From dying young to diabetes: The potential 'dangers' of low T

From dying young to type 2 diabetes: Potential dangers of testosterone deficiency revealed as experts warn ‘male menopause’ is leaving millions of men to suffer in silence

  • Low testosterone levels can cause extreme fatigue, low libido and weight gain 
  • But studies show men with ‘low T’ are also more likely to die prematurely
  • And they may be at risk of developing type 2 diabetes, depression and dementia 

It’s a crisis that doctors have warned leaves millions of men suffering in silence. 

But could the ‘neglected’ medical issue of low testosterone be putting men at risk of life-altering health problems?

According to experts, two-fifths of men over the age of 45 are thought to have ‘low T’ — which can cause extreme fatigue, a low sex-drive, night sweats and weight gain.

And research suggests men with low levels of the hormone are five times more likely to die early and could also have a greater risk of developing type 2 diabetes, dementia and depression.

Research suggests men with ‘low T’ are five times more likely to die prematurely and could also be at risk of developing type 2 diabetes, dementia and depression

Once men hit their 30s, their hormone readings start to tail off at a rate of about one per cent a year, simply due to ageing.

A similar trend is seen among women, whose hormone levels plummet when they hit the menopause, usually in their fifties.

The NHS says men’s natural decline in testosterone is unlikely to cause problems and that many of the symptoms linked with low levels of the hormone are more likely down to stress or anxiety.

But studies suggest low testosterone is something to watch out for, while the British Society for Sexual Medicine claim it ‘has long been neglected’ as a medical issue.

MailOnline looked at some potential dangers associated with testosterone deficiency.

Are private clinics selling men expensive testosterone they will never need? Proponents insist it could help millions more men in the UK, while sceptics fear it is being over-marketed 

Pictured: a man applying testosterone replacement therapy gel)

Type 2 diabetes 

Testosterone deficiency could put you at greater risk of developing diabetes, says Professor Geoffrey Hackett, a consultant in urology and sexual medicine at the Spire Hospital in London. 

He claimed studies have shown that men with low testosterone have a three times greater risk of developing the condition. 

He added: ‘If you develop diabetes, your life expectancy is reduced by 10 years.’ 

And research has suggested that regular injections of the hormone could even prevent men over the age of 50 developing the condition.  

An Australian study, published in The Lancet last year, followed 1,007 pre-diabetic men for two years. All participants were given gym memberships and lifestyle and diet advice to ensure they were not ‘just sat on the sofa’.

Half were given testosterone injections, while the others received a placebo.

Results showed those who had been receiving the testosterone injections had a 40 per cent lower chance of developing type 2 diabetes. 

And a 2018 study, by researchers at Jinshan Hospital of Fudan University in Shanghai, found that higher testosterone can ‘significantly decrease the risk of type 2 diabetes in men’.

Scientists are still investigating the link between testosterone levels and diabetes. But studies suggest not having enough of the hormone increases visceral fat — stored around the abdominal organs — which can raise the risk of type 2 diabetes. 


As well as type 2 diabetes, experts have claimed low testosterone levels could increase the risk of dementia in older men.

That is based on one Australian study, published in the Alzheimer’s Association journal last year, which followed nearly 150,000 men aged between 50 and 73 for seven years, on average.

Of those men, 826 developed dementia over the course of the study.

The researchers found lower testosterone levels were associated with a higher risk of dementia and Alzheimer’s disease. 

This echoes the findings of a 2010 study led by Dr Leung-Wing Chu, chief of the division of geriatric medicine at Queen Mary Hospital at the University of Hong Kong.

Professor Geoffrey Hackett, a consultant in urology and sexual medicine at the Spire Hospital in London, referenced the increased likelihood of early death for those with low testosterone

Dr John Morley, a US geriatric medicine professor and the study’s co-investigator, claimed having low levels of the hormone could make you more vulnerable to Alzheimer’s — the most common type of dementia. 

This study followed 153 Chinese men, aged 55 or older, who didn’t have dementia. 

Of those men, 47 had mild cognitive impairment — or problems with clear thinking and memory loss. 

Within a year, 10 men, who all were part of the cognitively impaired group, developed probable Alzheimer’s disease.

Analysis of their tissue samples revealed that these men had low testosterone.

Dr Morley said: ‘It’s a very exciting study because we’ve shown that a low level of testosterone is one of the risk factors for Alzheimer’s.’ 


Testosterone is the male sex hormone and is mostly made in the testicles, but also in adrenal glands, which are near the kidneys.

It causes the voice to deepen, body hair to grow and the genitals to become larger during puberty.

As well as affecting sex drive and sperm production, it also plays a role in developing strong bones and muscles, and how the body distributes fat.

Women also create small amounts of the hormone in the ovaries and adrenal glands, and it affects their fertility and bones and muscles.

Testosterone levels which are too high or too low can cause various problems.

Low testosterone in men can cause erection problems, low sex drive, infertility, weakened muscles and bones, body fat gain and hair loss.

Too much testosterone, however, can trigger puberty in boys under the age of nine, is linked to aggression, and can increase the risk of prostate problems, including cancer.

Male testosterone levels tend to be highest when he is around 20 years old, and decline naturally with age. 

Experts have suggested the reason behind the link is that the male brain is highly dependent on appropriate levels of testosterone for healthy function.

Therefore, low testosterone may result in increased neurodegeneration and decline in brain function. 

Early death

Research has also shown men over the age of 40 whose testosterone levels are low are up to five times more likely to die prematurely. 

Professor Hackett said: ‘There aren’t many things that are that big a risk.’ 

One 2006 study, by University of Washington academics, which followed more than 850 male veterans aged over 40 for four years, found those with low testosterone levels had an 88 per cent greater chance of dying prematurely.

Low levels were defined as less than 8.7 nmol/l (a measure of how much hormone there is in a litre of blood). The NHS cut off for low testosterone is less than 8 nmol/l, while a healthy reading is 12 or higher.

Another study conducted in 2013, led by endocrinologists from the Robert Hague Centre for Diabetes and Endocrinology in Barnsley, came to a similar conclusion. 

Some experts believe the heightened risk of premature death is as a result of low testosterone increasing your likelihood of having or developing poor overall health.

However, a 2014 analysis, by US behavioural sciences expert Dr Molly Shores, concluded that the role of testosterone in the risk of dying early is unclear.  


Some research has suggested there may be a link between testosterone deficiency and depression.

In 2018, researchers at a German university reviewed 27 clinical trials into whether testosterone replacement therapy (TRT) could alleviate depressive symptoms.

The review, which collectively looked at nearly 2,000 men, concluded that there was a ‘significant’ improvement in depressive symptoms among men given testosterone compared with those who did not have the treatment or were given a placebo. 

However, the researchers stressed that the trials they examined had different scopes, making it challenging to compare them.

And separate research has failed to spot a link depression and low T, meaning the relationship between the two is disputed.

Testosterone increases the release of dopamine, which is a neurotransmitter in your brain responsible for your feelings of pleasure, so experts believe this may be why the deficiency could be linked to depression. 

They have also suggested that there may be a connection between testosterone levels and the function of serotonin, as a decrease in serotonin activity in the brain is linked to feelings of depression.

‘I put on weight and became so hairy I looked like Jeff Goldblum out of the fly’ 

David McCaffrey assumed the two stone he had put on in just a few months was down to being lazy during lockdown.

But over time he realised that wasn’t to blame.

The 47-year-old would wake up soaked as a result of night sweats, found his memory to be worsening, lost his libido and noticed a drop in his attention span.

Father-of-three Mr McCaffrey, from Redcar, told MailOnline: ‘I started putting on weight, which I put down to the gym being closed and that I had become a little bit lazy with my diet. 

‘But I also started to get hairier on my back. I used to make a joke to my wife that I had like three hairs on me, that was my thing, so I made jokes about how I was starting to look like Jeff Goldblum out of the fly.’

David McCaffrey (pictured), 47, who received treatment privately after discovering he had the deficiency, said that during lockdown he was changing his t-shirt three to four times a night as a result of night sweats

Mr McCaffrey said during lockdown he noticed that he was getting hairier and joked that he ‘was starting to look like Jeff Goldblum out of the fly (pictured)’

He had never considered that the symptoms were connected. 

But a company came to his gym offering to carry out blood tests, which is when Mr McCaffrey, an NHS infection control nurse, was told his testosterone levels were ‘really low’.

He then made an appointment with a GP to follow up.

Staring down a wait of a couple of months to see a specialist and not wanting to ‘burden’ the NHS, Mr McCaffrey said he sourced testosterone online.

He began injecting himself with the self-sourced hormone – something he now warns against.

Mr McCaffrey did not say where he bought the testosterone from. 

The nurse said he felt significantly better within a matter of weeks, noticing his energy levels increase dramatically.

Professor Hackett said the guidelines for accessing TRT in the UK are strict and that you need to have a combination of multiple symptoms and a blood test showing low testosterone levels

But with his hormone levels now higher again, it then took longer to get NHS help once his appointment date came, as he was told to come off testosterone for two to three months to be accurately assessed. 

He said: ‘I thought “I know exactly how I’m gonna feel now”, and it affects your mental health as well in a way that I have a history of, you know, my own anxiety and depression issues. 

‘But how much of that was contributed to testosterone or not? I don’t know because nobody checks your hormone levels as a man when you go to say you’ve got low mood issues.’

It was then he was approached by a former colleague who introduced him to a private clinic offering regular blood tests and check-ups.

Mr McCaffrey is convinced testosterone replacement therapy gave him back his life. 

When it was first tested, his reading was just 6.9 nmol/l. After he began having injections in autumn 2021, his energy levels, sex drive and muscle strength all bounced back to normal within weeks, and he has even been able to come off his antidepressants. 

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