Diabetes: Briefly Stated
Diabetes, also known as diabetes mellitus, is a disease characterized by raised levels of blood sugar due to problems with insulin in the body. Insulin is a hormone that helps sugar move from the blood and get into the innumerable cells of your body to provide energy. When insulin becomes defective or deficient or both, sugar remains trapped in the blood, leading to raised blood sugar levels. Persistently high levels of blood sugar tend to damage almost all organs of the body and, over time, may lead to such dreadful complications as blindness, kidney failure, amputation, heart attack, and stroke.
BLOOD SUGAR MECHANISM: BASIC FACTS. Your body needs energy to live, grow, and function. Glucose, which is a form of sugar, is the main nutrient that provides this energy. Carbohydrates (sugars and starches in your meals) are the principal source of glucose. When you eat carbohydratecontaining foods, they break down into their simple sugars in the digestive tract, and are absorbed as glucose (sugar) into the bloodstream. To provide energy, sugar should go inside the cells and muscles of the body. However, sugar by itself cannot enter the cells and needs help. This help is provided by insulin, which helps sugar get into the cells where it is used as a fuel for energy. Insulin Secretion. Insulin, which is secreted by the pancreas, is the key player in the blood sugar mechanism of the body. The pancreas is an organ situated below and behind your stomach.
A normal pancreas contains about 1 million cells called the islets of Langerhans. These cells are found in clusters in the pancreas. Each islet
contains four types of cells in which two types, alpha and beta cells, are especially significant in regulating blood sugar. Beta cells secrete insulin, whereas alpha cells secrete another hormone called glucagon (more on this later). Insulin, as just noted, is the most important agent in blood sugar control. The pancreas secretes insulin in two modes:
• Insulin secreted in response to meals. After you eat food, the pancreas in a parallel action, releases a matching amount of insulin that helps sugar move from the blood and enter into billions of cells throughout your body. This way blood sugar is maintained at normal levels. When you eat excess food, sugar is generated in a greater amount than your body immediately needs. In such situations, insulin helps excess sugar to be stored as a reserve in the liver and muscles of the body in the form of glycogen. Your body uses stored sugar reserves (glycogen) as a quick source of energy when you are not eating and sugar is not entering your circulation. In addition, insulin helps store a part of excess sugar in the form of fat in the body.
• The other mode of insulin secretion is called basal secretion. In this mode, the pancreas continuously secretes insulin in very small amounts. In this mode:
– Insulin suppresses the production of sugar by the liver, thereby helping control blood sugar. (The liver produces sugar in two
ways: by breaking down its sugar reserves, and by producing
more sugar through a process called gluconeogenesis.)
– Insulin delivers sugar to the brain cells continuously in very
small amounts. (Continuous supply of blood sugar is essential
for functioning of the brain.)
Glucagon Secretion. Unlike insulin, which lowers blood sugar, glucagon
(secreted by alpha cells) raises blood sugar levels. Glucagon stimulates the
liver to convert its glycogen reserves into sugar and release it into the bloodstream
• Your blood sugar is falling
• You need extra energy such as while you are exercising
• You are fasting or between the meals (when sugar is not entering
Glucagon secretion in the above situations helps prevent low blood sugar.
However, most people with type 1 diabetes within 5 years of having this disease,
tend to develop a defect in which glucagon does not respond to falling
blood sugar and fails to offset this fall. Such a condition exposes these
people to high risks associated with low blood sugar levels (see chapter 3).
The mechanisms of insulin secretion, insulin action, and glucagon
secretion are all well tuned and balanced when you are healthy. In such a
condition when you eat food, beta cells secrete the right amount of insulin
to process sugar, which is absorbed from your meals. The insulin so released
moves sugar fast from the blood and delivers it effectively to the cells of
your body. This makes blood sugar return quickly to its normal range. On
the other hand, secretion of glucagon prevents low blood sugar. In the
presence of well regulated blood sugar mechanism in normal health, sugar
circulating in the blood is neither high nor low but remains within the
normal range of 60 to less than 100 mg/dL (3.3 to less than 5.6 mmol/L).
