Growth hormone response to GHRH during lifespan

Area of Science:

• Endocrinology
• Neuroendocrinology
• Human Physiology

Background:

• Growth hormone-releasing hormone (GHRH) is crucial for investigating growth hormone (GH) secretion pathophysiology.
• Direct GHRH administration is limited for assessing pituitary somatotrophic function due to high variability.
• Combined administration of GHRH with somatostatin-inhibiting agents enhances pituitary response assessment.

Purpose of the Study:

• To evaluate the utility of GHRH in studying GH secretion across different physiological states.
• To explore factors influencing GH response to GHRH, including age and hormonal status.
• To understand the mechanisms behind impaired GH secretion in aging.

Main Methods:

• Administration of GHRH in animal and human studies.
• Combination therapy using GHRH with agents like pyridostigmine and arginine.
• Analysis of GH secretion patterns in relation to age, sex, and menopausal status.

Main Results:

• GH hyperresponsiveness is observed in the immediate postnatal period, likely due to decreased somatostatin sensitivity.
• GH responses to GHRH remain stable during puberty but decline after the fourth decade in men and post-menopause in women.
• The capacity to release GH is preserved during aging, suggesting impaired hypothalamic GHRH function and increased somatostatinergic influence.

Conclusions:

• GHRH is a valuable tool for studying GH secretion, particularly when combined with agents that reduce somatostatinergic inhibition.
• Age-related decline in GH secretion is attributed to hypothalamic GHRH deficiency and enhanced somatostatin activity.
• Understanding these dynamics is key for diagnosing and managing disorders of GH secretion.