What Is Diabetes Mellitus

What Is Diabetes Mellitus

WHAT IS DIABETES MELLITUS?

by Arturo Rolla, MD, and
Joan Stout

Diabetes is a metabolic disorder that occurs when

the body cannot properly use glucose (a form of sugar), the body's main source of fuel.

During digestion, most of the carbohydrates we eat are converted to glucose, which passes

into the bloodstream, where it is available to the cells for use as energy. 80% of the

glucose in the blood goes to the muscles. But in order for glucose to enter the cells and

be used as energy, insulin, a hormone secreted in the islets of the pancreas, must be

present. Without insulin, the body cannot convert food into energy.

The cells that produce insulin are called beta

cells. They are normally stimulated to produce insulin by the rising level of blood

glucose. In that way, the body has a system by which the right amount of insulin is

secreted for the right amount of glucose present. Once the glucose has entered the cells,

the blood glucose level decreases, and the beta cells stop secreting insulin.

Q: What are the different types of diabetes?

A: There are basically two types of diabetes. In

one type, the beta cells are destroyed by the immune system and no longer secrete insulin.

This is called type 1 diabetes and is characterized by an absolute deficit of insulin. The

other type, called type 2 diabetes, is due to "insulin resistance," an initial

resistance of the body's cells to obey the orders of insulin. To overcome this resistance,

the beta cells secrete more insulin, and glucose is eventually forced into the cells.

Glucose is maintained within normal limits, but at the expense of increased insulin

secretion by the beta cells. After many years of such increased secretion, the beta cells

become "tired" from working overtime, and the fatigue process begins. This

fatigue tends to be progressive, and in time the compensation of insulin resistance

disappears. At that point, blood glucose levels start going up.

Type 1 diabetes is also called insulin-dependent

diabetes (IDDM) and was previously known as juvenile diabetes. We now recognize that type

1 can appear at any age, even though it is most often diagnosed before the age of 40. Type

1 is an autoimmune disease, which means that the body's defense against infection, the

immune system, attacks part of the body. In type 1, the immune system attacks the beta

cells in the islets of the pancreas and destroys them. The pancreas then produces very

little or no insulin, and the patient needs daily insulin injections to live. Symptoms

typically appear over a brief period of time, although the destruction of the beta cells

may occur over a period of months or years. These symptoms include:

Increased thirst and urination, weight loss

despite increased hunger and food intake, blurred vision, extreme tiredness, and itching.

Coma and death can follow if diabetes is not diagnosed and treated.

Type 2 diabetes is also called

noninsulin-dependent diabetes (NIDDM) and was previously known as adult-onset diabetes.

Type 2 usually occurs in adults over 40, but it can appear at a much earlier age,

including early adolescence (maturity-onset diabetes of the young, MODY). About 80% of

people diagnosed with type 2 diabetes are overweight. In type 2, the pancreas produces

insulin, but the body is unable to effectively use the insulin. Insulin resistance is

common, and the patient may have large amounts of insulin present in the bloodstream.

Symptoms of type 2 typically develop gradually, over a period of months or years. Symptoms

include: Increased thirst, increased urination (especially at night), fatigue, weight

loss, blurred vision, frequent infections, and slow healing of sores. Because type 2 can

be present for many years before diagnosis, symptoms may include complications of

diabetes, such as heart disease, kidney disease, nerve problems, or vision problems.

Q: What causes type 1 diabetes?

A: At this point, we do not know why the body's

immune system attacks the beta cells and destroys them. The cause may be a virus, an

exposure to cow's milk at an early age, genetics, or more likely a combination of factors.

Doctors can determine who is at a high risk of developing type 1 by testing their blood

for antibodies against the islets in the pancreas and by testing their capacity to secrete

insulin. The hope is to prevent further beta cell destruction.

Q: What causes type 2 diabetes?

A: Most people who develop type 2 diabetes are

overweight. Overweight people have excess adipose tissue in the body, and the extra fat

increases their resistance to insulin, not only in the fat tissues but also in all the

other cells. Diabetes is not caused by eating too much sugar, but being overweight

increases the chances of developing type 2 diabetes.

