06/23/2011 at 09:35 PM EDT
For more than a decade, Missy "Misdemeanor" Elliott was one of the leading ladies of hip-hop.
But in the last three years, Elliott, 39, had been largely out of the spotlight. The reason, she explains, has been her private battle with Graves' Disease, an autoimmune illness that affects the thyroid.
"You live with it for the rest of your life," the Grammy winner told PEOPLE in its latest issue.
The disease – which Elliott was diagnosed with in 2008 – first began affecting her motor skills, followed by a string of symptoms: dizzy spells, lumps in her throat, mood swings, hair loss, a fast heart rate and bulging eyes.
But after undergoing radiation combined with medication, she's back and feeling better.
Last fall, she performed at VH1 Hip Hop Honors, has been writing and producing for other artists and is now working on her own album.
"I feel great," says Elliott, the subject of VH1's Behind the Music premiering June 29. "Under my doctor’s supervision, I’ve been off medication for about a year and I’m completely managing the condition thru diet and exercise.”
For more on Missy Elliott's battle with Graves' Disease, pick up this week's issue of PEOPLE, on newsstands Friday