Soni PY, Wang Y, Eckert GJ, et al. - In view of the utility of C-peptide values in assessing residual β-cell function and as endpoints in clinical trials, it is important to have normative standards as a reference. This analysis of healthy non-diabetic adolescents incorporated in the NHANES dataset was an attempt to unveil fasting C-peptide values and variations across demographics in this population. Findings will contribute novel information helpful in evaluating residual β-cell function and response to intervention therapy.

• The 1999-2004 NHANES dataset was used to analyze fasting C-peptide data for 2,063 participants ages 12 to < 18 years old (mean±SE age was 14.99±0.06 years; 992 females and 1071 males, more than 80% had a BMI percentile of < 85%).

• In males, geometric mean C-peptide levels elevation from 0.51 nmol/L at age 12, to 0.65 nmol/L at age 15 years was most remarkable.

• Fluctuation of levels around a geometric mean of 0.67 nmol/L was seen in females.

• Significantly higher mean log-transformed C-peptide levels were detected in females vs males post-adjusting for age, race, and BMI percentile category.

• In both genders, post-adjustment for age and BMI percentile category, significantly lower C-peptide levels were found in non-Hispanic blacks, vs non-Hispanic whites and Mexican Americans.

• Despite this, greater insulin as well as HOMA-IR were identified in non-Hispanic blacks vs non-Hispanic whites.

• These observations offer vital insight into assessing racial disparities in endogenous insulin release and clearance.