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What is Testosterone?

Mary McMahon
Updated: Mar 03, 2024

Testosterone is the principal androgen, or male sex hormone, although it appears in both genders. It is classified as an anabolic steroid because it will bulk up body tissues and encourage the retention of protein by the body. In both men and women, testosterone is produced in the gonads, and it is derived from cholesterol. In addition to occurring naturally in the body, this hormone is also used to treat certain medical conditions, and some athletes take it to bulk up for competition, although this practice is outlawed by most professional sports organizations.

In both genders, a testosterone production spike during early puberty helps to mature the body, encouraging the growth of body hair, sparking a growth spurt, and creating more oily skin and hair. In boys, the spike deepens the voice, causes the testicles to descend, and contributes to the development of other sex characteristics. Throughout the life of a man, his body will continue to produce testosterone, although the production rate will decline in old age.

Testosterone also contributes to physical differences between male and female brains. The male brain is actually larger, as are many other organs of the male body, because the hormone causes a greater growth rate. However, the corpus callosum, or connection between the hemispheres of the brain, is larger in females. The exact impact that this has on cognition and abilities is unclear, although numerous studies on the issue have been undertaken.

Therapeutically, testosterone is often used to treat conditions caused when not enough is naturally produced by the body. A blood test can be performed to see how much the body is creating, and if a doctor deems it necessary, he or she will prescribe therapeutic hormones. It is also used in the treatment of some cancers which have been shown to respond well to steroids, and in the treatment of women with gender dysmorphia to assist them in developing male sex characteristics while they transition.

Like other steroids, testosterone may be harmful in excess, especially when extra is taken without proper medical supervision; acne, highly oily skin, growth of some cancers, difficulty sleeping, and other complications are associated with abnormally high testosterone levels. However, a deficiency can also be harmful, and will have an impact on libido, energy, and maintenance of general health. Most human bodies are able to regulate hormone levels naturally, requiring no medical intervention. Some older men participate in androgen replacement therapy programs when their natural testosterone levels decline in order to maintain their younger state of health and vigor.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a The Health Board researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By anon142004 — On Jan 11, 2011

because of this information,I have learned so many things about the human development. Also, it helps me a lot on doing my reports and assignments.

By XXYGuy — On Nov 20, 2010

Fascinating stuff about male brains. My brain can't possibly be as big as a woman's brain, since my skull bones fused early in infancy and I have a rather small head circumference. I'm definitely male, maybe my brain is more dense than most? (that's an intended pun by the way)

I also have really small hands and really small feet and I used to have really small testes too! Ah, but unlike my hands and feet I could fix the apparent size of my testes. (that's another pun if it's allowed?)

And testosterone is an androgenic / anabolic steroid otherwise known as an AA Steroid. It's amazing what tit bits of basically useless information can be gained when you're XXY and really want to know everything about everything that affects why we are the way we are.

By XXYGuy — On Nov 17, 2010

@d0592 I know of two diseases that bring about low or no production of testosterone.

The first one I suffer from is called Klinefelter's syndrome, where the testes are incapable of producing sufficient testosterone due to malformation: Hypergonadtrophic Hypogonadism or Primary hypogonadism.

The second one is called Kallmann syndrome where the testes are not sent the right hormone signals to start producing testosterone: Hypogonadtrophic Hypogonadism or Secondary Hypogonadism.

By XXYGuy — On Nov 17, 2010

@fabulian: Provided your testes and adrenal glands are left in place, I know of no reason why you won't still produce testosterone and other androgens, but you should discuss this with your surgeon.

By fabulian — On Jun 16, 2009

i will be having my prostate removed, it is cancerous. will my body still produce testosterone after my surgery?

By d0592 — On Dec 04, 2008

What are some things that can cause low testosterone? (diseases, health issues etc,...)

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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