Missy Elliott suffering from Graves' disease

The reason for the six-year wait for a new Missy Elliott album became clear yesterday, when the groundbreaking rapper and producer revealed she is suffering from Graves' disease, which affects the autoimmune system and thyroid gland. Elliott told People magazine the illness had made even simple, everyday tasks difficult. "I couldn't write because my nervous system was so bad – I couldn't even use a pen," she said.

Elliott, 39, was diagnosed with the condition three years ago. She realised she had a problem while driving, when she lost control of her muscles. "I was trying to put my foot on the brake, but my leg was jumping," she said. "I couldn't keep the brake down and almost crashed."

Elliott went on to suffer other symptoms, including hair loss and mood swings. But her condition improved after she underwent radiation therapy, and spent more time at the gym. "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."

And new music is coming. This winter, she reunited with Timbaland, the producer with whom she made tracks such as Work It, Get Ur Freak On and The Rain (Supa Dupa Fly). In January, she guested on a Timbaland song called Take Ur Clothes Off, and she claims her long-promised seventh album – now dubbed Block Party – is truly on its way.

Elliott will discuss that upcoming record, and her struggle with Graves' disease, on a 29 June episode of VH1's Behind the Music.