NEW YORK CITY — Zoë Armstrong visits middle and high schools around New York City with the Endometriosis Foundation to educate students about the disease. Her advocacy follows a diagnosis at age 29 by a doctor who also had the disease, concluding an 18-year period of symptoms that began in childhood.

Armstrong experienced her first symptoms of endometriosis at age 11, which included stabbing pains on her left side. As an adult, she experienced severe pain, nausea, heavy periods, acne, and rupturing ovarian cysts. The condition causes tissue similar to the lining of the uterus to grow on other parts of the body.

This tissue is usually found on organs such as the bladder, bowel, or ovaries, but in rare cases can appear outside the pelvis. Symptoms may include bloating, fatigue, infertility, and pain during periods, intercourse, and bowel movements.

The American College of Obstetricians and Gynecologists states that people can wait a decade or more after the onset of symptoms to receive a diagnosis of endometriosis. Patients and doctors often normalize period pain, which contributes to delayed diagnoses of endometriosis, according to experts. "I very much knew what I was feeling in my own body," Armstrong said.

She received an ultrasound report showing signs of endometriosis at age 31. An ultrasound found an endometrioma, a fluid-filled cyst, in Armstrong. "To see it on paper, I was like, 'I'm not crazy,'" Armstrong said.

Following her diagnosis, Armstrong underwent excision surgery to remove endometriosis lesions and scar tissue. She currently sees about three doctors a week for pelvic floor therapy and other issues. Endometriosis afflicts 1 in 10 women worldwide.

Dr. Megan Billow, DO at the Cleveland Clinic, said symptoms of endometriosis can overlap with those of other conditions, and not all healthcare providers have knowledge or expertise in endometriosis. Dr. Drorit Or, MD at Mount Sinai West, said it can be debilitating pain that makes you not be able to go to school or work or be in bed for days at a time.

Or suggested that patients keep a diary tracking when pain occurs, where it is located, and how intense it is. "Then when you come to the doctor, you come prepared," Or said. She added that patients can definitely ask: Do you think I have endometriosis?

"You don't have to live in pain," Or said. "You can have a very, very good life managing this disease," Or said. She said they need to know what to look out for -- not just for endo, but for other women's health conditions in general.

Why It Matters

New diagnostic tests for endometriosis are available in some countries but have not been approved by the U.S. Food and Drug Administration. EndoSure is a half-hour test that detects endometriosis by measuring electrical signals in the gut using sensor pads on the abdomen. Endotest analyzes a saliva sample for microRNAs that can indicate whether endometriosis is present, providing results in 2 to 3 weeks. In the United Kingdom, an institute that provides national health advice published draft guidance recommending EndoSure and Endotest be used by the National Health Service for 3 years while more evidence is collected.

The French company Ziwig is taking steps to make Endotest available to U.S. patients through a pathway that allows lab-developed tests to be made available through certain certified laboratories without FDA approval. Tamer Ahmet Seckin founded the Endometriosis Foundation of America (EFA) with Padma Lakshmi in 2009. Armstrong works with this organization to raise awareness among younger demographics.