Type 1 Diabetes Mellitus

Content provided by the Faculty of the Harvard Medical School

Type 1 Diabetes Mellitus

What Is It?

There are three types of diabetes mellitus: type 1 diabetes, type 2 diabetes and gestational diabetes . Only about 5% to 10% of people with diabetes have type 1. Type 1 diabetes, previously called insulin-dependent diabetes or juvenile diabetes, occurs when some or all of the insulin-producing cells of the pancreas are destroyed. Since the pancreas is the only place in the body where insulin is produced, this leaves the patient with little or no insulin until type 1 diabetes is treated.

Diabetes mellitus prevents the body from efficiently processing and using the energy-giving nutrients in foods. During digestion, food is broken down into basic components, such as fats, amino acids from proteins and simple sugars from carbohydrates. All of these nutrients can be processed by the liver into one type of simple sugar, glucose, which then enters the bloodstream. The hormone insulin acts somewhat like a gatekeeper — its job is to help glucose enter body cells. Because there is not enough insulin in the body, glucose (sugar) accumulates in the bloodstream instead of being channeled into muscle cells and other body cells where it can be used for energy.

Diabetes can lead to additional changes in the body's chemistry. When cells can't use glucose for energy, they have to use something else. In an effort to provide alternative fuels for the body, the liver produces acidic substances called ketones, and these build up in the blood. When ketones are made in large quantities, the blood becomes abnormally acidic. This creates a severe, potentially life-threatening condition called ketoacidosis. Ketoacidosis can cause heart problems and affect the nervous system, and within hours of causing its initial symptoms, it may put a person with type 1 diabetes at risk of coma or death.

Type 1 diabetes is an autoimmune disease, which means it begins when the body's immune system attacks cells in the body. In this case, the immune system destroys insulin-producing cells (beta cells) in the pancreas.

What causes the immune system to attack the beta cells remains a mystery. Experts suspect that a genetic (inherited) factor makes a person predisposed to the disease, and an environmental factor triggers the start of the disease. Viral infections and diet are two possible triggers. The Coxsackie, rubella and mumps viruses are all possible triggers because the disease sometimes starts after one of these infections. Cow's milk is one dietary factor that may be related to the development of type 1 diabetes. Babies who are breastfed have a lower risk of type 1 diabetes than babies who are not breastfed. Type 1 diabetes is not caused by the amount of sugar in a person's diet before the disease develops.

Type 1 diabetes is a chronic (long-lasting) disease that typically begins before age 35. It is not unusual for children ages 1 to 4 years to develop the disease, but it is diagnosed most commonly between ages 10 and 16. Type 1 diabetes affects males and females in equal numbers.

Symptoms

Symptoms usually come on suddenly and strongly, and include extreme thirst, frequent urination and vomiting. Children may start to wet the bed after having been dry at night for some time. Weight loss, with no loss of appetite, can be one of the first signs of type 1 diabetes in children. If the disease is left untreated, sugar and acid (ketone) buildup in the blood can cause weakness, confusion, coma and even death.

Type 1 diabetes affects all body systems and can cause serious, potentially life-threatening complications, including:

• Eye damage (retinopathy) — In this disorder, tiny blood vessels at the back of the eye are damaged by high blood sugar. Caught early, retinopathy can be stopped by tightly controlling blood sugar and by using laser therapy. If blood sugar remains too high, retinopathy eventually causes blindness.

• Nerve damage (neuropathy) — High blood sugar can damage nerves, leading to pain or numbness of the affected body part. Damage to nerves in the feet, legs and hands (peripheral neuropathy) is most common. Nerves that control body functions, such as digestion and urination, also can be damaged (autonomic neuropathy).

• Foot problems — Sores and blisters commonly occur on the feet of people with diabetes. If peripheral neuropathy causes numbness, a sore may not be noticed and it can become infected. Blood circulation can be poor, leading to slow healing. Left untreated, a simple sore can lead to gangrene (the death of soft tissue due to lack of blood flow), and sometimes the leg or a portion of it may need to be removed surgically (amputated).

• Kidney disease (nephropathy) — High blood sugar can damage the kidneys. If blood sugar remains high, it can lead to kidney failure.

• Heart and artery disease (atherosclerosis) — Heart and blood vessel problems can result from high blood sugar. People with type 1 diabetes are more likely to have heart disease, strokes and problems related to poor circulation.

• Diabetic ketoacidosis — This occurs when acidic substances called ketones are made by the body as a substitute energy fuel instead of glucose. Symptoms include nausea and vomiting, abdominal pain, fatigue, lethargy, and eventually (without treatment) coma and death.

• Hypoglycemia — Low blood sugar, called hypoglycemia, can result if too much insulin is taken or not enough carbohydrates are taken in to balance the insulin. Symptoms include weakness, dizziness, trembling, sudden sweating, headache, confusion, irritability, and blurry or double vision. Hypoglycemia can lead to coma if it is not corrected by eating or drinking carbohydrates, or by an injection of glucagon, a substance that makes the liver release glucose into the bloodstream.

