Insulin-dependent diabetes.

Insulin-Dependent Diabetes

Insulin-dependent diabetes (IDDM) is a chronic disease that usually begins in childhood. It is not the most common form of diabetes-IDDM accounts for only 5 percent or less of diabetes in this country. Often, though, IDDM has a much greater impact on a person's life than the more common adult-onset form of diabetes, known as noninsulin-dependent diabetes (NIDDM).

The onset of IDDM is usually more swift and severe than that of NIDDM. A child with IDDM can become sick very quickly. If treatment does not begin shortly after the first symptoms, the child may need to be hospitalized. Once the diagnosis is made, a person with IDDM needs daily injections of the hormone insulin to survive.

Insulin, discovered in the 1920's, has literally made the difference between life and death for thousands of people with IDDM. Insulin is not a cure for diabetes, however. Even with careful insulin treatment, people who have had diabetes for years are at greater than average risk of developing problems that involve the heart, blood vessels, eyes, kidneys, and nerves. While most of those with IDDM can lead physically active and professionally challenging lives, they do not have the luxury of taking their health for granted.

Research is adding rapidly to our knowledge of diabetes. Besides searching for a cure, scientists are learning how to help people with diabetes enjoy a longer life with fewer health problems.

What Is Diabetes?

Diabetes mellitus impairs the way the body uses digested food for energy. The sugars and starches (carbohydrates) in the food we eat are broken down by digestive juices into a simple sugar called glucose. Glucose circulates in the blood as the major energy source for the body. For cells in muscles and other tissues to use glucose for energy, the hormone insulin must be present. Insulin is produced by the pancreas gland located behind the stomach. When the right amount of insulin is present, glucose is either used as fuel for energy or stored in the liver for future use.

In diabetes, however, the pancreas may not make enough insulin, or the body does not respond to the insulin that is present. Sometimes, a person with diabetes can have both these problems. As a result, glucose builds up in the blood and tissues, overflows into the urine, and is excreted. Thus, the body loses its main source of fuel.

In IDDM the pancreas makes little or no natural insulin, and a person with IDDM needs daily injections of the hormone to stay alive. IDDM generally occurs in children and adolescents, though it can appear at any age. An estimated 300,000 to 500,000 persons in the United States have IDDM. International statistics on IDDM are unreliable. In general, however, IDDM is unknown or rare in some ethnic groups, including the Japanese, Chinese, American Indians, Polynesians, and South African blacks. On the other hand, Sweden and Finland have very high rates: in Sweden it is estimated that 3 children in 1,000 have IDDM versus 1.6 in 1,000 in the United States. The reasons for these differences are not yet known.

NIDDM is the more common form of diabetes. Of the 11 million Americans who have diabetes, over 95 percent have NIDDM. Fully half of those with NIDDM don't know they have it. NIDDM usually occurs after age 40. In NIDDM, the pancreas can produce insulin, but the body does not use it efficiently. For this reason, most people with NIDDM can control their diabetes with careful dieting and regular exercise. When diet and exercise fail to control NIDDM, insulin or oral drugs can be used to help control the condition.

Effective treatment exists for both IDDM and NIDDM. Even with treatment, however, both types of diabetes can cause long-term damage to the eyes, nerves, heart, and kidneys. These complications can lead to blindness, heart attack, stroke, kidney disease, and serious infections that may require limb amputation. In IDDM, episodes of very high or low blood sugar can cause a coma. Careful treatment of diabetes is the most effective way to minimize the chances of complications.

Symptoms

The symptoms of IDDM can be sudden and severe. They may include frequent urination, extreme thirst, constant hunger, bluffed vision, and extreme fatigue. Because people with IDDM lack insulin, glucose builds up in the blood. The kidneys, trying to remove the excess sugar, excrete large amounts of water and essential body elements, causing frequent urination and thirst.

Because the body cannot use glucose, its first source of energy, it turns to stored fat and protein for fuel. As the body uses fat and protein, weight is lost. Breakdown products of fat collect in blood and raise its acid content. If levels of these products are high enough, a critical condition called ketoacidosis can develop, requiring prompt treatment.

How Is Diabetes Treated?

