TYPE I DIABETES MELLITUS

What Is Type I Diabetes? The full name of this disease is type I diabetes mellitus (DM); it is also known as insulin-dependent DM (IDDM), juvenile diabetes, and early-onset diabetes, as the disease is usually diagnosed before age 30. Essentially, DM is characterized by an inability to control the level of blood glucose. After eating, food is broken down into small molecules (e.g. glucose) and absorbed into the blood stream, causing the level of blood glucose to rise. In normal individuals, this triggers the pancreas to release insulin, a hormone which lowers blood glucose by stimulating cells to utilize or store it. In type I diabetes, the insulin-producing cells (B cells, or islet cells as they are also called) have been destroyed; thus blood glucose cannot be controlled. This differs from type II diabetes, in which insulin is produced, but the body's response to it is inadequate: this is known as insulin resistance.

What Causes Type I Diabetes? Type I diabetes is a genetic disorder; that is, it tends to run in families, although the genes responsible have yet to be identified, and the pattern of inheritance is not always predictable. It is an auto-immune disease, meaning that the body's own immune system acts against the B cells of the pancreas as though they were disease-causing or foreign cells. Eighty to ninety percent of the B cells must be destroyed before high blood sugar and symptoms result; therefore the disease process may be present long before diagnosis.

What Are The Signs And Symptoms Of Type I Diabetes? The signs and symptoms of type I diabetes are due to uncontrolled high blood sugar (hyperglycemia). They include frequent urination, increased thirst, and weight loss, without decreased dietary intake. High blood sugar also renders the patient prone to minor infections like vaginal yeast infections or skin infections. Diagnosis is made by measurement of blood sugar after fasting for 8 to 12 hours. If levels of insulin drop dangerously low, patients are susceptible to a serious complication called diabetic ketoacidosis (DKA); in this state, blood sugar is incredibly high and the body processes fats into ketoacids, which alter the acid-base balance of bodily fluids. DKA causes nausea, abdominal pain, vomiting, and increased urination. If untreated, DKA can lead to severe dehydration and even coma.

How Is Type I Diabetes Treated? The goal of treatment in diabetes is to maintain near-normal levels of blood sugar in order to prevent the short- and long-term complications discussed below. Type I diabetics require insulin administered by injection. Many different formulations are available, differing mostly in their length of action. A treatment regimen should be designed to suit a patient's lifestyle; multiple daily injections corresponding with meal times offer the best blood sugar control, but may be inconvenient for some individuals. Patients must closely monitor their own blood sugar to ensure that it remains neither too high nor too low. Consultation with a dietitian is an important part of treatment. A significant recent Canadian contribution to treatment has been the demonstration that islet cells from human donors can be injected into diabetic recipients, survive in their livers and successfully control their levels of blood sugar for at least a year. The recipients must take drugs that suppress the immune response to prevent rejection of the transplanted cells. The full potential of this promising approach remains to be assessed; the obtainment of an adequate supply of donor cells remains a considerable problem.

What Are The Complications Of Diabetes? A recent large-scale study of sugar control in diabetics has shown that maintenance of normal-range blood sugar is crucial in the prevention of the long-term complications of diabetes. Sustained high levels of blood sugar lead to a number of major complications: retinopathy, kidney disease, neuropathy, diabetic foot, and atherosclerosis. Diabetic retinopathy is a disease of the tiny blood vessels of the retina in the eye, causing growth of new vessels and scar tissue formation which can lead to blindness. As some degree of retinopathy will occur in more than 90% of diabetics, yearly referral to an ophthalmologist is recommended. Diabetic kidney disease, affecting up to 15% of type I diabetics, is also caused by changes to small arteries in the kidneys. The result is protein loss in the urine, scarring and atrophy of the kidneys, and in some patients, end-stage renal disease requiring dialysis or transplant. High blood sugar can be detrimental to the nerves supplying all parts of the body, a condition known as diabetic neuropathy. The most common manifestation of diabetic neuropathy is known as "glove and stocking" syndrome, in which the patient loses sensation in the hands and feet, causing susceptibility to cuts and other minor trauma. The combination of vascular problems, neuropathy and vulnerability to infection can lead to serious wounds, ulcers, and inflammatory conditions in the feet which, unnoticed, can progress so far as to require amputation. The leading cause of death in patients with diabetes is macrovascular disease, or disease of larger arteries. The risk of heart attack is doubled in men with diabetes, and quadrupled in women; in both sexes, the risk of stroke is doubled. To follow the development of macrovascular complications, blood pressure, cholesterol, and other risk factors must be closely monitored.