Diagnosis

Diabetes is diagnosed by testing the blood for sugar levels. With the fasting plasma glucose (FPG) test, blood is taken in the morning after fasting (not eating anything) overnight. Typically, the body keeps blood sugar levels between 70 and 100 milligrams per deciliter (mg/dL), even after fasting. Diabetes is diagnosed if a blood sugar level after fasting is greater than 126 mg/dL. Another test, the oral glucose tolerance test (OGTT), involves measuring the blood sugar 2 hours after drinking 75 grams of glucose. Diabetes is diagnosed if the 2-hour blood sugar level is 200 mg/dL or higher. The American Diabetes Association recommends the FPG because it is easier, faster and less expensive to perform.

Expected Duration

Type 1 diabetes is a lifelong disease. People with type 1 diabetes need regular checkups, careful daily monitoring of blood sugar levels, and insulin treatment throughout life.

A small number of people with diabetes who require kidney transplants because of severe kidney damage from the disease can become exceptions to this rule. That's because a pancreas transplant occasionally can be performed at the same time that a kidney transplant is done. Since the new pancreas can make insulin, this can cure the diabetes. Because organ transplantation requires people to take medicines that suppress the immune system for the rest of their lives, pancreas transplant is not a treatment that is recommended by itself (it is only recommended for people who must have another organ transplanted, who will already require those medications long term).

Prevention

There is no way to prevent type 1 diabetes. Mothers sometimes are advised not to give cow's milk to their babies for the first year of life to prevent allergies, and possibly to prevent type 1 diabetes in genetically susceptible infants, but there is no definite proof that this prevents the disease.

Treatment

Treatment of type 1 diabetes requires insulin to be injected under the skin to make up for the insulin that is not produced by the body. Most people with type 1 diabetes need two to four injections per day. Some people use a syringe for injections. Other patients use semiautomatic injector pens that help to measure precise amounts of insulin. An increasing number of patients use insulin pumps, which deliver a regulated dose of insulin from a pack, worn at the waist or elsewhere on the body, through a needle implanted under the skin. Other ways to deliver insulin, such as inhalation, are being investigated.

In order to properly regulate insulin intake, people with type 1 diabetes need to monitor their blood sugar levels several times per day by testing a sample of blood. This is done by pricking the finger, usually with a spring-loaded device that makes the process less painful. A small drop of blood is placed on a test strip, which then is inserted into a device called a glucose monitor. A highly accurate reading of blood sugar levels is returned within seconds. Newer glucose monitors have test strips that take the blood directly from the spot that was pricked, a process that can require less blood. Some newer monitors also allow blood to be taken from the forearm, thigh or the fleshy part of the hand, which can be less painful.

People with diabetes also need to watch their diets and get regular exercise. A healthy diet for someone with type 1 diabetes is one that keeps the amount of glucose in the blood relatively constant, which makes it easier to control with insulin. A person with type 1 diabetes typically is advised to eat, exercise and take insulin at about the same times every day. Regular habits help to keep glucose levels within the normal range. Some methods of tight blood sugar control involve testing blood sugar several times during the day and taking a fast-acting insulin as needed, depending on the amount of carbohydrates being taken in. Your doctor or dietitian will help you determine the best insulin and diet schedule for you or your child.

Exercise helps to keep the heart and blood vessels healthy and helps to control blood sugar by causing muscles to use glucose and by keeping body weight down. Ask your doctor for guidance on how much and when to exercise to best control your diabetes.

When To Call a Professional

Call your health care professional if you experience a sudden increase in thirst and urination, with or without vomiting, nausea, fatigue or confusion. Unexplained weight loss always should be reported to a physician.

If you or your child have type 1 diabetes, see your doctor regularly (as your doctor advises) to make sure that you are keeping good control of your blood sugar, and to be checked for early signs of complications such as heart disease, eye problems and skin infections. Your doctor most likely will suggest that you also visit other specialists regularly, such as a podiatrist to check your feet and an ophthalmologist to check your eyes for signs of diabetes complications.

Prognosis

People with type 1 diabetes generally adjust quickly to the time and attention that is needed to monitor blood sugar, treat the disease and maintain a normal lifestyle. As time goes on, the risk of complications is substantial, but can be reduced greatly if blood glucose levels are strictly monitored and controlled.

Additional Info

American Diabetes Association ATTN: National Call Center 1701 N. Beauregard St. Alexandria, VA 22311 Toll-Free: 1-800-342-2383 http://www.diabetes.org/

American Dietetic Association 120 South Riverside Plaza Suite 2000 Chicago, IL 60606-6995 Toll-Free: 1-800-877-1600 http://www.eatright.org/

National Diabetes Information Clearinghouse 1 Information Way Bethesda, MD 20892-3560 Phone: 301-654-3327 Toll-Free: 1-800-860-8747 Fax: 301-907-8906 http://diabetes.niddk.nih.gov/

National Institute of Diabetes & Digestive & Kidney Disorders Office of Communications and Public Liaison Building 31, Room 9A04 31 Center Drive, MSC 2560 Bethesda, MD 20892-2560 Phone: 301-496-4000 http://www.niddk.nih.gov/

Weight-Control Information Network 1 Win Way Bethesda, MD 20892-3665 Phone: 202-828-1025 Toll-Free: 1-877946-4627 Fax: 202-828-1028 http://www.niddk.nih.gov/health/nutrit/win.htm

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Last updated:	January 23, 2008