Hip-hop star Missy Elliot explains why she’s been away from the music scene and revealed she has been quietly suffering with a major auto-immune disease.

Missy was diagnosed with Graves' disease in 2008 - a disorder which affects the thyroid - and she admits the symptoms came on so fast, she almost lost her ability to do everyday things like drive and write.

She told People magazine:  "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.  I couldn't write because my nervous system was so bad.  I couldn't even use a pen."

After suffering various other side effects, including hair loss and mood swings, Elliot turned to radiation, which ultimately improved her condition.

She added:  "I'm 30 lbs lighter because I've been exercising. 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."

Missy Elliott is to appear in VH1’s ‘Behind The Music’ documentary on June 29 in the US.

Watch Missy perform 'Get Ur Freak On' live, below: