For years, “low T” was an insult largely confined to the internet: a phrase used in corners of the manosphere to mock men deemed weak, submissive or insufficiently masculine.

It was shorthand for a broader anxiety about male decline – a belief, promoted by online influencers and commentators, that men were losing status, strength and power.

Now, the language of testosterone has moved far beyond the forums and podcasts where it flourished and into the vocabulary of the US government.

Senior figures in Donald Trump’s administration have repeatedly invoked testosterone as a marker of male health and national strength. And while experts have welcomed the open discussion of a once-stigmatised issue, many have said the “masculinity crisis” fuelled by low testosterone is overblown.

Robert F Kennedy Jr, the 72-year-old health secretary, has been among the most prominent figures to elevate testosterone to the realm of national concern.

He has previously said he takes testosterone as part of an “anti-ageing protocol” and, since becoming health secretary, has warned, without evidence, that American teenagers have “50 per cent of the testosterone of a 65-year-old man”. He has also claimed that Mr Trump had “the highest testosterone levels” he has ever seen in a person over 70.

But this week, Pete Hegseth, the defence secretary, took the idea a step further. He announced plans for the Pentagon to introduce annual “testosterone deficiency screenings” for troops aged 30 and above. The programme, he said, would help ensure service members have the “right testosterone levels” to perform at their “absolute best”.

On Thursday, Eric Trump used the phrase “low-T” to attack the “mainstream media”, describing journalists as “low-T” – a reflection of how language once confined to online male subcultures has entered mainstream political rhetoric.

Meanwhile, the Trump administration has embraced an ultra-macho aesthetic. Mr Kennedy and Sean Duffy, the transport secretary, for example, had a pull-up contest during a bizarre press conference in December. Similarly, Mr Hegseth has repeatedly called for instilling a “warrior ethos” in the military and said that women should not serve in combat roles.

In June, to celebrate Mr Trump’s birthday and the 250th anniversary of American independence, the White House hosted perhaps the most hyper-masculine of events imaginable: an Ultimate Fighting Championship (UFC) bout.

Not all concerns about testosterone lack basis. Levels have been slowly declining worldwide over recent decades, a trend that Mr Kennedy has seized on as an “existential” threat to humanity.

Clinically low testosterone is a recognised medical condition that can cause muscle loss, fatigue, obesity and sexual dysfunction. It has also been linked to serious health problems, including diabetes, cardiovascular disease, osteoporosis and depression.

Some experts have welcomed the measures taken by the Trump administration. Just last month, the health department proposed changed to the labels on testosterone-replacement therapies to remove certain safety and effectiveness warnings.

That announcement reflected “science finally catching up to reality”, Dr Jamin Brahmbhatt, a urologist and men’s health expert, told CNN.

Meanwhile, Dr Abraham Morgentaler, a health and longevity fellow at Harvard Medical School, welcomed Mr Hegseth’s plans to test the military because “service members often undergo intense physical training, chronic stress and periods of sleep deprivation, all of which can contribute to lower testosterone levels”.

“There may be value in screening rather than waiting for individuals to seek medical attention,” he told the health news website Stat.

Low testosterone is thought to be underdiagnosed. About 5.6 per cent of men aged 30 to 79 have testosterone deficiency, a figure that rises significantly with age, yet no more than one in five of those men receives treatment.

Doctors have argued that this has created a complicated picture.

While many men with genuine testosterone deficiency remain untreated, testosterone replacement therapy has also become increasingly popular among men without a clinical diagnosis.

Researchers say online cultures centred on hyper-masculinity have fuelled demand, encouraging younger men to see testosterone not simply as a treatment for a medical condition but as a route to strength, confidence and status.

Support for issues such as women’s rights became synonymous with “low T” in Right-wing circles. An indication that it was beginning to take hold came during the 2016 presidential campaign, during which Mr Trump took the unusual step of revealing his testosterone level.

Then, as backlash against the MeToo movement grew the following year, which was framed as an attack on traditional masculinity, declining testosterone levels were apparently just one way in which men were being suppressed.

In 2022, Tucker Carlson, then a Fox News anchor, hosted a documentary about it called The End of Men, during which he decried the fact that “no one in Washington seems interested at all”.

Around the same time, testosterone replacement therapy was becoming popular among those interested in longevity and wellness.

And perhaps no one has done more to popularise it than Joe Rogan, the podcaster, comedian and doyen of the manosphere, who started taking testosterone when he was 40.

“Hormone replacement therapy exists for a reason, and that reason is that it makes you feel way better and makes your body work way better,” he said in 2018.

Since then, more fitness and wellness influencers have been open about their use of testosterone, whether that’s as a replacement therapy or as a performance-enhancing drug.

In May, the inaugural Enhanced Games saw athletes compete who had been allowed to use drugs banned from Olympic events, including testosterone. Mr Trump’s son, Donald Trump Jr, is an investor in Enhanced Games.

As more and more people have spoken about testosterone, it has also become easier for people to access.

Many US telehealth companies offer at-home kits for testing your testosterone levels and will ship your prescription directly to your door.

Prescriptions for testosterone replacement therapy have risen dramatically, reaching almost 12 million in 2025 compared with fewer than one million in 2000, according to IQVIA data provided to the New York Times. Those figures probably underestimate overall use, as growing numbers of men obtain testosterone through private clinics and other providers.

The American Urological Association has said that roughly a third of men prescribed testosterone do not meet the criteria for deficiency, leading critics to argue that treatment has, in some cases, become a legal form of low-dose steroid use.

Experts have warned that patients should have in-depth discussions with their doctors about whether testosterone therapy could be helpful.

Research published in the journal Social Science & Medicine found that young men are increasingly targeted online by influencers and wellness companies promoting hormone tests and treatments as essential to being a “real man”, despite medical guidelines generally not recommending routine testosterone screening for most men in this age group.

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A study by the University of Sydney recently found that manosphere influencers used fear-based messaging to promote testosterone products, with 72 per cent of the analysed accounts having a financial interest in related products.

Earlier this year, Dana White, the UFC boss and long-time pal of Mr Trump, was asked by The Wall Street Journal what connected his two spheres of influence – mixed martial arts and the Maga movement?

“Testosterone,” he replied.