Diabetes Mellitus

Diabetes Mellitus

History of diabetes

Incidence of diabetes

Types of diabetes

Pre-diabetes

Tests for diabetes

Treatment for diabetes

Resources

Diabetes mellitus, what is informally called diabetes, is a group of diseases characterized by high levels of glucose in the blood resulting from defects in insulin production (insulin deficiency), insulin action (insulin resistance), or both. Insulin is a hormone produced by the pancreas. When eaten, foods are converted to a type of sugar called glucose that enters the bloodstream. Insulin is needed to move glucose into the body cells where it is used for energy, and excesses are stored in the liver and fat cells. Insufficient amounts of working insulin cause blood sugar levels to rise and large amounts of glucose are excreted in the urine. Consistently high levels of glucose in the bloodstream damage the nerves and blood vessels, and can lead to heart disease, stroke, high blood pressure, blindness, kidney disease, amputations, and dental disease.

The exact cause of diabetes is unknown, although genetics and environmental factors such as obesity and lack of exercise appear to play roles. Diabetes can be associated with serious complications and death, but people with diabetes can take an active role in controlling the disease and lowering the risk of complications.

History of diabetes

The history of diabetes mellitus dates back to ancient Egypt, where its symptoms were described around 2000 BC. The Greeks later gave the disease its name in the first century AD. The word diabetes means siphon, which describes a major symptom of the condition, frequent urination. Mellitus means honey, and depicts one of the early signs of diabetes, sugar in the urine.

Incidence of diabetes

Over 18 million people in the United States had diabetes as of 2005, or about 7% of the population. About one-third of diabetes victims are unaware that they have the disease. Higher rates of diabetes occur in certain populations: 13% of African Americans, 10.2% of Latino Americans, and 15.1% of Native Americans has diabetes. Prevalence of diabetes increases with age. Approximately 176, 500 people less than 20 years of age have diabetes (which is about one in every 400 to 600 children and adolescents [about 0.2%]), but about 9.6% of all people age 20 years or older has diabetes and approximately 20.9% of all people age 60 and older has diabetes. In the United States, 8.8% of all women and 10.5% of all men have diabetes. Over 1.5 million people over the age of 20 years are newly diagnosed with diabetes each year. Over 450, 000 deaths each year in the United States are attributed to diabetes.

Types of diabetes

There are three major types of diabetes: type 1, type 2, and gestational diabetes. Type 1 diabetes was previously called insulin-dependent diabetes or juvenile-onset diabetes. Type 1 diabetes develops when the body’s immune system destroys pancreatic beta cells, the only cells that produce insulin. The body, in turn, produces little or no insulin, resulting in insulin deficiency. Without insulin, the body is unable to use glucose for energy and begins to break down fats for fuel. Ketones are formed when fat is burned for energy. Excess ketones build up in the blood and lower the blood pH value leading to ketoacidosis.

Symptoms of type 1 diabetes usually appear suddenly and include increased thirst, frequent urination, increased hunger, tiredness, and weight loss. Risk factors for type 1 diabetes include autoimmune, genetic, and environmental factors. Although it usually begins when people are under the age of 30 years, type 1 diabetes may occur at any age. Almost 10% of the United States diabetes population has type 1 diabetes.

Type 2 diabetes was previously called noninsulin-dependent or adult onset diabetes. It begins as insulin resistance, a disorder in which normal-to-excessive amounts of insulin is made by the body, but the cells cannot use insulin properly. The ability to make insulin gradually decreases with time due to the progressive nature of the disease. In its early stages, type 2 diabetes often has no symptoms. When they do occur, symptoms may initiate gradually and include fatigue, dry skin, numbness or tingling in hands or feet, frequent infections, slow healing of cuts and sores, problems with sexual function, and increased hunger and thirst. With type 2 diabetes, hyperosmolar coma can develop from blood glucose levels (often referred to as blood sugar) becoming dangerously high. If the elevated blood sugar is not adequately controlled, it can cause severe dehydration, a serious condition requiring immediate treatment. Type 2 diabetes is associated with obesity, family history of diabetes, prior history of gestational diabetes, impaired glucose tolerance, physical inactivity, and race/ethnicity. Type 2 diabetes is diagnosed in children and adolescents in increasing numbers. About 85% of the U.S. diabetic population has type 2 diabetes.

