According to AARP, Ronstadt, 67, began to show symptoms of Parkinson's as long as eight years ago, but she attributed her inability to sing to a tick bite and the shaking in her hands from shoulder surgery.
"Parkinson's is very hard to diagnose, so when I finally went to a neurologist and he said, 'Oh, you have Parkinson’s disease,' I was completely shocked," said Ronstadt. "I wouldn't have suspected that in a million, billion years."
She added, "No one can sing with Parkinson's disease. No matter how hard you try."
Ronstadt's memoir "Simple Dreams" will be released Sept. 17 and chronicles her life and musical career, but does not discuss her diagnosis or the loss of her voice.
Ronstadt has also appeared on Broadway in Canciones De Mi Padre as a vocalist.