The effect of age and body size on the urinary excretion of C-peptide from birth to 14 years of age

Abstract

The daily excretion of C-peptide in the urine was measured in 105 healthy infants and children from birth to 14 years of age. For technical reasons no studies were performed from 1-3 years of age. The excretion of C-peptide showed a close positive correlation with age and weight. The relationship with weight was already apparent in the 1st days of life. The C-peptide/weight and the C-peptide/creatinine ratios were constant throughout most of childhood with the exception of the age range of 1 month-1 year when the C-peptide/creatinine was significantly higher. In obese children the C-peptide/weight and C-peptide/creatinine ratios were similar to those found in children with normal weight. In growth hormone deficiency these ratios were low and increased during the 1st week of growth hormone therapy. It is concluded that urinary C-peptide is a reliable indicator of integrated insulin production and gives new information about insulin secretion in various conditions.

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

“…Both insulin and C‐peptide plasma concentrations have been shown to increase with age in children; therefore, it is expected that neonates would have lower plasma insulin and C‐peptide concentrations than adults. Insulin‐resistant individuals have been found to have an increased urinary excretion of C‐peptide per unit of energy ingested when compared with insulin‐sensitive individuals …”

“…Urine diluted to 20% was more accurate for the adult urine, which had a higher (10‐ to 20‐fold) C‐peptide concentration. The higher concentration of urinary C‐peptide in adults is consistent with the work of Gacs et al ., where plasma and urine C‐peptide concentrations were shown to be higher in adults than in children . This same work with respect to neonates showed a fourfold higher urinary C‐peptide UER in older children compared with neonates.…”

“…C‐peptide renal clearance is influenced by glomerular filtration, tubular reabsorption and degradation by peritubular uptake . Of the C‐peptide, 5–10% is excreted unchanged in the urine, as compared with 0.1% of insulin . The concentration of C‐peptide in urine is usually 10–20 times higher than plasma and is more chemically stable because of the absence of proteases in urine .…”

Exploring C-peptide loss in type 1 diabetes using growth curve analysis

“…For future intervention studies it would be useful to be able to predict disease course in individual patients from factors available soon after diagnosis. Age is the strongest predictor of beta cell loss; a younger age at diagnosis is associated with a lower starting beta cell reserve [ 8 – 10 ] as well as a more rapid rate of loss [ 11 , 12 ]. Diabetic ketoacidosis is also unsurprisingly associated with poor beta cell recovery; perhaps as a marker of low beta cell mass [ 13 , 14 ].…”

The Urinary C‐Peptide Excretion in Normal Healthy Children

“…Estimation of the 24 h urinary C-peptide excretion rate has been used to assess the residual beta cell function in children suffering from type I diabetes (Sll). Measurements in normal healthy children have so far been carried out only to a limited extent (8,9,10,12). In recent years it has become increasingly evident that insulin, in addition to its anabolic effects, also plays an important role as a growth factor, acting synergistically with somatomedins and other growth promoting peptides (13).…”