GH (Growth hormone), also known as growth hormone, somatotropin or somatotropic hormone (STH), is a peptide produced by the pituitary gland (hypophysis). During adolescence, plasma GH levels increase considerably, stimulating statural growth, increasing nitrogen retention and favoring the oxidation of lipid stocks. All these effects are mediated by IGF-1 (somatomedin or similar insulin growth factor), a powerful 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.
In humans, plasma GH values range from 1 to 5 ng / ml, with peaks of even 10 ng / ml under stress or after overtraining. The secretion is pulsatile with more frequent and wider peaks in the first hours of sleep at night.
Discovered in 1912 by Evans, the growth hormone has long been studied to evaluate its therapeutic properties and possible side effects.
A GH deficiency in the child compromises body growth (pituitary dwarfism) and the development of genitals and facial features; at the same time, fatty deposits also increase in the abdominal region.
If the deficiency of the growth hormone affects the adult, there is instead a reduction in muscle mass and a simultaneous increase in adipose tissue, the appearance of metabolic alterations, an increased fragility of bone and a reduced tolerance of physical exercise.
DEFICIENT HORMONE OF GROWTH | ||
| CHILD | ADULT | |
| Reduced statural growth (NANISM) | Reduced quality of life, due to reduced energy, difficulty concentrating, low self-esteem | |
| increases the waist / hip ratio, the lean mass decreases | ||
| reduced functionality and cardiac mass, bradycardia | ||
| reduced tissue uptake of oxygen | ||
| atherosclerosis, insulin resistance | ||
Pituitary dwarfism affects one in 4000 children and is more common in males, who are 2.5 times more likely to develop it than females. This condition can be significantly 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. GH was in fact extracted from the pituitary gland of 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 technique (rhGH). Despite the particularly high costs, the popularity of GH has grown a lot in recent years; its use has in fact been extended to anti-aging therapies (especially in the United States) and has found considerable success even in sports where it is used as a doping drug.
Even the GH coming from the black market is now of synthetic origin and derives, mostly, from thefts, false recipes and sales by parents of children suffering from this hormone deficiency. However, maximum attention is recommended as there are many counterfeit drugs due to the high cost of the product. Many of these contain HCG (human chorionic gonadotropin), a hormone quite similar to GH usually used to reactivate testicular testosterone production (for example after taking high-dose anabolic steroids). Since hCG levels increase significantly during gestation, to expose its presence it is sufficient to perform a urinary pregnancy test in the morning, after having taken a substantial dose of the product before the night rest.
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 gland. On the other hand, somatostatin 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 countering the dangerous effects induced by an overproduction of GH (acromegaly, gigantism).
Under physiological conditions, GH secretion is episodic, with larger peaks at night. Somatostatin regulates the rhythm and duration of peaks while GHRH regulates its amplitude.
Also the IGF-1 produced by the liver tends to inhibit the secretion of growth hormone.
In the circulatory stream the growth hormone circulates linked to a transport protein called GHBP, mainly produced in the liver. Once in the target cell, GH, due to its protein nature, binds to a membrane receptor, which interacts by activating a whole series of intracellular signals mediated by tyrosine kinases.
During childhood, GH secretion increases until it reaches its peak in puberty
In adulthood, after the age of 30, it begins to decline
At 50 years the secretion of GH within 24 hours is halved compared to that of the young adult
At 70 years the growth hormone secretion is further reduced and is equal to 1/3 of that of the young adult
Exercise helps counteract this physiological decline
