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12/05/2009 02:53 PM

C-peptide test

Posts: 5
New Member

Has anyone here ever had or heard of having a normal result on a c-peptide test but still having an insulinoma ?

12/20/2009 09:58 PM
Posts: 31

Hello Johnny

I was always given the impression that my blood test results were inconclusive to me having an insulinama even thought I thought I was hypoglycemic.

My C-Peptide levels were never inapproptiate to my blood glucose values. (Doctor talk)

I have since had an insulinoma removed and now no longer need jelly beans and glucose tablets with me every where I go. Yippee

I never had nausia mind you.

Good luck with your investigations


07/22/2012 03:09 AM
Posts: 16
New Member

I'm wondering that exact same thing myself - I'll try to find out for sure during my Endocrinology appointment on 7/30/2012.

'Normal' C-Peptide (according to my primary, can't see that result - just the Hemoglobin A1C that returns 'normal'), but I also have an absolutely NOT normal fasting blood-Insulin at 16mU/L (7/6/2012). Supposed to be between 3-11 mU/L (though I've heard 6mU/L is cause for concern). And which of course makes no sense at all because Proinsulin splits into a perfect 1:1 ratio (or is supposed to), that's actual Insulin (removed from the blood by all of the cells in the body requiring it, and all excesses by the liver) and then C-Peptide (removed by the kidneys, at 5x later than actual Insulin).

Apparently from what I am reading some people, case studies, who had Insulinoma didn't even present with Hypoglycemic events/attacks, while others are told they don't have Hypoglycemia (despite having a majority or all of the symptoms) because of their A1C or even because its not caught on the glucose tests (go figure). It appears to be different for almost everyone, symptoms and labs. That's why these suckers are so damn hard to diagnose (properly)...

07/23/2012 12:22 AM
Posts: 16
New Member

Here's something I've found (unfortunately, can't get the full article BUT):

Abnormalities of proinsulin processing in functioning insulinomas: clinical implications 2265.2004.02095.x/abstract


OBJECTIVE Abnormal proinsulin processing in insulinomas may result in secretory granules containing both insulin and proinsulin, a finding not encountered in healthy β-cells. The aim of this study was to test whether such abnormalities in the proinsulin to insulin conversion have clinical implications in patients with hypoglycaemic disorders.

DESIGN Case-series.

PATIENTS AND METHODS Fifteen patients with histologically confirmed insulinoma and two patients with islet cell hyperplasia were included. The immunohistochemical distribution pattern of proinsulin within the tumour cells was classified as Golgi pattern (predominantly perinuclear immunolabelling) or diffuse pattern (immunolabelling in the periphery of the cells, indicating the presence of proinsulin in secretory granules). Data obtained from the 72-h fast and arterial calcium stimulation and hepatic venous sampling (ASVS) test were related to the morphological classification.

RESULTS Six insulinomas exhibited a diffuse proinsulin distribution pattern, while nine insulinomas and two islet cell hyperplasias disclosed a Golgi pattern. Median proinsulin concentrations at the termination of the fast tended to be higher in patients with the diffuse proinsulin distribution pattern than in patients with the Golgi pattern (86•9 vs. 18•8 pmol/l, P = 0•07). Higher insulin (P < 0•005) and proinsulin (P < 0•05) concentrations were significantly correlated with earlier occurrence of hypoglycaemia during the prolonged fast. During the ASVS test, tumours with the diffuse proinsulin distribution pattern exhibited a higher increase in both insulin (median, 37•3- vs. 10•5-fold, P < 0•05) and proinsulin (6•3- vs. 1•6 fold, P < 0•005) concentrations following calcium stimulation than the tumours with the Golgi pattern.

CONCLUSIONS Abnormalities in the proinsulin to insulin conversion in patients with insulinomas and islet cell hyperplasia correlate with impaired regulation of both insulin and proinsulin secretion during the prolonged fast as well as the ASVS test.

With that stated... it sure sounds like a strong possibility for me. I cannot find anything else anywhere (other than with diabetics who OD on synthetic Insulin accidentally - or others intentionally in the case of suicide) to explain how it is possible to have a ‘normal' C-Peptide but an abnormally high blood-Insulin level, like I do. It is medical law, basically, that Proinsulin splits into a perfect 1:1 molecule ratio of actual Insulin and C-Peptide (in “normal, healthy people”)...

07/23/2012 01:13 AM
Posts: 16
New Member

Here's another one:

Insulin, C-peptide and proinsulin for the biochemical diagnosis of hypoglycaemia related to endogenous hyperinsulinism


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