Human growth hormone (HGH) is one of the major hormones influencing growth and development in humans. Such is the complexity of human growth, a period extending from birth to the age of 20 years, that a very large number of hormones influence it, producing many complex interactions. Besides HGH, the hormones, testosterone, oestradiol, cortisol, thyroxine and insulin have important roles at different stages of growth and development.

The most obvious action of HGH is that it stimulates somatic growth in pre-adolescents, but it also has metabolic effects. The importance of these metabolic actions in homeostatic regulation of fuel usage and storage is unclear as is the overall role of HGH in the adult. Receptors for HGH are present on the surface of every cell in the body. Discussion of the actions of HGH is futher complicated by the involvement of the plasma growth factors or somatomedins in the action of HGH. HGH stimulates the release mainly from the liver of two hormonal polypeptides, somatomedin C (or insulin-like growth factor I) and somatomedin A (insulin-like growth factor II).

In this chapter somatomedin C (insulin-like growth factor I) will be known as IGF-I and somatomedin A (insulin-like growth factor II) as IGF-II. IGF-I is the most important of these IGFs but there is still doubt whether many, if any, of the important metabolic effects of HGH are mediated via IGFs.

HGH seems to have some effects on muscle growth but the effect of IGF-I is greater. This action appears similar to that of insulin in that it promotes amino acid uptake and stimulates protein synthesis resulting, in children, in an increase in the length and diameter of muscle fibers, while only the latter growth occurs in adults. This stimulation of muscle protein synthesis and growth is qualitatively different to that induced by work, since insulin is required for HGH-stimulated muscle growth but not for that induced by work. However, the action of insulin is more likely to be an anti-catabolic effect on muscle protein rather than a direct stimulatory effect on muscle protein synthesis.

The actions of HGH on metabolism are complex at both the cellular and organ level and appear to be biphasic. In the first or acute phase, which seems to involve the action of HGH alone, amino acid uptake into muscle and liver is stimulated, and there is increased glucose uptake into muscle and adipose tissue together with reduced fat metabolism. During the second, chronic phase, mediated by the IGFs, there is increased lipolysis in adipose tissue resulting in a rise in the plasma concentration of fatty acids and increased fatty acid utilization, thus sparing glucose.

It is worth considering the HGH response to exercise in more detail. Within 20 minutes of beginning exercise to 75-90 per cent VO2max, HGH level rise. The intensity of the response depends on age, level of fitness and body composition. The type of exercise undertaken also produces varying HGH responses. Intense exercise produces earlier HGH secretion, endurance exercise produces HGH peaks in mid-term, while intermittent intense exercise is claimed to result in the highest HGH levels.

The potential risks of HGH therapy in children have been mentioned together with the close monitoring required in paediatric patients. The recommended standard replacement dose of HGH is about 0.6 IU/kg body weight per week. It is widely assumed that athletes who abuse the drug are taking 10 times this dose. Major side-effects include skeletal changes, enlargement of the fingers and toes, growth of the orbit and lengthening of the jaw. The internal organs enlarge and the cardiomegaly which is produced is often one of the causes of death associated with HGH abuse. Although the skeletal muscle increase in size, there are often complaints of muscle weakness. Biochemical changes include impaired glucose regulation, hyperlipidaemia and insulin resistance. At least once report, however, has found that clinical doses of HGH did not produce diabetic symptoms in children with short stature. These changes described above contribute to the prevalence of diabetes in HGH abusers. Arthritis and impotence often occur after chronic HGH abuse.

Human Growth Hormone is produced by many reputable pharmaceutical companies such as:

Jintopin 4IU by GenSci China
Jintopin 10IU by GenSci China
Hygetropin by Hygene China
SciTropin by Sciroxx

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• Jintopin 4IU

  Manufacturer: GenSci China
  Substance: Human Growth Hormone
  Pack: 1 kit (5 vials x 4iu/vial + 5 Syringes)

  
  

• Jintopin 10IU

  Manufacturer: GenSci China
  Substance: Human Growth Hormone
  Pack: 1 kit (5 vials x 10iu/vial + 5 Syringes)

  
  

• Hygetropin

  Manufacturer: Hygene China
  Substance: Human Growth Hormone
  Pack: 1 kit (20 vials x 8iu/vial)

  
  

• SciTropin

  Manufacturer: Sciroxx
  Substance: Human Growth Hormone
  Pack: 1 kit (10 vials x 10iu/vial)