What causes Causes of Diabetes ? 

Other types of diabetes have a variety of possible causes.
                
Genetic Mutations Affecting Beta Cells, Insulin, and Insulin Action
                
Some relatively uncommon forms of diabetes known as monogenic diabetes are caused by mutations, or changes, in a single gene. These mutations are usually inherited, but sometimes the gene mutation occurs spontaneously. Most of these gene mutations cause diabetes by reducing beta cells ability to produce insulin.
                
The most common types of monogenic diabetes are neonatal diabetes mellitus (NDM) and MODY. NDM occurs in the first 6 months of life. MODY is usually found during adolescence or early adulthood but sometimes is not diagnosed until later in life. More information about NDM and MODY is provided in the NIDDK health topic, Monogenic Forms of Diabetes.
                
Other rare genetic mutations can cause diabetes by damaging the quality of insulin the body produces or by causing abnormalities in insulin receptors.
                
Other Genetic Diseases
                
Diabetes occurs in people with Down syndrome, Klinefelter syndrome, and Turner syndrome at higher rates than the general population. Scientists are investigating whether genes that may predispose people to genetic syndromes also predispose them to diabetes.
                
The genetic disorders cystic fibrosis and hemochromatosis are linked to diabetes. Cystic fibrosis produces abnormally thick mucus, which blocks the pancreas. The risk of diabetes increases with age in people with cystic fibrosis. Hemochromatosis causes the body to store too much iron. If the disorder is not treated, iron can build up in and damage the pancreas and other organs.
                
Damage to or Removal of the Pancreas
                
Pancreatitis, cancer, and trauma can all harm the pancreatic beta cells or impair insulin production, thus causing diabetes. If the damaged pancreas is removed, diabetes will occur due to the loss of the beta cells.
                
Endocrine Diseases
                
Endocrine diseases affect organs that produce hormones. Cushings syndrome and acromegaly are examples of hormonal disorders that can cause prediabetes and diabetes by inducing insulin resistance. Cushings syndrome is marked by excessive production of cortisolsometimes called the stress hormone. Acromegaly occurs when the body produces too much growth hormone. Glucagonoma, a rare tumor of the pancreas, can also cause diabetes. The tumor causes the body to produce too much glucagon. Hyperthyroidism, a disorder that occurs when the thyroid gland produces too much thyroid hormone, can also cause elevated blood glucose levels.
                
Autoimmune Disorders
                
Rare disorders characterized by antibodies that disrupt insulin action can lead to diabetes. This kind of diabetes is often associated with other autoimmune disorders such as lupus erythematosus. Another rare autoimmune disorder called stiff-man syndrome is associated with antibodies that attack the beta cells, similar to type 1 diabetes.
                
Medications and Chemical Toxins
                
Some medications, such as nicotinic acid and certain types of diuretics, anti-seizure drugs, psychiatric drugs, and drugs to treat human immunodeficiency virus (HIV), can impair beta cells or disrupt insulin action. Pentamidine, a drug prescribed to treat a type of pneumonia, can increase the risk of pancreatitis, beta cell damage, and diabetes. Also, glucocorticoidssteroid hormones that are chemically similar to naturally produced cortisolmay impair insulin action. Glucocorticoids are used to treat inflammatory illnesses such as rheumatoid arthritis, asthma, lupus, and ulcerative colitis.
                
Many chemical toxins can damage or destroy beta cells in animals, but only a few have been linked to diabetes in humans. For example, dioxina contaminant of the herbicide Agent Orange, used during the Vietnam Warmay be linked to the development of type 2 diabetes. In 2000, based on a report from the Institute of Medicine, the U.S. Department of Veterans Affairs (VA) added diabetes to the list of conditions for which Vietnam veterans are eligible for disability compensation. Also, a chemical in a rat poison no longer in use has been shown to cause diabetes if ingested. Some studies suggest a high intake of nitrogen-containing chemicals such as nitrates and nitrites might increase the risk of diabetes. Arsenic has also been studied for possible links to diabetes.
                
Lipodystrophy
                
Lipodystrophy is a condition in which fat tissue is lost or redistributed in the body. The condition is associated with insulin resistance and type 2 diabetes.