US Defence Secretary Pete Hegseth has announced that military personnel aged 30 and older will undergo testing for testosterone deficiency as part of annual health screenings.

In a video posted on X, captioned "High-T Department", Hegseth said he was authorising the screening programme for troops to ensure "you have the right testosterone levels to operate at your absolute best".

Troops with low testosterone levels will be offered voluntary hormone replacement therapy. The tests will be optional for those younger than 30.

Hegseth did not specify whether the screening would apply to women, whose testosterone levels also decline as they age.

"We owe our warriors the absolute best medical care in the world, and this programme delivers on that obligation," Hegseth said in Wednesday's video.

"Taking care of your long-term health means ensuring you remain strong, resilient and capable - not just for your next deployment, but for the rest of your life, so you can thrive long after you take off the uniform," he added.

Taking testosterone for non-medical reasons, like artificial muscle enhancement without a doctor's prescription, is strictly prohibited in the military.

Hegseth said in the video that the new programme was "not about artificial enhancement".

Pentagon spokesman Sean Parnell said in a statement that the mandatory screening for testosterone deficiency would be effective immediately for all active duty and reserve component personnel aged 30 and older.

"The protocol will enable the Department to establish a comprehensive baseline and offer targeted testosterone therapy, ensuring that it sustains a healthy, capable, and decisively dominant fighting force," he said.

Asked whether both male and female troops would be tested, and if female troops would be able to be evaluated for oestrogen-based therapy as they enter perimenopause, the Pentagon said it had no comment to add to Hegseth and Parnell's statements.

Democratic Senator Tammy Duckworth of Illinois, an Iraq war veteran and member of the armed services committee, called on the defence secretary to make hormone testing available for both men and women.

Congresswoman Chrissy Houlahan, a Pennsylvania Democrat and Air Force veteran, dismissed it on X as Hegseth's "latest culture-war obsession".

Dr Mohit Khera, who led a US Food and Drug Administration (FDA) expert panel last year on screening and testosterone utilisation in the military, told the BBC on Wednesday that all men over 30 should get screened because it is the top marker of a person's overall current and future health.

"The key here is that many young men have low testosterone levels, which puts them at a disadvantage in terms of muscle mass, energy, and that could be an issue if you are in combat," Khera, a professor of urology at Baylor College of Medicine, said.

He added: "You have to be careful not to just give someone testosterone unless they do have some kind of symptoms."

The benefits of the hormone replacement therapy, he explained, are increased muscle mass, decreased fat deposition, and decreased risk for depression. Over time, Khera added, it can also help with bone mineral density.

He cautioned, though, that it is not meant for everyone.

"If young men do take testosterone, it can make them infertile," Khera said. "You got to be careful. If someone's in the reproductive years, you need to make sure they understand it's going to make you infertile."

It can also result in a theoretical increased cardiovascular risk, he noted.

Hegseth's announcement comes after US Health Secretary Robert F Kennedy Jr and other administration officials have sought to remove barriers for medical professionals to prescribe men testosterone.

The health secretary has floated it as a solution to a national "fertility crisis".

The FDA last month requested the removal of safety and effectiveness language on testosterone replacement therapy product labelling, and proposed loosening prescribing limits for testosterone products. (BBC)

Update news