Diabetes Mellitus Type I

Risk: Type I diabetes is usually diagnosed during childhood or adolescence, although adults can develop this disease. Approximately 12 million non-Hispanic whites had type I diabetes in 2002. However, Native Americans and Alaska Natives are about 2.3 times as likely and non-Hispanic blacks and Latinos are about 1.5 times as likely as to have diabetes as non-Hispanic whites of similar age ("National Diabetes Statistics").

Although type I diabetes tends to run in families, siblings of individuals with type I diabetes may not always get diabetes. Even though an identical twin of an individual with this disease has close to a 50% chance of developing type I diabetes, it is believed that some environmental exposure is also responsible for the development of the disease.

Individuals who have other autoimmune diseases such as Graves' disease, Hashimoto's thyroiditis, and Addison's disease are also more susceptible to type I diabetes.

Incidence and Prevalence: Approximately 1.3 million people over the age of 20 are diagnosed with type I diabetes mellitus each year ("National Diabetes Statistics"). However, it is estimated that millions have undiagnosed diabetes.

History: Symptoms may develop suddenly or gradually over days to weeks and vary widely from person to person. Common symptoms include excessive thirst and water intake (polydipsia), excessive urination (polyuria), weight loss despite normal or increased food intake, fatigue, headaches, muscle wasting, muscle cramps, vision changes, visible weight loss from loss of body fluids, anxiety, nausea, vomiting, and diarrhea and/or constipation. Excessive food intake (polyphagia) is a classic but uncommon symptom of this disease; loss of appetite (anorexia) is more commonly reported.

Physical exam: Physical findings vary with the suddenness and severity of onset of the disease. Some findings include signs of dehydration such as low blood pressure (hypotension), weak rapid pulse, dry mucous membranes (especially the mouth), and blurred vision. Breathing may be deep and rapid. Individuals with this disease tend to be thin, usually with little body fat at the time of diagnosis. However, heavy individuals can also have type I diabetes. A fruity odor to the breath may indicate ketoacidosis, a common complication of this disease.

Tests: A urine dipstick will measure glucose and ketones in the urine (both will be positive). A random blood glucose level and fasting blood glucose level will be elevated. A 2-hour-after-eating (postprandial) blood glucose level will also be elevated. Other blood tests will reflect dehydration and the effects on other blood chemicals (serum electrolytes). Further testing is usually not needed to make the diagnosis, although blood typing for human leukocyte antigen (HLA)-DR3 and HLA-DR4, considered to be specific markers for susceptibility to type I diabetes mellitus, may be helpful. Autoimmune association may also be determined by baseline thyroid function tests (for Hashimoto's thyroiditis), and measurement of morning cortisol levels (for Addison's disease) and autoantibodies (for celiac disease). In addition, the presence of antibodies to pancreatic islet cells (glutamic acid decarboxylase antibodies, or GAD antibodies) is a marker of islet cell destruction, which is typical to type I diabetes mellitus.

Periodic testing of glycosylated hemoglobin (Hb), or the HbA1c test, can give an estimate of plasma glucose control over the preceding 1 to 3 months, and may help the physician adjust the individual's insulin requirements. The insulin C-peptide test may be performed to determine if any insulin is still being produced by the body, which can guide treatment using replacement insulin.