Diabetes mellitus type 1

The most important forms of diabetes are characterized by decreases in, or the complete absence of, the production of insulin (Type 1 diabetes), or decreased sensitivity of body tissues to insulin (type 2 diabetes). The most useful 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 to date has included no C-peptide. Lack of insulin resistance, determined by a glucose tolerance test, would also be suggestive of Type 1. Many Type 2 diabetics still produce some insulin internally, and all have some degree of insulin resistance. Type I diabetes is usually an autoimmune disorder, in which the body's own immune system attacks the beta cells in the Islets of Langerhans of the pancreas, destroying them or damaging them sufficiently to reduce or eliminate insulin production. The autoimmune attack may be triggered by reaction to an infection, for example by one of the viruses of the Coxsackie virus family.

Some researchers believe that the autoimmune response is influenced by antibodies against cow's milk proteins. A large retrospective controlled study published in 2006 strongly suggests that infants who were never breast fed had twice the risk for developing Type 1 diabetes as infants who were breast fed for at least 3 months. The mechanism, if any, is not understood. Research has not been able to establish a connection between autoantibodies, antibodies to cow's milk proteins, and Type 1 diabetes. [A subtype of type 1 (identifiable by the presence of antibodies against beta cells) typically develops slowly and so is often confused with Type 2. In addition, a small proportion of Type 1 cases have the hereditary condition maturity onset diabetes of the young (MODY) which can also be confused with Type 2.

Vitamin D in doses of 2000 IU per day given during the first year of a child's life has been connected in one study in Northern Finland (where intrinsic production of Vitamin D is low due to low natural light levels) with a reduction in the risk of getting type I diabetes later in life (by 80%). Some suggest that vitamin D3 may be an important pathogenic factor in type 1 diabetes independent of geographical latitude.

Some chemicals and drugs specifically destroy pancreatic cells. Vacor (N-3-pyridylmethyl-N'-p-nitrophenyl urea), a rodenticide introduced in the United States in 1975, selectively destroys pancreatic beta cells, resulting in Type 1 diabetes after accidental or intentional ingestion. Vacor was withdrawn from the U.S. market in 1979. Zanosar is the trade name for streptozotocin, an antibiotic and antineoplastic agent used in chemotherapy for pancreatic cancer, that kills beta cells, resulting in loss of insulin production.

Other pancreatic problems, including trauma, pancreatitis, or tumors (either malignant or benign), can also lead to loss of insulin production. Currently, type 1 is treated with insulin replacement therapy, carbohydrate counting and careful monitoring of blood glucose levels using Glucose meters. Insulin delivery is also possible via an insulin pump, which allows continuous infusion of basal insulin for prolonged periods at preset levels, and the capability to program 'push doses' (i.e. boluses) of insulin as needed at meal times.

Insulin treatment must be continued indefinitely. Continuous glucose monitors are also available to alert the presence of dangerously high or low blood sugar levels. Experimental replacement of beta cells (by transplant) is being investigated in several research programs and may become clinically available in the future. Thus far, beta cell replacement has only been performed on persons over the age of 18. About 5-10% of North American diabetics 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 great part .