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What Does Testosterone Do In Men? (9 Main Functions)

Isaac Robertson
Published by Isaac Robertson
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: April 10, 2023

The male sex hormone testosterone is possibly one of the most misunderstood hormones, especially in the athletic world.

See, most people simply associate it with anabolic steroids and athletes testing positive for banned substances.

But maintaining normal testosterone levels is vital for men’s health, and to help you better understand what it does in the male body, we’ve done some extensive research into the physiology of testosterone.

And no, this is not going to be an endorsement of testosterone therapy; we simply want to make sure that our readers understand why testosterone levels are such an important part of their health.

Quick Summary

  • Testosterone in men triggers sex drive, sperm count, mood, muscle mass, bone density, body hair, and weight management.
  • Having too much testosterone levels can trigger heart attack, high blood pressure, blood clots, or even prostate cancer.
  • Low testosterone levels affects a man's sex drive, sperm count, triggering hair loss, and also results into muscle loss.

What Does Testosterone Trigger?

man with tape measure and pants with hands

Testosterone affects men in 7 key areas, and these have varying impacts on health and fitness levels. Let’s take a look at each of them.

Sex Drive

Reduced testosterone in men is the most common cause of low libido. The same sex hormones responsible for adolescent boys going into sex overdrive also impact the opposite effect as men grow older.

And because from the age of 30, male sex hormones decrease by 1% per year, it’s often something that goes unnoticed for a while.

Many couples simply put it down to natural aging. But if you want to light a spark in those bedroom activities, then getting your body to produce more testosterone is a great place to start.

Sperm Count And Quality

condoms and paper sperms

Male levels of testosterone also play a key role in fertility. When it comes to conceiving a baby, it’s not just about having the sexual drive to take action. It’s even more important to focus on sperm production and quality.

Lower testosterone may lead to low levels of sperm cells.

And even if production is ramped up, the quality of the sperm needs to be high to conceive successfully.

While there are many other reasons why your sperm quality and production are low, addressing a problem with your testosterone level is a great place to start and rule out other issues.

Muscle Mass

There’s a very good reason that many athletes and bodybuilders resort to intramuscular injections of testosterone to create more muscle bulk. It is an almost guaranteed way to achieve more muscle mass.

But the health risks are huge, and such testosterone therapy should only be considered with the help of a doctor.

There are ways to address low testosterone levels and their impact on muscle growth in a natural way without requiring testosterone treatment. Natural boosters can raise the levels of testosterone and help you maintain and grow muscle tissue.


frustrated man

The less testosterone you have in your body, the more susceptible you are to mood swings. The sex hormones, or the balance of them, to be precise, play a key role in your emotional state.

That’s as true for men as it is for women. It’s just that women have regular fluctuations, and they notice these things as being common.

With very low levels of testosterone, men might even suffer from depression [1].

And with very high testosterone levels or sudden spikes, men can suffer from aggressive behavior that is very out of character.

Bone Density

Testosterone levels also have a direct impact on bone density and structure that, in extreme cases, can lead to premature osteoporosis.

It’s believed that testosterone plays a similar role in encouraging bone tissue growth as it does with muscles.

A study has highlighted some correlations where male hypogonadism and brittle bones often go hand in hand, especially in younger men [2]. With an increased risk of fractures, the long-term consequences of a sex hormone imbalance can be severe.

Body Hair

belly with body hair

The same testosterone levels that cause facial and body hair to appear on teenage boys are also going to impact older men.

Ironically, abnormally high testosterone levels can lead to balding but at the same time cause more body hair to grow in other places, including pubic hair.

But even normal fluctuations with age will impact facial hair growth in men, and it is something to keep an eye on to identify a problem with too little testosterone.

Related: Does More Body Hair Mean Higher Testosterone Levels

Weight Management

Testosterone has also been linked to obesity, and there is a vicious cycle that men can end up in. As testosterone levels drop, fitness and athletic performance levels also go down, and there is an overall increased risk of storing more belly fat [3].

That increased belly fat then further transforms more testosterone into estrogen, causing even lower testosterone levels.

Making sure that adult men over age 30 have enough testosterone is one of the most important factors to avoid a gradual slip into obesity.

It’s not a magic bullet to counteract a crap diet, but a healthy lifestyle could transform weight issues.

Understanding Free And Total Testosterone

hand view of a person doing blood tests

When you go for blood tests, your doctor will ultimately give you details about your blood levels of testosterone. And those are measured in two ways.

Total Testosterone

Your body will produce testosterone in the testicles, mainly during the night. But not all of that testosterone is freely available to trigger different body functions. Some of it ends up tied to enzymes like sex hormone-binding globulin (SHBG).

What total testosterone tells you is how well your testes and adrenal glands are releasing it. But it won’t necessarily tell you whether it’s all available to send those signals, including increased muscle size.

Free Testosterone

This is the value that will tell you whether your blood serum sex hormone levels are sufficient. It’s this free testosterone that travels around your body and activates certain responses. And in aging men, it’s low levels of free testosterone that are the main problem.

Some of those problems might be the result of what the pituitary gland does. See, it’s the pituitary gland that releases SHBG, and this, in turn, binds to testosterone and transforms it into estrogen.

So, your testes could be doing their part for testosterone, but if you’re producing too much SHBG, then you’re going to run into trouble. And men from age 30 need to keep this in mind as it’s increasingly common.

Similar Article: What to Look For in a Testosterone Booster?

Can Too Much Testosterone Be A Problem?

man contemplating

While the effects of testosterone deficiency can be serious health issues, if testosterone levels rise suddenly or are extremely high, then you could also encounter several health problems.

This is a common issue with testosterone replacement therapy, and doctors need to monitor the signs of high testosterone carefully.

The impacts of having too much include blood clots, high blood pressure, heart attack, and even prostate cancer.

Figuring Out Your T-Levels

We always advise clients to get a blood test done before they start with T-boosters. It gives them a good idea of what their starting level is to compare progress to. And doing the same test every 3 to 6 months is a great way to keep an eye on levels to ensure they don’t go too high.

Causes Of High Testosterone

The most common underlying cause of high testosterone is testosterone replacement therapy. But other health conditions can also cause issues with the hormone-producing glands.

There’s also the potential for an issue with the pituitary gland, which is a bit more difficult to determine.

What the pituitary gland does is release SHBG, which binds to testosterone and transforms it into estrogen. This is a necessary process to control levels, and if it gets disrupted, you could run into issues.


Does Testosterone Only Impact Sex Drive?

No, testosterone production doesn’t only impact sex drive. Too little testosterone may also impact muscle mass, bone density, and even weight management. That’s why it's so important not to look at your T-levels with a blinkered view.

Can Low Testosterone Cause Health Issues?

Yes, low testosterone can cause many health issues that have long-lasting effects. In extreme cases, some form of testosterone therapy might be needed, but testosterone therapy should always be a last resort.

Avoiding Testosterone Deficiency In Men

Men of all ages should be paying a lot more attention to maintaining normal testosterone levels. It’s not just about being a stud in the bedroom.

So many other health issues can be tied back to T-levels, with weight gain being a major one for middle-aged men.

This doesn’t automatically mean you need testosterone therapy, but starting with a natural booster is a good option.

Check out our article on recommended supplements and see if you can avoid testosterone therapy altogether.


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