Missy Elliott hasn't been in the spotlight too much during the past couple of years, and now her fans are finding out why. According to E! Online, the 'Work It' rapper has been battling Graves' disease since 2008, and she has kept her ailment under wraps until now.

Graves' disease is an autoimmune disease that results in an overactive thyroid gland. The disease is very serious, and Elliott has been struggling just to complete everyday tasks, like writing or driving a car, since her diagnosis.

"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, 39, said. "I couldn't write because my nervous system was so bad -- I couldn't even use a pen."

Not only did Elliott have a hard time with normal activities, but she also suffered from hair loss and drastic and debilitating mood swings. Elliott underwent radiation to treat her hyperthyroidism, and the treatment helped curb her symptoms of Graves' disease.

There is no cure for Graves' disease, but people who catch the illness early on can often maintain it for some time. However, victims of Graves' will often slowly see their symptoms worsen over time.

As of right now, Elliott is doing pretty well. "I'm 30 pounds lighter because I've been exercising," she 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."

In other Missy news, the rapper will be releasing a comeback album and is also working on some new tracks with collaborator/friend Timbaland. She will also be featured on the June 29 premiere of VH1's 'Behind the Music,' in which she will also reportedly share her story of being molested as a child.

Watch the Missy Elliott 'Ching-A-Ling' Video