Fasting serum C-peptide level may not be low in young-onset diabetes

Background: Diabetes mellitus (DM) is one of the growing health problems among the young population. Secretory defect of insulin is an important cause, and it can be assessed by measuring fasting serum C-peptide level. Aim: The aim of this article is to assess fasting serum C-peptide in young-onset DM individuals. Materials and Methods: This case–control study was conducted in the Department of Endocrinology, Bangabandhu Sheikh Mujib Medical University (BSMMU) from March 2015 to February 2017. For this purpose, 40 individuals with DM (irrespective of DM type; age range: 11–29 years) were enrolled as case and an equal number of young healthy individuals as control. Demographic profiles, clinical profiles, and serum C-peptide were recorded in a standard and pre-tested structured datasheet. C-peptide was measured by the chemiluminescent immunometric assay. Results: Median fasting C-peptide was 2.67 [interquartile range (IQR) 1.06–4.07, range 0.12–20.0] ng/mL in diabetes individuals, whereas it was 2.19 (IQR 1.36–2.94, range 0.44–9.85) ng/mL in the control group; the difference was insignificant (P = 0.331). Waist circumference (WC) was significantly higher in the young diabetes group in comparison to that of control subjects and so were the plasma glucose values and diastolic blood pressure (P < 0.05 for all). Diabetic participants with low C-peptide group had significantly lower body mass index (BMI) and WC and higher fasting plasma glucose (FPG) and HbA1c in comparison to others (P < 0.05 for all); whereas the high C-peptide group had opposite body indices (higher BMI and WC) and glycemic parameters (lower FPG and HbA1c) (P < 0.05 for all). The classic hyperglycemic symptoms were more common in the low C-peptide group (P = 0.029). In participants with diabetes, C-peptide positively correlated with BMI and WC, whereas it showed a negative correlation with age (P < 0.05 for all). In the control group, C-peptide positively correlated with WC only (P = 0.018). Conclusion: The level of fasting serum C-peptide in diabetic subjects was similar to healthy controls, and it was higher in those subjects who had higher BMI, WC, and lower age.