25 May 2012

What is testosterone?

Testosterone is a steroid hormone which is made in the testes in males and in the ovaries in women (a minimal amount is also made in the adrenal glands). 

Testosterone has two major functions in the human body

Testosterone is needed to form and maintain the male sex organs and promote secondary male sex characteristics (in both men and women) such as voice deepening and hair growth patterns. This function is related to its androgenic properties Testosterone is the facilitation of muscle growth as well as bone development and maintenance. This is a result of its anabolic properties.

Testosterone production is regulated by hormones released from the brain. The hypothalamus and pituitary gland located in the brain produce hormonal signals that ultimately result in the production of testosterone. The hypothalamus is located just above the brain stem, and among its many functions, it produces gonadotrophin releasing hormone (GRH). GRH 

then travels a short distance to the pituitary gland, which is located in the base of the brain, and stimulates this gland to release FSH (follicle stimulating hormone) and LH (luteinizing hormone). These hormones travel through the bloodstream to activate the sex organs in both men and women. Subsequently, these hormones have a role in regulating testosterone levels in the bloodstream.

The majority of testosterone circulates in the blood bound to a carrier protein (many hormones that are produced in one area and affect another area have a carrier protein that helps their travel through the bloodstream). In this case the carrier protein is called "sex hormone binding globulin," or SHBG. When testosterone is being carried by SHBG, it is considered "bound". Bound testosterone does not play an active role in the body; only the unbound or "free" 

testosterone is able to enter the different cells of the body and exert its androgenic and anabolic effects. Thus, 
anything that affects the function or the amount of SHBG can also affect the total circulating amount of active 


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