Growth hormone(somatotropic hormone)

Growth hormone(GH) is endogene substance that is synthetized in adenohypophysis. Hormone is made of 191 amino-acids that are related by peptid connections.

Growth hormone(GH) stimulates protein synthesis and causes growth of almost all tissues in organism, including bones, skin, muscles and visceral organs.

Its effect on tissue growth is exposed by stimulating mitosis and increase of cell volume. The biggest number of soft tissues can grow under influences of specified factors during whole life. Bone growth in length stops in the moment when epyphisis are closed, at the end of adolescence. Further bone growth can be done only through thickening.

Too big growth hormone secretion(hypophysis tumor) before the end of adolescence causes gigant growth. Acromegalia is disorder which is created when pathologically big amount of this hormone is present after the growth is ended. Defects in hormone growth secretion, when its secretion is insufficient, lead to dwarf growth.

Metabolic effects of growth hormone

Physiological secretion of growth hormone is featured by low basal levels suddenly stopped by secretory jumps on 3-4 hours.

Level of chormone in blood can be increased under the influence of various stress types, hypoglycemia and amino-acids, especially arginine. Release of GH can be inhibited through increase in level of glucose and glucocorticoids.

Effects on protein metabolism:

• GH stimulates entrance of some amino-acids into cells
• Stimulation of protein synthesis in ribosoms
• RNK creation stimulation
• Increase of protein catabolism and use of amino-acids in the process of gluconeogenesis

Effects on fat metabolism:

• Stimulation of free fat acids from the fat depoes
• Stimulation of free fat acids decomposition to Acetil-Co-A and further decomposition and energy release

Effects on carbohydrates metabolism:

• GH leads to decreased glucose use
• Stimulation of synthesis and glycogen delaying in cells
• Decreased glucose take over into the cells, after cells saturation with glycogen

Regulation of growth hormone secretion

Hormones that are synthetized and released in hypothalamus are the main regulators of adenohypophysis hormone secretion, and along with that growth hormone secretion. Influence of various parts of central nervous system are integrated in hypothalamus that secrets two chormones(releasing factors). One is hormone of growth hormone(HG-GH) that stimulates GH secretion, and second is somatostatine that inhibits secretion of HR from hypophysis.

Factors that continuously control secretion of growth hormone are stress and nutrition.

Acute condition of hypoglycemia works as stronger stimulus for growth hormone secretion, related to amino-acids level in blood.

Somatomedins(IGF) as intercessors in growth hormone effects

Biology effects of growth hormone are done in two ways:

1)      direct effect of growth hormone

2)      indirect effect over IGF-1

Therapy appliance

Today therapy appliance of growth hormone is justified in following conditions:

• dwarf growth – occurred due to growth hormone deficit
• healing of primary and secondary osteoporosis
• conditions related to aging process
• acceleration of healing process and wound growth process

Appliance in sports

Basic motives for growth hormone use in sports are:

• Muscle mass increase
• Reduction of fat percent in organism. In many sports excess of fat materies represents unneeded part, especially in body-buiding and power sports
• Increase of glycogene depoes in muscles represents benefit in endurance sports types
• Acceleration in regeneration of injured muscle-skeletal tissues.

In sports pharmacological and physiological stimulators of growth hormone secretion are used. Used drugs are: levodopa, klonidin, propranolol.

Use of amino-acids is widespread, too(arginine, lysine, tryptophane and ornitine), that in normal methabolism stimulate release of endogene growth hormone.

Harmful effects

Problems can be medical and ethical.

Long term use of high growth hormone doses leads to numerous and serious disorders in organism:

• Acromegaly
• Diabetes
• Arthritis
• Myopathys
• Autoantibody creation on GH, which leads to relative deficiency of this hormone
• Hepatitis and HIV/AIDS

Detection

It is a fact that till today there are no well controlled studies that can confirm growth hormone true effects on work capacity.

Methods for clear detection of this hormone abuse are not developed till now.

“Doping in sport”, Marina Djordjevic Nikic