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Diabetes Overview
Almost everyone knows someone who has diabetes. An estimated 23.6 million people in the United States -- 7.8 percent of the population -- have diabetes, a serious, lifelong condition. Of those, 17.9 million have been diagnosed, and about 5.7 million people have not yet been diagnosed. Each year, about 1.6 million people aged 20 or older are diagnosed with diabetes.
What is diabetes?
Diabetes is a disorder of metabolism -- the way our bodies use digested food for growth and energy. Most of the food we eat is broken down into glucose, the form of sugar in the blood. Glucose is the main source of fuel for the body.
After digestion, glucose passes into the bloodstream, where it is used by cells for growth and energy. For glucose to get into cells, insulin must be present. Insulin is a hormone produced by the pancreas, a large gland behind the stomach.
When we eat, the pancreas automatically produces the right amount of insulin to move glucose from blood into our cells. In people with diabetes, however, the pancreas either produces little or no insulin, or the cells do not respond appropriately to the insulin that is produced. Glucose builds up in the blood, overflows into the urine, and passes out of the body. Thus, the body loses its main source of fuel even though the blood contains large amounts of sugar.
Who gets diabetes?
Diabetes is not contagious. People cannot "catch" it from each other. However, certain factors can increase the risk of developing diabetes.
Type 1 diabetes occurs equally among males and females, but is more common in whites than in nonwhites. Data from the World Health Organization's Multinational Project for Childhood Diabetes indicate that type 1 diabetes is rare in most African, American Indian, and Asian populations. However, some northern European countries, including Finland and Sweden, have high rates of type 1 diabetes. The reasons for these differences are unknown.
Type 2 diabetes is more common in older people, especially in people who are overweight, and occurs more often in African Americans, American Indians, some Asian Americans, Native Hawaiians and other Pacific Islander Americans, and Hispanic Americans. On average, non-Hispanic African Americans are 1.6 times as likely to have diabetes as non-Hispanic whites of the same age. Hispanic Americans are 1.5 times as likely to have diabetes as non-Hispanic whites of similar age. American Indians have one of the highest rates of diabetes in the world. On average, American Indians and Alaska Natives are 2.2 times as likely to have diabetes as non-Hispanic whites of similar age. Although prevalence data for diabetes among Asian Americans and Pacific Islanders are limited, some groups, such as Native Hawaiians and Japanese and Filipino residents of Hawaii aged 20 or older, are about twice as likely to have diabetes as white residents of Hawaii of similar age.
The prevalence of diabetes in the United States is likely to increase for several reasons. First, a large segment of the population is aging. Also, Hispanic Americans and other minority groups make up the fastest-growing segment of the U.S. population. Finally, Americans are increasingly overweight and sedentary. According to recent estimates, the prevalence of diabetes in the United States is predicted to reach 22.9 percent of the population by 2025.
What are the types of diabetes?
The three main types of diabetes are
type 1 diabetes
type 2 diabetes
gestational diabetes
Type 1 Diabetes
Type 1 diabetes is an autoimmune disease. An autoimmune disease results when the body's system for fighting infection (the immune system) turns against a part of the body. In diabetes, the immune system attacks the insulin-producing beta cells in the pancreas and destroys them. The pancreas then produces little or no insulin. A person who has type 1 diabetes must take insulin daily to live.
At present, scientists do not know exactly what causes the body's immune system to attack the beta cells, but they believe that autoimmune, genetic, and environmental factors, possibly viruses, are involved. Type 1 diabetes accounts for about 5 to 10 percent of diagnosed diabetes in the United States. It develops most often in children and young adults, but can appear at any age.
Symptoms of type 1 diabetes usually develop over a short period, although beta cell destruction can begin years earlier. Symptoms include increased thirst and urination, constant hunger, weight loss, blurred vision, and extreme fatigue. If not diagnosed and treated with insulin, a person with type 1 diabetes can lapse into a life-threatening diabetic coma, also known as diabetic ketoacidosis.
Type 1 Diabetes
Type 1 diabetes occurs when the body's own immune system destroys the insulin-producing cells of the pancreas (called beta cells).