WHAT GOES WRONG IN DIABETES. When you have diabetes, your
pancreas either produces insufficient insulin or no insulin or the insulin it
produces cannot work because your body resists its action. As a result, the
normal mechanism of blood sugar control breaks apart. Sugar, instead of
going into the cells of your body to nourish them, accumulates in the blood,
raising your blood sugar levels. Also, because of the defect in insulin, sugar
produced and released by the liver is not properly controlled, a condition
that further raises blood sugar levels.
Accumulation of excess sugar in the blood is harmful in at least three
ways. First, sugar remains trapped in the blood and does not go inside the
cells of the body where it is needed as a fuel for energy. As a result, the
body is not properly nourished. Second, when sugar level in the blood
becomes high, some sugar is excreted in the urine. Sugar is energy and
its loss through the urine makes the body weak. Third, raised blood sugar
levels, which remain persistently high, act like a poison, damaging
almost all the organs of the body.
MEASURING BLOOD SUGAR. Blood sugar is measured in mg/dL
(milligrams of sugar per deciliter of blood) or mmol/L (millimoles of sugar
per liter of blood). In some countries, including the United States, the
common practice is to express blood sugar in mg/dL; in other countries it is
expressed in mmol/L. To convert mg/dL values into mmol/L, divide the
mg/dL value by 18. By this calculation, a blood sugar value of 126 mg/dL
will be equal to 7 mmol/L.
CLASSIFICATION OF DIABETES. The Expert Committee on the Diagnosis
and Classification of Diabetes Mellitus currently classifies diabetes into
three main categories: Type 1, Type 2, and Gestational Diabetes Mellitus
(GDM). Afourth category of Other Types of Diabetes may also be added to
include diabetes induced by certain drugs and other specific causes.
Under the present classification, the old terms of insulin-dependent
diabetes mellitus (IDDM) and juvenile-onset diabetes for type 1, and noninsulin
dependent diabetes mellitus (NIDDM) and adult-onset diabetes for
type 2 diabetes have been dropped.
TYPE I DIABETES. Type 1 diabetes is a disease in which the insulin
producing cells of the body are destroyed. As a result, the pancreas produces
little or no insulin, and administration of insulin injections becomes
necessary to control blood sugar for survival. Out of every 100 people
with diabetes, 5 to 10 persons have type 1 diabetes.
CAUSE OF TYPE 1 DIABETES. Both genetic tendency and environmental
factors are responsible for causing type1diabetes. It is suspected that
several underlying genes are involved in raising the risk of developing this
disease. Research shows that about 85 to 90 percent of people who get
type 1 diabetes have a major disease gene known as HLA. When the disease
gene interacts with some unidentified environmental factor, a chain reaction
occurs that leads to the development of type 1 diabetes. It is generally
believed that when some unidentified virus present in the environment
(during an infectious disease such as a common cold or mumps) attacks a
person already having a genetic tendency of developing an immune disorder,
his or her immune system goes wrong, and the body mistakenly destroys its
own insulin-producing cells (beta cells).
Sometimes destruction of beta cells is rapid (over a few days or a few
weeks), especially in children, or slow, mainly in adults. But ultimately, the
beta cells are destroyed, resulting in a lifelong problem of absolute
deficiency in people with type 1 diabetes. Studies show that the immune
disorder (defect in body’s defense system), which leads the body mistakenly
destroy its own insulin producing cells, can be detected in most people long
before their beta cells are completely destroyed. Scientists believe that type
1 diabetes could be prevented if the immune system of the body is treated
before the occurrence of diabetes symptoms. Research is in progress to
ascertain if type 1 diabetes can be prevented or delayed from occurring.
Efforts, including development of a vaccine known as DiaPep 277, are
currently under way to prevent type 1 diabetes.
TYPE 2 DIABETES. Type 2 diabetes is the most common form representing
about 90 to 95 percent of all cases of diabetes. The main difference between
type 1 and type 2 diabetes lies in the availability of natural insulin in the
body. In type 1 diabetes, the pancreas produces little or no insulin (absolute
insulin deficiency). In type 2 diabetes, however, the pancreas produces
insulin but has any of the following insulin problems:
• The pancreas produces insulin but it is not enough (insulin
Who Gets Type 1 Diabetes
The following groups of individuals are at increased risk of getting
type 1 diabetes:
• A child or a young adult. Nearly 75 percent of all newly diagnosed
cases of type 1 diabetes occur in people younger than 18 years.
