What is Human growth hormone
Human growth hormone (HGH) is also called somatotropin (STH) is a 191 amino acid, single chain polypeptide hormone which is
synthesized stored and secreted by the somatotroph cells within the lateral wings of the anterior pituitary gland, which
stimulates growth and cell reproduction in humans.
Structure and gene of molecule
Human growth hormones have their genes localized in the q22-24 region of chromosome 17 (GH1) which are closely related to
human chorionic somatomammotropin (hCS, also known as placental lactogen) genes.
Human growth hormone (HGH), human chorionic somatomammotropin (hCS), and prolactin (PRL) are a group of homologous hormones
with have growth-promoting and lactogenic activity. The human growth hormone is a protein of 191 amino acids, having a
molecular weight of 22,000 Daltons,
Secretion of growth hormone
The growth hormones in circulation in the body are bound to a protein (growth hormone binding protein, GHBP), that are derived
from the growth hormone receptor. The growth hormones are secreted in the blood by the somatotrope cells of the anterior
pituitary gland in large amount than any other pituitary hormone.
During puberty the secretions level is very high, and the transcription factor PT1, (a protein that works with other proteins
to either promote or suppress the transcription of genes), stimulates the development of these cells to produce growth
hormone. If these cells fails to develop as well the destruction in the anterior pituitary glands, a growth hormone deficiency
Functions of growth hormone
Growth hormone (GH) acts by interacting with specific receptors on the surface of the cells. Increase in height is one of the
best known effects of growth hormone (GH) actions in children and it is stimulated by two mechanisms.
Growth hormone directly stimulates division and multiplication of chondrocytes of cartilage. These are primarily the cells in
the growing ends (epiphyses) of children long bones (arms, legs, digits). Also, growth hormone also stimulates production of
insulin-like growth factor 1 (IGF-1, a hormone homologous to proinsulin.
The major target organ of growth human for this process is the liver, and is the primary region of production of IGF-1. The
insulin-like growth factor IGF-1 has growth stimulating effects on varieties of tissues.
Other functions of growth hormone
Apart from increasing height in children growth hormone, growth hormone carries out many other metabolic functions such as
increasing the calcium retention, strengthens and increases the mineralization of the bone, increase in muscle mass through
the creation of new cells, promotes lipolysis, resulting in reduction of the adipose tissue (body fat), increases promote
synthesis and stimulates the growth of all internal organs, reduces the liver uptake of glucose, an effect that opposes that
of insulin, helps in the maintenance of pancreatic islets, promotes liver gluconeogenesis (glucose generation), plays a role
in fuel homeostatis and it also stimulates the immune system
Growth hormone deficiency
Deficiencies of growth hormone differs at various ages, children with growth deficiencies have short stature while in adults
the effects of the deficiencies are not easily noticeable and may include decrease in strength, energy, and bone mass as well
as increased cardiovascular risk.
Other causes of growth deficiencies include mutations of specific genes, congenital malformations involving the hypothalamus
or pituitary gland, and damages to the pituitary gland from injury, surgery or disease.
Growth hormone replacement
Human growth hormone deficiencies are treated by replacing growth hormone. All the growth hormone presently in use is a
biosynthetic version of human growth hormone, manufactured by recombinant DNA technology.
Since growth hormone is a large protein molecule, it must be injected into subcutaneous tissue (or muscles) to get it into the
blood. A patient having a long-standing deficiency of growth, the benefits derived from the treatment are dramatic and
gratifying and side effects are rare. Growth hormone treatment is a replacement therapy in adults with GH deficiency of either
childhood-onset (after completing growth phase) or adult-onset (usually as a result as result of acquired pituitary tumor).