Endometriosis affects one in 10 women of reproductive age in the UK, yet there’s limited research into what causes it.
The condition occurs when tissue that behaves like the lining of the womb is found in different areas of the body such as the ovaries, the lining of the pelvis behind the uterus and the top of the vagina.
The condition can cause sufferers to experience painful or heavy periods, pain during sex and fertility issues.
It takes (on average) seven years for women to get a diagnosis from the onset of their symptoms, according to health charity Endometriosis UK.
Here are seven famous women who have opened up about living with the condition, in a bid to raise awareness and help fellow sufferers seek diagnosis.
Kate Ford recently opened up about her monthly struggles with endometriosis on Twitter. The star revealed that living with the condition is "not easy".
She later told the Mirror: "Endometriosis
is a chronic condition that has affected me for many years and every month is a struggle.
“As well as pain, there are also psychological symptoms. I’m working alongside a fabulous gynaecologist now to try to manage the condition.
"I’m pleased my tweet has raised awareness for a condition that is not fully understood.”
Star Wars actress Daisy Ridley took to Instagram to reveal that she had been battling endometriosis since her teens.
She said she was diagnosed with the illness aged 15 and her self-esteem suffered as a result. “Eight years down the line, pain was back (more mild this time!) and my skin was the worst,” she wrote.
Ridley asked others to speak to their doctor if they noticed something wasn't quite right. “My point is, to any of you who are suffering with anything, go to a doctor; pay for a specialist; get your hormones tested, get allergy testing; keep on top of how your body is feeling and don’t worry about sounding like a hypochondriac," she said.
"From your head to the tips of your toes we only have one body, let us all make sure ours our working in tip top condition, and take help if it’s needed."
Steve Granitz via Getty Images
Lena Dunham is perhaps currently the most vocal celebrity when it comes to endometriosis. The 'Girls' star revealed last year that she was going to take time out from filming because of the condition.
"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 on Instagram.
"So many women with this disease literally don't have the option of time off and I won't take it for granted."
She has since shared a photo of herself in a bikini, with her endometriosis scars on show, which once again kickstarted conversations around what it's like to live with the condition.
Stuart C. Wilson via Getty Images
Emma Bunton revealed that she was diagnosed with the "painful" condition in 2004 and shared fertility concerns.
"My doctors seem to think it is easing off, which would make it hopeful for me to have children," she said.
In 2012, Bunton revealed she was pregnant with her first child. She now has two sons, Beau and Tate.
Ben Gabbe via Getty Images
Whoopi Goldberg spoke about the condition back in 2009 and was surprised to hear that many other women didn't know about it. After asking her daughter whether she'd heard of endometriosis, Goldberg knew she had to use her voice to get the message out.
Speaking at the Endo Foundation’s Blossom Ball, she said: "I thought we all knew about endometriosis
. I thought we all knew that it was there and existed, why it happens."
"It occurred to me...that there are hundreds of thousands [of] girls out there that don’t know."
Jason LaVeris via Getty Images
Susan Sarandon, who suffered from irregular bleeding and fainting, was first made aware of her condition back in 1983. She has since spoken at numerous events to raise awareness of endometriosis.
Despite doctors telling her she may struggle to have children due to the condition, she went on to have three.
She has since asked men to support the women in their lives who suffer with endometriosis.
"Help [the woman in your life] to remove the taboos and the loneliness surrounding this disease," she said at the Blossom Ball in 2011.
"Be understanding, show empathy, and don’t accuse her of being sensitive, delicate, or overly dramatic – this is a big opportunity for you guys to show that you care and to be a real man."
Gary Miller via Getty Images
Dolly Parton underwent a partial hysterectomy in 1984, aged 36. The surgery was reportedly related to endometriosis.
Years later, the singer opened up about how she had sunk into a deep depression during that time because she was no longer able to have children.