The Truth About Testosterone: What Every Man Needs to Know

What low T really does to your brain and body - and how to bounce back

It may be best known as the hormone that makes you hairy and horny, but there’s far more to testosterone than beards and bonking.

As the primary male sex hormone, it’s responsible for making you, well, a man. It drives male physical development, making us - on average - bigger, stronger, faster and hairier than women, but it also plays a big role in energy, mood, motivation, drive, determination, muscle mass, bone density, body fat levels, metabolism, sleep and more.

So when your testosterone levels decline - which begins naturally in your thirties, but can be accelerated by poor sleep, high stress, weight gain and other lifestyle habits - you don’t just feel less like a man, you feel less like yourself.

Here’s what’s really going on with T, and what you can do to look, feel and perform at your best.

What is testosterone?
It’s your body’s main male hormone. It’s mostly made in the testicles, but the signal to produce it starts in the brain - specifically in the hypothalamus and pituitary gland. Once released, most of it gets bound up by proteins like SHBG (sex hormone-binding globulin), meaning it can’t actually do much. Only a small portion floats around freely - that’s called free testosterone - and that’s the bit that really matters, fuelling how you think, feel and function.

What does T actually do?
Lots. On top of its widely known role helping you build muscle and maintain strength, it also plays a major role in burning fat, keeping your energy up, sharpening your focus, lifting your mood, driving motivation and helping you sleep. So when levels drop, it doesn’t just affect the gym - it affects your daily performance everywhere from the meeting room to the bedroom.

Why is it so important?
Because without it, life starts to unravel - fast. Low testosterone can leave you feeling drained, distracted, unmotivated and disconnected - not just from sex, but from friends, family, your partner, and even yourself. It’s like life’s gone from colour to black and white - with the volume turned down.

When does testosterone peak?
Testosterone rises at several points during childhood and puberty, but adult levels hit their highest sustained peak in your late teens to early twenties - the years when your body is geared for strength, growth and reproduction.

And when do T levels fall?
From your thirties onwards, levels start to decline by about 1-2% per year. Yet that slow drop can turn into a steep slide if you’re not taking care of yourself. High levels of chronic stress, poor sleep, carrying excess body fat and not exercising enough are common causes of accelerated testosterone decline. Most men start to notice symptoms creeping in during their forties or fifties - especially if lifestyle habits have taken a hit.

What are the symptoms of low testosterone?
They can be subtle at first. You feel flat. Your sex drive fades. You’re more tired than usual, even after sleep. You gain weight around your middle, lose muscle tone, struggle to concentrate and get irritated more easily. You feel like you’ve lost your edge. You might even start to worry whether this is really it - you’ve peaked, and it’s all downhill from here.

Can I increase my testosterone levels naturally?
In many cases, yes. Prioritising good sleep, building resilience to better manage stress, cleaning up your diet, lifting weights, reducing body fat and cutting back on alcohol can all help bring borderline testosterone levels back to where they should be. What’s more, these positive lifestyle changes don’t just boost T - they’ll also make you feel better across the board, giving you more energy, more motivation and more lust for life.

What if that’s not enough?
If your symptoms stick around and blood tests confirm that your testosterone is genuinely low, testosterone replacement therapy (TRT) might be worth exploring. For some men with clinically low levels, it can be life-changing. But it’s not a quick fix – it needs proper medical oversight, regular check-ins and a long-term plan – because once you’re on it, you’ll need it for life. It’s also unlikely to be covered by the NHS or private health insurance, so you’ll need to factor in the cost – and it’s not cheap.

Want to know more about testosterone?
Check out Testosterone: The Story of the Hormone that Dominates and Divides by Dr Carole Hooven - an insightful, engaging and evidence-based deep dive into how testosterone shapes our bodies, brains and behaviour. It’s a brilliant read for anyone who wants to understand the science behind the sensational headlines.

Thanks for reading - and if you have any questions, just let me know!
Joe