Gestational diabetes occurs during pregnancy and affects 4% of all pregnant women. During pregnancy, the placenta supplies the baby with glucose and water from the mother’s blood. Hormones made by the placenta are needed for pregnancy, but can keep the mother’s insulin from functioning efficiently. As the pregnancy continues, more of these hormones are manufactured. When the mother is not able to make enough insulin to compensate for the increased hormone levels and to maintain normal blood glucose, gestational diabetes develops. Treatment is required to normalize maternal blood glucose levels to avoid complications in the fetus. After pregnancy, up to 10% of women with gestational diabetes are found to have type 2 diabetes. Women who have had gestational diabetes have a 20 to 50% chance of developing diabetes in the next five to ten years.

Pre-diabetes

Before type 2 diabetes fulminates (fully develops), people with diabetes usually have a pre-diabetic condition in which blood glucose levels are higher than normal, but not yet high enough for a diagnosis of diabetes. At least 16 million people in the United States between the ages of 40 to 74 years have pre-diabetes. Pre-diabetes is sometimes referred to as insulin resistance, impaired glucose tolerance or impaired fasting glucose. With pre-diabetes, a person is likely to develop diabetes and may already be experiencing the adverse health effects Research has shown that long term damage to the heart and circulatory system may already be occurring during pre-diabetes. Diet, increased activity level, and medication may help to prevent or delay type 2 diabetes from developing. If untreated, most people with pre-diabetes develop type 2 diabetes within three to ten years.

Tests for diabetes

There are three test methods used to diagnose diabetes and each must be confirmed, on a subsequent day, by any one of the three methods. The first method includes symptoms of diabetes (increased urination, increased thirst, unexplained weight loss) plus a casual plasma glucose concentration (blood test taken any time of day without regard to time since last meal) of equal to or greater than 200 mg. The second test method is a fasting plasma glucose (no caloric intake for at least eight hours) of equal to or greater than 126 mg. The third method is a two-hour after meal blood sugar of equal to or greater than 200 mg during an oral glucose tolerance test. Testing for diabetes should be considered in all individuals at age 45 years and above (particularly if overweight), and if normal, should be repeated every three years. Testing should be considered at a younger age or carried out more frequently in individuals who are overweight and who have additional risk factors among the following:

• First-degree relative with diabetes,

• Habitually physically inactive lifestyle,

• Member of high-risk ethnic population (African-American, Hispanic-American, Native American, Asian American, Pacific Islander),

KEY TERMS

Autoimmune response— Misdirected immune response in which the body’s immune system accidentally recognizes the body’s own cells as foreign and destroys them. Type 1 diabetes results from an auto-immune response in which the body destroys the beta cells in the pancreas.

Gestational diabetes— A type of diabetes that occurs in pregnancy.

Glucose— Simple sugar made from other carbohydrates that is circulated in the blood at a narrow limit of concentration. Also known as blood sugar.

Hyperosmolar coma— A coma related to high levels of glucose in the blood and requiring emergency treatment. Ketones are not present in the urine; can occur in Type 2 diabetes that is out of control.

Impaired fasting glucose— A condition in which fasting glucose levels are greater than 110 mg, but less than 126 mg. Now known as pre-diabetes.

Impaired glucose tolerance— A condition in which blood glucose levels rise after meals to levels that are higher than normal. Now called pre-diabetes.

Insulin deficiency— A condition in which little or no insulin is produced by the body. Insulin resistance—Inability to use the insulin made by the body

Ketoacidosis— Formation of ketones (acetones) in the blood from lipid (fat) metabolism and a high blood acid content. Occurs in uncontrolled Type 1 diabetes.