However, type 1 diabetes can happen at any age, even in old
people in their eighties and nineties.
• Elderly people having long-standing type 2 diabetes. These people
may develop type1diabetes when the pancreas becomes exhausted
and stops producing insulin.
• People whose blood tests show the presence of antibodies against
insulin and insulin producing cells.
• People who have first degree relatives with type 1 diabetes. If you
have any of the following first degree relatives with type 1 diabetes,
your overall risk of developing this disease may be as indicated below:
If your relative is: Your risk is:
- Identical twin 35 percent
- Non-identical twin 20 percent
- Father 9 percent
- Mother 3 percent
- Both parents Up to 30 percent
• The pancreas produces enough insulin but the cells and muscles of
the body are resistant to the action of insulin (insulin resistance).
• The pancreas does not produce enough insulin and whatever insulin
it produces is not properly used by the body.
In the presence of any of these problems, sugar in the blood remains high.
Persistently high levels of blood sugar further impair insulin secretion,
insulin action, or both. As a result, control of type 2 diabetes becomes
worse. Good control of blood sugar for a prolonged period, however, has
been shown to reverse some of the defects of insulin action, and improve
insulin secretion in people with type 2 diabetes.
CAUSE OF TYPE 2 DIABETES. The exact cause of type 2 diabetes is not
known. But it is believed that both genetic tendency and external factors
(such as unhealthy diet) are responsible for causing this disease. Scientists
are trying to identify which specific gene is involved in causing this disease.
The risk for type 2 diabetes, however, increases in the presence of any of the
• Obesity, especially abdominal obesity.
• Unhealthy diet. The Lancet reported the findings of a 15- year
prospective study called CARDIA, which show that fast food consumption
heightens the risk for type 2 diabetes. The reason is that
in fast food snacking you eat more fat, drink sweetened soft
drinks; and consume less whole grain products, low fat milk,
fruit, vegetables, and fiber. Such a diet increases weight and
decreases the action of insulin in the body, factors that are
strongly involved in promoting type 2 diabetes.
• Lack of physical activity.
• Advancing age.
• Heredity and genetic tendency.
• Inflammation such as in gum disease.
• Low HDL (good) cholesterol/raised triglyceride pattern in the blood
is now being recognized to be closely related to the degree of high
Who Gets Type 2 Diabetes
The following groups of people are at increased risk of developing
type 2 diabetes:
• People who have a family history of type 2 diabetes. Type 2 diabetes
generally runs in families.
• Women who develop diabetes during pregnancy (gestational
diabetes). When the pregnancy is over, women are likely to develop
type 2 diabetes in the future.
• Women with certain ovarian disorders.
• Children born of mothers with preexisting type 2 diabetes or diabetes
developed during pregnancy. These children have threefold
higher risk of getting type 2 diabetes at a young age than the
children who are born before their mothers had developed diabetes.
• Children with low birth weight followed by adult obesity.
• African Americans, Native Americans, and Hispanic Americans.
These people are genetically more likely to develop type 2 diabetes
• Men with waistlines greater than 40 inches and women with waistlines
greater than 35 inches.
– whose age is more than 45 years.
– who are obese with a BMI 27 or greater (see chapter 9).
– who are not obese by the standard criteria, but are obese at the
abdomen (central obesity).
– with short stature.
– who are physically inactive.
– with high blood pressure (140/90 mm Hg or higher).
– whose HDL (good) cholesterol is less than 40 mg/dL.
– with triglyceride level of 200 mg/dL or greater.
• People with chronic hepatitis C virus infection are at increased risk
of developing type 2 diabetes.
IDENTIFYING TYPE 1 AND TYPE 2 DIABETES. Typical features of type 1
and type 2 diabetes (see table below) will help you differentiate between the
two types and guide you in their identification.
