Insulin (C-peptide) C-peptide and the hormone insulin are created from a larger molecule called proinsulin and stored in the beta cells of the pancreas. Intact proinsulin undergoes enzymatic cleavage to become des-31,32-proinsulin and des-64,65-proinsulin and eventually, insulin and C-peptide (an inactive peptide chain). Although insulin and C-peptide are secreted in equimolar amounts from beta-cells, C-peptide has a longer half-life and is present in peripheral blood in higher molar concentrations than insulin, making it less prone to marked fluctuations. The measurement of plasma insulin, C-peptide and proinsulin concentrations has been identified as the most useful test in identifying the cause of hypoglycaemia. Type 1 and type 2 are the two most common types of diabetes and although both of the types are characterized by high blood glucose, the pathogenesis between the two differ. The insulin/C-peptide test is useful in order to differentiate insulin-dependent patients from non-insulin-dependent patients. Overall raised plasma insulin, C-peptide, and proinsulin concentrations in the presence of hypoglycemia can indicate endogenous hyperinsulinaemia which is often seen in people with early stage type 2 diabetes mellitus. In general, c-peptide is considered to be a reliable marker of residual beta-cell function and serum or urine C-peptide determinations, in conjunction with blood glucose and insulin levels, aid in the differential diagnosis of hypoglycemia. Early assays for insulin, proinsulin, and C-peptide were competitive RIAs, however most commercial assays are now competitive (Insulin and C-peptide) or two-site enzyme immunoassays (total of intact proinsulin).
Reagents for Immunoassay Development
Mab to C-peptide • Reacts with C-peptide of human proinsulin • > 98% pure (sequential precipitation using caprylic acid and ammonium sulphate)
Suitable for use in Competitive ELISA
Endocrine Disorders - Reagents for Assay Development
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