Background: C-peptide values are used for evaluation of residual β-cell function as well as endpoints in clinical trials. Therefore, it is crucial to have normative standards as a reference. This study aims to report normative fasting C-peptide values and variations across demographics in healthy adolescents included in the NHANES dataset.
Materials and Methods: In this analysis, we used fasting C-peptide data (n=2063) from the 1999-2004 NHANES dataset for participants ages 12 to < 18 yrs old.
Results: The mean ± SE age of participants was 14.99 ± 0.06; 992 were females and 1071 were males. The majority (>80%) of females and males had a BMI percentile (%ile) <85%. Among males, geometric mean C-peptide levels increased from 0.52 nmol/L at age 12, to 0.66 nmol/L at age 15 yrs. Mean values decreased slightly at age 16 and increased back to 0.66 nmol/L at age 17 yrs. Among females, C-peptide levels fluctuated around a geometric mean of 0.67 nmol/L and age did not have a significant effect on C-peptide (p=0.15). Females had significantly higher mean log-transformed C-peptide concentrations than males (p<0.0001) after adjusting for age, race, and BMI %ile category. After adjusting for age and BMI %ile category, we found that in males, non-Hispanic blacks had significantly lower C-peptide levels than non-Hispanic whites (p=0.0026), Mexican Americans (p<0.0001) and other races including multiracial (p=0.0186). Similarly, in females, non-Hispanic blacks had significantly lower concentrations than non-Hispanic whites (p=0.0093), Mexican Americans (p<0.0001), and other Hispanics (p=0.0187). BMI %ile category was positively correlated with C-peptide levels in both males and females after adjusting for age and race.
Conclusions: Here we describe normative fasting C-peptide in a healthy adolescent population. These data will provide novel information which can be used in assessing residual β-cell function and response to intervention therapy.
P. Y. Soni: None. Y. Wang: None. G. J. Eckert: None. H. M. Ismail: None.
