diabetes mellitus

a disorder of carbohydrate metabolism in which sugars in the body are not oxidized to produce energy due to lack of the pancreatic hormone insulin. The accumulation of sugar leads to its appearance in the blood (hyperglycaemia), then in the urine; symptoms include thirst, loss of weight, and the excessive production of urine. The use of fats as an alternative source of energy leads to disturbances of the acid-base balance, the accumulation of ketones in the bloodstream (ketosis), and eventually to diabetic coma. There appears to be an inherited tendency to diabetes; the disorder may be triggered by various factors, including physical stress.

Diabetes that starts in childhood or adolescence is usually more severe than that beginning in middle or old age. It is known as type 1 (or insulin-dependent) diabetes mellitus as patients have little or no ability to produce the hormone and are entirely dependent on insulin injections for survival. In type 2 (noninsulin-dependent or maturity-onset) diabetes mellitus, which usually occurs after the age of 40 but can develop in young people (see maturity-onset diabetes of the young), the pancreas retains some ability to produce insulin but this is inadequate for the body's needs; alternatively, the body becomes resistant to the effects of insulin. Patients may require treatment with oral hypoglycaemic drugs or insulin. Gestational diabetes develops during pregnancy. In all types of diabetes the diet must be carefully controlled, with adequate carbohydrate for the body's needs. Lack of balance in the diet or in the amount of insulin taken leads to hypoglycaemia. Long-term complications of diabetes include damage to blood vessels, which can affect the eyes (diabetic retinopathy), kidneys (diabetic nephropathy), and nerves (diabetic neuropathy).