation. While insulin was originally produced from natural sources such as porcine pancreas, most insulin used today is produced through genetic engineering, either as a direct copy of human insulin, or human insulin with modified molecules that provide different onset and duration of action. Insulin can also be delivered continuously by a specialized pump which subcutaneously provides insulin through a changeable catheter.
Diabetes can cause many complications. Acute complications (hypoglycemia, ketoacidosis or nonketotic hyperosmolar coma) may occur if the disease is not adequately controlled. Serious long-term complications include cardiovascular disease (doubled risk), chronic renal failure, retinal damage (which can lead to blindness), nerve damage (of several kinds), and microvascular damage, which may cause impotence and poor healing. Poor healing of wounds, particularly of the feet, can lead to gangrene, which may require amputation. Adequate treatment of diabetes, as well as increased emphasis on blood pressure control and lifestyle factors (such as not smoking and keeping a healthy body weight), may improve the risk profile of most aforementioned complications. In the developed world, diabetes is the most significant cause of adult blindness in the non-elderly, the leading cause of non-traumatic amputation in adults, and diabetic nephropathy is the main illness requiring renal dialysis in the United States.
In type 1 diabetes, your immune system — which normally fights harmful bacteria or viruses — attacks and destroys the insulin-producing cells in the pancreas. This leaves you with little or no insulin. Instead of being transported into your cells, sugar builds up in your bloodstream. The exact cause of type 1 diabetes is unknown. Genetics may play a role. Exposure to certain viruses may serve as a trigger as well.
When you have type 2 diabetes, your body is resistant to the effects of insulin — a hormone that regulates the absorption of sugar into your cells — or your body produces some, but not enough, insulin to maintain a normal glucose level. Left uncontrolled, the consequences of type 2 diabetes can be life-threatening. There's no cure for type 2 diabetes, but there's plenty you can do to manage — or prevent — the condition. Start by eating healthy foods, including physical activity in your daily routine and maintaining a healthy weight. If diet and exercise aren't enough, you may need diabetes medications or insulin therapy to manage your blood sugar. In type 2 diabetes, this process works improperly. Instead of moving into your cells, sugar builds up in your bloodstream. This occurs when your pancreas doesn't make enough insulin or your cells become resistant to the action of insulin. Exactly why this happens is uncertain, although excess fat — especially abdominal fat — and inactivity seem to be important factors.
Symptoms:
The classical triad of diabetes symptoms is polyuria, polydipsia and polyphagia, which are, respectively, frequent urination; increased thirst and consequent increased fluid intake; and increased appetite. Symptoms may develop quite rapidly (weeks or months) in type 1 diabetes, particularly in children. However, in type 2 diabetes the symptoms develop much more slowly and may be subtle or completely absent. Type 1 diabetes may also cause a rapid yet significant weight loss (despite normal or even increased eating) and irreducible fatigue. All of these symptoms except weight loss can also manifest in type 2 diabetes in patients whose diabetes is poorly controlled.
When the glucose concentration in the blood is raised beyond the renal threshold, reabsorption of glucose in the proximal renal tubuli is incomplete, and part of the glucose remains in the urine (glycosuria). This increases the osmotic pressure of the urine and inhibits the reabsorption of water by the kidney, resulting in increased urine production (polyuria) and increased fluid loss. Lost blood volume will be replaced osmotically from water held in body cells, causing dehydration and increased thirst.
Prolonged high blood glucose causes glucose absorption, which leads to changes in the shape of the lenses of the eyes, resulting in vision changes. Blurred vision is a common complaint leading to a diabetes diagnosis; type 1 should always be suspected in cases of rapid vision change whereas type 2 is generally more gradual, but should still be suspected.
Patients (usually with type 1 diabetes) may also present with diabetic ketoacidosis (DKA), an extreme state of metabolic dysregulation characterized by the smell of acetone on the patient's breath; a rapid, deep breathing known as Kussmaul breathing; polyuria; nausea; vomiting and abdominal pain; and any of many altered states of consciousness or arousal (such as hostility and mania or, equally, confusion and lethargy). In severe DKA, coma may follow, progressing to death. Diabetic ketoacidosis is a medical emergency and requires hospital admission.
A rarer but equally severe possibility is hyperosmolar nonketotic state, which is more common in type 2 diabetes and is mainly the result of dehydration due to loss of body water. Often, the patient has been drinking extreme amounts of sugar-containing drinks, leading to a vicious circle in regard to the water loss.
