Human
growth hormone:
Growth hormone: A hormone made in the pituitary gland
that stimulates the release of another hormone called
somatomedin by the liver, thereby causing growth. Also
known as somatotropin. Growth hormone is a protein produced
by the anterior pituitary gland, the front section of
the gland, and is a polypeptide that consists of 191
amino acids . Growth hormone is given to children with
pituitary dwarfism (short stature due to underfunction
of the anterior pituitary) to help them grow. Excessive
growth hormone production in children can lead to gigantism,
and in adults it can lead to acromegaly.
Human Growth Hormone stimulate growth of bone and muscle. Human growth hormone is the most abundant hormone produced by the pituitary gland in the brain. It peaks during the rapid-growth phase of adolescence, then steadily declines with age. HGH stays in the bloodstream for only a few minutes. However, this is long enough to stimulate its uptake by the liver, causing the production of Insulin-like growth factor-1. Growth hormone affects specific target tissues in its role as a chemical messenger, working with IGF-1 to affect uptake of nutrients into the cell. HGH helps boost the immune system, increase lean body mass, stimulate neuroendocrine system balance and promote medical mental and physical performance.
Growth
factors
Small proteins produced by the human body that enable
cells to communicate and effectively coordinate activities
between one another. Growth factors in the body affect
the individual cells by binding to growth-factor-specific
receptors on the cell surface. A specific growth factor
may have many cell sources and can use different signal
transduction pathways at different times and with different
cells. Growth factors are involved in complex feedback
loops between the immune, nervous and endocrine systems,
and have significant effects on RNA, DNA protein synthesis,
and cell division.
Insulin like growth factor (IGF-1)
Polypeptides with considerable sequence similarity to
insulin. They are capable of eliciting the same biological
responses, including mitogenesis in cell culture. On
the cell surface, there are two types of insulin like
growth factor receptor, one of which closely resembles
the insulin receptor (which is also present). IGF-1
is primarily secreted by the liver in response to a
signal from growth hormone (hGH). It is also released
by many different tissues throughout the body, and affects
almost every cell to some degree. The major target tissues
affected by IGF-1 are muscle, cartilage, bone, liver,
kidney, nerves, skin, and lungs. IGF-1 additionally
regulates cell growth by moving cells from a resting
phase to an active phase of the cell cycle. IGF-1 also
increases the cell's ability to complete DNA synthesis.
IGF-1 acts within the nervous system and is critical
for the growth and development of nerve cells. IGF-1
plays an active role at the neuromuscular junction,
where interaction between nerve and muscle cells occurs.