Diabetes Mellitus


What is Diabetes?

Diabetes mellitus is the name given to a group of conditions in which the body cannot adequately control the amount of glucose (a form of sugar) in the blood. There are two major forms of diabetes.  Type 1 diabetes (formerly called juvenile-onset diabetes or insulin-dependent diabetes) is caused by a failure of insulin production.  Type 1 diabetes most often occurs in children. Type 2 diabetes (also known as adult-onset diabetes or non-insulin-dependent diabetes) results when the cells of the body become resistant to the effects of insulin. Type two is far more common and most often affects adults. The following table summarizes the differences between Type 1 and Type 2 diabetes:

Diabetes characteristic Type 1 Type 2
Insulin problem Insulin production low or absent Cells resistant to insulin
Age at diagnosis Usually in childhood (average age 12) Usually in adulthood (average age 47)
Need for daily insulin injections Usually necessary for survival Often needed for optimal glucose control

Normal glucose regulation

Origin of the Term "Diabetes Mellitus"

The word “diabetes” in the term diabetes mellitus was derived from an ancient Greek word meaning “siphon”, primarily because the most common symptom of diabetes is frequent urination (like a constantly draining siphon).  Another condition known as diabetes insipidus, while completely unrelated, is also characterized by frequent urination.  At one time physicians would distinguish between these diseases by tasting their patients’ urine.  “Mellitus” (meaning “sweetened with honey”) was the designation for those with excess sugar in the urine.  Those without a sweet taste were called “insipidus” (meaning “bland”). Diabetes mellitus is by far the more common disease, and when people say simply “diabetes,” diabetes mellitus is what they mean.

Diabetes results from a problem with normal glucose regulation. First, some background. Human cells primarily use glucose (a type of sugar) for their energy needs. If humans maintained a slow, steady level food consumption, the body would have a constant, steady eneregy intake--and diabetes would be much less of a problem.   Instead, most people eat three big meals a day and fast in between. This is where insulin comes in.

When a person is eating (high energy intake) or just sitting around (low energy use), glucose levels in the blood start to increase. In response, the pancreas releases insulin, which allows the body to store glucose for later use.  Muscle and liver cells respond to the insulin by converting glucose to glycogen, a complex sugar chain that can be quickly accessed when needed.  Adipose cells react to the insulin by using glucose to make fat, a more long-term energy store.

Later, when activity increases or the body has been without food for some time, the blood glucose level falls. Insulin release then tapers off, while other hormones kick in to encourage the release of glucose into the blood. This process helps the body maintain a more constant level of energy, even while eating large meals and experiencing periods of inactivity. If all goes well, the blood glucose concentration of the body stays within a tight range of 80-120 milligrams per deciliter (mg/dL). In a person who has diabetes, this process is broken. The chart below illustrates the blood glucose level of a person with diabetes vs. a person without diabetes.

In diabetes, the body can not adequately control blood glucose levels.

Diabetes: Abnormal Glucose Regulation

The major difference in persons with type 2 diabetes is the development of “insulin resistance” (or “insulin insensitivity”), meaning that while the pancreas continues to produce insulin, the target cells (muscle, liver, fat, and others) become less responsive and less able to pull glucose out of the blood.   The exact reason for this change is complex and not fully understood, but the end result is a rise in the blood glucose level.  The excess glucose causes malfunction of body proteins and damage to nerves, blood vessels, kidneys, parts of the eyes, and many other structures. These effects are the reason diabetes is such a dangerous disease.

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