Diabetes mellitus type 1 (Type 1 diabetes, T1D, T1DM, IDDM, juvenile diabetes) is a form of diabetes mellitus. Type 1 diabetes is an autoimmune disease that results in destruction of insulin-producing beta cells of the pancreas. Lack of insulin causes an increase of fasting blood glucose (around 70-120 mg/dL in nondiabetic people) that begins to appear in the urine above the renal threshold (about 190-200 mg/dl in most people), thus connecting to the symptom by which the disease was identified in antiquity, sweet urine. Glycosuria or glucose in the urine causes the patients to urinate more frequently, and drink more than normal (polydipsia). Classically, these were the characteristic symptoms which prompted discovery of the disease.
Type 1 diabetes is fatal unless treated with exogenous insulin. Injection is the traditional and still most common method for administering insulin; jet injection, indwelling catheters, and inhaled insulin has also been available at various times, and there are several experimental methods as well. All replace the missing hormone formerly produced by the now non-functional beta cells in the pancreas. In recent years, pancreas transplants have also been used to treat type 1 diabetes. Islet cell transplant is also being investigated and has been achieved in mice and rats, and in experimental trials in humans as well. Use of stem cells to produce a new population of functioning beta cells seems to be a future possibility, but has yet to be demonstrated even in laboratories as of 2008.
Type 1 diabetes (formerly known as "childhood", "juvenile" or "insulin-dependent" diabetes) is not exclusively a childhood problem; the adult incidence of type 1 is noteworthy—in fact, many adults who contract type 1 diabetes are misdiagnosed with type 2 due to confusion at this point.
There is currently no clinically useful preventive measure against developing type 1 diabetes, though a vaccine has been proposed and anti-antibody approaches are also being tested. Most people who develop type 1 were otherwise healthy and of a healthy weight on onset, although some can be mildly overweight to slightly obese upon diagnosis of type one. Unfortunately, however, they can lose weight quickly and dangerously, if not promptly diagnosed. Although the cause of type 1 diabetes is still not fully understood, the immune system damage is characteristic of type 1.
The most definite laboratory test to distinguish type 1 from type 2 diabetes is the C-peptide assay, which is a measure of endogenous insulin production since external insulin has not (to date) included C-peptide. The presence of anti-islet antibodies (to Glutamic Acid Decarboxylase, Insulinoma Associated Peptide-2 or insulin), or lack of insulin resistance, determined by a glucose tolerance test, would also be suggestive of type 1. Many type 2 diabetics continue to produce insulin internally, and all have some degree of insulin resistance.
Testing for GAD 65 antibodies has been proposed as an improved test for differentiating between type 1 and type 2 diabetes as it appears that the immune system malfunction is connected with their presence. Further, injections with GAD65 has in clinical trials delayed the destruction of beta cells for at least 30 months, without serious adverse effects. Patients treated with the substance showed higher levels of regulatory cytokines, thought to protect the beta cells. Phase III trials are under way in the USA and in Europe, with most sites actively pursuing participants.
Type 1 treatment must be continued indefinitely in essentially all cases. Treatment need not significantly impair normal activities, if sufficient patient training, awareness, appropriate care, discipline in testing and dosing of insulin is taken. However, treatment is burdensome for patients; insulin is replaced in a non-physiological manner, and this approach is therefore far from ideal. The average glucose level for the type 1 patient should be as close to normal (80–120 mg/dl, 4–6 mmol/L) as is ''safely'' possible. Some physicians suggest up to 140–150 mg/dl (7-7.5 mmol/L) for those having trouble with lower values, such as frequent hypoglycemic events. Values above 400 mg/dl (20 mmol/L) are sometimes accompanied by discomfort and frequent urination leading to dehydration. Values above 600 mg/dl (30 mmol/L) usually require medical treatment and may lead to ketoacidosis, although they are not immediately life-threatening. However, low levels of blood glucose, called hypoglycemia, may lead to seizures or episodes of unconsciousness and absolutely must be treated immediately, via emergency high-glucose gel placed in the patient's mouth, intravenous administration of dextrose, or an injection of glucagon.
It is estimated that about 5%–10% of North American diabetes patients have type 1. The fraction of type 1 in other parts of the world differs; this is likely due to both differences in the rate of type 1 and differences in the rate of other types, most prominently type 2. Most of this difference is not currently understood. Variable criteria for categorizing diabetes types may play a part. The longest surviving Type I diabetes patient is Gladys Dull, who has lived with the condition for over 83 years.
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