Abstract
In 115 normal children (3 to 14 years old) and 143 children with insulin-dependent diabetes mellitus (6 to 15 years old), the urinary C-peptide (C-peptide immunoreactivity) was measured for evaluation of the pancreatic B cell function.
The urinary C-peptide excretions during O-GTT corresponded to the change of serum C-peptide levels in normal children (n=27) and the mean value of the excretions in younger children was significantly low. Age did not significantly affect basal serum C-peptide levels (ng/ml) and urinary C-peptide excretions (μg/h) before O-GTT, but significant differences in serum ΣC-peptide (ng/ml) and urinary C-peptide (μg/3 h) during O-GTT were noted between the younger group and the older group (p<0.01).
In 39 normal children on an inactive routine, mean values of the 24 h urinary C-peptide for children aged from 3 to 6, 7 to 10 and from 11 to 14 years old, were 28.2±12.6 μg/day, 32.3 ± 8.4 μg/day and 37.6±10.6 μg/day (mean±SD) respectively with significant differences according to age (younger group vs older group, p<0.05). The effects of daily routine on 24 h urinary C-peptide were studied in normal children. In children on an active routine, the C-peptide excretion was significantly less than in the same individuals on an inactive routine (26.9±9.9 μg/day vs 34.3±14.5 μg/day, p<0.01).
In children with insulin-dependent diabetes mellitus, 24 h urinary C-peptide excretion was studied to evaluate residual pancreatic B cell function. Urinary C-peptide was measurable in 47 of the 143 diabetic children, suggesting that most of the pancreatic B cells had deteriorated in the other 96 patients. In the 96 patients without B cell function, the averages of daily dose of insulin and 24 h-U·glucose/TAG ratio were significantly higher than those in the 47 patients who had pancreatic B cell function estimated by measuring urinary C-peptide (p<0.001).
In additional studies on the 43 diabetic children with residual pancreatic B cell function, who had had the disease for five years or less, the 24 h urinary C-peptide excretion (μg/day) correlated weakly but significantly with the duration of the disease (r=-0.28, p<0.05).
Patients who had had the disease longer and who were controlled with larger doses of insulin had less of the 24 h urinary C-peptide. 44 of the 48 patients who had had the disease longer than 5 years had no measurable urinary C-peptide.
24 h urinary C-peptide measurement is only a non-invasive method for determining an integrated measure of physiological insulin secretion.
On the other hand, in children with insulin-dependent diabetes mellitus, it seems clinically very important for diabetic control to assess the residual pancreatic B cell function measured by urinary C-peptide excretion.
