Role Of Human Growth Hormone In Muscle Growth

Generally we see that weight lifters will develop muscles very much. Weight lifters have excessive muscle growth because of release of insulin growth factor-1 from the muscle cells and not from the liver. The IGF-1 produced from liver will be different from that obtained from the muscle cells. In order to study and know about the role of GH and IGF-1 in growth of the muscle it is necessary to probe the pathway of IGF-1 as well as to know the mechanism of growth of the muscle. It is also essential to study the autocrine and paracrine role of this hormone. The people who have undergone weight lift training due to their activity enable the muscle tissue to regenerate. The muscle tissues have the ability to respond to the physical or mechanical activities by taking the help from satellite cells. Satellite cells are precursor cells of the muscle. These cells are existing around the muscle cells. These pro-muscle cells remain idle until they are called upon by the hormone factor like IGF-1. It is studied that due to IGF-1, cells can regenerate and differentiate into cells that are similar to the nucleus of the muscle cells. The pre muscle cells are prepared in this way from satellite cells which also take part in muscle growth.

Muscle growth involves both hypertrophy and hyperplasia. The nucleus in the muscle cell also possesses the ability to divide. Unless there are many number of nuclei the muscle cannot develop, grow bigger and not repair the damaged tissue. The nuclei should be multiplied when there is muscle growth. Nuclei should be allowed to divide because of the presence of signature of all the proteins necessary for the metabolism of the cells in them. During muscle growth the cells divide and grow and make the DNA in the nucleus also to divide. DNA replication provides the machinery as genes which are necessary for the protein synthesis in the cells to grow further. This division of nuclei occurs as muscle becomes larger and as they need more nuclei to accommodate the genes required for protein synthesis in the enlarged muscle. This growth in number of nuclei and muscle cells will maintain number to volume ratio. When the satellite cells reproduce nuclei, they do it till the muscle cells area can bear the number of nuclei and later stops. From this it is concluded that exercise can induce the satellite cell stimulation which in turn is triggered by growth factors like IGF-1.

When IGF-1 or HGH are injected into the muscle cells, studies show that these hormones enhance the satellite cell function, DNA of the muscle, protein quantity in the muscle, weight of the muscle, and area of the muscle.