What is diabetes?
Diabetes mellitus is a group of metabolic diseases characterized by high
blood sugar (glucose) levels, that result
from defects in insulin secretion, or action, or both. Diabetes mellitus,
commonly referred to as diabetes (as it will be in this article) was first
identified as a disease associated with "sweet urine," and excessive
muscle loss in the ancient world.
Elevated levels of blood glucose (hyperglycemia) lead to spillage of
glucose into the urine, hence the term sweet urine.
Normally, blood
glucose levels are tightly
controlled by insulin, a hormone produced by the
pancreas. Insulin lowers the blood glucose level. When the blood glucose elevates
(for example, after eating food), insulin is released from the pancreas to
normalize the glucose level. In patients with diabetes, the absence or
insufficient production of insulin causes hyperglycemia. Diabetes is a chronic
medical condition, meaning that although it can be controlled, it lasts a
lifetime.
What is the impact of diabetes?
Over time, diabetes can lead to blindness, kidney
failure, and nerve damage.
These types of damage are the result of damage to small vessels, referred to as
microvascular
disease.
Diabetes is also an important factor in accelerating the hardening and
narrowing of the arteries (atherosclerosis), leading to strokes, coronary
heart disease,
and other large blood vessel diseases. This is referred to as macrovascular
disease.
Diabetes affects approximately 17 million people (about 8% of the population)
in the United States. In addition, an estimated additional 12 million people in
the United States have diabetes and don't even know it.
From
an economic perspective, the total annual cost of diabetes in 1997 was
estimated to be 98 billion dollars in the United States. The per capita cost
resulting from diabetes in 1997 amounted to $10,071.00; while healthcare costs
for people without diabetes incurred a per capita cost of $2,699.00. During
this same year, 13.9 million days of hospital stay were attributed to diabetes,
while 30.3 million physician office visits were diabetes related. Remember,
these numbers reflect only the population in the United States. Globally, the
statistics are staggering.
Diabetes
is the third leading cause of death in the United States after heart disease
and cancer.
What causes diabetes?
Insufficient
production of insulin (either absolutely or relative to the body's needs),
production of defective insulin (which is uncommon), or the inability of cells
to use insulin properly and efficiently leads to hyperglycemia and diabetes.
This latter condition affects mostly the cells of muscle and fat tissues, and
results in a condition known as "insulin
resistance."
This is the primary problem in type 2 diabetes. The absolute lack of insulin,
usually secondary to a destructive process affecting the insulin producing beta
cells in the pancreas, is the main disorder in type 1 diabetes. In type 2 diabetes, there also is a
steady decline of beta cells that adds to the process of elevated blood sugars.
Essentially, if someone is resistant to insulin, the body can, to some degree,
increase production of insulin and overcome the level of resistance. After
time, if production decreases and insulin cannot be released as vigorously,
hyperglycemia develops.
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| ORGANS INVOLVED IN BLOOD GLUCOSE REGULATION |
Glucose
is a simple sugar found in food. Glucose is an essential nutrient that provides
energy for the proper functioning of the body cells. Carbohydrates are broken down in
the small
intestine and the glucose in
digested food is then absorbed by the intestinal cells into the bloodstream,
and is carried by the bloodstream to all the cells in the body where it is
utilized. However, glucose cannot enter the cells alone and needs insulin to
aid in its transport into the cells. Without insulin, the cells become starved
of glucose energy despite the presence of abundant glucose in the bloodstream.
In certain types of diabetes, the cells' inability to utilize glucose gives
rise to the ironic situation of "starvation in the midst of plenty".
The abundant, unutilized glucose is wastefully excreted in the urine.
Insulin is a hormone that is produced by
specialized cells (beta cells) of the pancreas. (The pancreas is a deep-seated
organ in the abdomen located behind the stomach.) In addition to helping glucose
enter the cells, insulin is also important in tightly regulating the level of
glucose in the blood. After a meal, the blood glucose level rises. In response
to the increased glucose level, the pancreas normally releases more insulin
into the bloodstream to help glucose enter the cells and lower blood glucose
levels after a meal. When the blood glucose levels are lowered, the insulin
release from the pancreas is turned down. It is important to note that even in
the fasting state there is a low steady release of insulin than fluctuates a
bit and helps to maintain a steady blood sugar level during fasting. In normal
individuals, such a regulatory system helps to keep blood glucose levels in a
tightly controlled range. As outlined above, in patients with diabetes, the
insulin is either absent, relatively insufficient for the body's needs, or not
used properly by the body. All of these factors cause elevated levels of blood glucose (hyperglycemia).
