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Diabetes
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Diabetes mellitus is a medical disorder characterized by varying or persistent
hyperglycemia (elevated blood sugar levels), especially after eating.
Hypoglycemia (low blood sugar) is rare except as a side effect of treatment
(usually misapplication of medication in particular circumstances). While there
are different types of diabetes mellitus, most are asymptomatic for a (variable)
time after onset, but all share similar symptomatology and complications at
advanced stages. This disease involves multiple casual factors and clinical
aspects, all of which should be well understood for better management. Patient
understanding and participation is highly desired as blood glucose levels change
continuously in response to exercise, diet, physical and psychological stress,
infection, accident (i.e., trauma), hormonal changes, and even (perhaps) phase
of the moon; the diabetic patient is the only person present or experiencing all
of these.
Hyperglycemia itself can lead to dehydration and ketoacidosis. Longer-term
complications include cardiovascular disease (doubled risk - equal rates to
those with heart attacks from advanced atherosclerotic disease), renal failure
(worldwide, diabetes mellitus is the most common cause of chronic renal failure
requiring renal dialysis), retinal damage with eventual blindness, nerve damage
and eventual gangrene with probable loss of toes, feet, and even legs.
Conversely, successfully keeping blood sugar normal at all times, despite the
difficulty of doing so (especially 0.5 to about 4 hours after eating) has been
compellingly shown to reduce/prevent each of these problems. Other factors that
can, and should, be controlled to reduce problems associated with diabetes
include not smoking, optimizing lipoprotein cholesterol patterns, reducing body
fat, and exercising regularly, preferably with increasing intensity (Pima
Indians often cease to be diabetic after becoming long distance runners).
Historicaly, physicians have focused on two factors that are characteristic of
diabetes mellitus - decreased production of insulin (the first recognized
basis), or decreased sensitivity of body tissues to insulin (the more common),
or a combination of both. The distinction between these two circumstances
remains important.
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Statistics:
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In 2004, according to the World Health Organization, more than 150 million
people worldwide suffer from diabetes. Its incidence is increasing rapidly, and
it is estimated that by the year 2025 this number will double. Diabetes mellitus
occurs throughout the world, but is more common (especially Type 2) in the more
developed countries. In 2002 there were about 18.2 million diabetics in the
United States alone. Diabetes is in the top 10, and perhaps the top 5, of the
most significant diseases in the developed world, and is gaining in significance
(see big killers). For at least 20 years, diabetes rates in North America have
been increasing substantially. The Centers for Disease Control has termed the
change an epidemic. The National Diabetes Information Clearinghouse estimates
that diabetes costs $132 billion in the United States alone every year.
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Causes and types of diabetes mellitus:
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The role of insulin Since insulin is the principal hormone that makes it
possible for many cells (primarily muscle and fat cells) to use glucose from the
blood, deficiency of insulin or its action plays a central role in all forms of
diabetes.
Most of the carbohydrates in food are rapidly digested to glucose, the principal
sugar in blood. Insulin is produced by beta cells in the pancreas in response to
rising levels of glucose in the blood, as occurs after a meal. Insulin makes it
possible for most body tissues to remove glucose from the blood for use as fuel,
for conversion to other needed molecules, or for storage. Insulin is also the
principal control signal for conversion of glucose, the basic sugar unit, to
glycogen for storage in liver and muscle cells. Lowered insulin levels result in
the reverse conversion of glycogen to glucose when glucose levels fall -- though
only in the liver not muscle tissue. Higher insulin level increase many anabolic
("building up") processes such as cell growth, cellular protein synthesis, and
fat storage. Insulin is the principal signal in converting many of the
bidirectional processes of metabolism from a catabolic to an anabolic direction.
if the amount of insulin produced is insufficient, if cells respond poorly to
the effects of insulin (resistance or insulin insensitivity), or if the insulin
itself is defective, glucose is not handled properly by body cells (about 2/3
require it) nor stored appropriately in the liver and muscles. The net effect is
persistent high levels of blood glucose, poor protein synthesis, and other
metabolic derangements.
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Type 1 diabetes mellitus:
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Type 1 diabetes is most commonly diagnosed in children and adolescents, but can
occur in adults as well. It is an autoimmune disorder, in which the body's own
immune system attacks the beta cells in the Islets of Langerhans of the
pancreas, destroying them or damaging them sufficiently to reduce insulin
production. The autoimmune attack may be triggered by reaction to an infection,
for example by one of the viruses of the Coxsackie virus family. A subtype of
Type 1 (identifiable by the presence of antibodies against beta cells) develops
slowly and so is often confused with Type 2. In addition, a small proportion of
Type 1 cases has the hereditary maturity onset diabetes of the young (MODY).
