"I am currently going through a rough patch with the illness and my body (along with my amazing doctors) let me know, in no uncertain terms, that it's time to rest."

By Kathleen Felton
Updated February 09, 2016
Credit: Getty Images

Lena Dunham announced yesterday that she'll be canceling all of her Girls press appearances at the urging of her doctors, as she continues to battle endometriosis. "I am currently going through a rough patch with the illness and my body (along with my amazing doctors) let me know, in no uncertain terms, that it's time to rest," she wrote in identical posts on Instagram and Facebook. The actress was scheduled to promote the fifth season of her hit HBO show, which returns later this month.

Endometriosis is a gynecological disorder that occurs when the endometrium—the tissue on the lining of your uterus—forms on the outside of the uterus. Tissue can end up on the ovaries, bowels, or elsewhere in the pelvis, resulting in severe cramps, unusually heavy bleeding, and pelvic pain during menstruation. Researchers believe possible causes could include genetics or what's called retrograde menstruation, when the uterine lining that's released during a period flows backward into the abdomen. Recent studies have also linked higher rates of the disorder with exposure to certain chemicals, such as pesticides and even sunscreen.

Because it's so common for women to experience some degree of menstrual pain, doctors frequently miss endometriosis. Sometimes a pelvic exam can detect endometrial tissue or cysts, but in other cases an ultrasound or even surgery might be necessary for a definitive diagnosis. To treat the disorder, doctors usually prescribe a progestin-based contraceptive to slow the growth of endometrial tissue, or a short course of Lupron, which reduces estrogen levels. But in more severe cases, patients may need laparoscopy, a procedure which requires making a small incision in the belly to find and remove endometrium tissue.

Dunham recently opened up about her struggle with endometriosis in the eighth edition of her Lenny Letter newsletter last November, explaining that she has suffered from crippling pain and chronic exhaustion since her teens. "From the first time I got my period, it didn't feel right. The stomachaches began quickly and were more severe than the mild-irritant cramps seemed to be for the blonde women in pink-hued Midol commercials," she wrote. "During the worst of it, my father brought me to the ER, where they prodded my appendix and suggested it might be food poisoning and that we should go home and wait it out. My mother placed a pillow under my lower back, and I moaned in the guest room, where no one could hear me."

After years of mood swings, irregular periods, and pelvic pain, Dunham underwent laparoscopic surgery. What her doctor found: "enough endometrial tissue and scarring to cause significant pain, especially during sex or exercise, as well as an appendix that showed signs of long-term chronic infection."

Dunham's symptoms subsided for six months, then reappeared in the form of "nonstop vaginal bleeding" and migraines. She began getting monthly injections of Lupron to stop estrogen production and curb the growth of endometrial cells. "It's a temporary menopause of sorts, and while it solves certain issues, others pop up like whack-a-moles," she wrote, explaining that the medication had given her side effects such as achy hip joints and trouble regulating her body temperature.

In her social media announcement yesterday, Dunham expressed gratitude for her doctors, the support of "the whole Girls gang," and fact that she is able to take this break to allow her body to rest. "So many women with this disease literally don't have the option of time off and I won't take it for granted."