Human growth hormoneHuman 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 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
hGH also stimulates the immune system and increases body mass.
Diseases associated with hGH:Growth hormone.
HGH and the black market
HGH has also gained popularity amongst body builders and other athletes who use anabolic steroid because of it's effects on muscle growth, creating an black market for the hormone.