Lena Dunham has her ovary removed a year after hysterectomy

The former "Girls" star wants to be an advocate for women in similar situations.

Just months after Lena Dunham revealed that she'd had a hysterectomy at 31 due to crippling endometriosis, the former "Girls" star told her 3 million Instagram followers that she's unable to promote her new HBO series, "Camping." because she recently had a procedure to remove her left ovary.

In a post from Wednesday morning, Dunham, who co-created the new show with Jenni Konner, explained that the two-hour surgery was necessary because the organ was "encased in scar tissue & fibrosis, attached to my bowel and pressing on nerves."

She also addressed critics who commented that her hysterectomy should have "fixed" her reproductive system issues, and those who suggested she try acupuncture, take supplements, or seek psychological help.

Her health, she explained, "isn't linear," and she wrote that despite spending some time in debilitating pain, "I feel blessed creatively and tickled by my new and improved bellybutton and so so so lucky to have health insurance as well as money for care that is off my plan."

"But I’m simultaneously shocked by what my body is and isn’t doing for me and red with rage that access to medical care is a privilege and not a right in this country and that women have to work extra hard just to prove what we already know about our own bodies and beg for what we need to be well. It’s humiliating," she continued. "My health not being a given has paid spiritual dividends I could never have predicted and it’s opened me up in wild ways and it’s given me a mission: to advocate for those of us who live at the cross section of physical and physic pain, to remind women that our stories don’t have to look one way, our pain is our gain and oh s--- scars and mesh 'panties' are the f---ing jam. Join me, won’t you?"

According to ABC News' chief medical correspondent Dr. Jennifer Ashton, the key with surgical treatment of endometriosis is two-fold: to reduce or remove scar tissue and/or to remove hormonal stimulation, which comes from the ovaries.

"Ideally, women have as few surgeries as possible but often with endometriosis multiple surgeries are common," she explained. "With a young woman, if the ovaries are left in -- one or both -- she can continue to have residual pain even after a hysterectomy because the microscopic implants or lesions respond to hormonal stimulation by the ovaries."

Dunham, 32, revealed this past February in an essay for Vogue magazine that last summer, she had her uterus and cervix removed following years of pain from endometriosis and nine related surgical procedures. Having previously tried "pelvic-floor therapy, massage therapy, pain therapy, color therapy, acupuncture, yoga," Dunham wrote that she checked herself into the hospital and said, "I am not leaving until they stop this pain or take my uterus." Twelve days later, she had the elective procedure, and learned that her uterus was "worse than anyone could have imagined."

"In addition to endometrial disease, an odd humplike protrusion, and a septum running down the middle, I have had retrograde bleeding, a.k.a. my period running in reverse, so that my stomach is full of blood. My ovary has settled in on the muscles around the sacral nerves in my back that allow us to walk. Let’s please not even talk about my uterine lining," she wrote. "The only beautiful detail is that the organ -- which is meant to be shaped like a lightbulb -- was shaped like a heart."

Jay-Sheree Allen, a family medicine resident physician at the Mayo Clinic in Minnesota and a resident at the ABC News Medical Unit, explained at the time that endometriosis is a chronic condition that occurs when endometrial tissue appears in places other than the uterus, including the ovaries, bowel, diaphragm, or bladder. There is no known cause for endometriosis, which some studies suggest affects 1 to 7 percent of women and has been reported in up to 50 percent of women with infertility.