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Binding protein for human growth hormone: effects of age and weight
R W Holl1, R Snehotta, B Siegler
1Department of Pediatrics I, University of Ulm, FRG.
Insights
Human growth hormone binding protein (GHBP) levels are absent in newborns, rise rapidly in early childhood, and are influenced by weight and height. These findings may explain growth differences between fetal and postnatal development.
Area of Science:
- Endocrinology
- Human Physiology
- Growth Hormone Research
Background:
- A specific binding protein for human growth hormone (GHBP) exists in serum, identical to the extracellular part of the hepatic GH receptor.
- GHBP plays a role in regulating growth hormone action and availability.
Purpose of the Study:
- To investigate the developmental changes and influencing factors of GHBP levels in human serum.
- To explore the relationship between GHBP, age, weight, and height in children.
Main Methods:
- Serum samples were incubated with radioactive [125I]-GH.
- Bound and free radioactivity were separated using gel chromatography to quantify GHBP.
Main Results:
- GHBP was virtually absent in newborns and infants under 2 months.
- GHBP levels increased significantly during the first two years of life, with slower increases thereafter.
- Standardized weight (SDS) positively correlated with GHBP, while standardized height (SDS) showed a negative correlation when controlling for weight and age.
Conclusions:
- GHBP levels exhibit distinct developmental patterns from birth through puberty.
- Weight and height are significant determinants of GHBP concentration, suggesting a link to growth regulation.
- These findings may elucidate the transition from intrauterine to postnatal growth and growth acceleration in obese children.
Abstract:
In human serum, a specific binding protein with high affinity for human growth hormone (GHBP) is found which is identical to the extracellular portion of the hepatic GH receptor. GHBP is assessed by incubating serum samples with [125I]-GH, followed by separation of bound and free radioactivity using gel chromatography. In newborns and children younger than 2 months, GHBP was practically absent and no 'big-big' GH could be found. GHBP values increased rapidly during the first 2 years of life, followed by a slower increase during childhood and puberty. No difference was found between male and female subjects. Apart from age, standardized weight (SDS = z score) had a major positive effect on GHBP concentration. Interestingly, SDS height correlated negatively with GHBP when weight and age were controlled for. These data may relate to two clinical findings: (1) the developmental switch between GH-independent intrauterine and GH-dependent postnatal growth mechanisms, and (2) the accelerated growth velocity encountered in adipose children.