diabetes

diabetes or diabetes mellitus , chronic disorder of glucose (sugar) metabolism caused by inadequate production or use of insulin , a hormone produced in specialized cells (beta cells in the islets of Langerhans) in the pancreas that allows the body to use and store glucose. It is a leading cause of death in the United States and is especially prevalent among African Americans. The treatment of diabetes was revolutionized when F. G. Banting and C. H. Best isolated insulin in 1921.

The Disorder

The lack of insulin results in an inability to metabolize glucose, and the capacity to store glycogen (a form of glucose) in the liver and the active transport of glucose across cell membranes are impaired. The symptoms are elevated sugar levels in the urine and blood, increased urination, thirst, hunger, weakness, weight loss, and itching. Prolonged hyperglycemia (excess blood glucose) leads to increased protein and fat catabolism, a condition that can cause premature vascular degeneration and atherosclerosis (see arteriosclerosis ). Uncontrolled diabetes leads to diabetic acidosis, in which ketones build up in the blood. Patients have sweet-smelling breath, and may suffer confusion, unconsciousness, and death. There are two distinct types of diabetes mellitus: insulin-dependent and noninsulin-dependent.

Insulin-dependent Diabetes

Insulin-dependent diabetes (Type I), also called juvenile-onset diabetes, is the more serious form of the disease; about 10% of diabetics have this form. It is caused by destruction of pancreatic cells that make insulin and usually develops before age 30. Type I diabetics have a genetic predisposition to the disease. There is some evidence that it is triggered by a virus that changes the pancreatic cells in a way that prompts the immune system to attack them. The symptoms are the same as in the non-insulin-dependent variant, but they develop more rapidly and with more severity. Treatment includes a diet limited in carbohydrates and saturated fat, exercise to burn glucose, and regular insulin injections, sometimes administered via a portable insulin pump. Transplantation of islet cells has also proved somewhat successful since 1999, after new transplant procedures were developed, but the number of pancreases available for extraction of the islet cells is far smaller than the number of Type I diabetics. Patients receiving a transplant must take immunosuppressive drugs to prevent rejection of the cells, and many ultimately need to resume insulin injections, but despite that transplants provide real benefits for some whose diabetes has become difficult to control.

Noninsulin-dependent diabetes

Noninsulin-dependent diabetes (Type 2), also called adult-onset diabetes, results from the inability of the cells in the body to respond to insulin. About 90% of diabetics have this form, which is more prevalent in minorities and usually occurs after age 40. Although the cause is not completely understood, there is a genetic factor and 90% of those affected are obese. As in Type I diabetes, treatment includes exercise and weight loss and a diet low in total carbohydrates and saturated fat. Some individuals require insulin injections; many rely on oral drugs, such as sulphonylureas, metformin, acarbose or another alpha-glucosidase inhibitor, thiazolidinediones, or dipeptidyl peptidase-4 (DPP-4) inhibitors.

Complications

Diabetes affects the way the body handles fats, leading to fat accumulation in the arteries and potential damage to the kidneys, eyes, heart, and brain, and statins (cholesterol-lowering drugs) may be prescribed to prevent heart disease. It is the leading cause of kidney disease. Many patients require dialysis or kidney transplants (see transplantation, medical ). Most cases of acquired blindness in the United States are caused by diabetes. Diabetes can also affect the nerves, causing numbness or pain in the face and extremities. A complication of insulin therapy is insulin shock, a hypoglycemic condition that results from an oversupply of insulin in relation to the glucose level in the blood (see hyperinsulinism ).

Bibliography

See A. Bloom, Diabetes Explained (1973); Portland Area Diabetes Program, Diabetes and Insulin (1988); M. Davidson, Diabetes Mellitus: Diagnosis and Treatment (1991).

diabetes Disease characterized by lack of insulin needed for sugar metabolism. This leads to hyperglycaemia and an excess of sugar in the blood. Symptoms include abnormal thirst, over-production of urine and weight loss; degenerative changes occur in blood vessels. Untreated, the condition progresses to diabetic coma and death. There are two forms of the disease. Type 1 usually begins in childhood and is an autoimmune disease. Those affected owe their survival to insulin injections. Type 2 diabetes mostly begins in middle-age; there is some insulin output but not enough for the body's needs. The disease is managed with dietary restrictions, tablets to lower blood sugar levels and insulin injections. Susceptibility to diabetes mellitus is inherited and more common in males.

diabetes There are two distinct conditions: diabetes insipidus and diabetes mellitus. The latter condition is more common, and is generally referred to simply as diabetes or sugar diabetes. Haemochromatosis is known as bronze diabetes.

Diabetes insipidus is a metabolic disorder characterized by extreme thirst, excessive consumption of liquids and excessive urination, due to failure of secretion of the antidiuretic hormone.

Diabetes mellitus is a metabolic disorder involving impaired metabolism of glucose due to either failure of secretion of the hormone insulin (insulin‐dependent diabetes) or impaired responses of tissues to insulin (non‐insulin‐dependent diabetes). If untreated, the blood concentration of glucose rises to abnormally high levels (hyperglycaemia) after a meal and glucose is excreted in the urine (glucosuria). Prolonged hyperglycaemia may damage nerves, blood vessels, and kidneys, and lead to development of cataracts, so effective control of blood glucose levels is important.

Type I diabetes mellitus develops in childhood (juvenile‐onset diabetes) and is due to failure to secrete insulin, and hence is called insulin‐dependent diabetes. Treatment is by injection of insulin (originally purified from beef or pig pancreas, now biosynthetic human insulin), together with restriction of the intake of sugars.

Type II diabetes mellitus generally arises in middle age (maturity‐onset diabetes) and is due to resistance of the tissues to insulin action; secretion of insulin by the pancreas may be normal or higher than normal. It is referred to as non‐insulin‐dependent diabetes and can sometimes be treated by restricting the consumption of sugars and reducing weight, or by the use of oral drugs which stimulate insulin secretion and/or enhance the insulin responsiveness of tissues (sulphonylureas and biguanides). It is also treated by injection of insulin to supplement secretion from the pancreas and overcome the resistance. Impairment of glucose tolerance similar to that seen in diabetes mellitus sometimes occurs in late pregnancy, when it is known as gestational diabetes. Sometimes pregnancy is the stress that precipitates diabetes, but more commonly the condition resolves when the child is born.

Renal diabetes is the excretion of glucose in the urine without undue elevation of the blood glucose concentration. It is due to a reduction of the renal threshold which allows the blood glucose to be excreted. See also glucose tolerance.