A person with IDDM must have insulin injections to survive. Without insulin, symptoms worsen until the patient loses consciousness and slips into a coma. With daily insulin shots and a careful diet, however, most people with IDDM can lead active lives with the same ambitions and challenges as those without diabetes.

Treatment for IDDM includes a daily routine of insulin shots or use of an insulin pump. Following a doctor's instructions, a person with IDDM buys insulin and syringes and injects himself or herself daily. (The parent of a young child with IDDM can do this for the child.) More and more people are also using home blood glucose monitoring devices to measure their blood glucose during the day. In this way, they can tailor the insulin dose more closely to changes in their hour-to-hour blood glucose. Blood glucose monitoring is a more accurate way to monitor diabetes treatment than urine testing.

Eating the right foods at the right time is an important part of treatment. A person with IDDM needs to time meals with insulin doses to keep blood glucose from getting too high or low. The foods you choose can play a role in controlling blood glucose levels, too. Increasing the proportion of fiber and complex carbohydrates in your diet and avoiding refined sugar may aid in reducing drastic changes in blood glucose and may, in some people, permit lowering of insulin dose. Foods containing fiber include beans, whole grains, and some fruits, while complex carbohydrates, or starches, include potatoes, rice, and pasta.

Reducing fats and cholesterol can help reduce the risk of heart disease, which affects people with diabetes more often than those with normal glucose metabolism.

Exercise, like diet, can help reduce the risk of heart disease. Being fit can also bring a sense of well-being and strength that has special meaning for someone with a chronic illness like diabetes.

Exercise carefully, though. Strenuous exercise increases the muscles' use of glucose, so it can lower glucose in the blood. At the same time, exercise also stimulates the body to release glucose and fats for use as energy. This stimulus can have the effect of raising blood glucose. In order to exercise safely, you should balance insulin dose, meals, and the timing of exercise to keep blood glucose levels from getting too high or too low.

What Causes Diabetes?

No one knows exactly what causes IDDM. What is clear is that the body's own immune or disease-fighting system for some reason turns against the body's own tissues. Certain substances formed by the immune system attack the beta cells of the pancreas, destroying their ability to make insulin.

Research shows that most, if not all, people with IDDM may inherit traits that put them at risk for IDDM. However, not everyone who inherits these traits develops IDDM. One or more factors in the environment are believed to trigger the immune system to destroy the insulin-producing cells. In some cases, the trigger may be a viral infection. Scientists have, in a few cases, been able to link the onset of diabetes with a virus. In most cases, however, the trigger for diabetes is unknown.

Complications of Diabetes

The discovery of insulin in 1921 lengthened the lives of people with IDDM from weeks or months to decades. In spite of insulin's life-preserving effects, diabetes remains a deadly disease. This fact is largely due to the complications of diabetes that develop over many years of insulin treatment. The complications affect the heart, eyes, kidneys, and nerves. Much of the damage done to these organs involves changes in small blood vessels throughout the body. Research is under way to determine whether very careful control of blood glucose can prevent or delay diabetic complications. Studies are also under way to determine why some people with IDDM have trouble with complications while others live long, relatively healthy lives.

Until the answers to these questions are known, it is wise for people with IDDM to follow their doctor's advice in controlling blood glucose and to be aware of the signs and risk factors for complications of diabetes.

Acute Complications

The acute complications of diabetes are the rapid effects that can occur when blood glucose levels climb too high or fall too low. If an insulin injection is missed, for example, blood glucose rises, and the person affected may start to feel weak and hungry, and may urinate frequently. Since the body can't use glucose for energy, it shifts to using fats and protein. The products of fat and protein metabolism, substances called ketones, are toxic when they reach high enough levels. This condition is called ketoacidosis, and it can cause coma and death if untreated. Ketoacidosis can develop slowly over several days. The warning symptoms may include abdominal pain, nausea and vomiting, rapid breathing and a fruity odor on the person's breath, and drowsiness.

Glucose can also fall too low in diabetes. Going too long without a meal, engaging in strenuous exercise, or taking too large a dose of insulin can cause glucose to drop, a condition called hypoglycemia, or insulin shock. Common symptoms of hypoglycemia include trembling, nervousness, sweating, hunger, headache, nausea, drowsiness, or a feeling similar to drunkenness. Like ketoacidosis, hypoglycemia can cause coma and death if untreated. A quick, sugar-rich snack or drink such as orange juice or an injection of glucagon, a hormone that raises glucose levels, can restore normal glucose levels.