What are the different types of diabetes?
There are two major types of diabetes, called type 1 and type 2.
Type 1 diabetes was also called insulin dependent diabetes mellitus (IDDM), or
juvenile onset diabetes mellitus. In type 1 diabetes, the pancreas undergoes an
autoimmune attack by the body itself, and is rendered incapable of making
insulin. Abnormal antibodies have been found in the majority of patients with
type 1 diabetes. Antibodies are proteins in the blood that are part of the
body's immune system. The patient with type 1 diabetes must rely on insulin medication
for survival.
In autoimmune diseases, such as type 1 diabetes, the immune system
mistakenly manufactures antibodies and inflammatory cells that are directed
against and cause damage to patients' own body tissues. In persons with type 1
diabetes, the beta cells of the pancreas, which are responsible for insulin
production, are attacked by the misdirected immune system. It is believed that
the tendency to develop abnormal antibodies in type 1 diabetes is, in part, genetically inherited,
though the details are not fully understood.
Exposure to certain viral infections (mumps and Coxsackie
viruses) or other environmental toxins may serve to trigger abnormal
antibody responses that cause damage to the pancreas cells where insulin is
made. Some of the
antibodies seen in type 1 diabetes
include anti-islet cell antibodies, anti-insulin antibodies and anti-glutamic decarboxylase antibodies. These
antibodies can be measured in the majority of patients, and may help determine
which individuals are at risk for developing type 1 diabetes.
At present, the American Diabetes Association does not recommend general
screening of the population for type 1 diabetes, though screening of high risk
individuals, such as those with a first degree relative (sibling or parent)
with type 1 diabetes should be encouraged. Type 1 diabetes tends to occur in young, lean individuals,
usually before 30 years of age, however, older patients do present with this
form of diabetes on occasion. This subgroup is referred to as latent autoimmune
diabetes in adults (LADA). LADA is a slow, progressive form of type 1 diabetes. Of all the patients
with diabetes, only approximately 10% of the patients have type 1 diabetes and
the remaining 90% have type 2 diabetes.
Type 2 diabetes was also referred to as non-insulin dependent
diabetes mellitus (NIDDM), or adult onset diabetes mellitus (AODM). In type 2
diabetes, patients can still produce insulin, but do so relatively inadequately
for their body's needs, particularly in the face of insulin resistance as
discussed above. In many cases this actually means the pancreas produces larger
than normal quantities of insulin. A major feature of type 2 diabetes is a lack
of sensitivity to insulin by the cells of the body (particularly fat and muscle
cells).
In addition to the problems with an increase in insulin
resistance, the release of insulin by the pancreas may also be defective and
suboptimal. In fact, there is a known steady decline in beta
cell production
of insulin in type 2 diabetes that contributes to worsening glucose control. (This
is a major factor for many patients with type 2 diabetes who ultimately require
insulin therapy.) Finally, the liver in these patients continues to produce
glucose through a process called gluconeogenesis despite elevated glucose
levels. The control of gluconeogenesis becomes compromised.
While it is said that type 2 diabetes occurs mostly in individuals
over 30 years old and the incidence increases with age, we are seeing an
alarming number patients with type 2 diabetes who are barely in their teen years.
In fact, for the first time in the history of humans, type 2 diabetes is now more common than type 1
diabetes in childhood. Most of these cases are a direct result of poor eating
habits, higher body weight, and lack of exercise.
While there is a strong genetic component to developing this form
of diabetes, there are other risk factors - the most significant of which is obesity. There
is a direct relationship between the degree of obesity and the risk of
developing type 2 diabetes, and this
holds true in children as well as adults. It is estimated that the chance to
develop diabetes doubles for every 20% increase over desirable body weight.
Regarding age, data shows that for each decade after 40 years of
age regardless of weight there is an increase in incidence of diabetes. The prevalence of diabetes in persons 65 to 74 years of age
is nearly 20%. Type 2 diabetes is also more common in certain ethnic groups.
