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Comparative concentrations of growth hormone-binding protein in maternal circulation, fetal circulation, and amniotic
I Harada1, O Tsutsumi, M Momoeda
1Department of Obstetrics and Gynecology, Faculty of Medicine, University of Tokyo, Japan.
Insights
Growth hormone-binding protein (GHBP) levels in amniotic fluid may relate to fetal development. Fetal serum GHBP levels did not correlate with fetal growth, despite high fetal growth hormone (GH).
Area of Science:
- Endocrinology
- Reproductive Biology
- Fetal Development
Background:
- Circulating growth hormone (GH) levels are high in human fetuses, yet fetal growth is considered GH-independent.
- The role of GH in fetal development requires further elucidation, particularly concerning GH-binding protein (GHBP).
Purpose of the Study:
- To measure GHBP levels in maternal serum, amniotic fluid, and neonatal serum across gestation.
- To investigate the relationship between GHBP concentrations and fetal growth parameters.
Main Methods:
- GHBP levels were quantified using a ligand-mediated immunofunctional assay.
- Measurements were performed on serum from nonpregnant and pregnant women, neonates, and amniotic fluid at various gestational stages.
Main Results:
- GHBP concentrations in adult serum remained stable throughout pregnancy.
- A correlation existed between GHBP levels in umbilical artery and vein, but not with fetal weight or age.
- Neonatal GHBP levels were lower than in pregnant women, with no observed correlation.
- GHBP was detected in amniotic fluid at concentrations higher than cord serum, increasing with gestational age.
Conclusions:
- GHBP in amniotic fluid may play a role in fetal development or maturation.
- Low fetal serum GHBP might result from decreased GH receptors due to high circulating GH.
- GHBP likely originates from fetal organ GH receptors, potentially the fetal liver.
Abstract:
Fetal growth is thought to be independent of the concentration of GH, although circulating levels of GH are high in the human fetus. To elucidate the role of GH in fetal development, levels of GH-binding protein (GHBP) were measured in the serum of nonpregnant and pregnant women and neonates as well as in amniotic fluid obtained at various stages of gestation. Total GHBP (the sum of free GHBP and GHBP bound to GH) is measured by a ligand-mediated immunofunctional assay. GHBP concentrations in adult serum were not changed by pregnancy or the stage of gestation. A significant correlation was observed between the concentration of GHBP in the umbilical artery and vein. No correlations were observed between the GHBP concentration and such measures of fetal growth as fetal weight and fetal age. Although the neonatal concentrations of GHBP were significantly lower than those of pregnant women, no correlation was observed between them. GHBP was also present in the amniotic fluid from early to late gestation at concentrations higher than in the cord serum of the neonate. The amniotic GHBP concentration in late gestation was significantly higher than in early gestation. GHBP appears to be derived from GH receptors of fetal organs (most probably fetal liver). The low level of GHBP in fetal serum may be the result of a decrease in GH receptors caused by high levels of circulating GH. GHBP levels in amniotic fluids may be related to the development or maturation of the fetus.