Long-Term Complications

In young people, acute complications pose the greatest threat to survival for people with IDDM. As people grow older, the long-term complications become more important. Diabetes can damage many organs through its effects on blood vessels. How this occurs is not well understood, but the damage can lead to kidney, heart, eye, and nerve disease.

Kidney Disease

Kidney disease is the greatest threat to life in adults with IDDM. The kidneys have a complex network of small blood vessels that filter impurities from blood for excretion in urine. Diabetes can damage these small blood vessels so that the kidneys cannot perform their waste-filtering work. The kidneys are essential to life. People can live without one kidney, but those who lose both must have their blood cleansed by a dialysis machine or have a kidney transplant.

High blood pressure can increase the chances that someone will develop kidney disease, so keeping blood pressure under control is especially important for someone with IDDM.

Diabetes doubles the risk of heart disease. For reasons not yet well understood, fat and cholesterol collect more rapidly in the arteries of people with diabetes than in those without diabetes. These fatty deposits reduce the supply of blood to the heart and can lead to a heart attack.

Other risk factors for heart disease include hypertension or high blood pressure, obesity, high amounts of fats and cholesterol in blood, and cigarette smoking. The more these factors can be eliminated, the more a person reduces the risk of heart disease.

Eye Disease

The major threat to vision from diabetes is diabetic retinopathy. Retinopathy means disease of the retina, the light-sensing tissue at the back of the eye. Diabetes causes changes in the tiny vessels that supply the retina with blood. The blood vessels may swell and leak fluid. When retinopathy is more severe, new blood vessels may grow from the back of the eye and bleed into the clear gel, or vitreous, that fills the eye.

A yearly eye examination enables an eye doctor to detect changes before vision is affected and eye disease becomes harder to treat. Scientists have found that laser treatment for diabetic retinopathy can help prevent loss of vision and can, in some cases, restore vision lost as a result of this disease. A yearly eye exam by an eye doctor is the best way to make sure that changes in eyesight are diagnosed early and that effective treatment is carried out when it can be most helpful.

Diabetic Nerve Disease

Nerve damage from diabetes (diabetic neuropathy) can dull sensation in the feet, legs, and fingertips. When this happens, bruises or sores may go unnoticed until they become open or infected. Reduced blood flow caused by diabetes' effects on the blood vessels (peripheral vascular disease) can slow healing of foot sores. Because of diabetic neuropathy and peripheral vascular disease, people with diabetes are at increased risk of needing amputation when leg and foot sores become gravely infected.

Severe pain in the legs and feet sometimes comes with diabetic neuropathy. Pain-killing drugs and sometimes antidepressant drugs are used to treat painful neuropathy. In most cases, the pain subsides on its own with time.

Diabetic neuropathy can also affect body functions such as digestion. A doctor may prescribe drugs to relieve these symptoms. In addition, diabetes can, over time, affect the nerves that control erection in men. A doctor can find out whether impotence is the result of emotional or physical changes, such as diabetes, and then suggest treatment or counseling.

Pregnancy

With insulin treatment available, IDDM no longer poses the threat it once did to the health of the pregnant mother. The infant of a mother with IDDM does, however, have a higher than average risk of birth defects, stillbirth, respiratory distress, and other problems at birth. A mother's careful control of her glucose is essential to the health and life of her baby. With careful diabetes control, beginning before conception if possible, it is likely that the child will be healthy in every way.

Does Diabetes Run in Families?

A susceptibility to diabetes can be inherited. The brothers and sisters of a child with diabetes have a higher than average risk of developing IDDM. However, their risk remains small-only about 1 in 20 children with a diabetic sibling will develop IDDM. In fact, an identical twin of a child with IDDM has less than a 50 percent chance of developing the disease. Scientists are still doing research to determine how and why certain factors-both inherited and environmental-sometimes lead to diabetes.

Illness and Surgery

Illness, such as influenza, and stress, such as personal losses or conflicts, can affect the body's use of glucose. During times of illness and stress, a person needs to be even more careful about keeping glucose in control.