Compared with a 6% prevalence in
Caucasians, the prevalence in African Americans and Asian Americans is
estimated to be 10%, in Hispanics 15%, and in certain Native American
communities 20% to 50%. Finally,
diabetes occurs much more
frequently in women with a prior history of diabetes that develops during pregnancy (gestational diabetes
- see below).
Diabetes can occur
temporarily during pregnancy. Significant hormonal changes during pregnancy can lead to blood sugar elevation in
genetically predisposed individuals. Blood sugar elevation during
pregnancy is called gestational
diabetes. Gestational diabetes usually resolves once the baby is born.
However, 25%-50% of women with gestational diabetes will eventually develop
type 2 diabetes later in life, especially in those who require insulin during pregnancy and those who remain
overweight after their delivery. Patients with gestational diabetes are usually
asked to undergo an oral
glucose tolerance test about six
weeks after giving birth to determine if their diabetes has persisted beyond
the pregnancy, or if any evidence (such as impaired
glucose tolerance) is present that may be a clue to the patient's future risk for
developing diabetes.
"Secondary" diabetes refers to elevated blood sugar
levels from another medical condition. Secondary diabetes may develop when the
pancreatic tissue responsible for the production of insulin is destroyed by
disease, such as chronic
pancreatitis (inflammation
of the pancreas by toxins like excessive alcohol), trauma, or surgical removal
of the pancreas.
Diabetes can also result from other hormonal disturbances, such as
excessive growth hormone production (acromegaly) and Cushing's
syndrome. In acromegaly, a pituitary gland tumor at the base of the brain
causes excessive production of growth hormone, leading to hyperglycemia. In
Cushing's syndrome, the adrenal glands produce an excess of cortisol, which
promotes blood sugar elevation.
In addition, certain medications may worsen diabetes control, or
"unmask" latent diabetes. This is seen most commonly when steroid
medications (such as prednisone) are
taken and also with medications used in the treatment of HIV
infection (AIDS).
What are diabetes symptoms?
·
The early symptoms of untreated diabetes are related to elevated blood
sugar levels, and loss of glucose in the urine. High amounts of glucose in the
urine can cause increased urine output and lead to dehydration.
Dehydration causes increased thirst and water consumption.
·
The inability of insulin to perform normally has effects on
protein, fat and carbohydrate metabolism. Insulin is an anabolic hormone, that
is, one that encourages storage of fat and protein.
·
A relative or absolute insulin deficiency eventually leads to weight
loss despite
an increase in appetite.
·
Some untreated diabetes patients also complain of fatigue, nausea and vomiting.
·
Patients with diabetes are prone to developing infections of the bladder, skin,
and vaginal areas.
·
Fluctuations in blood
glucose levels can lead to blurred
vision. Extremely elevated
glucose levels can lead to lethargy and coma.
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| DIABETIC PATIENT AFFECTED BY UNHEALED WOUND |
How is diabetes diagnosed ?
The fasting
blood glucose (sugar)
test is the preferred way to diagnose diabetes. It is easy to perform and
convenient. After the person has fasted overnight (at least 8 hours), a single
sample of blood is drawn and sent to the laboratory for analysis. This can also
be done accurately in a doctor's office using a glucose meter.
·
Normal fasting plasma glucose levels are less than 100 milligrams
per deciliter (mg/dl).
·
Fasting plasma glucose levels of more than 126 mg/dl on two or
more tests on different days indicate diabetes.
·
A random blood glucose test can also be used to diagnose diabetes.
A blood glucose level of 200 mg/dl or higher indicates diabetes.
When fasting blood glucose stays above 100mg/dl, but in the range
of 100-126mg/dl, this is known as impaired fasting glucose (IFG). While
patients with IFG do not have the diagnosis of diabetes, this condition carries
with it its own risks and concerns, and is addressed elsewhere.
The oral glucose tolerance test
Though not routinely used anymore, the oral
glucose tolerance test (OGTT) is a gold
standard for making the diagnosis of type 2 diabetes. It is still commonly used
for diagnosing gestational diabetes and in conditions of pre-diabetes, such as polycystic
ovary syndrome. With an oral glucose tolerance test, the person fasts overnight
(at least eight but not more than 16 hours). Then first, the fasting plasma
glucose is tested. After this test, the person receives 75 grams of glucose
(100 grams for pregnant women). There are several methods employed by
obstetricians to do this test, but the one described here is standard. Usually,
the glucose is in a sweet-tasting liquid that the person drinks. Blood samples
are taken at specific intervals to measure the blood glucose.
