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The effect of exogenous and endogenous growth hormone on plasma growth hormone binding activity in prepubertal
Insights
Plasma growth hormone-binding protein (GHBP) levels in children correlate with age and BMI but inversely with growth hormone (GH) levels and height velocity. GHBP did not change during GH provocative tests, suggesting limited acute regulation.
Area of Science:
- Pediatric Endocrinology
- Hormone Regulation
- Growth Disorders
Background:
- Growth hormone (GH) exerts its effects via both free GH and GH-binding protein (GHBP).
- Understanding the relationship between GH and GHBP is crucial for diagnosing and treating growth-related conditions.
Purpose of the Study:
- To investigate the relationship between plasma GH and GHBP activity in children.
- To examine the effects of exogenous and endogenous GH on GHBP levels.
Main Methods:
- Studied 102 prepubertal children (69 males, 33 females), including short and normal-stature individuals.
- Measured integrated concentrations (IC) of GH and GHBP over 24 hours using continuous blood withdrawal.
- Assessed GH and GHBP responses to provocative tests and during GH therapy.
Main Results:
- Plasma GHBP positively correlated with age and body mass index (BMI).
- Plasma GHBP negatively correlated with integrated GH (ICGH) and height velocity standard deviation scores (SDS).
- No significant change in GHBP was observed during GH provocative tests, despite an abrupt increase in GH.
Conclusions:
- GHBP levels in children are influenced by age, BMI, and endogenous GH secretion.
- GHBP does not appear to be acutely regulated by GH surges during provocative tests.
- Findings suggest complex, long-term interactions between GH and GHBP rather than immediate feedback mechanisms.
Abstract:
To investigate the relationship between plasma growth hormone (GH) and plasma GH-binding protein (GHBP) activity we studied the effects of exogenous and endogenous GH on GHBP in children with a normal response to GH stimulation. The effect of exogenous GH on plasma binding activity was studied for 12 h after the administration of a subcutaneous GH bolus of 0.1 IU/kg and during the first year of GH therapy. The effect of endogenous GH secretion on GHBP was studied by measuring the integrated concentration (IC) of GH and GHBP over 24 h by means of a continuous blood withdrawal procedure. We also measured the GH and GHBP response to GH provocative tests. One hundred and two prepubertal children, 69 males, 33 females, age 8.8 +/- 2.2 years (mean +/- SD), were studied. Eighty-one were short, < 2 SDS for age and gender, and 21 were of normal height for age and gender. There was no difference in IC-GHBP between boys and girls. It correlated positively with age and body mass index (r = 0.802, p < 0.001 and r = 0.340, p < 0.001, respectively) but correlated negatively with ICGH (r = -0.412, p < 0.001) and with height velocity standard deviation scores (SDS, r = -0.355, p = 0.001). No correlation of ICGHBP with maximal GH response to provocative tests, insulin-like growth factor 1 levels, height in SDS or growth velocity after 1 year of GH therapy was found. During a provocative test there is an abrupt increase in GH but not change in GHBP.(ABSTRACT TRUNCATED AT 250 WORDS)