The move, backed by Health Secretary Robert F. Kennedy Jr. and other top officials, aligns with the advice of many online influencers and podcasters, including men’s health gurus who tout the hormone as a way to boost muscle and energy. On Tuesday, Defense Secretary Pete Hegseth said the military would begin screening for low testosterone and offering the hormone as a way to help troops operate at their “absolute best.”

The notion of testosterone as an all-purpose elixir for strength and vitality is not supported by the science. But medical experts say a decade of new research has bolstered the case for testosterone’s benefits for sexual health while allaying concerns about its impact on the heart.

“Many providers have been trained for years that these were real issues, and they were scared to get a testosterone reading from a patient or offer them testosterone therapy,” said Dr. Justin Dubin, a urologist at Baptist Health Miami Cancer Institute.

Last year, the Food and Drug Administration removed a bold safety warning about possible heart risks with testosterone pills, gels, injections and patches, based on recent data that showed no increase in those problems.

Last month, the agency proposed rewriting prescribing instructions to clear the way for using testosterone against age-related symptoms, such as low libido and erectile dysfunction. Currently the label emphasizes that the hormone is only approved for abnormally low testosterone levels caused by serious medical conditions or injury.

But experts who prescribe the drug say those patients are a small segment of people seeking help.

“The majority of people we see in our office are regular men complaining of these common symptoms because they’re dramatically affecting their quality of life,” said Dr. Helen Bernie, a urologist and director of sexual health at Indiana University.

Testosterone use has evolved over decades

Testosterone was first approved in the 1950s to treat hypogonadism, a condition defined by low testosterone levels caused by medical problems affecting the testes or other organs.

Testosterone declines naturally with age and can effect sexual function, mood, bone density and other measures. The question of how to diagnose and treat men with those issues has long been debated by researchers.

“These symptoms overlap with symptoms of human aging in men, so there’s a high risk of misdiagnosis and that’s led to the controversy” said Dr. Shalender Bhasin, of Harvard Medical School, who has co-authored several recent testosterone studies and guidelines.

Bhasin says increased willingness to prescribe testosterone reflects growing acceptance of the seriousness of men’s sexual health problems, beginning with the introduction of Viagra for erectile dysfunction in the 1990s.

Bhasin helped write the Endocrine Society’s current guidelines for testosterone, which recommend discussing testosterone with men who have documented symptoms and two blood test results confirming low hormone levels. One recent study by Michigan researchers found that just 12% of men getting a prescription met that criteria.

Prescriptions previously soared, despite little evidence

The potential for overprescribing testosterone is real and helped lead to current restrictions.

In the early 2010s, drugmakers spent millions on TV ads for gels, patches and other products promising relief from “low T,” including a laundry list of symptoms like fatigue, muscle loss, brain fog and weight gain.

By 2013, the drugs were generating more than $2 billion in sales annually, despite lacking FDA approval for most of the issues described. Doctors remain free to prescribe drugs off-label, or for unapproved uses, and many men today continue taking testosterone because they believe it improves energy, mood and appearance.

In 2015, the FDA hit drugmakers with a double whammy: They had to clarify that their drugs weren’t approved for routine problems and also add a boxed warning about possible heart risks.

FDA scrutiny led to new research

The FDA now says updated data warrants relaxing the restrictions.

An FDA-mandated study published in 2023 followed 5,000 men with a history of heart disease, with half receiving daily testosterone gel and the other half getting a sham drug. After two years there was no difference in heart attack, stroke and related problems between the two groups.

A series of studies by the National Institutes of Health also clarified the benefits of the hormone. Results from nearly 800 older men showed testosterone therapy improved erectile dysfunction, libido and other sexual measures and had a small effect on mood. There was little or no improvement in other measures like fatigue, memory or overall well-being.

The recent testosterone studies are the largest ever conducted, but Bhasin — who helped lead both efforts — says more research is needed on longer-term effects.

“I think FDA’s label changes are very welcome and they are bringing us a big step forward,” said Bhasin, who also co-authored the Endocrine Society’s guidelines. “But I think there’s a lot more to be done to better define the safety and efficacy.”

In recent comments submitted to the FDA, the Endocrine Society recommended studies of 15 to 20 years to assess conditions that evolve slowly, including prostate cancer, which remains a concern when prescribing testosterone.

Some men should not get testosterone

Experts agree that men who are hoping to have children in the near future shouldn’t take the hormone. Getting testosterone from a pill or gel shuts off the body’s natural process for making the hormone.

“It can stop the signal from your brain to your testicles to make testosterone, and so you stop making sperm,” Dubin said. “That can compromise fertility.”

Most guidelines also recommend careful consideration for men who have had prostate cancer or are at risk of the disease, given lingering questions about whether hormone therapy hastens tumor growth. But guidelines may soon change.

The FDA has proposed new language that would only suggest that men whose prostate cancer has spread to other parts of the body should avoid testosterone.

Be wary of online promotions

Dietary supplements promoted online to boost testosterone should be avoided because they aren’t FDA approved and probably don’t work.

FDA-approved testosterone drugs come in a variety of forms. Gels and pills generally need to be used daily. Injections, patches and implantable pellets can last for weeks or several months.

Many of these medications are available through telehealth services, though accessing them that way can have risks.

A 2022 paper by Dubin found that only 1 in 7 online prescribing companies asked basic screening questions, including whether men planned to have children. And most of the companies did not have a testing threshold for whether patients actually had low testosterone.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.