Return to the tutorial menu.What is diabetes mellitus?
Diabetes is a disease in which the body doesn't produce or properly use insulin. Insulin is a hormone produced in the pancreas, an organ near the stomach. Insulin is needed to turn sugar and other food into energy. When you have diabetes, your body either doesn’t make enough insulin or can’t use its own insulin as well as it should, or both. This causes sugars to build up too high in your blood.
Diabetes mellitus is defined as a fasting blood glucose of 126 milligrams per deciliter (mg/dL) or more. “Pre-diabetes” is a condition in which blood glucose levels are higher than normal but not yet diabetic. People with pre-diabetes are at increased risk for developing type 2 diabetes, heart disease and stroke, and have one of these conditions:
What are type 1 and type 2 diabetes?
Type 2 diabetes is the most common form. It appears most often in middle-aged adults; however, adolescents and young adults are developing type 2 diabetes at an alarming rate. It develops when the body doesn’t make enough insulin and doesn’t efficiently use the insulin it makes (insulin resistance).
Type 1 diabetes usually occurs in children and young adults. In type 1, the pancreas makes little or no insulin. Without daily injections of insulin, people with type 1 diabetes won’t survive.
Both forms of diabetes may be inherited in genes. A family history of diabetes can significantly increase the risk of developing diabetes. Untreated diabetes can lead to many serious medical problems. These include blindness, kidney disease, nerve disease, limb amputations and cardiovascular disease (CVD).
How are insulin resistance, diabetes and CVD related?
Diabetes is treatable, but even when glucose levels are under control, it greatly increases the risk of heart disease and stroke. In fact, most people with diabetes die of some form of heart or blood vessel disease.
Pre-diabetes and subsequent type 2 diabetes usually result from insulin resistance. When insulin resistance or diabetes occur with other CVD risk factors (such as obesity, high blood pressure, abnormal cholesterol and high triglycerides), the risk of heart disease and stroke rises even more.
Insulin resistance is associated with atherosclerosis (fatty buildups in arteries) and blood vessel disease, even before diabetes is diagnosed. That’s why it’s important to prevent and control insulin resistance and diabetes. Obesity and physical inactivity are important risk factors for insulin resistance, diabetes and cardiovascular disease.
How is diabetes treated?
When diabetes is detected, a doctor may prescribe changes in eating habits, weight control and exercise programs, and even drugs to keep it in check. It's critical for people with diabetes to have regular checkups. Work closely with your healthcare provider to manage diabetes and control any other risk factors. For example, blood pressure for people with diabetes and high blood pressure should be lower than 130/80 mm Hg.
AHA Recommendation
Diabetes is a major risk factor for stroke and coronary heart disease, which includes heart attack. People with diabetes may avoid or delay heart and blood vessel disease by controlling the other risk factors. It's especially important to control weight and blood cholesterol with a low-saturated-fat, low-cholesterol diet and regular aerobic physical activity. It's also important to lower high blood pressure and not to smoke.
For information on hyperglycemia and hypoglycemia, please see the related entry in this encyclopedia.
Related AHA publications:
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The islets of Langerhans are destroyed in type I diabetes mellitus. This occurs probably as a consequence of a genetic susceptibility, followed by the onset of autoimmune destruction triggered by some environmental factor such as a viral infection. Heavy lymphocytic infiltrates appear in and around islets. The number and size of islets are eventually reduced, leading to decreased insulin production and glucose intolerance.
The islets of Langerhans are normal in number or somewhat reduced with type II diabetes mellitus. Fibrosis and deposition of amylin polypeptide within islets are most characteristic of the chronic states of type II diabetes.
There are a variety of complications involving the kidney. Both nodular and diffuse glomerulosclerosis can lead to chronic renal failure. Diabetics are prone to infections, particularly pyelonephritis. Both bacterial and fungal infections can occur.
The eyes can be affected in several ways by diabetes mellitus. Diabetic retinopathy is one of the leading causes for irreversible blindness in the United States. This retinopathy can occur with either type I or type II diabetes mellitus, usually a decade or so after the onset of diabetes. Most persons with type I diabetes and many of those with type II diabetes develop some background (non-proliferative ) retinopathy. Proliferative retinopathy is more ominous and is more likely to occur when diabetes mellitus is poorly controlled.
In severe retinopathy, neovascularization may lead to adhesions (synechiae) between iris and cornea or iris and lens. Neovascularization of the iris leads to secondary glaucoma with blindness.
Cataracts are more common in diabetics. This predilection for development of cataracts is felt to result from hyperglycemia leading to accumulation of sorbitol that results in osmotic damage to the crystalline lens.
Persons with diabetes mellitus, either type I or type II, have early and accelerated atherosclerosis. The most serious complications of this are atherosclerotic heart disease, cerebrovascular disease, and renal disease. The most common cause of death with diabetes mellitus is myocardial infarction.
Peripheral vascular disease is a particular problem with diabetes mellitus and is made worse through the development of diabetic neuropathy, leading to propensity for injury.
This is a feared complication of diabetes mellitus. Diabetic ketoacidosis helps to potentiate the growth of Mucor. The site of involvement is typically the nasopharyngeal region, but the infection can spread to involve soft tissues and bone of the face, orbit, skull, and brain.