In the most common form of type 1 diabetes, antibodies attack the islets of langerhans, destroying all or most of the body's ability to make insulin. Each antibody attacks only one thing (sort of- some will attack a couple substances that are similar to each other) and there are many antibodies associated with diabetes.Different antibodies are associated with slightly different disease onsets and courses; most people diagnosed with type 1 diabetes have multiple antibodies at the time. In general, more antibodies = faster onset.
At my diagnosis I was tested for three; insulin antibodies (which are least likely to cause diabetes, and which I did not have), GAD-65 antibodies, which attack the glutamic acid decarboxylase around the islet cells (this antibody is the most common antibody in LADA adult onset type 1 diabetes- my levels were about 5x the upper limit of normal) and Islet Cell Antibody 512, which attacks the islets cells themselves and is more common in younger children diagnosed with type 1 diabetes- my levels of this antibody were more than 50x the upper limit of normal.
People with autoimmune complexes, particularly polyendocrine autoimmune disease, are more likely to get type 1 diabetes.
About 5% of people with Down Syndrome develop autoimmune type 1 diabetes (oddly enough, one study I read comparing adults with Down's and diabetes to adults with type 1 only showed those with Down's to have lower A1cs).
Cystic fibrosis affects the pancreas directly by impairing the pancreatic ducts. Most people with cystic fibrosis develop deficiencies of pancreatic enzymes, but have only minor dysfunction of the endocrine pancreas. However, a significant minority of people with cystic fibrosis have enough damage to the islet cells of the pancreas, or the areas nearby that allow the insulin to get out and circulate, that they have diabetes related to not having enough insulin.
In rare cases, babies are born without fully developed pancreases. In these cases, they have permanent neonatal diabetes.
Rarely, people with pancreatic cancer have their pancreata (the plural of pancreas is pancreata) removed and thereby have diabetes.
High blood sugar over times stresses the islet cells; chronic high blood sugar can lead to an inability to make insulin.
Alcoholism can damage the pancreas, sometimes to the extent that the pancreas's ability to make insulin is irrevocably impaired.
What diseases are missing from my list?