GH (Growth hormone), also known as growth hormone, somatotropin or somatotropic hormone (STH), is a peptide produced by the pituitary (pituitary) gland. During adolescence, plasma GH levels increase considerably, stimulating statural growth, increasing nitrogen retention and favoring the oxidation of lipid stocks. All of these effects are mediated by IGF-1 (somatomedin or insulin-like growth factor), a potent anabolic hormone produced by the liver in response to somatotropin.
After this period of life, GH levels decrease but the hormone continues to be produced anyway.
In humans, plasma GH values vary from 1 to 5 ng / ml, with peaks of up to 10 ng / ml under stress or after overtraining. The secretion is pulsatile with more frequent and wider peaks in the first hours of night sleep.
Discovered in 1912 by Evans, growth hormone has long been studied to evaluate its therapeutic properties and possible side effects.
A GH deficiency in the child impairs body growth (pituitary dwarfism) and the development of genitals and somatic features; at the same time, fatty deposits in the abdominal region also increase.
If the growth hormone deficiency affects the adult there is instead a reduction in muscle mass and a simultaneous increase in fat, the appearance of metabolic alterations, an increased bone fragility and a reduced tolerance of physical exercise.
GROWTH HORMONE DEFICIENCY
Pituitary dwarfism affects one in 4000 children and is more common in boys, who are 2.5 times more likely to develop it than girls. This condition can be greatly improved through the administration of GH (generally doses between 0.025 and 0.05 mg / kg / day are used).
The first growth hormone medicines contained biological somatotropin. In fact, GH was extracted from the pituitary gland of the corpses of young men or monkeys, with considerable ethical and health problems. This practice was highly dangerous and significantly increased the risk of contracting Creutzfeld-Jacob disease.
Today GH is produced in specialized laboratories using the recombinant DNA (rhGH) technique.
The endogenous synthesis of GH is regulated by two peptides called GHRH (somatotropin releasing hormone) and SST or SRIF (somatostatin) respectively. The first hormone stimulates the production and release of GH by the somatotropic cells of the anterior pituitary. Somatostatin, on the other hand, has a "negative feedback" effect and tends to inhibit the release of GH and many other hormones such as prolactin, insulin and thyroid hormones Its powerful inhibitory effect explains its effectiveness in counteracting the dangerous effects induced by an overproduction of GH (acromegaly, gigantism).
Under physiological conditions, GH secretion is episodic, with larger peaks at night. The somatostatin regulates the rhythm and duration of the peaks while the GHRH regulates the amplitude.
The IGF-1 produced by the liver also tends to inhibit the secretion of growth hormone.
In the bloodstream the growth hormone circulates bound to a transport protein called GHBP, produced mainly in the liver. Once GH reaches the target cell, due to its protein nature, it binds to a membrane receptor, which it interacts by activating a whole series of intracellular signals mediated by tyrosine kinases.
During childhood, GH secretion increases until it reaches its maximum in puberty
In adulthood, after the age of 30, it begins to decline
At the age of 50, the secretion of GH over 24 hours is halved compared to that of the young adult
At 70, the secretion of growth hormone is further reduced and is equal to 1/3 of that of the young adult
Exercise helps to counteract this physiological decline
Other articles on "GH Growth Hormone"
- GH - Growth Hormone
- Stimulate the synthesis of growth hormone
- GH hormone and doping
- GH and doping: acromegaly and health dangers
