Large genome-wide association studies have identified dozens of other genes associated with type 1 diabetes risk, mostly genes involved in the immune system. Chemicals and drugs
Some medicines can reduce insulin production or damage β cells, resulting in disease that resembles type 1 diabetes. The antiviral drug didanosine triggers pancreas inflammation in 5 to 10% of those who take it, sometimes causing lasting β-cell damage. Similarly, up to 5% of those who take the anti-protozoal drug pentamidine experience β-cell destruction and diabetes. Several other drugs cause diabetes by reversibly reducing insulin secretion, namely statins (which may also damage β cells), the post-transplant immunosuppressants cyclosporin A and tacrolimus, the leukemia drug L-asparaginase, and the antibiotic gatifloxicin. Pyrinuron (Vacor), a rodenticide introduced in the United States in 1976, selectively destroys pancreatic beta cells, resulting in type 1 diabetes after accidental poisoning. Pyrinuron was withdrawn from the U.S. market in 1979. Diagnosis
Diabetes is typically diagnosed by a blood test showing unusually high blood sugar. The World Health Organization defines diabetes as blood sugar levels at or above 7.0 mmol/L (126 mg/dL) after fasting for at least eight hours, or a glucose level at or above 11.1 mmol/L (200 mg/dL) two hours after an oral glucose tolerance test.
Pancreases from people with type 1 diabetes also have signs of beta cell apoptosis, linked to activation of the janus kinase and TYK2 pathways.Partial ablation of beta-cell function is enough to cause diabetes; at diagnosis, people with type 1 diabetes often still have detectable beta-cell function. Once insulin therapy is started, many people experience a resurgence in beta-cell function, and can go some time with little-to-no insulin treatment – called the "honeymoon phase". This eventually fades as beta-cells continue to be destroyed, and insulin treatment is required again. Beta-cell destruction is not always complete, as 30–80% of type 1 diabetics produce small amounts of insulin years or decades after diagnosis. Alpha cell dysfunction
Onset of autoimmune diabetes is accompanied by impaired ability to regulate the hormone glucagon, which acts in antagonism with insulin to regulate blood sugar and metabolism. Progressive beta cell destruction leads to dysfunction in the neighboring alpha cells which secrete glucagon, exacerbating excursions away from euglycemia in both directions; overproduction of glucagon after meals causes sharper hyperglycemia, and failure to stimulate glucagon upon hypoglycemia prevents a glucagon-mediated rescue of glucose levels. Hyperglucagonemia
Onset of type 1 diabetes is followed by an increase in glucagon secretion after meals. Increases have been measured up to 37% during the first year of diagnosis, while c-peptide levels (indicative of islet-derived insulin), decline by up to 45%. Insulin production will continue to fall as the immune system destroys beta cells, and islet-derived insulin will continue to be replaced by therapeutic exogenous insulin.