Hormone (Growth Hormone GH) somatropin Humana is a polypeptide compound with one hundred ninety-one amino acids and a molecular weight of about 21,500 daltons. The anterior pituitary contains between five and ten milligrams of GH, which is synthesized and accumulated in the somatotrophs cells. The production of GH is influenced both by age and sex and is estimated at 0.4 – 1.0 mg/day in the adult male, with values higher in adolescents and women. Moreover, to increase these hormone levels there are testosterone pills for men that are reliable.
Serum GH concentrations vary during the day, usually from 0.5 to 3.0 g/litre in the male adult, in accordance with the production, higher in adolescents and women. GHI know is metabolized in the liver and has a life plasma from seventeen to forty-five minutes.
The regulation of secretion of GH.
GH secretion by the pituitary gland is flow.jpg and is regulated by a feedback mechanism in which are involved two hormones, one of excitatory action, GH-Releasing Hormone (GHRH), and the other inhibitory action, somatostatin (SRIF). The response to the pituitary in the GHRH is influenced by many factors and may decrease with age. GH is excreted in response to numerous stimuli physiological and pharmacological acting on areas specific brain via routes controlled by adrenergic, serotoninergic, dopaminergic, and cholinergic neurons. Stimuli are integrated between them and can act synergistically or competitively, but ultimately include all in the common final pathway consisting of GHRH and SRIF.
There are sexual differences in GH secretory capacity: these are related to estrogen levels. During the day there are small episodes of GH secretion, the biggest of which takes place between 60 and 90 minutes after the start of the dream, which corresponds to the phase of deep sleep (slow EEG waves). The nocturnal secretion of GH can be increased in athletes due to the increase in physical activity.
Physical and psychological stress can increase the secretion of GH. Although the exact mechanism and its control center are not known with certainty, it is possible to act through the increase of central catecholamine secretion. GH secretion is stimulated by hypoglycemia and inhibited by hyperglycemia. Insulin Hypoglycemia is considered a test to assess pituitary function and involves an increase in GH in 85% of normal subjects.
Glucocorticoids stimulate GH at physiological concentrations, while hypercortisolism inhibits the response to stimuli. Also, amino acids (especially ARGININE) that stimulate the GH are effective when ingested orally or injected intravenously.
The secretion of Gh during physical exercise.
Physical exercise is a potent stimulus for the secretion of GH; a 20-minute exercise, which implies a consumption of oxygen between 75 and 90% of the maximum consumption, causes a response in the equivalent of the hypoglycemia GH insulin and greater than the response induced by sleep, arginine, and levodopa. The hormone response is influenced by the feature of the exercise (type, intensity, duration), the characteristic of the individual (age, sex, physical Constitution, degree of fatigue), and intake of drugs.
Levels of the hormone increase during exercise; the peak of this increase occurs so early the more intense is the physical exercise: the peaks are between 15 and 30 minutes once it has started. It has been shown that appears a GH response during the brief but intense exercise of rising of steps, but however, there is no response after a Trek done at a moderate speed (6.4 Km/H) for one hour and a half. A protocol for the lifting of weight, with a high load and few repetitions, causes an increase in GH, while a protocol of low and many repetitions, total weight and duration equivalent, does not cause any effect.
The increase of the temperature during exercise can be a stimulus for the secretion of GH; the exercise in a hot environment causes one response more GH than another analog carried out in cold weather.
Effects of GH in the intermediate metabolism.
GH displaces the oxidative metabolism towards the use of fatty acids, allowing the use of proteins of anabolic form and has a marked contrainsular action, stimulates the glucogenesis and hepatic glycogenolysis, the secretion of insulin by Hyperglycemia or by direct action on the beta cells of the pancreas, regardless of hyperglycemia.
On the other hand, GH increases the mobilization of lipids from adipose tissue. GH supply determines a reduction of fat reserves, an increase in the hepatic lipid content, and increases the concentration of plasma-free fatty acids. Some studies indicate that GH plays a significant role in the mobilization of fatty acids during exercise; nor should we forget that this hormone stimulates significantly the utilization of amino acids for protein synthesis.
Effects of GH in muscle tissue.
Muscular development is a complicated process that occurs as a function of physical activity on the one hand and on the other hormonal factors. Muscle grows through the action of sarcomeres at musculotendinous union and an increase in the number of myofibrils.
The proteins necessary for the growth of the fibers (actin, myosin, and tropomyosin) are synthesized in the polyribosomes which are found in the sarcoplasm of adjacent myofibrils already formed. By this mechanism acting exercise and some and some hormones, although then the finer cell mechanism seems to be different in both conditions.
When added, in vitro GH to muscle cells do not appear modifications for 20-30 minutes. After the silent initial evidenced an increase of the speed of uptake of amino acids for one or two hours.
Normal adults treated with GH for 21 days, have obtained an increase in the total weight of 20% (+ 26.2% quadriceps muscle) and an increase in the diameter of the muscle fibers from 6 to 12% with respect to the control group. The effects of GH on the recovery of muscle atrophic by immobilization are very interesting practical. In fact, the gastrocnemius muscle of a rat, atrophic after an immobilization, weighs 72% with respect to the weight of the contralateral muscle. GH supply increases the weight of the atrophic muscle by 19% by comparing it to the control animals not treated. GH also stimulates the synthesis of collagen to muscular levels.
There are two main ways to obtain increased hematic levels of GH: hormone injection or oral intake of various drugs able to induce their release by the pituitary gland. Until recently the only way to find GH in the trade (in limited quantities) was from the pituitary gland of cadavers. Its use was destined, almost exclusively, to therapy with children with deficiency of this hormone. The use of the GH extracted from cadavers has been abandoned for fear of various diseases. Currently, this GH commercially available biosynthetic human, obtained through the use of tecnicasde DNA.
On the other hand, it is possible to stimulate the pituitary GH synthesis, use medications such as propranolol, vasopressin, clonidine, or levodopa. The substances more easily achievable and used are amino acids. The use of amino acids such as arginine, lysine, ornithine, and tryptophan is widespread in athletes promoted in the form of specific preparations.
Possibility of use of GH in athletes.
There is enough evidence, especially by lifters in weight and bodybuilders about the powerfully beneficial effects of GH; They have been revealed increases in weight of lean mass after using GH. Some effects may be useful to bodybuilders so it has much importance the fat weight reduction and the obtaining of a bulky, well-defined muscle mass. The utility of this hormone in strength and power sports is certainly scarce. The apparent increase in muscle volume may be due to an increase of connective tissue only, and not to the elements of contractile.
In addition, as an alternative to the use of GH on healthy athletes, there may be some interesting potential applications of this hormone in the world of sport as a therapeutic agent. It has shown that GH can be experimentally increased the speed of consolidation of fractures when they have a problem. It has been also used in the treatment of primary and secondary osteoporosis with apparent success.
Problems concerning the use of the GH by competitors.
There are serious ethical and medical problems associated with the use of GH by healthy competitors. The acromegalic is the most insidious and irreversible of which derive from the excessive use of this hormone. Although there are just documents evidencing the occurrence of acromegaly in people taking GH, if there are numerous cases of athletes victims of its effects, such as the modification of the physiognomy: the increase in bone density of the face, hands, and feet. The medical aspects are only one facet of the problem: the ethical issues arising from the use of GH in athletes are even more delicate. The lack of scientific support in terms of efficacy and the potential dangers of its use should be sufficient arguments to dissuade athletes from its use.