Pain too much for record breaking superstar
It was an emotional event for the World Cup winner, in which he acknowledged that the physical demands of the beautiful game had grown too great for him to bear.
"I've lost the struggle against my body," he said.
"The ones who are close to me know the truth: I can't go up stairs without feeling pain.
"I gave my life to football and made incredible sacrifices. I don't regret anything."
The former Barcelona, Real Madrid and Inter star began by stating: "I am not going to say much. I am closing my career as a professional footballer."
He went on to celebrate a "wonderful, exciting career" full of great memories and friends, before moving on to give the real reason why his later career was plagued by weight problems.
"Four years ago in Milan I found out that I was suffering from a problem that is called hypothyroidism, a complaint which slows your metabolism, and that to control it I would have to take medication which is considered illegal in football," he said.
"A lot of people should feel bad about their comments on my weight: I just wanted to explain that, now that I have reached the end."
Ronaldo also affirmed that Corinthians' Copa Libertadores exit was a big factor in his decision to leave, and apologised to the fans of the club for his failure in continental tournament.
He continued: "Those results also made the fans go a little bit crazy, a little out of control. I want to thank the president and publicly apologise for having failed in the Libertadores project.
"You guys are my brothers, my time here was brilliant and I will continue linked to the club however you want me to be."
Ronaldo, who lit up European and world football over a glittering 18 years, identified the biggest moments of his career.
"With the Selecao in 2002 [winning the World Cup], which was the most important title for me, and the second was seeing these crazy, passionate fans right here and having them around me," the striker affirmed.
He dismissed any thought of him staying on as a director or coach, instead favouring an ambassador role promoting Corinthians worldwide. And in a reflective mood, the leading World Cup goalscorer insisted that he would not change any part of a sparkling career.
He added: "I don't regret anything I have done, I acted with honour in everything I have done and it was all an incredible experience. I don't know how my life will be from now on, I am going to miss that sensation of playing, of leading from the front.
"For now there won't be a farewell match, but in June or July I will try to bring together some players that were with me and have a goodbye party.
"My decision [to keep playing] was always led by my heart, and my love for football always helped me to break through the walls in front of me. It's hard for anyone to lose weight, and for me even more so. Hyperthyroidism slows my metabolism, but I always wanted to play."