The urinary C-peptide excretion in normal healthy children.

The 24 h urinary C-peptide excretion was determined in 137 normal healthy children, 52 girls and 85 boys, 3-15 years of age. No significant difference was found between boys and girls. Median value of urinary C-peptide for boys and girls was 0.24 nmol/kg/24 h with a range of 0.07-0.61 nmol/kg/24 h. Urinary C-peptide correlated positively and significantly with age, weight, height, body surface area and the 24 h urinary creatinine excretion. Since the values of C-peptide excretion were not normally distributed they were log transformed and plotted against body weight. The linear regression and the 95% confidence limits were then calculated. Girls at puberty, 11-15 years of age, had significantly higher C-peptide excretion per kg body weight and per body surface area than younger girls, 3-10 years of age. Boys 13-15 years of age had significantly higher C-peptide excretion per body surface area than younger boys, 5-12 years of age. This indicates that children during the maximal growth spurt have an increased insulin secretion as measured by urinary C-peptide per body surface area.