The endocrine system, along with the nervous and immune systems, helps humans deal with stress and other unusual events. One of the hormones produced by the endocrine glands is testosterone, which many associate with sports and competitiveness. But what is testosterone and how is it produced?
Testosterone is the male sex hormone and its counterpart in women is estrogen. The hormone is responsible for several key functions in men including sperm production, the development of the sexual organs, development of muscles and even the emergence of male sexual characteristics that are unique to men including facial hair and a deep, booming voice. Although women produce testosterone, its role in the bodies of members of the fairer sex is quite unclear.
About five percent of a man’s testosterone is produced in the adrenal glands while the rest is produced in the testicles. The production of the hormone begins with the brain. When the brain detects that the body needs more testosterone, the hypothalamus kick-starts the production of testosterone by secreting a gonadotropin-releasing hormone.
Once the pituitary gland notices the release of the gonadotropin-releasing hormone, it produces follicle-stimulating and luteinizing hormones which wind their way down to the testicles via the bloodstream. Upon reaching the testicles, the follicle stimulating hormone signals the production of more sperm. The luteinizing hormone, on the other hand, jumpstarts the production of more testosterone in the testicles.
The Leydig cells that can be found in the testicles produce testosterone by converting cholesterol from the food men eat. When the cholesterol level in the blood is low, the testicles produce a small level which it can use for the production of testosterone. At the end of the production of the hormone, testosterone is released to the bloodstream. A small percentage circulates freely around the body while the rest attaches to sex hormone-binding-globulin or SHBG and albumin proteins.
Testosterone can be classified into three types: free, SHBG-bound and albumin-bound.
Free testosterone is the small percentage of the hormone that freely circulates in the body. Unlike the other two types of testosterone, free testosterone does not attach itself to proteins, allowing it to immediately work with cells and receptors.
SHBG-bound testosterone accounts for 40 to 50 percent of the total amount of the hormone found in men. The protein is produced by the liver and plays an important role in controlling the amount of free testosterone in the body. Testosterone bound to SHBG cannot be used by the body for key male functions.
Just like SHBG, albumin is a protein created in the liver. Its primary role is to regulate extra-cellular fluid. Testosterone attached to the protein cannot be readily used by the body. But unlike the bond between testosterone and SHBG, the bond between the hormone and albumin is considerably weaker and can be broken down.