But Panettiere, 26, looked like the picture of health as she sat ringside to support her fiancé, heavyweight boxer Wladimir Klitschko, as he fought to defend his world title against British challenger Tyson Fury in Düsseldorf, Germany, on Saturday.
Panettiere entered a treatment facility in October, and spoke candidly about the condition a month earlier during an appearance on Live! with Kelly and Michael.
"There's a lot of misunderstanding," she said. "There's a lot of people out there that think that it's not real, that it's not true, that it's something that's made up in their minds, that 'Oh, it's hormones.' They brush it off. It's something that's completely uncontrollable. It's really painful and it's really scary and women need a lot of support."
On Saturday, Panetierre showed off a more lighthearted side, beaming as she draped a Ukrainian flag over her shoulders in support of Klitschko, 39, while wearing a cream striped sweater with a plaid miniskirt, black tights, and cute tan fedora.
Sadly, her gesture of support proved to be in vain: her fiancé's 11-year reign as World Heavyweight Champ came to a juddering halt on a unanimous points decision in favor of the British underdog.
In an echo of Fury's unexpected pre-fight serenade to Klitschko—when he suddenly broke into an acapella version of the Bette Midler classic "Wind Beneath My Wings"—Fury, 27, stunned boxing fans across the world with a live rendition of Aerosmith's "Don't Want to Miss a Thing" after his victory.
Luckily for Klitschko, this time the target of Fury's romantic crooning was his pregnant wife Paris, who stood visibly moved in the center of the ring as her man sung the classic rock love ballad in front of 50,000 fight fans and a global TV audience of millions.