Diagnosis:
The diagnosis of type 1 diabetes, and many cases of type 2, is usually prompted by recent-onset symptoms of excessive urination (polyuria) and excessive thirst (polydipsia), often accompanied by weight loss. These symptoms typically worsen over days to weeks; about a quarter of people with new type 1 diabetes have developed some degree of diabetic ketoacidosis by the time the diabetes is recognized. The diagnosis of other types of diabetes is usually made in other ways. These include ordinary health screening; detection of hyperglycemia during other medical investigations; and secondary symptoms such as vision changes or unexplainable fatigue. Diabetes is often detected when a person suffers a problem that is frequently caused by diabetes, such as a heart attack, stroke, neuropathy, poor wound healing or a foot ulcer, certain eye problems, certain fungal infections, or delivering a baby with macrosomia or hypoglycemia.
Diabetes mellitus is characterized by recurrent or persistent hyperglycemia, and is diagnosed by demonstrating any one of the following:
* fasting plasma glucose level at or above 126 mg/dL (7.0 mmol/l).
* plasma glucose at or above 200 mg/dL (11.1 mmol/l) two hours after a 75 g oral glucose load as in a glucose tolerance test.
* random plasma glucose at or above 200 mg/dL (11.1 mmol/l).
A positive result, in the absence of clinical symptoms of diabetes, should be confirmed by another of the above-listed methods on a different day. Most physicians prefer to measure a fasting glucose level because of the ease of measurement and the considerable time commitment of formal glucose tolerance testing, which takes two hours to complete. According to the current definition, two fasting glucose measurements above 126 mg/dL (7.0 mmol/l) is considered diagnostic for diabetes mellitus.
Patients with fasting glucose levels between 100 and 125 mg/dL (6.1 and 7.0 mmol/l) are considered to have impaired fasting glycemia. Patients with plasma glucose at or above 140 mg/dL or 7.8 mmol/l two hours after a 75 g oral glucose load are considered to have impaired glucose tolerance. Of these two pre-diabetic states, the latter in particular is a major risk factor for progression to full-blown diabetes mellitus as well as cardiovascular disease.
While not used for diagnosis, an elevated level of glucose irreversibly bound to hemoglobin (termed glycosylated hemoglobin or HbA1c) of 6.0% or higher is considered abnormal by most labs; HbA1c is primarily used as a treatment-tracking test reflecting average blood glucose levels over the preceding 90 days (approximately). However, some physicians may order this test at the time of diagnosis to track changes over time. The current recommended goal for HbA1c in patients with diabetes is <7.0%, which is considered good glycemic control, although some guidelines are stricter (<6.5%). People with diabetes who have HbA1c levels within this range have a significantly lower incidence of complications from diabetes, including retinopathy and diabetic nephropathy.
Treatment:
There is no practical cure now for type 1 diabetes. The fact that type 1 diabetes is due to the failure of one of the cell types of a single organ with a relatively simple function (i.e. the failure of the islets of Langerhans) has led to the study of several possible schemes to cure this form diabetes mostly by replacing the pancreas or just the beta cells. Only those type 1 diabetics who have received either a pancreas or a kidney-pancreas transplant (when they have developed diabetic nephropathy) and become insulin-independent may now be considered "cured" from their diabetes. A simultaneous pancreas-kidney transplant is a promising solution, showing similar or improved survival rates over a kidney transplant alone. Still, they generally remain on long-term immunosuppressive drugs and there is a possibility that the immune system will mount a host versus graft response against the transplanted organ.
Type 2 diabetes can be cured by one type of gastric bypass surgery in 80-100% of severely obese patients. The effect is not due to weight loss because it usually occurs within days of surgery, which is before significant weight loss occurs. The pattern of secretion of gastrointestinal hormones is changed by the bypass and removal of the duodenum and proximal jejunum, which together form the upper (proximal) part of the small intestine. One hypothesis is that the proximal small intestine is dysfunctional in type 2 diabetes; its removal eliminates the source of an unknown hormone that contributes to insulin resistance. This surgery has been widely performed on morbidly obese patients and has the benefit of reducing the death rate from all causes by up to 40%. A small number of normal to moderately obese patients with type 2 diabetes have successfully undergone similar operations.
