The 39-year-old singer revealed this week she has been suffering from the incurable autoimmune disease, Billboard.com reported.
"I was [driving and] trying to put my foot on the brake, but my leg was jumping. I couldn't keep the brake down and almost crashed," Elliott told People.com about what led her to seek medical attention. "I couldn't write because my nervous system was so bad -- I couldn't even use a pen."
Elliott said that since she has been working out and receiving treatment, her condition has improved.
"I'm 30 pounds lighter because I've been exercising," Elliott said. "My thyroid is functioning, so I haven't had to take medication in about nine months. [But] you live with it for the rest of your life."
Billboard.com said the recording artist is currently collaborating with Timbaland on a new record. She also will be featured on VH1's "Behind the Music" Wednesday.