Restoring Growth Hormone
It has been argued that the age-dependent decline in sex steroid, Growth Hormone, and IGF-I production is nature’s way of protecting us from cancer and heart disease, but a far more likely scenario is that once we reach our reproductive capacity, nature begins programming us for death.
Such programming begins as the second decade of life draws to a close, the negative consequences of which become more noticeable with each passing year. We begin to experience a steady decline in immune function. Our bodies increase production of glucocorticoids (catabolic hormones) and cytokines (inflammatory) which negatively impact metabolism, bone density, strength, exercise tolerance, cognitive function, and mood.
The hormones of sex, dehydroepiandrosterone (DHEA), Human Growth Hormone (HGH), and Insulin-like Growth Factor (IGF-1) are positively correlated with the health and well-being of the body in general and the specific functioning of metabolism, the cardiovascular system, the musculature skeletal system, cognitive function & the immune system. However these hormonal levels naturally decline as we age and as a consequence those systems necessary to maintain optimal health decline as well.
A progressive decline in lean body mass, atrophy of its component organs & reduction in their function and increased deposition of adipose tissue mass characteristic of the aging human body result partially from the body's diminished secretion of HGH. These negative changes resulting from growth hormone deficiency have been shown to be reversible by replacement doses of HGH.
HGH is a vital anabolic hormone whose positive stimulatory effects on protein synthesis (particularly in the liver, muscle, bone, cartlidge, spleen, kidney, skin, thymus, and red blood cells) and on lipolysis (the breakdown of fat stored in fat cells) contributes greatly to growth, repair & well-being.
HGH secretion is primarily regulated by the release of two peptides, Growth Hormone-Releasing Hormone (GHRH) and Somatostatin. The hypothalamus region of the brain releases these hormones in response to signals from the central nervous system. GHRH once released makes its way to the receptors on the somatotrope cells of the pituitary gland of the brain where it stimulates HGH release. Somatostatin once released makes its way to the receptors on the somatotrope cells of the pituitary gland of the brain where it inhibits HGH release.
The primary physiological action of somatostatin is to inhibit synthesis and release of GH. The primary physiological action of Growth Hormone-Releasing Hormone (GHRH) is to stimulate synthesis and release of HGH. The end product of this cascade, HGH once secreted exerts its effect in the body as a whole both directly and indirectly through its initiation of Insulin-like Growth Factor (IGF-1) synthesis in the liver. IGF-1 in turn exerts its effect in the body and its rise in turn begins to inhibit any further HGH release.
HGH is released periodically within the body in a controlled pulsating fashion. This periodic pattern plays an important role in transmitting the HGH "growth, repair & well-being" message to tissue. A review of several studies involving HGH replacement in HGH-deficient animals reveals the biological significance of episodic secretion. These studies conclude that HGH released in a pulsatile pattern is far more efficient in improving mammalian growth and repair than the method of HGH administration by constant infusion.
In males HGH pulses occur approximately every three (3) hours, a frequency that appears across most mammals. The secretion bursts are preceded and followed by almost undetectable levels of plasma HGH. In females however HGH pulses occur more frequently and the base level of plasma HGH remains higher than males who have fewer HGH pulses but the amplitude of which are more pronounced. HGH pulse amplitudes are increased during slow wave sleep such that particularly in males, most HGH secretion occurs at night. HGH secretion is highest during the growing years of youth and early adulthood. In humans the secretion rate starts to noticeably decrease during the third decade of life and strongly decreases during the fourth decade of life. As we age the daytime secretory pulses diminish first, while the sleep associated HGH pulse persists and diminishes gradually.
Nudging Nature
HGH levels may be increased either by exogenically administering HGH or by administering Growth Hormone-Releasing Hormone which then endogenically stimulates the somatrope cells of the pituitary to secrete additional HGH. The primary advantage of GHRH is that HGH ends up being released in physiological conformance to the body’s natural biorhythm. This biorhythm is pulsatile.
Studies have concluded that endogenous Growth Hormone Releasing Hormone (GHRH) is the principal regulator of pulsatile HGH secretion in humans and that continuous GHRH infusion augments pulsatile HGH release. Whereas exogenic administration of HGH raises overall HGH levels but has no effect on amplifying the pulses.
People of all ages naturally continue to possess the ability to secrete HGH from stores within the pituitary. Most studies are in agreement on this point. One study in particular examined the effects of administration of GHRH & a Growth Hormone Releasing Peptide on all adult age groups from those in their 20's to those above 75 years of age. They observed substantial increases in HGH release as a direct result of administration of GHRH & GHRP-6. This prompted them to conclude, "...that the lack of side-effects & safety of the protocol and the discovered lack of age-related decline in the 'GHRH-GHRP-6-mediated' GH release opens the possibility of using it as a therapeutical tool to revert some deleterious manifestations of aging in man."