Normally, the body's immune system fights off foreign invaders like viruses or bacteria. But for unknown reasons, in people with type 1 diabetes, the immune system attacks various cells in the body. This results in a complete deficiency of the insulin hormone.
Some people develop a type of diabetes – called secondary diabetes -- which is similar to type 1 diabetes, but the beta cells are not destroyed by the immune system but by some other factor, such as cystic fibrosis or pancreatic surgery.
Understanding Insulin and Type 1 Diabetes
Normally the hormone insulin is secreted by the pancreas in low amounts. When you eat a meal, sugar (glucose) from food stimulates the pancreas to release insulin. The amount that is released is proportional to the amount that is required by the size of that particular meal.
Insulin's main role is to help move certain nutrients -- especially glucose -- into the cells of the body's tissues. Cells use sugars and other nutrients from meals as a source of energy to function.
The amount of sugar in the blood decreases once it enters the cells. Normally that signals the beta cells in the pancreas to lower the amount of insulin secreted so that you don't develop low blood sugar levels (hypoglycemia). But the destruction of the beta cells that occurs with type 1 diabetes throws the entire process into disarray.
In people with type 1 diabetes, sugar isn't moved into the cells because insulin is not available. When sugar builds up in the blood instead of going into cells, the body's cells starve for nutrients and other systems in the body must provide energy for many important bodily functions. As a result, high blood sugar develops and can cause:
Dehydration.
The build up of sugar in the blood can cause an increase in urination (to try to clear the sugar from the body). When the kidneys lose the glucose through the urine, a large amount of water is also lost, causing dehydration.
Weight loss.
The loss of sugar in the urine means a loss of calories which provide energy and therefore many people with high sugars lose weight.
(Dehydration also contributes to weight loss.)
Diabetic ketoacidosis (DKA).
Without insulin and because the cells are starved of energy, the body breaks down fat cells. Products of this fat breakdown include acidic chemicals called ketones that can be used for energy. Levels of these ketones begin to build up in the blood, causing an increased acidity. The liver continues to release the sugar it stores to help out. Since the body cannot use these sugars without insulin, more sugars piles into the blood stream. The combination of high excess sugars, dehydration and acid build up is known as "ketoacidosis" and can be life-threatening if not treated immediately.
Damage to the body.
Over time, the high sugar levels in the blood may damage the nerves and small blood vessels of the eyes, kidneys, and heart and predispose a person to atherosclerosis (hardening) of the large arteries that can cause heart attack and stroke.
Who Gets Type 1 Diabetes?
Although the disease usually starts in people under the age of 20, type 1 diabetes may occur at any age.
The disease is relatively uncommon, affecting 1 in 250 Americans. The condition is more common in whites than in blacks and occurs equally in men and women.
What Causes Type 1 Diabetes?
Doctors don't know all the factors that lead to type 1 diabetes. Clearly, the susceptibility to the condition can be inherited.
Doctors have identified that an environmental trigger plays a role in causing the disease. Type 1 diabetes appears to occur when something in the environment -- a toxin or a virus (but doctors aren't sure) -- triggers the immune system to mistakenly attack the pancreas and destroy the beta cells of the pancreas to the point where they can no longer produce sufficient insulin. Markers of this destruction -- called autoantibodies -- can be seen in most people with type 1 diabetes. In fact, they are present in 85% to 90% of people with the condition when the blood sugars are high.
Because it's an autoimmune disease, type 1 diabetes can occur along with other autoimmune diseases such as hyperthyroidism from Grave's disease or the patchy decrease in skin pigmentation that occurs with vitiligo.
What Are the Symptoms of Type 1 Diabetes?
The symptoms of type 1 diabetes are often subtle, but they can become severe.
They include:
Increased thirst
Increased hunger (especially after eating)
Dry mouth
Nausea and occasionally vomiting
Abdominal pain
Frequent urination
Unexplained weight loss (even though you are eating and feel hungry)
Fatigue (weak, tired feeling)
Blurred vision
Heavy, labored breathing (Kussmaul respiration)
Frequent infections of the skin, urinary tract, or vagina
Signs of an emergency with type 1 diabetes include:
Shaking and confusion
Rapid breathing
Fruity smell to the breath
Abdominal pain
Loss of consciousness (rare)
How Is Type 1 Diabetes Diagnosed?
