Former Brazil striker Ronaldo announced his retirement on Monday, ending one of the most successful careers in soccer.

The 34-year-old three-times FIFA World Player of the Year, twice World Cup winner and the record goalscorer in World Cup tournaments, said injuries and fitness problems prevented him from playing to his best form.

“I came here to say today that I’m ending my career as a professional player,” Ronaldo, with his two sons at his side, told a packed news conference at Corinthians’ training complex in Sao Paulo.

Ronaldo, who had a contract with Corinthians until the end of the year, said his fitness problems were the overriding reason for his decision.

He said he discovered while playing for AC Milan in Italy that he was suffering from a thyroid problem.

“Four years ago at Milan I discovered I was suffering from a complaint called hypothyroidism, which slows down your metabolism and to control it I would have to take some hormones that are not permitted in football because of anti-doping,” Ronaldo said.

“I wanted to clarify this on the last day of my career,” added Ronaldo, who has struggled to keep his weight down and often suffered the jibe of “fatty” during his career.

Ronaldo broke down in tears when he apologised to the Corinthians fans for failing to deliver the major prize of the Libertadores Cup and said he would still go to their matches as a supporter.

Corinthians were dumped out of South America’s elite club competition, which they have never won, in the preliminary round two weeks ago.

They went out in the round of 16 in 2010, their centenary year.