Ketones— Acids indicating insufficient insulin that converts fat into glucose in the blood.

Type 1 diabetes— A condition in which the body makes little or no insulin (insulin deficiency). People with this type of diabetes must take injections of insulin.

Type 2 diabetes— A condition in which the body makes insulin but the cells cannot use it well (insulin resistance). It is treated with diet, exercise, and diabetes medication.

• Previous delivery of baby weighing greater than 9 lb (4.1 kg) or history of gestational diabetes,

• High blood pressure,

• HDL cholesterol less than 35 mg or a triglyceride level greater than 250 mg,

• PCOS (polycystic ovarian syndrome),

• Impaired glucose tolerance or impaired fasting glucose, and

• History of vascular disease.

other tests used in the management of diabetes include c-peptide levels and hemoglobin A1c levels. C-Peptide levels determine if the body is still producing insulin. C-Peptide is the connecting peptide portion of the insulin molecule that is produced in the pancreas. C-Peptide and insulin are secreted into the bloodstream in equal amounts by the pancreas. Measurement of C-Peptide is a reliable indicator of the amount of insulin produced by the person’s pancreas. HbA1c (hemoglobin A1c) measures the average blood sugar control over a two to three month period. The A1c goal recommended by the American Diabetes Association is less than 7%, which correlates with average blood sugars of less than 150 mg.

Treatment for diabetes

Diabetes is treated with meal planning, exercise, medication, and blood glucose monitoring. Meal planning involves eating the right amount of food at the right time. Carbohydrates have the greatest impact on blood sugars. Keeping track of carbohydrates and spreading them throughout the day helps to control blood sugars. Exercise helps to reduce stress, control blood pressure and blood fats, and improves insulin resistance.

Diabetes medications include oral agents and insulin. There are several classes of oral medications. Sulfonylureas and meglitinides help the pancreas to produce more insulin. Alpha-glucosidase inhibitors slow down the digestion and absorption of starches and sugars. Biguanides stop the liver from releasing extra sugar when it is not needed. Thiozolidinediones treat insulin resistance.

Various types of insulin are available and have different action times designed to match to physiological needs of the body for persons who no longer make enough insulin. The body requires a continuous, low level of insulin acting to meet baseline needs. Long-acting insulins provide the baseline or basal insulin needs. The body also requires insulin to cover carbohydrates eaten. Short-acting insulins provide coverage for meal boluses. With the wide variety of diabetes medications, the physician can determine a treatment plan that works best for the individual.

Blood glucose monitoring serves as the cornerstone tool for measuring the effects of food, exercise, and diabetes medications. Patients can check their blood sugars at various times of the day to keep track of how well the current treatment plan is keeping the sugars under control. Results of tests are recorded and taken to the physician’s office for the doctor to evaluate trends and adjust the treatment plan.

Additional management of diabetes is geared toward prevention of complications. Eye problems may have no symptoms in their early, treatable stages; therefore annual dilated eye examinations are needed. Urine should be checked annually for the protein microalbumin. Poor circulation, nerve damage, and difficulty fighting infections can make foot problems serious considerations for people with diabetes. Daily self-foot examinations and foot exams at each physician visit can help identify problems early. Blood fat (lipids–cholesterol and triglyceride) levels should be checked annually.

See also Acids and bases; Metabolic disorders; Metabolism.

Resources

BOOKS

Collazo-Clavell, ed. Mayo Clinic on Managing Diabetes. Rochester, MN: Mayo Clinic, 2006.

Kahn, C. Ronald, ed. Joslin’s Diabetes Mellitus. Philadelphia, PA: Lippincott Williams & Wilkins, 2005.

PERIODICALS

Davidson, Mayer B, MD. “American Diabetes Association: Clinical Practice Recommendations 2003.” Diabetes Care (2003): 26 Supp1.

OTHER

American Diabetes Association <http://www.diabetes.org/main/application/commercewf> (accessed November 28, 2006).

Margaret Meyers

Phyllis Tate