The Pentagon has introduced mandatory testosterone screening for active-duty service members aged 30 and older, with US Defence Secretary Pete Hegseth saying the policy is intended to strengthen combat readiness.
Announcing the programme earlier this month, Hegseth said it would help ensure troops remained “strong, resilient and capable”. He argued that the demands of modern warfare required “maximum psychological and mental readiness”.
He also stressed that the initiative had “nothing to do with artificial enhancement”.
Male hormone decline is a global issue that has raised concerns in many other countries including China, where some experts argue a long-term shift in hormone levels could affect the future of military strategy.
“From now on, it will all be robot wars,” a urologist at Shanghai First People’s Hospital, one of mainland China’s top-tier hospitals, told the South China Morning Post.
“No matter how developed the muscles of carbon-based life forms are, they can’t defeat robots,” said the doctor, who asked to remain anonymous due to the sensitivity of the subject matter.
An international meta-analysis of 118,593 men from six countries found that average total testosterone levels declined by 54 per cent between 1972 and 2019, with the rate of decline accelerating after 2000 and exceeding what could be explained by age alone, according to The Jerusalem Post on July 11.
China has been rapidly expanding its robotics industry, developing increasingly capable humanoid and industrial robots that could eventually undertake tasks considered too dangerous or physically demanding for humans.
According to the International Federation of Robotics (IFR) “World Robotics Report 2025”, China deployed 295,000 new industrial robots in 2024 – 54 per cent of the global total – and the total number in operation surpassed 2 million, more than any other country.
The Pentagon’s screening policy has meanwhile fuelled debate over whether testosterone levels meaningfully influence soldiers’ combat performance.
Testosterone, the main male sex hormone, plays a key role in muscle growth, strength, bone density, red blood cell production, sexual function, mood and recovery from physical stress.
Clinical guidelines recommend testosterone replacement therapy (TRT) only for men diagnosed with testosterone deficiency accompanied by symptoms such as fatigue, reduced libido and loss of muscle mass.
The policy comes amid growing concern over a long-term decline in testosterone levels among men in many developed countries.
One analysis found that average testosterone levels among American men aged 15 to 39 fell by about 25 per cent between 1999 and 2016, a trend researchers have linked to rising obesity, sedentary lifestyles and other factors, although no single cause has been established.
Testosterone levels can also drop sharply under extreme physical and psychological stress.
A 2019 review found that strenuous military training frequently suppressed testosterone by 40 to 65 per cent.
During the US Army’s eight-week Ranger School, for example, hormone levels fell to around one-third of baseline because of severe energy deficits, prolonged sleep deprivation, sustained psychological stress and continuous high-intensity exercise.
The issue has become politically contentious in the United States. Democratic lawmakers have questioned the scientific basis for mandatory screening and warned against expanding medical treatment without clear evidence of benefit.
Medical experts likewise argue there is little evidence that raising testosterone levels beyond the normal physiological range in otherwise healthy men improves strength, endurance, cognition or combat performance.
Clinical trials over the past two decades have shown that TRT can increase lean muscle mass, improve bone mineral density and reduce fatigue in men with clinically low testosterone.
However, reviews by the Endocrine Society and other medical organisations conclude that testosterone levels within the normal range do not necessarily translate into superior athletic or military performance.
Studies involving military personnel present an even more complex picture.
Testosterone often declines during periods of extreme physical stress, meaning a low reading does not necessarily indicate that a soldier is medically unfit for combat.
International comparisons further complicate the debate.
A 2013 study found that healthy American men aged 18 to 24 had higher total testosterone concentrations than their counterparts in Hong Kong, but there was no significant difference in free or bioavailable testosterone – the forms more readily available for use by the body.
A 2025 meta-analysis also reported differences in free testosterone among racial and ethnic groups in the US, with black men recording higher levels than white men, and Asian men lower levels.
Researchers caution that individual variation is far greater than population averages, making testosterone levels alone a poor predictor of physical capability or overall health. -- SOUTH CHINA MORNING POST
