Fasting C-peptide in Gestational Diabetes Mellitus

IntroductionInsulin secretion and sensitivity are thought to vary in gestational diabetes mellitus (GDM) as well as in different trimesters within the same individual.ObjectivesTo see the fasting serum C-peptide in subjects with GDM as an indicator of basal insulin secretion and to compare it to the normal glucose tolerance (NGT) control.MethodThis case-control study investigated and compared fasting serum C-peptide in 35 GDM subjects with 37, age, BMI, and trimester-matched control. GDM was diagnosed by WHO 2013 criteria. Plasma glucose was measured by the glucose oxidase method and C-peptide by a chemiluminescent immunometric assay.ResultFasting serum C-peptides were significantly higher in the GDM group than that of the NGT (NGT vs. GDM: 1.45±0.76 vs. 1.99±1.28, mean±SD, p=0.032), but no difference was observed between GDM and NGT with a BMI <25kg/m2(NGT vs. GDM: 1.25±0.44 vs. 1.37±0.77, mean±SD, p=0.597). Within the NGT group, fasting C-peptide was similar with a BMI cut-off 25kg/m2(<25 vs. ≥ 25: 1.25±0.44 vs. 1.61±0.94, p=0.159); however, within the GDM group, the fasting C-peptide was significantly higher with a BMI ≥25 kg/m2(<25 vs. ≥ 25: 1.37±0.77 vs. 2.45±1.41, mean ±SD, p=0.011). We did not observe any trimester-specific difference in fasting C-peptide between the NGT and the GDM (NGT vs. GDM: 1.55±0.45 vs. 1.67±0.57, p=0.736; 1.43±0.95 vs. 2.13±1.10, p=0.085; 1.43±0.71 vs. 1.97±1.60, p= 0.204; ng/dl, mean ± SD, for 1st, 2nd, and 3rdtrimester, respectively). Pearson correlation revealed BMI (r=0.389, p=0.001), Systolic BP (r=0.531, p<0.001), Diastolic BP (r=0.355, p=0.002), FPG (r=0.32, p=0.006) and 1hr PG on OGTT (r=0.423, p<0.001) had significant positive correlation with fasting C-peptide.ConclusionFasting C-peptide increased significantly in GDM with BMI ≥25kg/m2, but not with <25kg/m2