Asked by Steve, San Bruno, California
What is the difference between type 1 and type 2 diabetes?
Dr. Otis Brawley
Chief Medical Officer,
American Cancer Society
First, the formal name for what we commonly call diabetes is diabetes mellitus, which translates from the Greek as making lots of urine with sugar in it or making lots of sweet urine.
Type 1 and type 2 diabetes mellitus are diseases that have in common, sugar in the urine and the increased urination.
When there are high amounts of sugar in the blood, the kidneys filter sugar into the urine. Sugar can be measured in the urine through a lab test commonly called a urinalysis. Urine dipsticks are also used to show sugar in the urine.
Patients who develop diabetes mellitus most commonly have initial symptoms of increased thirst, increased urination and blurred vision due to high amounts of sugar in the fluids of the eye.
Type 1 diabetes results from a rheumatoid-like autoimmune reaction in which one's own body attacks and destroys the beta cells of the pancreas. These are the cells that normally produce insulin. Type 1 is a disease in which the patient in a relatively short time has no insulin production.
All patients with type 1 diabetes can also develop a serious metabolic disorder called ketoacidosis when their blood sugars are high and there is not enough insulin in their body. Ketoacidosis can be fatal unless treated as an emergency with hydration and insulin.
Type 1 was once commonly called juvenile diabetes mellitus because it is most commonly diagnosed in children. It should be noted that even older adults in their 60s have occasionally been diagnosed with type 1 diabetes mellitus.
One should think of it as a disease of high blood sugars due to a deficiency of insulin production. It must be treated by administration of insulin. Insulin is given at least twice a day and is often given four times a day in type 1 diabetes.
Type 2 diabetes rates are growing dramatically in the United States and Western Europe. Type 2 is the result of the muscles and other tissues of the body developing a resistance to insulin produced by the beta cells of the pancreas. The pancreas first tries to overcome this resistance to insulin by making more insulin. The blood sugar goes up as a patient's body is no longer able to make enough insulin.
Most patients with type 2 diabetes mellitus are overweight or obese. For most, but not all, maintenance of a normal weight and a good diet will prevent development of type 2 diabetes.
Most type 2 diabetes is diagnosed after age 40. For this reason, many have referred to type 2 as adult-onset diabetes mellitus. This latter name has lost favor as the obesity epidemic has caused a number of people to be diagnosed with type 2 as early as 10 or 11.
Type 2 can often be treated with diet modification and can improve significantly with weight loss and exercise. Some patients will be effectively treated with medications such as metformin that increase peripheral sensitivity of organs to insulin.
Still more severe disease will require oral medications that encourage the pancreas to make more insulin such as glyburide or glipizide Some patients with even more severe type 2 disease are treated with subcutaneous injections of insulin.
The higher amounts of insulin in the body overcome the peripheral resistance to insulin and bring blood sugar levels back toward normal range. In a few type 2 patients, years of insulin overproduction cause the beta cells to burn out and stop making insulin. These patients can develop ketoacidosis just like the type 1 diabetic, and they must be treated with insulin injections.
The result of both long-term type 1 and type 2 diabetes mellitus is end-organ damage. Patients can develop blindness, kidney failure and vascular disease.
The blindness is due to diabetic retinopathy in which additional blood vessels grow into the retina of the eye. The vascular disease can manifest itself as decreased blood flow to the feet leading to foot sores, ulceration and infection requiring leg amputation. Vascular disease can also lead to heart attacks and strokes.
All of these complications are best delayed through good blood sugar control.
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