If your health care provider suspects diabetes, he will first check for abnormalities in your blood (high blood sugar level). In addition, he may look for glucose or ketone bodies in the urine.
There is currently no way to screen for or prevent the development of type 1 diabetes.
Learn more about diabetes blood tests.
How Is Type 1 Diabetes Managed?
Many people with type 1 diabetes live long, healthy lives. The key to good health is keeping your blood sugar levels within your target range, which can be done with meal planning, exercise and intensive insulin therapy. All people with type 1 diabetes must use insulin injections to control their blood sugar.
You will also need to check your blood sugar levels regularly and make adjustment of insulin, food and activities to maintain a normal sugar.
Consequences of Uncontrolled Type 1 Diabetes
When type 1 diabetes isn't well controlled, a number of serious or life-threatening problems may develop, including:
Retinopathy.
This eye problem occurs in 75% to 95% of adults who have had diabetes for more than 15 years. Diabetic retinopathy in type 1 diabetes is extremely rare before puberty no matter how long they have had the disease. Medical conditions such as good control of sugars, management of high blood pressure, and regulation of blood fats like cholesterol and triglycerides are important to prevent retinopathy. Fortunately, the vision loss isn't significant in most people with the condition.
Kidney damage.
About 35% to 45% of people with type 1 diabetes develop kidney damage, a condition called nephropathy. The risk for kidney disease increases over time and becomes evident 15 to 25 years after the onset of the disease. This complication carries significant risk of serious illness -- such as kidney failure and heart disease.
Poor blood circulation.
Damage to nerves and hardening of the arteries leads to decreased sensation and poor blood circulation in the feet. This can lead to increased risk of injury and decreased ability to heal open sores and wounds, which in turn significantly raises the risk of amputation. Damage to nerves may also lead to digestive problems such as nausea, vomiting, and diarrhea.
Type 2 Diabetes
The most common form of diabetes is type 2 diabetes. About 90 to 95 percent of people with diabetes have type 2. This form of diabetes is associated with older age, obesity, family history of diabetes, previous history of gestational diabetes, physical inactivity, and ethnicity. About 80 percent of people with type 2 diabetes are overweight.
Type 2 diabetes is increasingly being diagnosed in children and adolescents. About 3,700 people under the age of 20 were diagnosed with diabetes based on 2002-2003 data.
When type 2 diabetes is diagnosed, the pancreas is usually producing enough insulin, but for unknown reasons, the body cannot use the insulin effectively, a condition called insulin resistance. After several years, insulin production decreases. The result is the same as for type 1 diabetes -- glucose builds up in the blood and the body cannot make efficient use of its main source of fuel.
The symptoms of type 2 diabetes develop gradually. Their onset is not as sudden as in type 1 diabetes. Symptoms may include fatigue or nausea, frequent urination, unusual thirst, weight loss, blurred vision, frequent infections, and slow healing of wounds or sores. Some people have no symptoms.
Diabetes is a number of diseases that involve problems with the hormone insulin. While not everyone with type 2 diabetes is overweight, obesity and lack of physical activity are two of the most common causes of this form of diabetes. It is also responsible for nearly 95% of diabetes cases in the United States, according to the CDC.
This article will give you a better understanding of the causes of type 2 diabetes, what happens in the body when type 2 diabetes occurs, and specific health problems that increase your risk of type 2 diabetes. Each section links to more in-depth information on that topic.
In a healthy person, the pancreas (an organ behind the stomach) releases insulin to help your body store and use the sugar from the food you eat. Diabetes happens when one of the following occurs:
When the pancreas does not produce any insulin.
When the pancreas produces very little insulin.
When the body does not respond appropriately to insulin, a condition called "insulin resistance."
Unlike people with type 1 diabetes, people with type 2 diabetes produce insulin; however, the insulin their pancreas secretes is either not enough or the body is unable to recognize the insulin and use it properly. This is called insulin-resistance. When there isn't enough insulin or the insulin is not used as it should be, glucose (sugar) can't get into the body's cells. When glucose builds up in the blood instead of going into cells, the body's cells are unable to function properly.
