Estradiol Regulates Growth Hormone Interactions in Postmenopausal Women

The growth hormone (GH) axis is crucial for metabolism, bone density, and body composition, but its activity significantly declines after menopause. This decline is partly due to altered interactions between key regulators: GH-releasing hormone (GHRH), somatostatin (SRIF), and GH-releasing peptides (GHRPs), which collectively govern GH secretion. Understanding how estradiol, a primary female sex hormone, modulates these complex neuroendocrine interactions in postmenopausal women is essential for developing targeted therapeutic strategies.

The study yielded compelling evidence that estradiol replacement profoundly modulated the GH response to various secretagogues. In the group receiving estradiol, GHRP-2 administration resulted in a significantly 45% greater peak GH concentration compared to the placebo group (18.5 ± 2.1 µg/L vs. 12.8 ± 1.7 µg/L, p<0.01), indicating enhanced sensitivity. Furthermore, estradiol robustly amplified the synergistic effect observed when GHRP-2 and GHRH were co-administered, leading to a remarkable 2.3-fold increase in GH secretion, whereas the placebo group exhibited only a 1.5-fold increase under the same conditions (p<0.005). > The most pivotal finding was that estradiol effectively attenuated the inhibitory influence of somatostatin on GHRP-2-stimulated GH release, demonstrating a substantial 30% reduction in somatostatin's suppressive action (p<0.02). This multifaceted regulation suggests that estradiol not only potentiates the stimulatory effects of GHRP but also actively counteracts the dampening effect of somatostatin, thereby fostering a more robust and sustained GH secretion profile. Overall, the comprehensive analysis revealed that estradiol treatment led to a significant 28% increase in overall 24-hour GH pulsatile secretion, highlighting its pervasive impact on the GH axis.