|
 Diabetes is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. All types of diabetes 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 more common in people who have a difficult time controlling their blood sugars with medications (glycemic control).
The most important forms of diabetes are due to decreased or the complete absence of the production of insulin (type 1 diabetes), or decreased sensitivity of body tissues to insulin (type 2 diabetes, the more common form). The former requires insulin injections for survival, while the latter is generally managed with diet, weight reduction and exercise in about 20% of cases, the majority require these strategies plus oral medication and insulin is used if the tablets are ineffective.
Patient understanding and participation is vital as blood glucose levels change continuously. Treatments which return the blood sugar to normal levels can reduce or prevent development of the complications of diabetes. Other health problems that accelerate the damaging effects of diabetes are smoking, elevated cholesterol levels, obesity, high blood pressure, and lack of regular exercise.
The role of insulinSince 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 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 glucose so produced in the liver goes into the blood. 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.
If the amount of insulin available 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.
Types of DiabetesType 1 diabetes (formerly known as type I diabetes, insulin-dependent diabetes, childhood diabetes, or juvenile onset diabetes) is most commonly diagnosed in children and adolescents, but can occur in adults as well. It is characterized by ß-cell destruction, which usually leads to an absolute deficiency of insulin. Most cases of type 1 diabetes are immune-mediated characterized by autoimmune destruction of the body's ß-cells in the Islets of Langerhans of the pancreas, destroying them or damaging them sufficiently to reduce insulin production. However, some forms of type 1 diabetes are characterized by loss of the body's ß-cells without evidence of autoimmunity.
Currently, type 1 diabetes 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.
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 often 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. If these fail, insulin therapy may be necessary to maintain normal glucose levels.
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.
There are several causes of diabetes which do not fit into type 1, type 2, or gestational diabetes
• Genetic defects in beta cells.
• Genetically related insulin resistance.
• Diseases of the pancreas.
• Caused by hormonal defects.
• Caused by chemicals or drugs.
Signs and symptomsType 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 irreducible fatigue. These symptoms may also manifest in Type 2 diabetes in patients who present with frank poorly controlled diabetes.
Thirst develops because of osmotic effects — sufficiently high glucose (above the 'renal threshold') in the blood is excreted by the kidneys but this requires water to carry it and causes increased fluid loss, which must be replaced. The lost blood volume will be replaced from water held inside body cells, causing dehydration.
Another common presenting symptom is altered vision. Prolonged high blood glucose causes changes in the shape of the lens in the eye, leading to blurred vision and, perhaps, a visit to an optometrist. All unexplained quick changes in eyesight should force a fasting blood glucose test. These are now quick (less than 5 minutes total), inexpensive (materials less than USD $1), and can be safely performed by almost anyone with trivial training.
Especially dangerous symptoms in diabetics include the smell of acetone on the patient's breath (a sign of ketoacidosis), Kussmaul breathing (a rapid, deep breathing), and any altered state of consciousness or arousal (hostility and mania are both possible, as is confusion and lethargy). The most dangerous form of altered consciousness is the so-called "diabetic coma" which produces unconsciousness. Early symptoms of impending diabetic coma include polyuria, nausea, vomiting and abdominal pain, with lethargy and somnolence a later development, progressing to unconsciousness and death if untreated.
|