GESTATIONAL DIABETES MELLITUS (GDM). Diabetes that develops in
women during pregnancy is called gestational diabetes mellitus (GDM) or
gestational diabetes for short. Two main reasons account for the development
of gestational diabetes. First, major hormonal changes occur in the body
Table 1.1 Typical Features of Type 1 and Type 2 Diabetes
Type 1 Diabetes Type 2 Diabetes
Age at diagnosis Less than 30 years Greater than 40 years
(See chapter 9)
Less than 25
(normal or low weight)
Greater than 27 (obese)
Ketones in urine Moderate to large Nil or low
present at diagnosis
Rapid death without
during pregnancy. These changes increase the body’s requirement for
insulin. If the pancreas is not strong enough to produce the increased
amount of insulin needed during pregnancy, the chances increase for the
development of gestational diabetes. In addition, hormones secreted during
pregnancy tend to decrease the effectiveness of insulin, leading to raised
blood sugar levels. Nearly 2 to 5 percent of women who do not have preexisting
diabetes develop gestational diabetes toward the end of the fourth
month of their pregnancies. In most cases, gestational diabetes ends when
pregnancy is over. However, the very presence of diabetes during pregnancy
indicates the inherent weakness of the blood sugar mechanism in these
women. Such a condition increases their chances of developing diabetes,
usually type 2 diabetes, in the future. Evidence shows that children born of
mothers with gestational diabetes tend to become obese, and they are at
increased risk of developing type 2 diabetes in their teenage years.
OTHER SPECIFIC TYPES OF DIABETES. Though rare, specific factors
such as listed below may increase the risk for diabetes:
• Genetic defect. MODY (maturity onset diabetes of the young) is an
example of diabetes caused by genetic defect. MODY is an
Who is at Risk of Gestational Diabetes
The risk of developing gestational diabetes increases in pregnant
• Who are high risk candidates of type 1 or type 2 diabetes.
• Who are 25 years or older when they become pregnant.
• Who had gestational diabetes in the past or have a family history
of gestational diabetes in their first degree relatives.
• Who gain abnormal weight during pregnancy (A weight gain of
about 20 to 30 pounds in pregnancy is, however, normal).
uncommon form of type 2 diabetes that typically develops in people
in their teens and twenties.
• Diseases of the pancreas, including tumor and cancer.
• Excess amount of certain hormones such as growth hormone,
cortisol, and glucagon produced in the body. These hormones blunt
insulin action and raise blood sugar.
• Certain drugs may raise blood sugar as a side effect. These drugs
– Thiazide pills. These are water pills (diuretics), which increase
output of the urine and lower high blood pressure. These drugs
taken in large doses raise blood sugar probably because they
reduce the action of insulin in the body.
– Beta-blocker drugs. These are high blood pressure-lowering
drugs that tend to depress secretion of insulin from the pancreas,
resulting in raised blood sugar.
– Steroids, which include hydrocortisone, dexamethasone, and
prednisolone (used to treat inflammation such as in rheumatoid
arthritis, and severe cases of asthma). Steroids tend to raise
blood sugar. Even when you inhale these steroids as vapors or
rub them on the skin as ointment, they are absorbed into the
bloodstream and can raise your blood sugar.
– Niacin. When niacin, a component of vitamin B complex, is
taken in large doses (such as 5 to 6 grams a day to lower blood
cholesterol), it may raise blood sugar as a side effect. However,
a small dose of niacin used as a part of vitamin B complex does
not raise blood sugar.
• Viruses. The viruses of certain infections such as German measles
and mumps are linked to the destruction of insulin-producing cells,
causing type 1 diabetes.
• Certain genetic diseases such as Down syndrome (a condition
characterized by mental retardation, short stature, and flattened
face) may induce diabetes.
• Diabetes insipidus. This is a disease quite different from diabetes
mellitus and is caused by a deficiency of pituitary hormone (a
hormone that influences your body’s growth and development).
Diabetes insipidus may lead to the development of diabetes
PRE-DIABETES. Before developing type 2 diabetes, people go through a
stage called pre-diabetes. This is a condition in which blood sugar levels
are higher than normal but less than the levels to be classified as diabetes.
Nearly 20 million people in the United States are affected by this condition.