Gestational diabetes typically resolves with delivery of the child, however types 1 and 2 diabetes are chronic conditions. All types have been treatable since insulin became medically available in 1921. Type 1 diabetes, in which insulin is not secreted by the pancreas, is directly treatable only with injected insulin, although dietary and other lifestyle adjustments are part of management. Type 2 may be managed with a combination of dietary treatment, tablets and injections and, frequently, insulin supplementation. While insulin was originally produced from natural sources such as porcine pancreas, most insulin used today is produced through genetic engineering, either as a direct copy of human insulin, or human insulin with modified molecules that provide different onset and duration of action. Insulin can also be delivered continuously by a specialized pump which subcutaneously provides insulin through a changeable catheter.
Diabetes can cause many complications. Acute complications (hypoglycemia, ketoacidosis or nonketotic hyperosmolar coma) may occur if the disease is not adequately controlled. Serious long-term complications include cardiovascular disease (doubled risk), chronic renal failure, retinal damage (which can lead to blindness), nerve damage (of several kinds), and microvascular damage, which may cause impotence and poor healing. Poor healing of wounds, particularly of the feet, can lead to gangrene, which may require amputation. Adequate treatment of diabetes, as well as increased emphasis on blood pressure control and lifestyle factors (such as not smoking and keeping a healthy body weight), may improve the risk profile of most aforementioned complications. In the developed world, diabetes is the most significant cause of adult blindness in the non-elderly, the leading cause of non-traumatic amputation in adults, and diabetic nephropathy is the main illness requiring renal dialysis in the United States.
In type 1 diabetes, your immune system — which normally fights harmful bacteria or viruses — attacks and destroys the insulin-producing cells in the pancreas. This leaves you with little or no insulin. Instead of being transported into your cells, sugar builds up in your bloodstream. The exact cause of type 1 diabetes is unknown. Genetics may play a role. Exposure to certain viruses may serve as a trigger as well.
When you have type 2 diabetes, your body is resistant to the effects of insulin — a hormone that regulates the absorption of sugar into your cells — or your body produces some, but not enough, insulin to maintain a normal glucose level. Left uncontrolled, the consequences of type 2 diabetes can be life-threatening. There's no cure for type 2 diabetes, but there's plenty you can do to manage — or prevent — the condition. Start by eating healthy foods, including physical activity in your daily routine and maintaining a healthy weight. If diet and exercise aren't enough, you may need diabetes medications or insulin therapy to manage your blood sugar. In type 2 diabetes, this process works improperly. Instead of moving into your cells, sugar builds up in your bloodstream. This occurs when your pancreas doesn't make enough insulin or your cells become resistant to the action of insulin. Exactly why this happens is uncertain, although excess fat — especially abdominal fat — and inactivity seem to be important factors.
Symptoms:
The classical triad of diabetes symptoms is polyuria, polydipsia and polyphagia, which are, respectively, frequent urination; increased thirst and consequent increased fluid intake; and increased appetite. Symptoms may develop quite rapidly (weeks or months) in type 1 diabetes, particularly in children. However, in type 2 diabetes the symptoms develop much more slowly and may be subtle or completely absent. Type 1 diabetes may also cause a rapid yet significant weight loss (despite normal or even increased eating) and irreducible fatigue. All of these symptoms except weight loss can also manifest in type 2 diabetes in patients whose diabetes is poorly controlled.
When the glucose concentration in the blood is raised beyond the renal threshold, reabsorption of glucose in the proximal renal tubuli is incomplete, and part of the glucose remains in the urine (glycosuria). This increases the osmotic pressure of the urine and inhibits the reabsorption of water by the kidney, resulting in increased urine production (polyuria) and increased fluid loss. Lost blood volume will be replaced osmotically from water held in body cells, causing dehydration and increased thirst.
Prolonged high blood glucose causes glucose absorption, which leads to changes in the shape of the lenses of the eyes, resulting in vision changes. Blurred vision is a common complaint leading to a diabetes diagnosis; type 1 should always be suspected in cases of rapid vision change whereas type 2 is generally more gradual, but should still be suspected.
Patients (usually with type 1 diabetes) may also present with diabetic ketoacidosis (DKA), an extreme state of metabolic dysregulation characterized by the smell of acetone on the patient's breath; a rapid, deep breathing known as Kussmaul breathing; polyuria; nausea; vomiting and abdominal pain; and any of many altered states of consciousness or arousal (such as hostility and mania or, equally, confusion and lethargy). In severe DKA, coma may follow, progressing to death. Diabetic ketoacidosis is a medical emergency and requires hospital admission.
