Effect of gestational age and blood glucose on C ‐peptide excretion rate and clearance in neonates

Aims The aim of this study was to measure urinary C ‐peptide concentrations, and then calculate C ‐peptide clearance ( C l), and excretion rate ( UER ) in neonates. In addition, the effect of gestational age ( GA ) and blood glucose levels ( BGL ) on C ‐peptide UER were investigated. Methods Insulin concentrations in plasma and C ‐peptide concentrations were measured in plasma and urine, in 20 neonates. Chemiluminescent immunoassays were used for insulin and C ‐peptide measurements, with urine diluted to 40% with bovine serum albumin 1% in phosphate buffered saline. Urine volume and time of collection were recorded and used to calculate UER and C l. Results The mean C l of C ‐peptide was 0.309 ± 0.329 mL/min/kg, and UER was 0.0329 ± 0.0342 pmol/min/kg. Correlations between C l or UER and GA were not significant ( P  > 0.05). No significant correlation was shown between C l or UER and BGL ( P  > 0.05). Conclusions Both C l and UER were highly variable in neonates, but were not correlated with GA . Additionally, BGL did not appear to affect C ‐peptide UER and C l. As GA and BGL did not appear to affect C l and UER , urinary C ‐peptide may provide a non‐invasive method of measuring insulin production in neonates.