The term pre-diabetes has been adopted by the American Diabetes
Association (ADA) and the National Institute of Diabetes and Digestive and
Kidney Diseases. According to the current criteria (see chapter 3), you will
be diagnosed with pre-diabetes if your blood sugar values in a lab test are:
• Fasting blood sugar ranging from 100 to 125 mg/dL, (5.6 to 6.9
mmol/L), a condition also called impaired fasting plasma glucose.
• Blood sugar, ranging from 140 to less than 200 mg/dL (7.8 to 11.1
mmol/L) in a glucose tolerance test (2 hours after taking glucose
mixed in water). This condition is also called impaired glucose
A peculiar feature of pre-diabetes is that although you may not be aware,
your heart and blood vessels are silently undergoing some long-term
damage in the pre-diabetes stage. People who are at increased risk of
developing type 2 diabetes (noted earlier in this chapter) should be screened
for pre-diabetes. A timely detection of this disorder, followed by simple
lifestyle changes, can prevent pre-diabetes from developing into fullfledged
diabetes and halt the damage it has been causing to the body.
SYMPTOMS OF DIABETES. These include:
Excessive Thirst and Urination. Excessive thirst (polydipsia) and frequent
urination (polyuria) are the classical symptoms of diabetes. High levels of
blood sugar make your blood thick and sticky and the body stimulates thirst
to add fluids to dilute sugar in the blood. When you drink plenty of water to
quench thirst, the kidneys drain out excess water in the form of urine and
protect the system of your body from being overloaded with fluid. But
frequent urination leads to water loss in the body, which in diabetes causes
sugar to concentrate again in the blood. This process repeats the abnormal
cycle of thirst and urination. These symptoms are more prominent in type 1
than type 2 diabetes and may often be absent in people with type 2 diabetes.
Loss of Fluids. Excessive urination results in severe loss of fluids, a
condition that leads to dehydration or water loss in the body. The dehydration
can cause various medical conditions, including general weakness
and the more serious condition in which the blood acids become very high
(ketoacidosis), especially in people with type 1 diabetes. Severe loss of
water can lead to coma and even death.
Severe Hunger. When your blood sugar is high, some sugar along with
other nutrients passes in your urine. These nutrients, as well as sugar, are a
source of energy to your body and their excretion through frequent urination
causes a heavy loss of energy. To regain energy, your body stimulates
hunger. Also, when sugar accumulates in the blood and does not reach the
innumerable cells and muscles that require it for energy, the cells begin to
starve and you feel hungry. (Excessive hunger, however, can also be a
symptom of low blood sugar, a dangerous medical condition. To be sure,
test your blood sugar.)
Weight Loss. In diabetes, you may be eating a lot and yet be losing your
weight. Reason: when sugar is high in the blood, you may spill over some
sugar in the urine (noted before). Because sugar is energy (4 calories per
gram), you lose a large number of calories when you excrete large amounts
of sugar in the urine. Loss of calories results in loss of weight. Rapid weight
loss is a marked feature in people with type 1 diabetes that may be absent in
people with type 2 diabetes.
Changes in Vision. Frequent changes in blood sugar levels make your
vision blurred or clear. When blood sugar remains high, the eye lens swells
and distorts the vision; when blood sugar returns to the normal level, the eye
lens recovers from swelling and the vision becomes clear. Blurred vision
caused by raised blood sugar levels is a self-correcting condition, which
people with diabetes may frequently experience. This condition sharply
differs from the serious eye disease called retinopathy in which high levels
of blood sugar damage the retina, and may lead to blindness in extreme
Fatigue. When the insulin in your body is not enough or it cannot
work efficiently, sugar is not properly delivered to the cells of the body
where it is required for energy. When your body does not get proper nourishment,
it lacks energy and you feel fatigued. The feeling of fatigue is
common when sugar in the blood is high such as when you have eaten a
heavy meal loaded with carbohydrates (because carbohydrates cause maximum
rise of blood sugar). However, keep in mind that fatigue can also be
a sign of low blood sugar. To be sure, test your blood sugar.
