In August 1998, an Associated Press reporter spotted a brown bottle in Mark McGwire’s locker at Busch Stadium. The bottle was androstenedione. McGwire was in the middle of the home-run chase that would end with him at 70 and Sammy Sosa at 66. He confirmed to reporters he had been taking the supplement for over a year. Major League Baseball, in 1998, had no anabolic-steroid testing programme. Androstenedione, in 1998, was legal.

The bottle made Patrick Arnold’s reputation, though Arnold’s name did not appear in the original coverage. Arnold was the synthetic organic chemist who had introduced androstenedione to the American supplement market two years earlier, in 1996, under the regulatory framework established by the Dietary Supplement Health and Education Act of 1994. Andro converted, in the body, to testosterone. The chemistry was uncontroversial. The legal classification, in 1996, was.

The DEA presentation

Around the year 2000, Arnold and his brother John asked Rick Collins, an attorney specialising in performance-enhancing drug cases, to lead a presentation to the Drug Enforcement Administration. The DEA was sceptical that Andro should be classified as a dietary supplement rather than as an anabolic steroid under the Anabolic Steroid Control Act as it then stood. Collins’s task, in his own words from the tribute he wrote the day Arnold died, was “convincing the skeptical DEA brass that Andro wasn’t an ‘anabolic steroid’ under the law as it was written.”

Collins and a panel of expert witnesses from the supplement industry prepared in a Pentagon City hotel suite the night before. The presentation itself was made before what Collins later described as “a packed room of government enforcers”. The legal argument turned on the chemistry: Andro was a steroid precursor, not a steroid per se. It converted to testosterone in the body but was not itself listed in the controlled-substances schedule. The legal architecture that would later send Arnold to federal prison over THG had not yet been built. In 1999, by the letter of the statute, Andro was a dietary supplement.

The DEA, after the presentation, did not move to schedule the compound. “We succeeded,” Collins wrote, “and Andro (and a whole lot of other prohormones like 1-AD and 4-AD) remained on the market until an act of Congress”.

That was Arnold’s regulatory peak. The window stayed open another four years.

The McGwire summer and what came after

The Andro segment of the supplement market grew substantially in the months after the McGwire revelations. Patrick Arnold, working from Champaign, Illinois, was the chemist behind the category. He had developed a synthesis for compounds that were already chemically known but had never been brought to market as supplements, and he had read the legal situation regarding dietary supplements correctly. Through ErgoPharm and the corporate vehicles that followed, Arnold introduced not only Andro but the prohormone generations that came after it; 1-AD, 4-AD, and what Arnold himself in 2023 described as “second and third generations” of the same chemistry.

Speaking to Unfiltered in December 2023, Arnold framed the era in his own retrospective terms. “I came up with these prohormone things, which are basically steroid compounds that convert to testosterone in the body. These were known compounds, but I developed a synthesis, and I identified… I also knew the legal situation regarding dietary supplements, and that such things could, at least at the time, be sold openly without any legal ramification.”

The phrase that mattered, in 2023, was “at the time”. Arnold’s prohormone era was the briefly available regulatory space in which an organic chemist could build a category. The chemistry, market and legal classification were all in place but none of the three would survive past 2004.

The Anabolic Steroid Control Act amendments

The Anabolic Steroid Control Act of 2004, signed by President George W Bush in October that year, added androstenedione and a list of its principal analogues to the Schedule III controlled-substances list. Andro became, with a single legislative stroke, the same legal category as testosterone itself. The supplement industry segment Arnold had built was, by 2005, gone from American retail shelves. A second wave of legislation in 2014, the Designer Anabolic Steroid Control Act, closed the remaining analogue loopholes that had survived 2004.

In the years between 1996 and 2004, according to Collins’s tribute, Arnold’s regulatory work extended beyond Andro. Collins names Arnold’s introduction of 1,3-dimethylamylamine — DMAA, to the supplement market as “Geranamine,” before FDA enforcement action against DMAA-containing products began in the early 2010s. Collins also describes a separate Assistant US Attorney probe in New England, triggered by the presence of a trace amount of androstenedione in Arnold’s 6-OXO product. “I was able to shut that down,” Collins wrote.

Each of these compounds had its own regulatory life. Each ended in legislative or enforcement action.

“There’s no room for a chemist”

What Arnold told Unfiltered in late 2023 about the current regulatory environment was a quiet eulogy for the prohormone era. “There’s no room for a chemist to identify, develop, synthesise — or develop a synthesis for manufacturing — these new compounds. That’s where I shined. The need for that is no longer there.” The compound classification system had hardened. The dietary-supplement loophole had closed. The new dietary ingredient approval process, what Arnold described as “hundreds of thousands of dollars for safety studies, efficacy studies” with the prospect of being turned down at the end, had become the only legal pathway. The pathway did not, in practice, exist for the kind of independent chemist Arnold had been.

The career Arnold had built in the late 1990s required three conditions: a chemistry capability, a regulatory window, and a manufacturing infrastructure willing to operate inside that window. The first he kept. The second closed in 2004. The third followed.

The era ended around him

Patrick Arnold died on 12 May 2026. Mark Bell, in his Instagram tribute that day, wrote that Arnold “was also known as the godfather of Pro Hormones”. Rick Collins, the attorney who had prepared the DEA presentation with him in that Pentagon City hotel suite in 1999 or 2000, called him “the smartest, most colorful and most enigmatic character in the Golden Age of sports nutrition”. The Golden Age, in Collins’s framing, was the period when “chemists were the rock stars of the hardcore health and fitness industry”. The 2004 amendments, and the second wave in 2014, ended that era.

Patrick Arnold was the chemist. The era ended around him but his legacy lives on.

Photography Alex Shuper