I’m a doctor – this is everything you need to know about testosterone

We’re all aware of testosterone and most of us have some idea of what it does to the body. At its core, it’s the evolutionary substance that makes something become masculine. But because testosterone is the “male hormone”, it’s become synonymous with what it means to be male – no other hormone has made it into everyday language in quite the same way.

Testosterone equates to muscles, virility, power, strength and youth. No matter your age or level of athleticism, testosterone has become imbued with an “elixir of life” aura – meaning every man wants more, whether they actually need it or not.

In reality, the stereotyped assumption that testosterone makes us look more manly is not wrong, per se, it’s just that, in most cases that’s where our understanding of this hormone stops. Supplement companies spend millions of dollars every year in an effort to convince men that we probably don’t have enough of it, and that we must go to great lengths to boost or add to it. In fact, we now know that testosterone is critical to both our physical and mental health; to longevity, and to our quality of life, rather than simply a contributor to a six-pack and a raging libido.

Testosterone is a hormone, and these are simply chemical messengers that travel through the bloodstream and bind to any organ or cell they have a receptor to, either switching on or off a specific chemical process. Generally hormones are designed to help regulate and coordinate bodily functions.

For example, we need to keep our blood sugars in a specific range, so if you were to eat a packet of Haribo sweets, your body would release the hormone insulin, to keep your sugar levels from going too high and causing damage to your body. Unlike insulin, testosterone has a dual purpose: it is both androgenic and anabolic. Anabolic means promoting metabolism and the synthesis of proteins (like muscles and bone), and androgenic means making something masculine.

In male mammals, including humans, testosterone is produced in the testicles (or testes). It then gets released into the bloodstream.

Testosterone defficieny

As with most things in the body, it makes sense that something could go wrong. Your testicles are surprisingly sensitive to lots of things, but broadly, there are three things that cause a reduced testosterone level: you don’t produce enough of the hormone from your testicles; your brain stops telling your testicles to produce testosterone; or there are other factors such as lifestyle and ageing which decrease the overall efficiency of the whole system

Testosterone contributes towards our drive, energy, metabolism, brain health, skeletal and heart health. We also know that low testosterone leads to a range of significant health problems ranging from milder symptoms of fatigue and grumpiness, to an increased risk of heart attack, brittle bone disease (osteoporosis), and even death.

How does this apply to you?

The big question, and the reason why testosterone is now becoming of increasing interest, is whether you actually still need this hormone once you’ve gone past your hormonal peak, and possibly fathereda child. For decades, the main scientific interest in testosterone revolved around its effects on younger people; specifically, puberty and fertility.

More recently, though, we have seen that testosterone has a sustained impact on our health as we age, and there are now challenges to the idea that you no longer require this important part of hormonal physiology once you hit the age of 30. There are doctors and academics who feel that the importance of testosterone in older men is misplaced, and that by challenging this we are medicalising normal ageing, but not so long ago, a similar rhetoric was expressed in relation to menopause and HRT too.

Is the male menopause real? A drop in the male sex hormone does have striking similarities to the way menopause affects women, and the diagnosis of low testosterone in men is well established in medicine. Testosterone deficiency, also known as male hypogonadism, androgen deficiency, or even andropause, is real.

Isn’t this just a normal part of ageing? One of the biggest problems in identifying and treating testosterone deficiency (TD) is the early stages do have many similarities with normal ageing. But there is overwhelming evidence that low testosterone in men is associated with poorer health outcomes. The bottom line is, you can choose to grow old, and become impotent and frail, or you can do something about it.

Sexual abstinence increases testosterone: This rather odd phenomenon, which has gained popularity online, involves individuals or groups advocating refraining from any masturbation or any sexual activity in the belief it will increase testosterone. We often hear of boxers or high-level sportsmen avoiding sex the night before a fight or event to maximise testosterone. Abstinence may make their libido climb, but the evidence it improves performance is sketchy. In 2001, one study looked at the effect of three weeks of abstinence in 10 men and found that over this time, blood testosterone levels went up. However, the study quality was poor, relying on an incredibly limited test group. Basically, there is no evidence that abstinence from sexual activity has any impact whatsoever on testosterone production.

Vasectomies reduce testosterone: Testosterone is not affected by a vasectomy because the blood supply to the testicle is not altered. The testicular artery still supplies the testicle as usual and is uninterrupted during a vasectomy procedure. This means that the hormones from the brain that signal the testicle to produce and release testosterone are unaffected, and in addition, the veins coming out of the testicle are not affected either, which it is released normally.

My libido is down – it must be testosterone: Many men, irrespective of age, often feel that their libido is not what it should be, and consequently, want to trial testosterone replacement therapy (TRT). While testosterone is clearly linked to sexual desire, libido is far more complex than just being down to one hormone. Libido is driven by multiple factors. It is influenced by testosterone, but also by oestrogen, thyroid hormones, lifestyle factors such as sleep, stress, weight, andmost importantly, experience.

I don’t have symptoms, so I can’t have low levels: It’s a widely held belief that low testosterone always presents with obvious symptoms. In reality, many men in the early stages of TD (or subclinical hypogonadism) may not experience classic signs. This silent phase can lull men into a false sense of security, yet hormonal imbalances may already be influencing metabolic health, mood stability, muscle-mass retention, and cardiovascular risk. Left undetected, this can escalate, leading to serious long-term health consequences.

TRT causes hair loss: Testosterone is converted to various metabolites including oestradiol and dihydrotestosterone (DHT), and it is DHT that makes us lose our hair. It is not the total DHT we have that is responsible, but rather how sensitive we are to whatever is in the bloodstream. So TRT does not in itself cause baldness.

A glass of wine boosts testosterone: Alcohol has widespread effects. In small amounts, it acts as a disinhibitor, which means that we feel more relaxed, and our libido tends to go up. But it has little effect on testosterone.

Am I too old for TRT? There is technically no age restriction for when men can start TRT. In young men, we should always be more cautious about starting testosterone treatments unless there is a clear reason.

Where should I go if I am worried? If you feel unwell, see your GP. But even if your levels come back low, you may not be eligible for NHS treatment. Furthermore, “normal” in the NHS does not always mean testosterone levels are healthy as they may not take into account such factors as “free testosterone” or more up-to-date reference ranges.

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  Edited extract by Matt Nixson from Optimal: Understanding Testosterone for Strength, Health, and Wellness, by Dr Jeff Foster, published by HQ, HarperCollins priced £20 and out now