Some poisons (e.g., a type of rat poison) work by selectively destroying certain
types of cells, including pancreatic beta cells, thus producing 'artificial'
Type 1 diabetes. Other pancreatic problems including trauma or tumor (either
malignant or benign) can also lead to loss of insulin production and Type 1.
Currently, Type 1 is treated with insulin injections, lifestyle adjustments, and
careful monitoring of blood glucose levels using blood test kits. The treatment
must be continued indefinitely. Experimental replacement of beta cells (by
transplant) is being investigated in several research programs and may become
clinically available in future. About 5-10% of all North American cases of
diabetes are Type 1 diabetics. The fraction of Type 1 diabetics in other parts
of the world differs; this is likely due to both differences in the rate of Type
1 and differences in the rate of other Types, most prominently Type 2. Most of
this difference is not currently understood. Formerly, Type 1 diabetes was
called "childhood" or "juvenile" diabetes or "insulin dependent" diabetes. Each
term is a misnomer, most especially since the obesity epidemic in recent years
has led to increased incidence of Type 2 diabetes in children and adolescents
and insulin is used in some Type 2 cases.
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Type 2 diabetes mellitus:
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Type 2 diabetes is characterized by "insulin resistance" as body cells do not
respond appropriately when insulin is present. This is a more complex problem
than type 1, but is sometimes easier to treat, since insulin is still produced
in many, especially in the initial years. Type 2 may go unnoticed for years in a
patient before diagnosis, since the symptoms are typically milder (no
ketoacidosis) and can be sporadic. However, severe complications can result from
unnoticed Type 2 diabetes, including hypertension, renal failure, and coronary
artery disease.
Type 2 diabetes was formerly known by a variety of partially misleading names,
including "adult-onset diabetes", "obesity-related diabetes", "insulin-resistant
diabetes", or "non-insulin-dependent diabetes" (NIDDM). It may be caused by a
number of diseases, such as hemochromatosis and polycystic ovary syndrome, and
can also be caused by certain types of medications (e.g., long-term steroid
use). About 90-95% of all North American cases of diabetes are Type 2, and about
20% of the population over the age of 65 is a Type 2 diabetic. The fraction of
Type 2 diabetics in other parts of the world varies substantially, almost
certainly for environmental reasons. There is also a very strong inheritable
genetic connection in type 2 diabetes - having relatives, especially close ones,
with type 2 is a considerable risk factor for developing type 2 diabetes. Most
patients with type 2 diabetes mellitus are obese - chronic obesity leads to
increased insulin resistance that can develop into diabetes, most likely because
fat tissue is a (recently identified) source of chemical signals (ie, hormones).
Type 2 is initially treated by changes in diet and through weight loss. This can
restore insulin sensitivity, even when the weight lost is modest (e.g. 10-15 lbs
or 5 kg). The next step, if necessary, is treatment with oral antidiabetic
drugs: the sulphonylureas, metformin, or (if these are insufficient)
thiazolidinediones). When these have failed, insulin therapy may be necessary.
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Type 3:
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All other specific forms of diabetes, accounting for up to 5% of all diagnosed
cases of diabetes, are termed Type 3:
Type 3A: genetic defect in beta cells.
Type 3B: genetically related insulin resistance.
Type 3C: diseases of the pancreas.
Type 3D: caused by hormonal defects.
Type 3E: caused by chemicals or drugs. |
Type 4:
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Gestational diabetes mellitus
Type 4 or Gestational diabetes mellitus appears in about 2-5% of all
pregnancies. It is temporary and fully treatable, but if untreated it
may cause problems with the pregnancy. It requires careful medical
supervision during the pregnancy. In addition, about 20-50% of these
women go on to develop Type 2 diabetes.
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Genetics:
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Both Type 1 and Type 2 diabetes are at least partly inherited. Type 1
diabetes appears to be triggered by infection, stress, or environmental
factors (e.g. exposure to a causative agent). There is a genetic element
in the susceptibility of individuals to some of these triggers which has
been traced to particular HLA genotypes (i.e. genetic 'self' identifiers
used by the immune system). However, even in those who have inherited
the susceptibility, Type 1 diabetes mellitus seems to require an
environmental trigger.
There is an even stronger inheritance pattern for Type 2 diabetes; those
with Type 2 ancestors or relatives have very much higher chances of
developing Type 2. It is also often connected to obesity, which is found
in approximately 85% of (North American) patients diagnosed with that
form of the disease, so inheriting a tendency toward obesity seems also
to contribute. Age is also thought to be a contributing factor, as most
Type 2 patients in the past were older. The exact reasons for these
connections are unknown. |
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