Diabetes Mellitus

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 I diabetes

and is characterized by an absolute deficit of insulin. The

other type, called type II 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 I diabetes is also called insulin-dependent

diabetes (IDDM) and was previously known as juvenile

diabetes. We now recognize that type I can appear at any

age, even though it is most often diagnosed before the age

of 40. Type I is an autoimmune disease, which means that

the body's defense against infection, the immune system,

attacks part of the body. In type I, 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 II diabetes is also called noninsulin-dependent

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

diabetes. Type II 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 II diabetes are

overweight. In type II, 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 II

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 II 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 I 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 I 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 II diabetes?

A: Most people who develop type II 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 II 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 II than for

type I, although a genetic component is present for both

types. For type II 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 II

diabetes than are children, while type I 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 I diabetes, the estimate of

diagnosed cases ranges up to 800,000. About 30,000 new

cases of type I are diagnosed each year. For type II

diabetes, the 1993 estimate was 7 to 7.5 million diagnosed

cases. About 595,000 new cases of type II 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 I diabetes. Many people with type I 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 II 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 II is treated with insulin.

People with type II 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 II. Blood glucose testing by the

patient is also an important part of treatment.

Both type I and type II 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 I 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 I diabetes, most doctors believe

that people with type II 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 I and type II 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.

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