Diabetes mellitus is a general term for several different conditions that result in high blood glucose. Insulin, a hormone released by the pancreas, control blood glucose regulation. Insulin allows sugar to enter cells, where it's used for energy. When insulin production slows or if the cells no longer process insulin effectively, blood glucose rises. There are several different types of diabetes mellitus: Type 1, Type 2 and gestational diabetes. Each has a different cause but the end result is the same in each. Blood glucose rises and damages tissues and blood vessels.
Type 1 Diabetes
Formerly called juvenile or insulin dependent diabetes, Type 1 diabetes affects around 10 percent of diabetics, and usually begins before age 30. Type 1 diabetes is the result of the body's immune system attacking and destroying cells that make insulin. Type 1 diabetes destroys 90 percent or more of the beta cells in the pancreas that produce insulin, the Merck Manual states.
It's not known exactly what triggers the immune system to turn on the beta cells and destroy them. A virus may initiate the process; some viruses that have been associated with the development of Type 1 diabetes are mumps, congenital rubella and Coxsackie viruses, the University of Maryland Medical university reports. In some cases, a genetic predisposition may exist, although most people with Type 1 diabetes don't have a close relative with the disease.
Type 2 Diabetes
Type 2 diabetes, previously called adult onset diabetes, is caused by increased insulin resistance. Insulin is produced, often in higher than normal amounts, but more insulin is needed to transport glucose into cells. Since the pancreas can't keep up with the increased demand for insulin, glucose levels rise in the blood.
Obesity is the main contributing factor to development of increased insulin resistance. Between 80 and 90 percent of people with Type 2 diabetes are overweight. More children now have type 2 diabetes, due to the rise in childhood obesity. The incidence of type 2 diabetes also increases as people age; the disease affects around 15 percent of people over age 70. Certain ethnicities are more likely to develop type 2 diabetes. Blacks, Hispanics and Native Americans are two to three times more likely to develop the disease, Merck reports.
Gestational Diabetes
Gestational diabetes, which affects around 4 percent of all pregnant women according to the American Diabetes Association, is high blood sugar that develops during the latter part of pregnancy and disappears after delivery. Women with gestational diabetes don't have diabetes before or after the pregnancy but have a higher risk of developing type 2 diabetes later in life. The exact cause of gestational diabetes isn't known, but hormones from the placenta may block the action of maternal insulin. Pregnant women need to produce three times as much insulin as non pregnant women, the ADA states. When the body can't produce enough insulin to meet the demand, glucose builds up in the blood. Elevated amounts of glucose cross the placenta, so the fetus has to increase its insulin production to handle the high levels of glucose. Babies born to diabetic mothers are at increased risk for developing diabetes later in life.
