Missy Franklin, whose four gold medals at the age of 17 made her one of the stars of the 2012 Olympics, has announced her retirement from competitive swimming.

Franklin was expected to dominate the pool in the same way as her compatriot Michael Phelps when she burst on to the world stage at the London Games, where she became the first American woman to win four golds in a single Olympics. That prediction appeared to be coming true at the 2013 World Aquatics Championships, at which she won six golds. However, injuries took their toll and her only medal at the 2016 Olympics came in the 4x200m freestyle relay.

Franklin, now 23, referenced her history of injuries in a retirement letter published on ESPN on Wednesday. “It took me a long time to say the words, ‘I am retiring,’” Franklin wrote. “A long, long time. But now I’m ready. I’m ready to not be in pain every day. I’m ready to become a wife, one day a mother. I’m ready to continue growing each and every day to be the best person and role model I can be. I’m ready for the rest of my life.”

In her letter, Franklin said that “surviving through those eight days [at the Rio 2016 Olympics] was the greatest accomplishment of my career” due to the mental and physical strain she was under.

“I’ve been very open about what I went through as I prepared for the Olympics in 2016 and talked openly about the struggles I endured, which included shoulder pain whenever I tried to train or compete, depression, anxiety and insomnia,” she wrote. “It was also the year when I began to fully accept the fact that something was wrong with my body and it wasn’t working the way it was supposed to work.”