Human Growth Hormone (HGH)

Human growth hormone (or hGH) is a polypeptide that is synthetised by somatotroph cells of the anterior lobe of pituitary gland. The genes for human growth hormone are localized in the q22-24 region of 17 chromosome and they are closely related to human chorionic sommatotropin (hCS) genes. The hormone is built of single polypeptide chain of 191 amino acid residues and has molecular weight of about 22,000. Despite marked structural similarities between growth hormone from different species only human and primate growth hormone is active in humans. Together with human chorionic sommatotropin (hCS) and prolactin (PRL) it forms a group of hormones with growth-promoting and lactogenic activity.

The biochemistry of HGH is complex. It seems that we all have plenty of HGH, but as we age it is prevented from being released from the pituitary by deficiency of HGH releasing hormone (HGHRH) which is made in the hypothalamus of the brain and by a substance called HGHP, a peptide of seven small amino acids. One day it may be possible to supplement with one or both of these two substances and cause the release of your own HGH; however as yet these are not commercially available. The main action of hGH is to stimulate the liver and other tissues to produce IGF-1. Hepatic IGF-1 is believed to be a homeostatic regulator of tissue growth on the level of the whole organism. Tissue IGF-1 is said to possess autocrine properties. During developmental stages hGH is essential to promoting linear growth; it stimulates the growth of bone and muscle. Other actions of hGH: increases protein synthesis (anabolic properties - positive nitrogen balance); hyperglycemic (antagonistic to insulin); lipolysis (increases levels of free fatty acids and glicerol); influences mineral and bone metabolism; prolactin-like activity.

Growth hormone (GH) is also called somatropin. GH is a polypeptide hormone which stimulates growth and cell reproduction in humans and other vertebrate animals. HGH refers to human growth hormone but this older abbreviation has begun to carry paradoxical connotations (see final paragraphs for fuller discussion of HGH). GH is secreted into the blood by the somatatotroph cells of the anterior pituitary gland. The transcription factor PIT-1 stimulates both the development of these cells and their production of GH. Failure of development of these cells, as well as destruction of the anterior pituitary gland, results in GH deficiency.

Peptides released by neurosecretory nuclei of the hypothalamus into the portal venous blood surrounding the pituitary are the major controllers of GH secretion by the somatotrophs. Growth hormone releasing hormone (GHRH) from the arcuate nucleus and ghrelin promote GH secretion, and somatostatin from the periventricular nucleus inhibits it. Although the balance of these stimulating and inhibiting peptides determines GH release, this balance is in turn affected by many physiologic stimulators and inhibitors of GH release. Stimulators of GH release include (among others) sleep, exercise, hypoglycemia, dietary protein, and estradiol. Inhibitors of GH secretion include dietary carbohydrate and glucocorticoids.

The amount and pattern of GH secretion change throughout life. Basal levels are highest in early childhood. The amplitude and frequency of peaks is greatest during the pubertal growth spurt. Healthy children and adolescents average about 8 peaks per 24 hours. Adults average about 5 peaks. Basal levels and the amplitude and frequency of peaks decline throughout adult life.

Several molecular forms of GH circulate. Much of the growth hormone in the circulation is bound to a protein (growth hormone binding protein, GHBP) which is derived from the GH receptor.

Human Growth Hormone (HGH) is produced, stored and secreted by the pituitary gland located at the base of the brain. It is a hormone that is widely known for its powerful anabolic (muscle building) effects as well as its lipotropic (breakdown and utilization of body fat) effects. The overall result of these effects is an increase in lean tissue mass and a decrease in body fat.
Human Growth Hormone (Hgh) is an endocrine hormone which declines with aging. Hgh has been shown to deter many of the effects of the aging process. Unlike other hormones, HgH has been shown to actually reverse the biological clock by as much as two decades!

It has been scientifically proven that one of the major factors in starting the aging process is caused by a decreased production of Hgh by the pituitary gland. Low levels of Hgh are associated with signs and symptoms such as wrinkles, forgetfulness, unexplained weight gain, decreased sex drive, bone and joint diseases, and hair loss.

HGH is in abundant supply in the normal young human being and is responsible for the final adult size of the body. It controls the size of muscles and internal organs and the length of bones. The bones of the legs and arms are lengthening in direct response to HGH until age eighteen. These bones fuse at age eighteen just at that place where lengthening is taking place. Final height and length of arms is determined by this event, since no further lengthening is possible after this fusion.

In childhood, HGH causes the growth of long bones and this brings a person to his or her final height. Traditionally, this was all HGH was thought to do. New research shows that every cell in the body has HGH receptors and that HGH is doing a host of jobs in human metabolism in every organ in the body. There are even receptors in the brain the activation of which results in the production of endorphans, molecules which keep one's mood even and upbeat. Skin cells respond to HGH with even growth producing the smooth appearance of children's skin. Cells in the brain respond by literally coming back to life (about 10% of the brain cells become non-functional each decade of life). Thus, HGH is the latest and most effective treatment for Alzheimer's disease, although the large double-blind clinical trials have not yet been done.

One consistent effect of HGH deficiency is irritability and when a person receives replacement therapy this reverts to a profound sense of well-being. Bone cells respond by making new bone and osteoporosis reverses, although this effect requires two or more years for completion. Fat cells respond by giving up their little lives as they are burned for energy. The weight gain around the middle which is so characteristic of HGH deficiency, melts away in a few months. Muscle cells respond by becoming larger and stronger, especially in the upper body. The strength and endurance of youth reappears. Many people are able to read without reading glasses again as the ciliary muscle of the eye becomes stronger again.

Human growth hormone (HGH) research information

Research with HGH and its medical disorders
Effects of human growth hormone in men over 60 years old
Growth hormone: uses and abuses
Growth hormone and function in elderly persons
Whither recombinant human growth hormone
Human growth hormone and creutzfeldt-jakob disease
Growth hormone (hgh) - the first "anti-aging" medication
The use of human growth hormone for children with idiopathic short stature