Two-time Olympic gold medallist USA swimmer Conor Dwyer has announced his retirement after being handed 20-month suspension for inserting testosterone pellets in his body.

The US Anti-Doping Agency (USADA) on Friday announced that an independent three-member panel of American Arbitration Association (AAA) had imposed the sanctions after Dwyer was tested positive for the prohibited substance.

Dywer, who claims he took the substance unknowingly, announced retirement following the decision. “I would never knowingly violate anti-doping rules. Today I’m announcing my retirement from professional swimming. It has been an incredible ride and I have accomplished more than my wildest dreams. It was an honor to represent my country alongside my teammates. Absent of these assurances, I never would have agreed to this medically necessary treatment,” Dwyer said.

As per USADA, the 30-year-old Dwyer’s 20-month period of ineligibility began on December 21, 2018, the date his provisional suspension was imposed. In addition, his competitive results obtained on and subsequent to November 15, 2018, the date his first positive sample was collected, have been disqualified, and any medals, points, and prizes are forfeited.

“As noted in the Panel’s decision, USADA is independent of sport and here to help athletes ensure they compete clean and protect their health and wellbeing within the rules,” USADA Chief Executive Officer Travis T. Tygart said in statement. “It’s frustrating that Mr. Dwyer did not take advantage of this support and hopefully this case will convince others to do so in order to protect fair and healthy competition for all athletes.”

Dwyer won relay gold medals at the 2012 London Olympics and the 2016 Rio games and 200m freestyle bronze in Rio.