If you're living with endometriosis, you already know it's more than period pain.
It's a complex condition that can affect your whole body. But why does it happen? What's going on inside your body that makes this disease so persistent and painful? While we don't yet fully understand how or why endometriosis develops, we do know that hormones, inflammation, the immune system and the nervous system all play an important role. Let's break it down in a way that actually makes sense.
What is endometriosis?
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Endometriosis happens when tissue similar to the lining of your uterus grows outside the uterus, called lesions.
Although it doesn’t belong there, it still responds to hormones, becomes inflamed, and causes pain.
We don’t yet fully understand how or why these lesions end up in other parts of the body – but we do know they can lead to significant inflammation, nerve changes, and immune system disruption, all of which contribute to the pain and other symptoms.
How do hormones affect endometriosis?
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Progesterone resistance
Progesterone is a hormone that normally helps calm things down. It reduces inflammation and helps balance out oestrogen (the hormone that makes things grow).
But in endometriosis, the cells outside the uterus don’t listen to progesterone like they should. This is called progesterone resistance.
As a result: inflammation goes unchecked, oestrogen becomes dominant, and lesions grow and pain worsens.
Oestrogen dominance
Endometriosis lesions make too much oestrogen, which only fuels the fire.
Oestrogen: increases inflammation and pain, helps the lesions grow and survive, and stimulates blood and nerve growth (which makes pain worse).
Why is inflammation so important in endometriosis?
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Endometriosis lesions often have low oxygen levels (called hypoxia).
This leads to:
- Growth of more blood vessels (to get oxygen)
- Growth of more nerves (which can make pain worse)
- Production of more oestrogen
All of these factors contribute to ongoing inflammation and can make symptoms more persistent and painful.
What role do the nervous and immune systems play in endometriosis?
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Endometriosis is not just a hormonal condition—it’s also a neuroimmune pain disorder.
Lesions grow their own nerve supply and communicate with your nervous system. They release nerve growth factors (NGF) and inflammatory chemicals that sensitise your nerves.
This is called neuroinflammation—when your nervous system stays “on high alert”, making even mild sensations feel painful.
Normally, your immune system clears away abnormal tissue. But in endometriosis:
- Macrophages (immune cells) promote growth instead of clearing lesions
- Natural killer cells (that destroy bad cells) are less effective
- T cells shift toward promoting inflammation
There’s also a cross-talk between immune cells and nerves, which can make pain even worse.
How can pelvic floor physiotherapy help with endometriosis?
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Endometriosis may be invisible to others – but your pain is real, and so is the science behind it.
Understanding what’s happening in your body is a powerful first step. And having a team of supportive healthcare professionals can make a huge difference in managing your symptoms and improving your quality of life.
Pelvic health physiotherapists are uniquely trained to help you with:
Personalised pain management strategies
Encouraging safe, healthy movement and exercise
Supporting pelvis and pelvic floor function
Regulating your nervous system to reduce pain sensitivity
Providing education, guidance, and empowerment
Addressing bladder, bowel, and sexual health concerns with compassion and care
Other Blogs in the Pelvic Pain Series
Deep dive into education written by our pelvic physiotherapist, Claire, all about the pelvic pain – including symptoms, treatment & understanding the range of associated factors and conditions.
Understanding Endometriosis: Why Is It More Than Just Period Pain?
Menstrual Cycle: Understanding Your Cycle for Pelvic Pain Symptoms