Infections. Diabetes tends to impair your body’s infection-fighting system,
resulting in an increased risk for developing infections. These infections are
slow to heal and tend to resist treatment. The infections most commonly
associated with diabetes include gum, urinary tract, foot, and skin infections,
and various kinds of wounds and ulcers that heal very slowly.
Acommon infection in diabetes is a yeast infection caused by the yeast
fungus called Candida. Both men and women with diabetes may develop
yeast infection but women are at increased risk. Yeast infection causes
vaginal yeast in women, a condition characterized by itching and irritation
in the vagina, inflammation of the vulva, and a white coating on the vaginal
walls. In men with yeast infection, the end of the penis may become red,
swollen, painful, and filled with sores covered with a cheese-like
Nerve Pain. Several years after having diabetes, people tend to develop
nerve pain or numbness in their legs, feet, arms, and hands. These conditions
are common symptoms of nerve damage (neuropathy) caused by
diabetes. Raised blood sugar levels tend to damage all blood vessels in your
body, including the tiny vessels that supply the blood to the nerves (see
chapter 23). When your nerves do not get enough blood, they become weak
and you feel nerve pain. Nerve pain may diminish or disappear with
improved control of blood sugar; however, it may come to stay when nerve
damage has become chronic and irreversible.
Other Symptoms. These may include: itching, gum disease, darkening of
the skin around eyes, and bad smell in breath.
WHAT IS THE HONEYMOON PHASE. In the early stages of type 1 diabetes,
there is a brief period in which blood sugar is well controlled. This period is
called the honeymoon phase. Two factors make this phase possible. First, in
the early stage of type 1 diabetes, destruction of beta cells is not complete
and some cells are still left that continue to release insulin. Second, insulin
therapy in the early stage of type 1 diabetes effectively controls raised blood
sugar levels. Because of these factors, blood sugar appears to have been
controlled and it seems as if diabetes were reversed. But this is not so. It is
a brief period of relief and the control of blood sugar is temporary. This
phase may last several weeks to several months. Ultimately beta cells are
completely destroyed in type 1 diabetes and all people with this disease
must take insulin to control their blood sugar.
WHAT IS INSULIN RESISTANCE. Insulin resistance is a condition in
which your body resists the action of insulin, and as a result, insulin fails
to control blood sugar. In an attempt to overcome insulin resistance and
to control blood sugar, your pancreas increases the production of insulin,
raising insulin levels in the blood. For several years of insulin resistance,
the pancreas continues producing excess insulin to control blood sugar,
thereby preventing diabetes from appearing on the surface. However, a
time eventually comes when beta cells of the pancreas become exhausted by
overwork and their capacity to secrete insulin declines. This is the stage
when lack of insulin production and increased insulin resistance both
combine and type 2 diabetes becomes evident.
Insulin resistance is a typical feature of type 2 diabetes, but the body’s
insensitivity to insulin action is also found in type 1 diabetes. People with
type 2 diabetes continue to produce insulin in the early stage of their
diabetes but their bodies continue resisting against the action of insulin. This
is the reason that most people with type 2 diabetes having insulin resistance
are not short of insulin. In contrast, they have excess insulin in their blood
which, however, is not able to work properly. Working over time, the beta
cells of these people are totally exhausted and produce little insulin. This is
the stage when people with type 2 diabetes have to take insulin injections to
control blood sugar. In addition, persistently raised blood sugar levels have
a poisoning effect on beta cells, a condition that further damages the insulin
secreting capacity of beta cells.
The factors that contribute to insulin resistance include heredity on
which you have no control, and controllable factors such as obesity, lack of
physical activity, tobacco smoking, and stress. Insulin resistance is the
major cause of type 2 diabetes and is believed to be responsible for the
presence of high blood pressure, and blood cholesterol and blood fat
disorders in people with type 2 diabetes. These disorders, in turn, heighten
the risk for heart disease and stroke.
This article has laid out the basics of diabetes, including its new classification,
the risk factors that increase its incidence, and the criteria that
help you distinguish between type 1 and type 2 diabetes. Having read this
article, you will be able to recognize and identify your risks, if any, for
developing diabetes and take steps that will empower you to defend yourself
against this disease.