The Role of Insulin in the Cause of Type 2 Diabetes
To understand why insulin is important, it helps to know more about how the body uses food for energy. Your body is made up of millions of cells. To make energy, these cells need food in a very simple form. When you eat or drink, much of your food is broken down into a simple sugar called "glucose." Then, glucose is transported through the bloodstream to the cells of your body where it can be used to provide the energy your body needs for daily activities.
The amount of glucose in your bloodstream is tightly regulated by the hormone insulin. Insulin is always being released in small amounts by the pancreas. When the amount of glucose in your blood rises to a certain level, the pancreas will release more insulin to push more glucose into the cells. This causes the glucose levels in your blood (blood glucose levels) to drop.
To keep your blood glucose levels from getting too low (hypoglycemia or low blood sugar), your body signals you to eat and releases some glucose from the stores kept in the liver.
People with diabetes either don't make insulin or their body's cells no longer are able to recognize insulin, leading to high blood sugars. By definition, diabetes is having a blood glucose level of 126 milligrams per deciliter (mg/dL) or more after an overnight fast (not eating anything).
Health Risk Factors for Type 2 Diabetes
Type 2 diabetes is believed to have a strong genetic link, meaning that it tends to run in families. Several genes are being studied that may be related to the cause of type 2 diabetes. If you have any of the following type 2 diabetes risk factors, it’s important to ask your doctor about a diabetes test. With a proper diabetes diet and healthy lifestyle habits, along with diabetes medication, if necessary, you can manage your type 2 diabetes just like you manage other areas of your life. Be sure to continue seeking the latest information on type 2 diabetes as you become your own health advocate.
Other type 2 diabetes risk factors include the following:
High blood pressure
High blood triglyceride (fat) levels
Gestational diabetes or giving birth to a baby weighing more than 9 pounds
High-fat diet
High alcohol intake
Sedentary lifestyle
Obesity or being overweight
Ethnicity: Certain groups, such as African Americans, Native Americans, Hispanic Americans, and Japanese Americans, have a greater risk of developing type 2 diabetes than non-Hispanic whites.
Aging: Increasing age is a significant risk factor for type 2 diabetes. The risk of developing type 2 diabetes begins to rise significantly at about age 45 years, and rises considerably after age 65 years.
Type 2 Diabetes Risk Factors
Do you have health risk factors for type 2 diabetes? The incidence of type 2 diabetes has doubled over the past three decades, according to the Framingham Heart Study. Although the causes of type 2 diabetes are unknown, there are some key risk factors. These health risk factors can increase your chances of getting this increasingly common type of diabetes.
It is estimated that 70 to 80 million Americans have insulin resistance syndrome -- a risk factor for type 2 diabetes. In the health topic on insulin resistance syndrome or metabolic syndrome, we explain the combination of diseases caused by insulin resistance. Once you learn more about insulin resistance, you may want to initiate some of the recommended lifestyle changes that can help decrease your chances of getting this serious problem.
A person with some or all of the following listed health risk factors may never develop type 2 diabetes. However, the latest medical findings show that the chances of getting type 2 diabetes increase the more health risk factors you have.
A family history of diabetes. If a parent or sibling in your family has diabetes, your risk of developing type 2 diabetes increases.
Age over 45. The chance of getting type 2 diabetes increases with age.
Race or ethnic background. The risk of type 2 diabetes is greater in Hispanics, blacks, Native Americans, and Asians.
Metabolic syndrome (also called insulin resistance syndrome)
Being overweight.
If you are overweight, defined as a body mass index (BMI) greater than 25, you're at higher risk of type 2 diabetes.
Hypertension.
High blood pressure increases the risk of developing type 2 diabetes.
Abnormal cholesterol levels.
HDL ("good") cholesterol levels under 35 mg/dL (milligrams per deciliter) and/or a triglyceride level over 250 mg/dL increases your risk of type 2 diabetes.
History of gestational diabetes. Getting diabetes during pregnancy or delivering a baby over nine pounds can increase your risk of type 2 diabetes.
Other health risk factors for type 2 diabetes include:
A history of polycystic ovary disease (PCOS)
Habitually inactive
History of vascular disease (such as stroke)
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