Human growth hormone

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 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

It is the most abundant hormone produced by the pituitary. The production of hGH peaks during the rapid-growth phase of adolescence, then steadily drops with increasing age. HGH in the blood is only active for a few minutes. In this short time, it activates the production of the [[Insulin-like growth factor]] 1 (IGF-1) in the liver. Production of the hormone in the pituitary is pulsatile and the quantity produced depends on age and sex. The most frequent and highest peaks of production appear in pubertal age.
hGH also stimulates the immune system and increases body mass.

Diseases associated with hGH:

• GH-dependent dwarfism
• acromegaly
• gigantism
• Laron dwarfism[?]

See also:

• Pygmy[?]

For more information see also Growth hormone.