For the test to give reliable results:
·
The person must be in good health (not have any other illnesses,
not even a cold).
·
The person should be normally active (not lying down, for example,
as an inpatient in a hospital), and
·
The person should not be taking medicines that could affect the
blood glucose.
·
For three days before the test, the person should have eaten a
diet high in carbohydrates (200-300 grams per day).
·
The morning of the test, the person should not smoke or drink
coffee.
The classic oral glucose tolerance test measures blood glucose
levels five times over a period of three hours. Some physicians simply get a
baseline blood sample followed by a sample two hours after drinking the glucose
solution. In a person without diabetes, the glucose levels rise and then fall
quickly. In someone with diabetes, glucose levels rise higher than normal and
fail to come back down as fast.
People with glucose levels between normal and diabetic have
impaired glucose tolerance (IGT). People with impaired glucose tolerance do not
have diabetes, but are at high risk for progressing
to diabetes. Each year, 1%-5% of people whose test results show impaired
glucose tolerance actually eventually develop diabetes .Weight
loss and exercise may help people with impaired glucose
tolerance return their glucose levels to normal. In addition, some physicians
advocate the use of medications, such as metformin (Glucophage), to help prevent/delay the onset
of overt diabetes.
Recent studies have shown that impaired glucose tolerance itself
may be a risk
factor for the
development of heart disease. In the medical community, most physicians are now
understanding that impaired glucose tolerance is nor simply a precursor of diabetes, but is its own clinical
disease entity
that requires treatment and monitoring.
Evaluating the results of the oral glucose tolerance test
Glucose tolerance tests may lead to one of the following diagnoses:
·
Normal response: A person is said to have a normal response
when the 2-hour glucose level is less than 140 mg/dl, and all values between 0
and 2 hours are less than 200 mg/dl.
·
Impaired glucose tolerance: A person is said to have impaired glucose
tolerance when the fasting plasma glucose is less than 126 mg/dl and the 2-hour
glucose level is between 140 and 199 mg/dl.
·
Diabetes: A person has diabetes when two diagnostic
tests done on different days show that the blood glucose level is high.
·
Gestational diabetes: A woman has gestational
diabetes when she has any two of the following: a 100g OGTT, a fasting plasma
glucose of more than 95 mg/dl, a 1-hour glucose level of more than 180 mg/dl, a
2-hour glucose level of more than 155 mg/dl, or a 3-hour glucose level of more
than 140 mg/dl
Interpretation of OGTT results:
·
Fasting
plasma glucose (measured before
the OGTT begins) should be below 6.1 mmol/l (110 mg/dl). Fasting
levels between 6.1 and 7.0 mmol/l (110 and 125 mg/dl) are borderline
("impaired
fasting glycaemia"), and fasting
levels repeatedly at or above 7.0 mmol/l (126 mg/dl) are
diagnostic of diabetes.
·
The 2 hour OGTT glucose
level should be below 7.8 mmol/l
(140 mg/dl). Levels between this and 11.1 mmol/l (200 mg/dl)
indicate "impaired glucose tolerance". Glucose levels above 11.1 mmol/l (200mg/dl)
at
2 hours confirms a diagnosis of
diabetes.
1999 WHO Diabetes criteria - Interpretation of Oral Glucose
Tolerance Test
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Glucose levels
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NORMAL
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impaired fasting glycaemia (IFG)
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impaired glucose tolerance (IGT)
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Diabetes Mellitus (DM)
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Venous Plasma
|
Fasting
|
2hrs
|
Fasting
|
2hrs
|
Fasting
|
2hrs
|
Fasting
|
2hrs
|
(mmol/l)
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<6.1
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<7.8
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> 6.1 &
<7.0
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<7.8
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<7.0
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>7.8
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>7.0
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>11.1
|
(mg/dl)
|
<110
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<140
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>110 & <126
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<140
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<126
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>140
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>126
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>200
|
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| DIGITAL INSTRUMENT TO TEST BLOOD GLUCOSE LEVEL |
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