In the study, the nonprofit Center for Countering Digital Hate says popular videos encouraging use of the products for aesthetic or athletic gain are being posted by influencers who often downplay the risks associated with them. It follows a warning issued by the U.S. Food and Drug Administration in April about performance-enhancing drugs being marketed to teenagers and young adults on social media platforms.

“They’re being marketed to young men by influencers who are deliberately saying, ‘If you want to be like Captain America, you’ve got to take these drugs’,” CCDH founder and CEO Imran Ahmed said.

The findings from the study show TikTok videos — under certain hashtags — promoting what researchers called “steroid-like drugs” have racked up more than 587 million views in the U.S. during the past three years, with 72% of those views coming from users aged 18 to 24. The report also alleges that several dozen influencers promoted websites that sold the drugs either directly or through affiliate marketing schemes that could allow them to benefit from sales.

TikTok spokesperson Ben Rathe criticized the report, saying the group’s methodology doesn’t distinguish between harmful videos and positive content that talks about recovery from steroids or their side effects. It’s not possible for the CCDH to know that based on the type of data they’re presenting and sheer volume of videos that are on TikTok, he said.

Researchers said they assessed the top 20 videos under some hashtags, and all of those under other hashtags that contained fewer than 20 videos.

The information for the report came from TikTok’s publicly available Creative Center tool. Researchers were unable to measure how many times users under 18 came across such content since the company does not provide that information. Ahmed said in an interview that his group has asked TikTok to make that type of data available for assessment.

Similar to Instagram, TikTok has a large fitness community made up of users who talk about various things, including exercise and steroid use. Popular videos posted on the app speculate on who’s “natty or not,” or who’s naturally fit or taking steroids.

The study looked at content associated with three classes of drugs: anabolic-androgenic steroids, or synthetic hormones that mimic the effects of testosterone; peptides that simulate the release of human growth hormones and aid in athletic performance; and selective androgen receptor modulators, which are known as “SARMs.” The substances can carry health risks and are prohibited in sports under the World Anti-Doping Code.

Anabolic steroids are also illegal to use without a prescription under U.S. law. Peptide hormones and SARMs are not approved by the U.S. Food and Drug Administration for over-the-counter use and should not be purchased in dietary supplements, according to the U.S. Anti-Doping agency.

Researchers with the nonprofit are urging lawmakers to investigate loopholes that allow sites selling the substances to operate online. They’re also calling on TikTok to better enforce its ban on content that promotes the use of recreational drugs.

Rathe, the TikTok spokesperson, said content that sells or depicts SARMS will be removed by the company when its detected.

TikTok is owned by the Chinese company ByteDance Ltd.