Matthew Hintz/PexelsThe United States Secretary of War Pete Hegseth has ordered all active duty and reserve personnel aged 30 and over be screened for testosterone deficiency as part of their periodic health assessment. Those younger than 30 can opt in.In a video called “The High T Department of War”, Hegseth said the initiative is “not about artificial enhancement”. Instead:it’s about restoring and optimising your natural capabilities, protecting your longevity, ensuring you have the biological foundation required to sustain the fight.Taken at face value, this is simply an announcement of a new health measure. But widespread screening for testosterone deficiency among otherwise healthy personnel is not established medical practice, and has potential drawbacks.The policy also presents testosterone levels as a measure of “manhood” and “lethality”. This not only embraces the manosphere, it embeds it into US government policy. Read more: From violence to sexism, the manosphere is doing real-world harm Yes, testosterone levels declineAs Hegseth notes, male testosterone levels decline with age, particularly after 40. But that’s not necessarily a health problem. It may simply reflect normal ageing.A lower testosterone level is no simple measure of military capability or strength. Training, sleep and nutrition are among other factors at play.A single testosterone result is also an unreliable basis for diagnosis.The American Urological Association guidelines state that diagnosing low testosterone requires two separate measurements, taken on different mornings (when blood testosterone peaks). That’s because single testosterone readings can fluctuate greatly between samples.The person must also have symptoms of low testosterone, such as reduced libido or erectile dysfunction.So mass screening of otherwise healthy men aged 30 and over – particularly active-duty personnel, who are generally healthier than the rest of the population – can lead to false positives. In other words, this could lead to men being told they are testosterone “deficient” when they are not. Read more: Testosterone and combat readiness: what does the evidence really show? Testosterone replacement carries risksHegseth says men will be given the choice to have testosterone therapy if they are found to have low levels. But choice in the military is not the same as choice as a civilian. Personnel who are offered testosterone therapy after a low screening result may feel pressure to accept treatment, even if they have no symptoms.For men with appropriately diagnosed low testosterone levels (hypogonadism) caused by a disorder affecting the testes, pituitary gland or hypothalamus, testosterone replacement therapy is an established treatment with clear benefits.But a one-off, low screening result, or the normal decline associated with ageing, does not necessarily justify treatment. For men without confirmed symptomatic hypogonadism who nevertheless begin testosterone therapy in search of a physical or psychological “boost”, treatment can introduce harms without an established medical benefit. Read more: What men should know before signing up for testosterone ‘optimisation’ Testosterone can raise the proportion of red blood cell volume (haematocrit). This requires regular monitoring to minimise the risk of major cardiovascular events, such as heart attack, stroke and venous thromboembolism.Other recognised risks include testicular shrinkage, reduced sperm production and infertility, acne, and breast enlargement.Testosterone therapy can lead to physiological dependence. This makes it difficult to stop treatment without symptoms such as fatigue, reduced libido and erectile dysfunction. Some men also rely on testosterone therapy to maintain perceived wellbeing, physical appearance or performance.How the manosphere became US policyThe manosphere has co-opted testosterone as a biological marker of masculinity, virility, power and now “lethality”. The message is that a low testosterone level – or “low T” – is something to fear and fix. But a “high T” is a marker of a “real man” or good soldier.A study out earlier this year looked at 46 high-engagement social media posts with “low T” content on Instagram and TikTok . The posts tended to portray testosterone as a marker of a “real man”. This type of content fits with manosphere norms of male dominance and hierarchy.The US government’s decision to screen military personnel for testosterone deficiency now gives this concern about supposedly “low T” men the official stamp of approval.This same cultural movement has helped fuel the T-maxxing phenomenon. This encourages mainly boys and young men to chase testosterone without medical need under the influence of figures who equate manhood with dominance.Such regressive expressions of masculinity have also become increasingly prominent in parts of the US political administration. Health Secretary Robert F. Kennedy Jr has said he takes testosterone. He has claimed (without support) that a US teenager now has less testosterone than a man in his late 60s.Earlier this year, the US Food and Drug Administration under Robert F. Kennedy Jr loosened restrictions on testosterone prescribing.Even for a soldier, ageing is normalThe military is unique. It demands exceptional health, fitness and cognitive standards from its workforce, who are placed in exceptional circumstances, such as active war zones.Testosterone is an important hormone. It is not, however, a reliable proxy for military capability, leadership or manhood. Military policy should be careful not to treat it as one.A low testosterone result in a 50-year-old may simply reflect normal ageing, not a degraded soldier.Timothy Piatkowski receives funding from National Health and Medical Research Council, Queensland Mental Health Commission, Queensland Injectors Health Network, Hyphen Health, and Enhanced. He is affiliated with Queensland Injectors Voice for Advocacy and Action (Vice Chair), The Loop Australia (Research Lead - QLD), and The Enhanced Games (Performance Enhancement Task Force). He is a co-founder of Safe Pulse a charity focused on harm reduction for individuals who use human enhancement drugs.Benjamin Bonenti and Samuel Cornell do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.