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What Is Testosterone & How Does It Impact The Body?

More people should be asking themselves, what is testosterone and how does it impact the body? This informative guide busts some myths and clarifies the facts.

Testosterone is often preceded by its reputation. Alpha males, muscle building and gym bros are some of the most common images that spring to mind with testosterone. 

But this is unfair. Testosterone is way more than just this.

Yes, testosterone plays a key role in gym progress and the development of male traits. But it’s also influential in other aspects of your health and wellbeing. Let’s take a look at what exactly testosterone is and how it can effect the body.

What is testosterone exactly?

Testosterone is a naturally occurring hormone. It’s classed as an androgen, which means it plays a crucial role in the development and maintenance of male characteristics. In fact, it’s the most important male health hormone there is.

However, it’s not just present in males. Females also produce testosterone, albeit to a much lesser extent. It’s been shown that circulating testosterone in males is around 15 times higher than females.

It’s not just present in adults either.

Testosterone’s influence is first felt during the first six weeks of foetal development. If you’ve had a baby, you’ve probably been to an ultrasound scan where they can tell you if it’s a girl or boy. I’ve recently been there and it’s amazing. Although the doctor did keep slipping up referring to the baby as ‘he’ even though we didn’t want to know!

This slip-up was only possible thanks to the vital role that testosterone had already played. We’ll let the doctor off, he did a great job.

Testosterone’s growing influence for young males

Throughout a young male’s life, testosterone continues to rise. It’s the essential hormone that stimulates all the change during the puberty years. In fact, teenage boys experience a 30-fold increase in testosterone production during puberty.

Levels peak during the late teens and early 20s, then it’s a sliding slope downhill after the age of around 30.

Unlike the quick hormonal changes during the female menopause, testosterone production in males gradually drops off around 1% every year.

image showing age related testosterone level decline

How is testosterone made?

In males, most testosterone is produced in the testicles. In females, this happens in the ovaries. Both sexes produce a small amount of the hormone in the adrenal glands located just above the kidneys.

The production of testosterone is tightly controlled by the brain. Primarily the hypothalamus

Depending on a variety of factors, electrical signals are sent to the pea-sized pituitary gland at the base of the brain, before these are then relayed to the testes.

Factors influencing testosterone production

Most males probably wish they could turn on the testosterone tap whenever they want. It’s not quite the case unfortunately.

But there are many well documented factors influencing testosterone production in the body that you do have control over. There are also a couple of factors that you don’t have control of such as genetics, age and natural daily rhythms.

Some of the environmental factors at play with testosterone production include:

  • Diet
  • Body weight
  • Exercise intensity
  • Stress levels
  • Sleep 
  • Alcohol consumption
  • Smoking

All of these factors operate on close-knit feedback loops. If you alter a factor drastically – for example, you start to eat unhealthily and gain major weight – your body will produce less and less testosterone.

If you start to exercise regularly with good intensity, your body will produce more testosterone.

The body will not just produce unlimited amounts of testosterone either when things are good. One way the male body regulates testosterone production is to convert a small amount to oestrogen via the aromatase enzyme. Yes, males produce the female hormone too.

The impact of oestrogen production is to mediate testosterone’s effect on the body. Even the body knows that you can have too much of a good thing!

It’s the ratios of testosterone to oestrogen that can have a powerful influence on the impacts laid out below.

As well as changing the factors above, you can also boost testosterone naturally through supplementation. You’ll notice that many natural testosterone boosters contain a few key ingredients, including fenugreek, Panax ginseng, ashwagandha, D-aspartic acid and tongkat ali.

How does testosterone impact the body?

You know what testosterone is and how it’s made. So, how does it impact the body?

The impact of testosterone all depends on how much there is circulating around your bloodstream. This is the amount of free or active testosterone. The more of this there is, the greater the biological impact it will have.

Testosterone’s impact on the body can be split into four main areas:

  • Sexual health 
  • Physical change
  • Muscle impact
  • Behavioural impact

Sexual health

As a sex-based hormone, testosterone contributes to all areas of sexual health. From the early days of puberty to sperm production, libido and sexual activity. It’s essential. 

With a 30-fold spike in testosterone levels during puberty, there are some big impacts on the body. All of this extra production is the driving force behind:

  • Maturation of sex organs
  • Body and pubic hair development
  • Physical growth spurts
  • Muscular development
  • Deepening of voice

Generally speaking, the more testosterone, the greater levels of sexual desire. On the flip side, low levels of testosterone can decrease desire and cause issues in the bedroom, which can quickly spiral into a negative feedback loop.

Physical change

Testosterone plays a key role in bone density and the production of red blood cells. There’s also a tight link with fat metabolism, which is down to androgen receptors.

Androgen receptors are important regulators of fat mass. They’re also triggered by circulating testosterone. It turns out that testosterone levels contribute to fat metabolism.

Higher testosterone levels lead to more fat metabolism and generally lower fat levels. Lower testosterone levels lead to less fat metabolism and greater fat levels in the body.

With an inverse feedback loop such as this, things can either improve or deteriorate quickly.

Muscle impact

Now, onto muscle. Testosterone directly impacts muscle mass. This has been known since ancient times when castration would negatively impact male development.

So, how does testosterone influence muscle?

Firstly, testosterone stimulates the release of growth hormone from the pituitary gland. Growth hormone is an anabolic, which means it stimulates cellular growth. Growth hormone is essential in building muscle and strength, which is why it’s often used as an anabolic steroid.

Testosterone also has a positive effect on muscle protein synthesis.

Studies have shown this through artificially injecting testosterone into the body. Without digging too much into the weeds, the presence of testosterone sets off androgen receptors, which then trigger a whole series of cascading cellular responses.

One of these includes the synthesis of proteins and muscle fibres. The end result is muscular gains.

The reason testosterone does this is all to do with the social and behavioural benefits.

Behavioural Impacts

Behaviour change is a lesser-known impact of testosterone on the body. But it’s arguably the most important.

For decades now, scientific studies have demonstrated the influence of testosterone concentrations on certain behaviours including:

  • Competitiveness
  • Aggression
  • Dominance

This is where the link with alpha males comes in. These pathways have been in place for many thousands of years and all relate back to social status. Back in the day it was either a case of maintaining social dominance and being able to reproduce, or becoming submissive to the leader to avoid future conflict.

But testosterone levels, particularly in relation to its mediator oestrogen, can also impact the wider picture, influencing feelings of wellbeing, confidence, optimism, stress, anxiety and motivation.

As this hormone likes feedback loops, the type of behaviour demonstrated has a subsequent impact on testosterone levels; for example, aggressive behaviour and winning lead to increased testosterone production.

Conversely, losing out and a lack of sexual activity lead to less testosterone production. It’s almost a case of a self-fulfilling prophecy.

Although there are additional and complex factors at play when it comes to behaviour, outcome-related changes in testosterone levels do have an impact on the body. 

Moving forward with testosterone

You might have a rough idea of where your testosterone levels sit. ‘Normal’ adult male testosterone levels can range anywhere from 300 to 1,000 nanograms per deciliter.

The only way to truly determine your testosterone levels is through blood analysis. As levels fluctuate throughout the day, tests need to be done at different times. The optimal testing window is thought to be between 7-10am. 

For many of you, this won’t be necessary. But a good understanding of how testosterone fits in to your fitness goals and wellbeing is necessary. Hopefully this article has given you that.






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