Q: Who gets diabetes?

A: The following people have an increased risk

for developing diabetes:

- people with family members who have diabetes

- people who are overweight

- African Americans

- Native Americans

- Hispanics

These risk factors are much higher for type 2

than for type 1, although a genetic component is present for both types. For type 2

diabetes, risk factors include older age, increased weight, decreased level of physical

activity, overfeeding or too rich diet, and family history of diabetes. Adults are much

more likely to get type 2 diabetes than are children, while type 1 tends to appear more

frequently in children.

Q: How many people have diabetes?

A: In 1995, the estimated prevalence of diabetes

in the United States was 16 million people, about half of them not yet diagnosed. For type

1 diabetes, the estimate of diagnosed cases ranges up to 800,000. About 30,000 new cases

of type 1 are diagnosed each year. For type 2 diabetes, the 1993 estimate was 7 to 7.5

million diagnosed cases. About 595,000 new cases of type 2 are diagnosed each year.

Approximately 4.2 million women and 3.6 million men have been diagnosed with diabetes. For

children age 19 years or younger, the estimate is 100,000 cases. For adults age 65 years

or older, the estimate is 3.2 million cases.

Q: How is diabetes treated?

A: Daily insulin injections are required to treat

type 1 diabetes. Many people with type 1 take multiple injections daily. A regimen of

three or more injections per day is called "tight control" or "intensive

management." The insulin must be balanced properly with food intake and exercise

(including regular daily activities). Frequent blood testing is performed by the patient

to monitor blood sugar levels. This involves pricking a finger for a drop of blood,

applying the blood to a test strip, and inserting the strip into a small machine that

reads the strip and displays the approximate level of blood sugar. Type 2 is sometimes

treated with diet and exercise only. Oral diabetes medications, which are NOT insulin, are

also used.

If these methods do not work, type 2 is treated

with insulin. People with type 2 must also balance their exercise and food intake with

their medication (whether oral medication or insulin). A weight loss diet is frequently a

part of treatment with type 2. Blood glucose testing by the patient is also an important

part of treatment.

Both type 1 and type 2 diabetes are best treated

with a team approach, with the patient being the most important part of the team. The goal

of treatment is to keep blood sugar levels as close to normal as possible and so prevent

long-term complications. As most of the daily care is the responsibility of the person who

has diabetes, patient education is imperative. Other team members should include a

diabetes doctor (endocrinologist or diabetologist), specialists as necessary

(ophthalmologist, podiatrist, and so on), a dietitian, and a diabetes educator.

A 10-year study called the Diabetes Control and

Complications Trial (DCCT) was completed in 1993. The study included over 1,400 people

with type 1 diabetes and compared the results of intensive management with

"standard" management. The participants who followed intensive management,

keeping their blood sugar at lower levels, had significantly lower rates of eye, kidney,

and nerve diseases than did the "standard management" group. Although the study

only focused on type 1 diabetes, most doctors believe that people with type 2 will also

benefit from keeping their blood sugar as close to normal as possible.

Q: What are the complications of diabetes?

A: Complications of both type 1 and type 2

include eye disease and blindness, heart disease, strokes, kidney disease and kidney

failure, amputations, nerve damage, skin infections, and gum disease. Diabetes can also

cause complications of pregnancy and congenital malformations. In 1992, diabetes

contributed to at least 169,000 deaths. In 1993, diabetes was the seventh leading cause of

death listed on death certificates in the United States.

Q: How much does diabetes cost?

A: In 1992, the total cost of diabetes in the

United States was estimated at $92 billion. This includes $45 billion for direct medical

costs (only those costs directly attributable to diabetes) and $47 billion for indirect

costs such as disability, work loss, and premature deaths.

Arturo Rolla, MD, is an endocrinologist at New

England Deaconess Hospital and an associate clinical professor of medicine at Harvard

Medical School. Joan Stout is a professional writer and editor.