Hayden Panettiere opens up about the loss of her younger brother Jansen.

“He was my only brother and it was my job to protect him,” the 35-year-old told People in an interview published Wednesday. “When I lost him, it felt like I lost half my soul.”

Jansen’s death came shortly after Panettiere quit drinking in 2020 after checking into rehab and ending an abusive relationship with her ex-boyfriend Brian Hickerson.

The “Amber Alert” star had even returned to acting after her brother died suddenly at age 28 from an undiagnosed heart condition, three weeks before the February 2023 premiere of “Scream 6.”

The former “Bring It On: All or Nothing” contestant did not leave her home after Jansen’s death, especially as photographers followed her in the days following the tragedy.

“I had to see horrible paparazzi photos of myself coming out of Jansen’s funeral, which was in a very private place, and it was shocking,” Panettiere said. “My agoraphobia came up, which is something I’ve struggled with in the past.”

Within days, her grief manifested in a physical reaction to the shock, and Panettiere said she was virtually unrecognizable. “I just blew up,” she said of the rapid weight gain she experienced.

Panettiere noted that the “stress and cortisol” in her body caused the sudden change, which lowered her self-confidence. “I didn’t feel confident enough to put on clothes and leave the house, but I also knew I had to get out there and keep moving or I would never look or feel like that again.”

She added: “It became a destructive hamster wheel of: Am I feeling well enough to go out?”

Through her publicist, Panettiere was introduced to personal trainer Marnie Alton and she slowly started exercising again.

The two had a personal connection: Panettiere shared her past stories with the fitness guru during long walks.

“These long, beautiful walks where we could blow off steam, and it would be a therapy session,” Panettiere told the outlet. “Marnie gave me strength.”

And in addition to the open dialogue, the endorphins Panettiere got from burning fat also improved his mood.

“My body just started responding, not just from the training. It allowed me to let go of the stress, the high expectations that I had always placed on myself,” she said.

As her confidence grew, her agoraphobia disappeared. “There’s nothing like looking in the mirror and feeling like you look good enough to walk out the door,” Panettiere admitted.

While still processing Jansen’s death, the Nashville veterinarian has also gained a new perspective after the loss.

“When something so big happens to you, you really learn to pick your battles and not let the little things get you down,” Panettiere said. “Because once something so terrible, so profound, so catastrophic happens in your life, there’s not a lot that can really affect you.”

The “Heroes” star is grateful that she feels more like herself these days and is looking forward to the release of her new film “Amber Alert,” which hits theaters on Sept. 27. But the trauma of Jansen’s death will linger for a long time.

“I’ll always be sad about it. I’ll never get over it,” Panettiere admitted. “No matter how many years go by, I’ll never get over his loss.”