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Growth Hormones and Exercise

Growth Hormones and Exercise

Physiological Functions of Growth Hormones.

All the major anterior pituitary hormones, except for growth hormones, exert their principal effects by stimulating target glands, including thyroid glands, adrenal cortex, ovaries,, testicles and mammary glands. The function of each of these pituitary hormones are so intimately concerned with the functions of the respective target glands that except for growth hormone. Growth hormones, in contrast to other hormones, does not function through a target gland but exerts its effects directly on all or almost all the tissues of the body.

Growth Hormone Promotes Growth of Many Tissues.

Growth hormone also called somatotropic hormone or sometotropin is a small protein molecule that contains 191 amino acids in single chain. It causes growth of almost molecular all tissues of the body that are capable of growing. It promotes increased size of the cells and increased mitoses, with development of greater number of cells and specific differentiation of certain types of cells such as bone growth cells and early muscle cells.


The rat given growth hormone in the early days of life and even after the two rates reached adulthood. In the early stages of development all organs of treated rat increased proportionately in size. After adulthood was reached most of the bones stopped lengthening, but many of the soft tissues continued to grow. The results from the fact that once the epiphyses of the long bones have united with the shafts, further lengthening  of bones can not occur, even though most other tissues of the body can continue to grow throughout life.

Growth Hormone has Several Metabolic Effects.

Aside from its general effect in causing growth, growth hormone has multiple specific metabolic effects including:

i)                   Increased rate of protein synthesis in most cells of the body.

ii)                 Increased mobilization of fatty acids from adipose tissues, increased free fatty acids in the blood, and increased use of fatty acids for energy.

iii)              Decreased rate of glucose utilization throughout the body. Thus in effect growth hormone enhances body protein uses up fat stores and conserves carbohydrates.

Growth Hormones Promotes Protein Deposition in Tissues.

Although the precise mechanisms  by which growth hormone increases protein deposition are not known a series of different effects are known, all of which could lead to enhanced protein deposition.

Enhancement of Amino Acids Transport Through the Cell Membranes.

Growth hormones directly enhances transport of at least some and perhaps most amino acids through the cell membranes to interior of the cells. This increases the concentration in the cells and presumed to be at least partly responsible for the increased protein synthesis. This control of the amino acid transport is similar to the effect of insulin in controlling glucose transport the membrane.

Enhancement of RNA Translation to Cause Protein Synthesis by Ribosomes.

Even when the amino acids concentration are not increased in the cells , growth hormone still increases RNA translation, causing protein to be synthesized in greater amounts by the ribosome in cytoplasm.

Increased Nuclear Transcription of DNA to Form RNA.

Over more prolonged periods 24 to 48 hours, growth hormone also stimulates the transcription of DNA in the nucleus, causing the formation of increased quantities of RNA. This promotes more protein synthesis and growth if sufficient energy, amino acids, vitamins and other requisites for growth are available. In the long run, this may be the most important function of the growth hormone.

Decrease Catabolism of Protein and Amino Acids.

In addition to the increase protein synthesis, there is a decrease in the breakdown of cell protein. A probable reason for this is that growth hormone also mobilizes large quantities of free fatty acids from the adipose tissue and these are used to supply most of energy for the body’s cells, thus acting as a potent ” protein sparer.”

Growth Hormone Enhance Fat Utilization.

Growth hormone has specific effect in causing the release of fatty acids from adipose tissue and therefore increased the concentration of fatty acids in the body fluids. In addition in the tissues throughout the body growth hormones enhance the conservation of fatty acids to acetyl coenzyme and its subsequent utilization for energy. Therefore under the influence of growth hormone, fat is used for energy in preference to the use of carbohydrates and proteins.

Growth hormone’s ability to promote fat utilization together with the protein anabolic effect, causing an increase in lean body mass. However mobilization of fat by growth hormone requires several hours to occur, where as enhancement of protein synthesis can begin in minutes under the influence of growth hormone.

“Ketogenic” Effects on Growth Hormone.

Under the influence of excessive amounts of growth hormone, fat mobilization from adipose tissue some time becomes so great that large quantities of acetoacetic acid are form by the live and release in to the body fluid, thus causing ketosis this excessive mobilization of fat from the adipose tissue also frequently causes of fatty liver.

Growth Hormone Decreases Carbohydrate Utilization.

Growth hormone causes multiple effects that influence carbohydrates metabolism, including :

i)                   Decreased glucose uptake in the tissues such as skeletal muscle and fat.

ii)                 Increased glucose production by the liver.

iii)              Increased insulin secretion.

Each of these changes results fro growth hormone induced “insulin resistance” which attenuates insulin’s action to stimulate the uptake and utilization of glucose in skeletal muscle and fat and to inhibit gluconeogenesis ( glucose production )  by the liver, this lead to increased blood glucose concentration and compensatory increase in insulin secretion.

For these reasons, growth hormone’s effects are called diabetogenic, and excess secretion of growth hormone can produce metabolic disturbance very similar to those found in patients with type II ( non insulin dependent) diabetes, who are  also very resistant to the metabolic effects of insulin.

Growth Hormone Stimulating Cartilage and Bone Growth.

Although growth hormone stimulates increased deposition of protein and increased growth almost all tissues  of the body, its  most obvious effect  is to increase growth of the skeletal frame. This results from multiple effects of growth hormone on bone including

There are two principal mechanisms of bone growth.

i)                   In response to growth hormone stimulation, the long bones grow in length at the epiphysieal cartilage, where the epiphyses at the end of the bone are separated from the shaft. This growth first causes deposition of a new cartilage, followed by its conversion into new bone. Thus elongated the shaft and pushing the epiphyses further and further apart. At the same time epiphysieal cartilage itself progressively used up, so that by late adolescence, no additional epiphysieal cartilage remains to provide for further long bone growth. At this time, bony fusion occurs between the shaft and the epiphysis at each end, so that no further lengthening of the long bone can occur.

ii)                 Osteoblasts in the bone periosteum and in some bone cavities deposit new bone on the surfaces of older bone. Simultaneously, Osteoblasts in the bone remove old bone. When the rate of deposition is greater than that of resorption, the thickness of bone increases. Growth hormone strongly stimulates blasts. Therefore the bones can continue to become thicker throughout the life under the influence of growth hormone. This is especially true for the membranous bones. For instance the jaw bones can be stimulated to grow even after adolescence causing forward protrusion of the chin and lower teeth. Likewise the bones of skull can grow in thickness and give rise to bony protrusions over the eyes.

Variation of Secretion of Growth Hormone.

Typically variation in growth hormone secretion throughout the day demonstrating the especially powerful effect of strenuous exercise and also high rate of growth hormone secretion that occurs during the first few hours of deep sleep.

8am to 01 Pm            30ng/ ml plasma

10pm to 4am             25ng/ ml plasma

Training Sessions as Per Growth Hormone Levels:

Training session from 9 am to 12 Noon following the rest of one to two hours can help in good recovery through natural process. At the time of noon release of growth hormone goes to peak and good to recover from the strenuous exercise.

The level of growth hormone also touch the max near to 30ng/ml during the midnight deep sleep. As per human physiology the peak secretion occurs twice in the 24 hours. Following the strenuous exercise the release of growth hormone helps in good recovery.


Khizer Hayat Raja

Sr. Lecturer in Physical Education & Sports

International Weightlifting Coach & Expert

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