Introduction: Type 1 diabetes is a disorder of chronic autoimmune destruction of pancreatic beta cells. Current model of type 1 diabetes shows that varying proportion of functioning beta cells persist even after symptomatic disease onset. This residual beta cell function can be assessed by measurement of fasting and stimulated C-peptide level. This residual proportion of beta cell mass could be associated with improved metabolic outcome.

Objectives: Measurement of fasting and post OGTT (oral glucose tolerance test) C-peptide level in type 1 diabetes population and it’s correlation with duration of diabetes and antibody status.

Methods: Observational, cross-sectional study carried out in the department of Endocrinology and metabolism, Medical College, Kolkata from march 2017 to January 2019.Total number of study subjects were 100 consecutive type 1 diabetes patients of 10 – 30 years of age.

Results: Diagnosis of diabetes in majority of cases done by 12-18 years of age. Male to female ratio was 0.78: 1. Fasting C-peptide was detectable in 75 % of cases and after stimulation detectable C- peptide increased to 89 %. Stimulated C-peptide values were significantly negatively correlated with duration of diabetes [rho= (-0.260) ; p=0.03]. Antibody positivity were found in 77 % of cases and out of that majority (47 %) cases were GAD-65 positive. Fasting and stimulated C-peptide values are significantly higher in antibody negative groups that antibody positive groups (p=< 0.001). Lowest mean fasting and stimulated C-peptide level were found in GAD-65 antibody positive groups. We found a significant negative correlation of stimulated C-peptide level with GAD-65 antibody titre in antibody positive groups (p=0.017).

Conclusion: It can be concluded that progressive decline in C-peptide level was observed with increasing duration of diabetes. Antibody negative groups had higher residual beta cell mass than antibody positive groups.

Keywords: Type 1 diabetes, C-peptide, Post OGTT, Duration of diabetes, GAD-65 antibody, IA-2 antibody, Beta cell mass.

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Dr Animesh Maiti

Associate Professor and Head, Department of Endocrinology, Medical College, Kolkata