Diabetes mellitus is a disease caused by the body's inability to use the hormone insulin. Insulin is normally produced in the pancreas, a gland attached to the small intestine. Its function is to convert carbohydrates into glucose. Glucose (also known as blood sugar) is the compound used by cells to obtain the energy they need to survive, reproduce, and carry out all their normal functions.
When cells are unable to use glucose for these functions, they use fat instead. One product of the metabolism of fats is a group of compounds known as ketones. Ketones tend to collect in the blood and disrupt brain functions.
Common signs of diabetes are excessive thirst, urination, and fatigue. The long-term effects of diabetes include loss of vision, decreased blood supply to the hands and feet and pain. If left untreated, diabetes can produce coma and cause death.
Two types of diabetes mellitus are known. Type I diabetes is also called juvenile or insulin-dependent diabetes. Type I diabetes occurs when the pancreas fails to produce enough insulin. Type II diabetes is also called adult-onset or noninsulin-dependent diabetes. Type II diabetes results when the pancreas does produce insulin but, for some reason, the body is unable to use the insulin normally. Type I diabetes can usually be controlled by doses of insulin and a strict diet. Type II diabetes is often caused by obesity and is usually controlled by diet alone.
Glucose: A simple sugar that serves as the source of energy for cells.
Hormone: Chemicals that regulate various body functions.
Insulin-dependent diabetes: Also known as juvenile or Type I diabetes; a form of diabetes that requires the daily injection of insulin.
Ketones: Organic compounds formed during the breakdown of fats that can have harmful effects on the brain.
Noninsulin-dependent diabetes: Also known as adult-onset or Type II diabetes; a form of diabetes that is often caused by obesity and can be controlled by diet, exercise, and oral medication rather than daily injections of insulin.
Pancreas: The organ responsible for secreting insulin.
More than 12 million Americans are affected by diabetes. An annual increase of about 5 percent in the disease is attributed both to the population's increased rate of longevity and a rising rate of obesity. Experts believe that for each reported new case of diabetes, there is an unreported one because symptoms of the early stages of adult diabetes tend to go unrecognized. Symptoms usually progress from mild to severe as the disease progresses.
Approximately 300,000 deaths each year in the United States are attributed to diabetes. Its prevalence increases with age, from about 0.2 percent in persons under 17 years of age to about 10 percent in persons aged 65 years and over. Females have a higher rate of incidence for the disease, while higher income groups in the United States show a lesser incidence than lower income groups. The incident rate is markedly different among ethnic groups. It is 20 percent higher in non-Caucasians than in Caucasians. However, for reasons as yet unknown, the rate of diabetes in ethnic groups such as Native Americans, Latin Americans, and Asian Americans is especially high and continues to rise.
The symptoms of diabetes were identified 3,500 years ago in Egypt and were also known in ancient India, China, Japan, and Rome. The Persian physician Avicenna (980–1037) described the disease and its consequences. The English epidemiologist Thomas Willis (1621–1675) was the first modern physician to discover that the urine of diabetics tasted sweet. This characteristic of the disease explains its name since diabetes refers to the frequent urination associated with the condition and mellitus refers to the honeylike taste of the urine.
The role of insulin in the metabolism of glucose was first suggested by the English physiologist Edward Sharpey-Schäfer (1850–1935) in 1916. Five years later, insulin was first isolated by the Canadian physiologists Frederick Banting (1891–1941) and Charles Best (1899–1978). In 1922, Banting and Best first used insulin to successfully treat a diabetic patient, 14-year-old Leonard Thompson, of Toronto, Ontario.