Age-dependent decrease in the growth hormone response to growth hormone-releasing hormone in normally cycling women

Area of Science:

• Endocrinology
• Aging Research
• Reproductive Endocrinology

Background:

• Growth hormone (GH) secretion patterns change with age.
• Understanding these changes in healthy, cycling women is crucial for hormonal health.
• Age-related alterations in neuroendocrine regulation of GH are not fully understood.

Purpose of the Study:

• To investigate age-related changes in GH secretion in normally cycling women.
• To compare GH responses to various stimuli in younger versus older women.
• To explore the role of cholinergic and somatostatinergic pathways in age-related GH decline.

Main Methods:

• Controlled clinical study involving nine younger (18-33 years) and nine older (41-46 years) healthy women.
• Administration of growth hormone-releasing hormone (GH-RH), pyridostigmine, arginine, and combinations thereof.
• Measurement of basal hormones including insulin-like growth factor-I (IGF-I) and GH levels post-administration.

Main Results:

• Basal hormone levels were similar, but IGF-I was lower in older women.
• Older women showed reduced GH responses to GH-RH and pyridostigmine, negatively correlated with age.
• GH response to arginine or GH-RH plus arginine was similar in both age groups.

Conclusions:

• Cholinergic stimulation of GH release is diminished in older cycling women.
• Reduced cholinergic tone may lead to increased somatostatinergic tone with age.
• Arginine's ability to normalize GH response suggests a modifiable pathway in aging.