Low Testosterone

Quick Facts

• Low testosterone is common – but underdiagnosed.
• An estimated 1 in 10 men over 40 have clinically low testosterone, yet the majority are never formally diagnosed.
• Symptoms often masquerade as “stress” or ageing.
• Fatigue, low libido, low mood, brain fog, poor sleep and reduced muscle mass are frequently dismissed – delaying investigation for years.
• Low testosterone affects far more than sex drive – It’s closely linked to metabolic health, bone density, cardiovascular risk, mood, and cognitive performance.

Low testosterone is one of the most under-recognised health issues affecting men today. Many go through years of fatigue, low mood, poor motivation, and declining physical health without realising their hormones are part of the problem.

Instead, men are often told it is just “stress,” “getting older,” or even prescribed antidepressants. I know this path well. Before discovering that my own low testosterone was the root of my struggles, I spent years trying to fix the symptoms rather than the cause.

How Testosterone is Made and Regulated

Testosterone is produced mainly in the testes under the control of the brain. 95% of a man’s testosterone comes from his testicles. The hypothalamus releases GnRH (gonadotropin-releasing hormone), which signals the pituitary gland to release LH (luteinising hormone). LH then stimulates the Leydig cells in the testes to produce testosterone. The pituitary gland also produces follicle stimulating hormone, which is involved in stimulating the production of sperm in the testicles.

FSH and LH Levels are regulated by a feedback loop. When testosterone rises, the brain reduces GnRH and LH release. When testosterone falls, the brain increases the signal.

This system can be disrupted by a range of factors. Chronic stress, poor sleep, obesity and inflammation, thyroid dysfunction, pituitary disorders, certain medications, nutrient deficiencies, and environmental toxins can all reduce testosterone production. When these disruptors are present, men may feel fatigued, less motivated, and be at higher risk of long-term health issues.

If the testes themselves are struggling, the brain’s signals rise to stimulate them. This condition is called primary hypogonadism. Blood tests typically show raised LH and FSH but low testosterone. The brain is essentially shouting at struggling testicles to do more, but they can’t cope.

If the problem originates in the brain or pituitary, LH and FSH remain low despite low testosterone. This is called secondary hypogonadism, and it means the pituitary gland is not signalling properly. The brain is not doing its job effectively hence the testicles don’t receive the messages to do more.

Recognising the Signs

Testosterone is more than a “sex hormone.” It influences energy, motivation, cognition, cardiovascular health, red blood cell production, and bone density. When levels drop, men can feel it in nearly every aspect of life.

Common symptoms include persistent fatigue (despite adequate sleep), sleep disruption, low mood, irritability or brain fog, declining libido and sexual performance, reduced muscle strength or slower recovery from training, increasing abdominal fat, and reduced stress resilience.

You do not need all the symptoms to have a problem. Even a few should raise suspicion.

Why Testosterone Levels Drop

There is often no single cause. Testosterone levels usually decline due to a combination of factors.

Modern lifestyle factors such as poor diet, excess alcohol, lack of sleep, chronic stress, and low physical activity all contribute. Obesity can disrupt hormonal signalling, particularly through leptin resistance and inflammation. Medical conditions, including thyroid dysfunction, haemochromatosis, pituitary disorders, and chronic illness, can suppress testosterone. Environmental exposures, including endocrine-disrupting chemicals, are also increasingly recognised as contributors.

In recent decades, average testosterone levels have been steadily declining, even after accounting for age. Rising obesity, chronic stress, poor lifestyle habits, and environmental exposures all play a role.

Why It Matters

Low testosterone is not just about symptoms. It affects overall quality of life and long-term health. Low levels are linked to depression, metabolic syndrome, cardiovascular disease, and osteoporosis.

Ignoring low testosterone does not just mean feeling unwell. It can contribute to serious long-term consequences.

Comprehensive Testing: Getting the Full Picture

A single blood test is rarely enough. Lab ranges often include unwell men and do not reflect optimal health. A full assessment should include total and free testosterone, oestradiol (E2), DHT, SHBG, LH, FSH, and prolactin.

Other important markers include thyroid function (TSH, Free T4, Free T3) and potentially thyroid antibodies (TPO, TgAb), DHEAS, iron studies and ferritin, liver and kidney function, full blood count, and metabolic markers such as fasting glucose/insulin/c peptide, hba1c, lipids, hsCRP, and a baseline PSA.

A comprehensive approach ensures you are addressing the root cause, not just chasing a number.

What To Do If You Suspect Low Testosterone

Get tested properly. Do not always rely on a single blood test or “within range” results.

Address lifestyle foundations: Try to optimise sleep, reduce excess body fat, build muscle, limit alcohol, and manage stress.

Investigate underlying health issues: Thyroid dysfunction, nutrient deficiencies, and metabolic problems often contribute.

Consider medical therapy when needed: Testosterone replacement therapy (TRT) can be transformative, but it must be individualised, monitored, and done without routinely blocking downstream hormones such as oestradiol or DHT.

Final Thoughts

Low testosterone is often the smoke alarm, not the fire.

Finding the root cause is key.

Optimising testosterone, through lifestyle, medical therapy, or both, can give men their lives back. When hormones are balanced, energy, clarity, drive, and resilience return.

It is not about chasing numbers. It is about reclaiming the best version of yourself.