Hayden Panettiere is about to release her memoir… so she’s been an open book about her life lately … and recently shared one shocking story about upsetting a skincare brand she endorsed after making postpartum comments.

HP recently said on the “On Purpose with Jay Shetty” podcast … she was taken aback by the negative reaction to her postpartum comments during a morning show interview in 2015.

As she tells it … after she randomly talked about her experience with postpartum on “Live! with Kelly and Michael,” she was immediately told Neutrogena was not pleased with the remarks … and that the company wanted to fire her on the spot. Her agent saved her job in the moment, but once her contract expired — she was cut loose.

Hayden said her reaction in the moment was complete and total shock, that — of all the things she could have done to break the morals clause in her contract — it was to talk about her health. She called it “heartbreaking” … because she’d been working with the company for a decade at that point — and says when they dropped her, there was not a peep from the brass.

In that 2015 interview, she told the hosts in part … “It’s something completely uncontrollable, and it’s really painful, and it’s really scary, and women need a lot of support.”

Panettiere’s memoir, “This Is Me: A Reckoning,” drops May 19.