Type 1 diabetes mellitus refers to the absolute deficiency of insulin due to non working of the pancreas. This is called, medically, insulinopenic. The treatment is by administration of exogenous insulin. The causes are usually auto immune. It may occur at any age and not necessarily during the young age, as was once believed.
Type 2 diabetes mellitus refers to those with insufficient insulin secretion or resistance to the effect of insulin.
Type 3 diabetes mellitus. Type 3a and 3b are not officially classified. However, 3a refers to genetic defects in beta cells and 3b refers to genetic defects in how the body responds to insulin. Type 3c is called pancreatogenic diabetes which is caused by destruction of the exocrine part of pancreas due to tumors( benign or malignant), surgery, recurrent infection of the pancreas( pancreatitis) , or hemtochromatosis. Type 3 diabetes is often referred to as diabetes of the brain.
Type 4 diabetes mellitus refers to the older population ( those above the age of 65 years) affected by diabetes, usually due to insulin resistance.
Type 5 diabetes mellitus is malnutrition induced diabetes affecting lean young adults and have severe insulin deficiency without insulin resistance .
Besides the above, Gestational Diabetes refers to those who have diabetes when pregnant and this resolves when the delivery is over. This is referred to as a pre-diabetes state in that such women may develop type 2 diabetes 5-6 years later.
Latent autoimmune diabetes of adults, referred to as LADA, is referred to as type 1.5 where the body habitus resembles that of those with type 2 diabetes, but the treatment is with insulin. This is due to an autoimmune destruction of the pancreas as is diagnosed by high titers of the antibody GAD65.
Those with type 2 diabetes may develop secondary failure of the pancreas as the age advances or duration of diabetes progresses. This may cause such patients to be non responsive to oral medicines and they need to be switched over to insulin. This does not mean they have been converted to type 1 diabetes.
Diabetes Insipidus is due to a defect in the hormone vasopressin produced by the pituitary gland that is characterized by excessive amounts of urine. This is not due to a pancreatic disorder.
