Wednesday, March 14, 2012

C-peptide a useful waste product of insulin production

    Making sense out of Facebook conversations is still a mystery to me, they seem like disjointed comments about various unrelated subjects. 
    I was struggling through my FaceBook discussions yesterday and saw a reference for the use of urine C peptide test in people over the age of 30 to help distinguish between people with type 1 and type 2 diabetes.  They discussed a lady who was able to discontinue her insulin as a result of this " simple urine test that can be done at home ". I was unable to find the article today but I will keep looking.
    A word of caution
    This caught my attention and my recall of an obese patient over the age of 30 lady who  discontinued her insulin and went into ketoacidosis after getting a positive test for C-peptide.
    What is c-peptide

    C-peptide is basically a waste product of insulin production.   
There is one molecule of C-peptide produced for each molecule of insulin. C-peptide can be measured in the blood and urine and can be used to determine if someone  is making insulin. The problem is that people with Type 1 and Type 2 Diabetes can continue making small amounts of insulin and C-peptide for a long time. Remember , people with Type 1 Diabetes are not the only ones with insulin deficiency. Insulin deficiency is also the primary problem for people with type 2 diabetes.

 I have attached an article abstract from Diabetes Care on this subject.

Tomorrow- C-peptide , a clue for the " Doctor / Detective ".

Have Fun , Be Smart and buy my book, ebook ,1phone or iPad App Diabetes Office Visit
David Calder, MD

    Diabetes Care
  1. Denise L. Faustman, MD, PHD
Author Affiliations
  1. Immunobiology Laboratories, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
  1. Corresponding author: Denise L. Faustman,


OBJECTIVE To examine persistence of C-peptide production by ultrasensitive assay years after onset of type 1 diabetes and factors associated with preserving β-cell function.
RESEARCH DESIGN AND METHODS Serum C-peptide levels, a marker of insulin production and surviving β-cells, were measured in human subjects (n = 182) by ultrasensitive assay, as was β-cell functioning. Twenty-two times more sensitive than standard assays, this assay’s lower detection limit is 1.5 pmol/L. Disease duration, age at onset, age, sex, and autoantibody titers were analyzed by regression analysis to determine their relationship to C-peptide production. Another group of four patients was serially studied for up to 20 weeks to examine C-peptide levels and functioning.
RESULTS The ultrasensitive assay detected C-peptide in 10% of individuals 31–40 years after disease onset and with percentages higher at shorter duration. Levels as low as 2.8 ± 1.1 pmol/L responded to hyperglycemia with increased C-peptide production, indicating residual β-cell functioning. Several other analyses showed that β-cells, whose C-peptide production was formerly undetectable, were capable of functioning. Multivariate analysis found disease duration (β = −2.721; P = 0.005) and level of zinc transporter 8 autoantibodies (β = 0.127; P = 0.015) significantly associated with C-peptide production. Unexpectedly, onset at >40 years of age was associated with low C-peptide production, despite short disease duration.
CONCLUSIONS The ultrasensitive assay revealed that C-peptide production persists for decades after disease onset and remains functionally responsive. These findings suggest that patients with advanced disease, whose β-cell function was thought to have long ceased, may benefit from interventions to preserve β-cell function or to prevent complications.

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Your comments and questions are appreciated. David Calder,MD