A rarer but equally severe possibility is hyperosmolar nonketotic state, which is more common in type 2 diabetes and is mainly the result of dehydration due to loss of body water. Often, the patient has been drinking extreme amounts of sugar-containing drinks, leading to a vicious circle in regard to the water loss.
Diagnosis:
The diagnosis of type 1 diabetes, and many cases of type 2, is usually prompted by recent-onset symptoms of excessive urination (polyuria) and excessive thirst (polydipsia), often accompanied by weight loss. These symptoms typically worsen over days to weeks; about a quarter of people with new type 1 diabetes have developed some degree of diabetic ketoacidosis by the time the diabetes is recognized. The diagnosis of other types of diabetes is usually made in other ways. These include ordinary health screening; detection of hyperglycemia during other medical investigations; and secondary symptoms such as vision changes or unexplainable fatigue. Diabetes is often detected when a person suffers a problem that is frequently caused by diabetes, such as a heart attack, stroke, neuropathy, poor wound healing or a foot ulcer, certain eye problems, certain fungal infections, or delivering a baby with macrosomia or hypoglycemia.
Diabetes mellitus is characterized by recurrent or persistent hyperglycemia, and is diagnosed by demonstrating any one of the following:
* fasting plasma glucose level at or above 126 mg/dL (7.0 mmol/l).
* plasma glucose at or above 200 mg/dL (11.1 mmol/l) two hours after a 75 g oral glucose load as in a glucose tolerance test.
* random plasma glucose at or above 200 mg/dL (11.1 mmol/l).
A positive result, in the absence of clinical symptoms of diabetes, should be confirmed by another of the above-listed methods on a different day. Most physicians prefer to measure a fasting glucose level because of the ease of measurement and the considerable time commitment of formal glucose tolerance testing, which takes two hours to complete. According to the current definition, two fasting glucose measurements above 126 mg/dL (7.0 mmol/l) is considered diagnostic for diabetes mellitus.
Patients with fasting glucose levels between 100 and 125 mg/dL (6.1 and 7.0 mmol/l) are considered to have impaired fasting glycemia. Patients with plasma glucose at or above 140 mg/dL or 7.8 mmol/l two hours after a 75 g oral glucose load are considered to have impaired glucose tolerance. Of these two pre-diabetic states, the latter in particular is a major risk factor for progression to full-blown diabetes mellitus as well as cardiovascular disease.
While not used for diagnosis, an elevated level of glucose irreversibly bound to hemoglobin (termed glycosylated hemoglobin or HbA1c) of 6.0% or higher is considered abnormal by most labs; HbA1c is primarily used as a treatment-tracking test reflecting average blood glucose levels over the preceding 90 days (approximately). However, some physicians may order this test at the time of diagnosis to track changes over time. The current recommended goal for HbA1c in patients with diabetes is <7.0%, which is considered good glycemic control, although some guidelines are stricter (<6.5%). People with diabetes who have HbA1c levels within this range have a significantly lower incidence of complications from diabetes, including retinopathy and diabetic nephropathy.
Treatment:
There is no practical cure now for type 1 diabetes. The fact that type 1 diabetes is due to the failure of one of the cell types of a single organ with a relatively simple function (i.e. the failure of the islets of Langerhans) has led to the study of several possible schemes to cure this form diabetes mostly by replacing the pancreas or just the beta cells. Only those type 1 diabetics who have received either a pancreas or a kidney-pancreas transplant (when they have developed diabetic nephropathy) and become insulin-independent may now be considered "cured" from their diabetes. A simultaneous pancreas-kidney transplant is a promising solution, showing similar or improved survival rates over a kidney transplant alone. Still, they generally remain on long-term immunosuppressive drugs and there is a possibility that the immune system will mount a host versus graft response against the transplanted organ.
Type 2 diabetes can be cured by one type of gastric bypass surgery in 80-100% of severely obese patients. The effect is not due to weight loss because it usually occurs within days of surgery, which is before significant weight loss occurs. The pattern of secretion of gastrointestinal hormones is changed by the bypass and removal of the duodenum and proximal jejunum, which together form the upper (proximal) part of the small intestine. One hypothesis is that the proximal small intestine is dysfunctional in type 2 diabetes; its removal eliminates the source of an unknown hormone that contributes to insulin resistance. This surgery has been widely performed on morbidly obese patients and has the benefit of reducing the death rate from all causes by up to 40%. A small number of normal to moderately obese patients with type 2 diabetes have successfully undergone similar operations.
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