Utility of C-peptide for a reliable estimate of insulin secretion in children with growth hormone deficiency

Growth Horm IGF Res. 2016 Aug:29:71-77. doi: 10.1016/j.ghir.2016.05.001. Epub 2016 May 9.

Abstract

Objective: GH treatment (GHT) can lead to glucose metabolism impairment through decreased insulin sensitivity and impaired pancreatic β-cell function, which are the two key components of the pathogenesis of diabetes. Therefore, in addition to insulin sensitivity, during GHT it is very important to perform a reliable evaluation of insulin secretion. However, conflicting data exist regarding the insulin secretion in children during GHT. C-peptide provides a more reliable estimate of β-cell function than insulin, but few studies evaluated it during GHT. Our aim was to assess the usefulness of C-peptide in the evaluation of insulin secretion in GH deficiency (GHD) children.

Design: In 48 GHD children, at baseline and after 12 and 24months of GHT, and in 56 healthy subjects we evaluated fasting and glucagon-stimulated (AUCCpep) C-peptide levels in addition to other commonly used secretion indexes, such as fasting and oral glucose tolerance test-stimulated insulin levels (AUCINS), Homa-β, and insulinogenic index. The main outcomes were the change in C-peptide during GHT and its correlation with the auxological and hormonal parameters.

Results: At baseline GHD children showed a significant lower AUCCpep (p=0.006), while no difference was found for the other indexes. Both fasting C-peptide (beta 0.307, p=0.016) and AUCCpep (beta 0.379, p=0.002) were independently correlated with IGF-I SDS, while no correlation was found for all other indexes. After 12months an increase in Homa-β (p<0.001), fasting C-peptide (p=0.002) and AUCCpep (p<0.001) was found. At multivariate analysis, only fasting C-peptide (beta 0.783, p=0.001) and AUCCpep (beta 0.880, p<0.001) were independently correlated with IGF-I SDS.

Conclusions: C-peptide, rather than the insulin-derived indexes, has proved to be the most useful marker of insulin secretion correlated to IGF-I levels in GHD children. Therefore, we suggest the use of glucagon test both as diagnostic test for the GH assessment and as a useful tool for the evaluation of insulin secretion during GHT in children.

Keywords: C-peptide; Glucose metabolism; Growth hormone treatment; Insulin secretion.

MeSH terms

  • Area Under Curve
  • C-Peptide / blood*
  • Case-Control Studies
  • Child
  • Child, Preschool
  • Fasting
  • Female
  • Glucagon
  • Glucose Tolerance Test
  • Hormones
  • Human Growth Hormone / deficiency*
  • Human Growth Hormone / therapeutic use
  • Humans
  • Hypopituitarism / drug therapy
  • Hypopituitarism / metabolism*
  • Insulin / metabolism*
  • Insulin Resistance
  • Insulin Secretion
  • Insulin-Like Growth Factor I / metabolism*
  • Insulin-Secreting Cells / metabolism
  • Male
  • Prospective Studies

Substances

  • C-Peptide
  • Hormones
  • IGF1 protein, human
  • Insulin
  • Human Growth Hormone
  • Insulin-Like Growth Factor I
  • Glucagon