C-peptide levels in pediatric type 2 diabetes in the Pediatric Diabetes Consortium T2D Clinic Registry

Objective: To describe C-peptide levels in a large cohort of children with type 2 diabetes T2D and examine associations with demographic and clinical factors.

Methods: The Pediatric Diabetes Consortium (PDC) T2D Registry has collected clinical and biologic data from youth with T2D cared for at eight US Pediatric Diabetes Centers. In this study, we assessed C-peptide levels in 331 youth with T2D (mean age, 16.1 ± 2.5 yr; median T2D duration, 2.4 yr).

Results: Median (interquartile range) for 90 fasted C-peptide measurements was 3.5 ng/mL (2.3-4.8 ng/mL) [1.2 nmol/L (0.8-1.6 nmol/L)] and for 241 random non-fasted C-peptide measurements were 4.2 ng/mL (2.6-7.0 ng/mL) [1.4 nmol/L (0.9-2.3 nmol/L)]. C-peptide levels were lower with insulin therapy (p < 0.001), lower body mass index (p < 0.001), hemoglobin A1c (HbA1c) ≥9% (p < 0.001), and T2D duration ≥ 6 yr (p = 0.04). Among those with duration ≥6 yr being treated with insulin and with a HbA1c level ≥9.0% (75 mmol/L), 75% of the fasted and 80% of the non-fasted C-peptide values were above 0.2 nmol/L.

Conclusions: In youth with T2D, a decline in C-peptide is associated with deterioration of metabolic control and the need for insulin treatment. C-peptide levels decrease over time. However, even insulin-treated patients with 6 or more years of T2D and elevated HbA1c levels retain substantial endogenous insulin secretion.