Markers of beta cell function in type 1 diabetes mellitus

Type 1 diabetes mellitus is a multifactorial autoimmune disease characterized by destruction of insulin producing pancreatic beta cells that results in insulin deficiency and fasting hyperglycemia. It is now well known that the clinical onset of the disease represents the end stage of an immunological process that occurs over a course of months to years. During this period the presence of autoantibodies against different islet antigens can be detected by the use of standardized assays. The rate of beta cell loss is quite variable among different individuals and at onset ketoacidosis represents still a life threatening complication of the disease. The Diabetes Control and Complication Trial (DCCT) has clearly shown that the preservation of beta cell function in type 1 diabetic subjects results in a better metabolic control and significantly reduces the risk of microvascular complications. Consequently, markers of beta cell function represent important tools to make an early diagnosis and to evaluate the impact of new therapies on the natural history of the disease. The present review will focus on clinical markers currently available (intravenous glucose tolerance test, i.v.GTT, oral glucose tolerance test, OGTT, basal and stimulated C-peptide) to assess the beta cell function in type 1 diabetes.