Testosterone and some anabolic steroids act as protein synthesis in skeletal muscle cells. Testosterone is secreted from the testes via luteinizing hormone (LH) from the pituitary gland. The largest amount of testosterone secreted daily occurs between the age of 18 and 25. About 97% of the testosterone becomes loosely bound with blood proteins or more tightly bound to sex-hormone binding globulin, and circulates in the blood for 30 to 60 minutes. By this time it either becomes fixed to tissues or is degraded into inactive products and excreted. Only about 1 to 3% is able to interact with receptors in target cells and initiate protein synthesis.
Testosterone is responsiblie for the masculine body. It enhances sex drve, builds muscle and trims fat, improves mood, lowers cholesterol, protects against heart disease and stimulates memory. Testosterone is involved in body hair growth, baldness, bass voice, and increased acne.
The main effect testosterone has on the growth process is to increase the level of transcription within the muscle cell nucleus. Testosterone enters the cell cytoplasm where it binds with a specific receptor protein. The combined receptor protein/testosterone is then transported into the nucleus where it binds at specific points on the DNA strands in the chromosomes. Testosterone exerts it’s effect by activating DNA dependent RNA polymerase enzymes. As a result, during transcription, the synthesis of ribosomal RNAs with ribosome formation, and messenger RNAs are increased with a subsequent activation of protein synthesis. The newly formed messenger RNA (mRNA) then diffuses into the cytoplasm where it promotes the translation process at the ribosomes to from new proteins, which is the building of muscle tissue.
Daryl Conant, M.Ed