C-peptide
| Category | Biochemistry >> Endocrinology |
|---|---|
| Test background |
Pro-insulin is cleaved to form connecting peptide (C-peptide) and insulin prior to secretion into the portal circulation. They are secreted in equi-molar concentrations, however C-peptide is metabolised more slowly than insulin. C-peptide can be helpful in the differential diagnosis of type 1 and 2 diabetes mellitus. The insulin:C-peptide ratio can be used to diagnose use of exogenous insulin. |
| Clinical Indications |
Investigation of hypoglycaemia, where it is a useful aid to differentiate between factitious (exogenous) insulin administration and insulinoma or other forms of endogenous hyperinsulinism. It is useful to monitor pancreatic status (e.g. following pancreatectomy or pancreal/islet cell transplant) and to differentiate between type I type 2 diabetes. |
| Reference range | See report |
| Sample & container required | SST (gold top) or serum (red top) on ice rush to laboratory |
| Sample volume | 1 mL |
| Sample collection | Collect into tube on ice, centrifuge and freeze serum immediately. |
| Transport storage | Send to lab frozen. |
| Turnaround time | 1 week |
| Notes | Grossly haemolysed samples are unsuitable for this assay. |