Growth hormone-binding proteins of human serum: developmental patterns in normal man

Area of Science:

• Endocrinology
• Biochemistry
• Human Physiology

Background:

• Growth hormone (GH) exerts its effects by binding to specific receptors.
• GH binding proteins (GHBPs) modulate GH bioavailability and activity.
• Understanding GHBP dynamics is crucial for interpreting GH action throughout life.

Purpose of the Study:

• To investigate the developmental changes in GH binding by low-affinity binding protein (LA-BP) and high-affinity binding protein (HA-BP) in human serum from birth to adulthood.
• To compare the age-dependent binding patterns of LA-BP and HA-BP.
• To assess the impact of pregnancy on GHBP levels.

Main Methods:

• Serum samples from individuals aged birth to adulthood were collected.
• Pooled serum samples were analyzed for LA-BP and HA-BP binding using Sephadex chromatography.
• Radioiodinated GH ([125I]GH) was used to quantify binding.

Main Results:

• Both LA-BP and HA-BP showed minimal GH binding in cord blood.
• LA-BP binding increased fourfold by age 5, remained stable through adolescence with a pubertal dip, and declined in early adulthood.
• HA-BP binding increased six- to eightfold, peaking between ages 23-25 and remaining stable in adults; pregnancy increased LA-BP but not HA-BP.

Conclusions:

• GHBP levels exhibit distinct developmental trajectories, with LA-BP peaking in childhood and HA-BP in adulthood.
• These age-related changes in GHBP may influence GH action and signaling throughout human life.
• Pregnancy specifically enhances LA-BP, suggesting a role in modulating GH availability during gestation.