C-Peptide ELISA

C-Peptide is the abbreviation for connecting peptide,
it is a 31-amminoacid peptide. C-Peptide of insulin is
the C-terminal cleavage product produced during
processing of the insulin prohormone to the mature
insulin molecule. Proinsulin is splited when it is
released from the pancreas into the blood - one CPeptide
for each insulin molecule. C-Peptide is devoid
of any biological activity but appears to be necessary
to maintain the structural integrity of Insulin.
In-vitro determination of Insulin and C-Peptide level
help in differential diagnosis of liver disease,
acromegaly, Cushing sindrome, familial glucose
intolerance, Insulinimia, renal failure, ingestion of
accidental oral hypoglicemic drugs or C-Peptide
induced factitious hypoglicemia.
Newly diagnosed diabetes patient often get their CPeptide
levels measured, to find if they are type 1
diabetes or type 2 diabetes. The pancreas of patients
with type 1 diabetes is unable to produce insulin and
they will therefore usually have a decreased level of
C-Peptide, while C-Peptide levels in type 2 patients is
normal or higher than normal. Measuring C-Peptide in
patients injecting insulin can help to determine how
much of their own natural insulin these patients are
still producing.
C-Peptide assays may be analytically more sensitive
than insulin assays. Measurement of the C-Peptide
may be useful in evaluating endogenous insulin
secretion in a variety of clinical conditions. Insulin and
C-Peptide are secreted into portal circulation in
equimolar concentrations, fasting levels of C-Peptide
are 5 – 10 fold higher than those of Insulin owing to
the longer half-life of C-Peptide. The liver does not
extract C-Peptide however; it is removed from the
circulation by degradation in the kidneys with a
fraction passing out unchanged in urine. Hence the
urine C-Peptide levels correlate well with fasting CPeptide
levels in serum.