Variations in biological and immunological activity of growth hormone during the neonatal period.
OBJECTIVE
It was postulated that a high growth hormone (GH) bioactivity might explain the rapid growth rate of neonates. The aim of this study is to verify changes in serum GH biological potency (Bio-/Immuno-GH ratio) and their effects on serum growth factors during the first month of life in term and preterm babies.


METHODS
Blood samples were collected from 10 small-for-gestational-age preterm (SGAPT), 17 appropriate for gestational age preterm (AGAPT) and 26 AGA term (T) neonates on days 4, 15 and 30 of life to evaluate serum GH values measured by IFMA (IFMA-GH) and bioassay (Bio-GH), serum insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3).


RESULTS
High serum Bio-GH values on the first few days of life correspond to high IFMA-GH values, suggesting full biological potency of circulating GH. Furthermore, IGF-I/IGFBP-3 molar ratio values in preterm babies were higher than in full-term infants.


CONCLUSIONS
These data confirmed the hypothesis that the higher growth velocity in the first month of life of preterm neonates is due to an increased bioavailability of IGF-I. A progressive maturation of the hypothalamic-pituitary-IGF-I axis without any alteration in the GH biological potency seems to underpin the increase of the growth factors early in life.
Pagani
S
S
Pediatric Department, University of Pavia, Italy.
Chaler
E A
EA
Radetti
G
G
Travaglino
P
P
Meazza
C
C
Bozzola
E
E
Sessa
N
N
Belgorosky
A
A
Bozzola
M
M
D001681:Biological Assay; D005260:Female; D015200:Fluoroimmunoassay; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood; D007236:Infant, Small for Gestational Age / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008223:Lymphoma; D008297:Male; D014407:Tumor Cells, Cultured
C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I