HGH DESCRIPTION HumanGrowthHormone (HGH) is a heterogenous mixture of polypeptides secreted by
the anterior pituitary gland. The principal form of HGH is a polypeptide
containing 191 amino acids with a molecular weight of 215,000 daltons. This form
of HGH is produced by recombinant DNA technology and is marketed for the
treatment of short stature in GrowthHormone (GH)-deficient children and
adolescents. Recombinant HGH or somatropin is also used for the treatment of
GH
deficiency in adults, short stature in association with renal insufficiency,
AIDS-related wasting and short stature associated with Turner's Syndrome. In all
of these cases, GH must be administered parenterally since it has very poor oral
bioavailability.
GH is the primary Hormone responsible for Growth in Humans, as well as other
mammals, and it helps regulate such metabolic processes as anabolism and
lipolysis. Normal Human aging is associated with decreased GH secretion. Mean
GH
level in those over the age of 60 is about half of that in young adults. The
reduction in GH levels with aging is believed to contribute to age-related
decreases in muscle mass and strength and decreased lipolysis.
The effects of GH are largely mediated via IGF-1 (insulin-like Growth factor 1).
IGF-1 is a mitogen and may promote some cancers, including prostate, breast and
colorectal cancers. Clearly, long-term safety studies, as well as efficacy
studies, are essential to evaluate the role, if any, of GH replacement in the
aging population.
The release of GH from somatotroph cells of the anterior pituitary gland is a
complex process involving multiple regulators. The hypothalamic peptide GHRH
(GrowthHormone-releasing Hormone) acts on the somatotrophs to release GH, while
the inhibitory peptide somatostatin blocks GH release. In addition, GH release
appears to be influenced by a third, separate mechanism, as well???a GrowthHormone secretagogue pathway. GH secretagogues, abbreviated GHSs, can be amino
acids, such as L-arginine, small peptides and nonpeptides. Further,
neurotransmitters, such as acetylcholine, dopamine and norepinephrine, and
neuropeptides, such as opioid peptides, are also involved in the control of GH
secretion.
Recently, HGH has entered the dietary supplement marketplace, as have IGF-1 (see
Insulin-Growth Factor 1) and several so-called GH secretagogues or releasers.
The substances being marketed as GH secretagogues or releasers include the amino
acids L-arginine, L-glutamine, L-ornithine, glycine, L-dopa, as well as such
substances as ornithine alpha-ketoglutarate (see Ornithine Alpha-Ketoglutarate)
and the herbs Macuna pruriens and Tribulus terrestris.
ACTIONS AND PHARMACOLOGY
ACTIONS
Supplemental HGH and secretagogues or releasers have putative anabolic and
lipolytic activities, as well as putative "anti-aging" activity.
MECHANISM OF ACTION
The mechanism of the putative actions of supplemental HGH and secretagogues or
releasers is unknown. The actions of endogenous GH and parenteral GH are thought
to be mediated via the anabolic HormoneIGF-1 and by interaction with specific
GH receptors that are widely distributed in body tissues.
PHARMACOKINETICS
Orally administered GH has very poor bioavailability. It is claimed that GH is
significantly absorbed from the oral mucosa if delivered by a spray. There is no
substantiation for this. It is likely that orally administered GH is digested in
the small intestine to the amino acids thah comprise the molecule.
INDICATIONS AND USAGE
There are no indications for the non-pharmaceutical use of HGH in any form.
Claims that it is an anti-aging substance, that it enhances athletic and sexual
performance, that it promotes joint health, is a sleep aid and an immune
enhancer, that it has antidiabetic and antiatherosclerotic effects, and is a
neuroprotector, are unsupported by credible evidence. Injected HGH may reduce
fat and increase lean body mass in some, but serious side effects may attend the
use of HGH for this purpose. There is preliminary evidence that injected HGH may
be of benefit in some with Crohn's disease and that it might be helpful in
treating dilated cardiomyopathy. There is some fear that high doses of HGH might
promote some cancers.
RESEARCH SUMMARY
Recombinant HumanGrowthHormone, given parenterally to men aged 61 to 81,
reportedly resulted in significant improvements in lean body mass, muscle tone,
skin thickness and density of lumbar vertebrae. Significant loss of adipose
tissue was also reported. The researchers concluded that "the effects of six
months of HumanGrowthHormone treatment on lean body mass and adipose tissue
were equivalent in magnitude to the changes incurred during 10 to 20 years of
aging."
Subsequent studies also demonstrated some positive effects of HGH replacement
therapy on body composition in those over 60. Some serious side effects were
also noted, however, including arthralgias of both small and large joints,
insulin resistance leading to higher serum fasting glucose levels, fluid
retention in the lower extremities, carpal tunnel syndrome, gynecomastia and
headaches. Due to the prevalence of some of these side effects, the researchers
who conducted the first Human trial reduced the dosage of HGH they had been
using by half.
In a preliminary study, recombinant HumanGrowthHormone, given parenterally for
three months to patients with idiopathic dilated cardiomyopathy, was reported to
increase myocardial mass and reduce the size of the left ventricular chamber.
These changes were associated with improved clinical status.
Recently, in another preliminary study, injected HGH was said to be beneficial
in some with Crohn's disease. Improvement was measured by scores on the Crohn's
Disease Activity Index over a four-month period.
There is no credible evidence that oral HGH has any health benefit.
CONTRAINDICATIONS, PRECAUTIONS, ADVERSE REACTIONS
(For information on the pharmaceutical use of somatropin, see Physicians' Desk
Reference.)
CONTRAINDICATIONS
Supplemental HumanGrowthHormone is contraindicated in those with any evidence
of active malignancy. It is also contraindicated in those who are hypersensitive
to any component of an HGH-containing product.
PRECAUTIONS
Pregnant women and nursing mothers should avoid the use of HGH-containing
supplements.
Adolescents should avoid the use of supplemental HGH.
Those with diabetes should avoid the use of supplemental HGH.
Oral forms of HGH are not meant to be used parenterally and should never be used
in such a manner.
