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Serum growth hormone-binding proteins in the human fetus and infant
G Massa1, F de Zegher, M Vanderschueren-Lodeweyckx
1Department of Paediatrics, University of Leuven, Belgium.
Insights
Growth hormone-binding protein (GH-BP) levels in infants vary with age and nutritional status. Higher GH-BP levels were observed in older infants and those with better intrauterine nutrition.
Area of Science:
- Endocrinology
- Pediatrics
- Biochemistry
Background:
- Growth hormone-binding protein (GH-BP) plays a role in regulating growth hormone (GH) availability.
- Understanding GH-BP levels in infants is crucial for assessing growth and development.
Purpose of the Study:
- To investigate growth hormone-binding protein (GH-BP) levels in cord serum of newborns and in infants aged 1-3 months.
- To examine the correlation between GH-BP levels and gestational age, birth weight, and intrauterine nutritional status.
Main Methods:
- Serum samples from 69 newborns and 14 infants were analyzed using HPLC-gel filtration with radiolabeled human growth hormone (125I-hGH).
- Two high molecular weight peaks (peak I-BP and peak II-BP) were identified, with peak II-BP representing GH bound to high-affinity GH-BP.
- The ponderal index was calculated to assess intrauterine nutritional state.
Main Results:
- Peak II-BP levels, indicating high-affinity GH-BP, were significantly different across preterm infants, term infants, and 1-3-month-old infants (p < 0.0001).
- Infants aged 1-3 months showed significantly higher peak II-BP levels (8.5%) compared to term (4.2%) and preterm infants (3.1%).
- Lower peak II-BP levels were observed in infants with a ponderal index below 2.35 (2.8%), suggesting a link to intrauterine nutrition (p < 0.05).
Conclusions:
- Infant GH-BP levels, particularly high-affinity GH-BP, increase significantly from birth to 3 months of age.
- Intrauterine nutritional status, as indicated by the ponderal index, may influence GH-BP levels at birth.
- These findings highlight developmental changes in the GH-BP system during early infancy.
Abstract:
Growth hormone-binding protein (GH-BP) levels were studied in cord serum of 69 human infants born after 24 to 41 wk of gestation and in serum of 14 infants aged 1 to 3 mo. GH-BP levels were measured by HPLC-gel filtration of serum incubated overnight with 125I-hGH. The radioactive elution profile revealed two small 125I-hGH peaks of high molecular weight and a large peak, corresponding to monomeric 125I-hGH. The first peak of high molecular weight was variable, showed some of the characteristics (high molecular weight, displaceability by a large excess of unlabeled hGH) of the described low affinity, high capacity GH-BP, and did not correlate with gestational age or birth weight (peak I-BP). The second peak was identified as 125I-hGH bound to the high affinity, low capacity GH-BP (peak II-BP). Mean +/- SD specific binding of 125I-hGH to this peak was significantly (p less than 0.0001) different between preterm infants (3.1 +/- 1.1%; n = 51), term infants at birth (4.2 +/ 1.1%; n = 18), and 1- to 3-mo-old infants (8.5 +/- 1.6%; n = 14). To evaluate the effect of intrauterine nutritional state, the ponderal index (weight/lengths) was calculated. Peak II-BP levels were lower (p less than 0.05) in infants with the ponderal index less than 2.35 (2.8 +/- 1.0%; n = 20) than in those with the ponderal index between 2.35 and 2.65 (3.4 +/- 1.2%; n = 29) or greater than 2.65 (3.8 +/- 1.2%; n = 20).(ABSTRACT TRUNCATED AT 250 WORDS)