Surgery also places unusual stress on the body. Surgical teams take special precautions when doing surgery on a person with IDDM. The best way to ensure that doctors are aware of a patient's diabetes is to tell them.

Research in Diabetes

Diabetes research is the best hope that one day a means of curing and possibly preventing diabetes will be found. In the last 10 years, diabetes researchers have made great strides in understanding this disease. Critical to this effort has been the technology developed in genetics, microbiology, immunology, and other disciplines that have given diabetes researchers the tools they need to examine at the cell level what happens in diabetes.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) was established by Congress in 1950 as an institute of the National Institutes of Health (NIH), whose mission is to improve human health through biomedical research. The NIH is the research arm of the Public Health Service under the U.S. Department of Health and Human Services.

The NIDDK conducts and supports a variety of research in diabetes and its complications. In the past several years, scientists have identified the genetic factors that are associated with both IDDM and NIDDM. A major goal of future research will be to clarify how inherited factors affect the immune or disease-fighting system to result in IDDM. Already, scientists have identified immune factors circulating in blood that indicate increased risk of developing IDDM. This information may lead to early identification of IDDM cases and will help pave the way to understanding why the immune system goes awry in IDDM.

Scientists also have a better understanding of how insulin works in glucose metabolism. For example, groups of researchers at Memorial Sloan-Kettering Cancer Center, New York; the University of California, San Francisco; Mt. Zion Hospital and Medical Center, San Francisco; and Stanford University, Stanford, California, recently cloned and analyzed the structure of the insulin receptor, a molecule on cell surfaces to which insulin must attach in order to act. Defects in receptor function have been linked to abnormalities in glucose metabolism.

Human insulin made by recombinant DNA techniques is commercially available, as are externally worn pumps that can be programmed by the wearer to deliver insulin through a catheter in the abdomen. Research is continuing on internally implantable pumps, and clinical trials on at least one such pump have been undertaken.

New treatments are being developed for the complications of diabetes. Laser photocoagulation therapy has been shown to reduce the risk of blindness in people with diabetic retinopathy. Preventive measures and medications are available to help control high blood pressure, to avoid lower extremity amputations, and to reduce the risk of tooth loss from periodontal (gum) disease. Understanding how maternal diabetes can affect the unborn child is increasing, and with it, strategies to improve the chances that such a child will be born normal and healthy.

Research on transplantation of the insulin-producing cells of the pancreas is ongoing. The aim of this research is to provide a means of transplanting insulin-producing cells into someone with diabetes without the need to suppress the immune system to prevent rejection. If successful, the procedure would eliminate the need for daily injections of insulin.

Clinical Trials

Clinical trials are one means to test new approaches to treatment that emerge from basic research. In a clinical trial, new and existing treatments are compared with each other or with no treatment.

The NIDDK is supporting and planning clinical trials that are designed to weigh the benefits and risks of various approaches to treatment of diabetes and its complications. For information about NIDDK-supported clinical trials, contact the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 31, Room 9A04, Bethesda, Maryland 20892.

Suggested Reading

The Diabetes Dictionary

Available from the National Diabetes Information Clearinghouse, Box NDIC, Bethesda, Maryland 20892, telephone [phone].

Diabetes Mellitus: Theory and Practice, Ellenberg, M., and Rifkin, H., Editors. This book is an example of medical textbooks that provide an overview of diabetes, its symptoms, epidemiology, and treatment. This text is revised periodically and published by Medical Examination Publishing Company. It is written for readers with a medical background and is available in medical libraries and possibly university libraries or through interlibrary loan at a public library.

Diabetes and Your Eyes

Available from the National Eye Institute, National Institutes of Health, Building 31, Room 6A32, Bethesda, Maryland 20892, telephone [phone].

The American Diabetes Association, listed on the next page, has a variety of periodicals and publications, at both a lay and technical level, on various aspects of diabetes.

Other Resources

American Diabetes Association National Service Center 1660 Duke Street Alexandria, Virginia 22314 [phone]

Juvenile Diabetes Foundation, International 432 Park Avenue, South, 16th Floor New York, New York 10016 [phone]

National Diabetes Information Clearinghouse Box NDIC Bethesda, Maryland 20892 [phone]