U.S. Secretary of Defense Pete Hegseth announced Wednesday plans to introduce a new military screening program that will test troops for “testosterone deficiency.”

In an announcement posted on X, Hegseth said the tests will become part of a mandatory health assessment undertaken by troops every year and that testosterone screening will be compulsory for soldiers over the age of 30.

“If treatment is recommended, it’s entirely your choice to receive testosterone replacement therapy,” he said.

“This initiative, it’s not about artificial intelligence or any other type of artificial enhancement, it’s about restoring and optimizing your natural capabilities, protecting your longevity and ensuring you have the biological foundation required to sustain the fight,” he said.

Both men and women have testosterone, though women have lower levels of the sex hormone, according to the Cleveland Clinic.

While the announcement did not specify if it would test both male and female soldiers, or only males, the move comes as other Trump administration officials have begun advocating for men to have easier access to testosterone replacement therapies.

When asked by The Associated Press what conditions Hegseth was looking to address with the new policy, the Pentagon referred to his remarks in the X post, which mentioned keeping troops “strong, resilient and capable” and noted that the rigours of the modern battlefield demand “maximum psychological and mental readiness.”

The Pentagon did not respond to the AP’s questions about what research or academic studies underpinned the move. It also did not say if female troops would be able to be evaluated for estrogen-based therapy as they entered perimenopause.

Testosterone levels naturally decline with age and in men are tied to issues such as erectile dysfunction, drops in libido, mood swings and weight gain, though there is longstanding debate among experts about how to diagnose those issues and whether they should be treated with hormone replacement therapies.

In women, testosterone naturally decreases after the age of 30 and lower levels can cause drops in libido, mood issues, and bone health problems.

Hegseth’s announcement comes as Health Secretary Robert F. Kennedy Jr. moves to make testosterone more readily available for doctors to prescribe; in June, the Food and Drug Administration (FDA) proposed loosening prescription limits on testosterone products.

Currently, the FDA specifies that testosterone replacement therapies such as pills, gels and patches are only available for men “who lack or have low testosterone levels in conjunction with an associated medical condition.”

According to several studies cited by the AP, including a series by the National Institutes of Health, taking testosterone improved erectile dysfunction, libido and other sexual measures and had a small effect on mood in older men. But there was little or no improvement in other measures such as fatigue, memory or overall well-being.

Other studies have shown potential improvements in muscle building, strength and bone density, it added. Still, Hegseth’s messaging that the use of testosterone can help as a way to stay strong and mentally sharp for combat is not a use accepted by some medical experts.

According to an article published by the Canadian Urological Association in the National Library of Medicine, “concerns relating to prostate and cardiovascular health, performance enhancement via steroid abuse, and the perception that TD [testosterone deficiency] is simply part of the ‘normal’ process of aging have resulted in reluctance of many health-care providers to diagnose and treat the condition.”

— with files from The Associated Press