This is a heterogeneous disorder in which there is both resistance to the action of insulin and relative insulin insufficiency. In contrast to type 1 diabetes, endogenous insulin secretion is at least partially preserved and thus most patients are not insulin dependent for acute survival (hence the former name, non-insulin-dependent diabetes). The circulating insulin levels are adequate to protect these patients from ketosis, except during periods of extreme stress. Some patients in this category can be treated with oral agents (sulfonylureas, metfor-min, and thiazolidinediones), but many are managed with insulin because their pancreases are unable to produce sufficient insulin to overcome their tissue insulin resistance. Obesity is a frequent contributing factor to the insulin resistance in this disorder.
Occasionally, it is difficult to determine whether a patient has type 1 or type 2 diabetes. This is particularly likely in a nonobese person older than 35 years of age who has never had significant ketosis but who has been treated with insulin. Unfortunately, there is no completely reliable diagnostic test. Measurement of autoantibodies in such people may not be helpful because patients with type 1 diabetes lose these markers with time. Several studies have shown that the plasma C-peptide level is a good discriminator between the two forms of diabetes. C-peptide is released during processing of proinsulin to insulin and, thus, is an indicator of endogenous insulin secretion. Values higher than 0.6nmol/l, either basal or following provocation with a 1 mg glucagon stimulus, indicate sufficient residual insulin secretion for a person to be considered in the type 2 diabetes class.
Was this article helpful?