Start where you are
Where are you right now? Pick the one that fits and we will take you to the part that matters most today.
This is not fair, and here is the proof
Before the numbers, the part that is not fair. One woman of reproductive age in ten has this disease. Here is how medicine has treated it, with the receipts.
is how long a woman waits, on average, from her first symptoms to a name for them, depending on the study. In France in 2026 the wait was ten years. Most were told their pain was normal.
a year is what the US National Institutes of Health spent on research per woman with endometriosis in 2022. Crohn's disease got about $130 per patient, diabetes about $31 per woman.
is how often the money favours men. When a disease mostly affects one sex, in nearly three quarters of cases the funding pattern favours the male-dominant one, once you account for how much suffering each disease causes. Endometriosis is among the most underfunded of all.
women who have surgery for this disease are operated on by a surgeon who does six or fewer of these operations a year. The busiest surgeons have the fewest complications and the fewest repeat operations.
is the year the United States made it law to include women in medical research. Before that, women of childbearing age were routinely left out of drug trials. The male body was the default patient for most of the century in which this disease was studied.
a day is the unpaid care work the average woman does, against 1 hour 23 minutes for a man. A woman with this disease is usually carrying that load through the pain, and being told to manage her stress.
Our working explanation, and what would prove it wrong
We are testing a simple explanation: this disease was neglected because it only happens to women, and medicine was built by and for men. It is a hypothesis, so we wrote down what would prove it wrong. If funding matched suffering equally for men's and women's diseases, we would drop it. So far the numbers above say we should keep it.
None of this is your fault, and none of it is your doctor's fault alone. It does mean you will often have to bring the facts into the room yourself. That is what this page is for.
The five numbers to know
women of reproductive age have endometriosis, about 190 million people worldwide.
is the average wait from first symptoms to a diagnosis, across studies. A French cohort published in 2026 put it at 10 years.
of the women given only a diagnostic look, with no treatment, had visibly worse disease six months later (a 39-woman trial). In 22% it had improved on its own.
have the disease come back within five years of conservative surgery; about one in five within two years.
per patient per year is what the US National Institutes of Health spent on endometriosis research in 2022, against about $130 per patient for Crohn's disease — 65 times more.
Ten years, or six weeks
The gap between what is possible and what most women get.
ACOG 2026 · ComPaRe cohort 2026 (France, 10 years) · Bryan Johnson, July 2026 · the affordable path, below
Could this be me?
No quiz can diagnose endometriosis, and this is not one. But a set of self-reported symptoms separated women with and without it well in one study (AUC 0.94 — a measure of ranking, not a hit rate), and these are the questions that mattered most. Tick what is true for you. If several are, it is worth saying the word to a clinician.
Tick what is true for you.
For parents: catching it at 14, not 30
About two thirds of women with endometriosis had symptoms before they were 20, and 38% before 15 (figures from a patient association's members, not every woman with the disease). Most were told it was normal. This is what a parent can watch for, and what to ask.
2020 review quoting the two-thirds figure · Endometriosis Australia, quoting the 38%
- Among girls whose pelvic pain did not respond to treatment and who went on to have keyhole surgery, 75% (237 of 314) had endometriosis. Those were girls already selected for surgery, so the review warns the figure may overstate how common it is. systematic review of 15 studies, 2013
- A mother or sister with the disease raises a girl's risk about seven-fold in a small 1993 study — the true figure could be anywhere from 2 to 24 times. ACOG puts it at 7 to 10. familial risk study, 1993 · second source
- In teenagers the pain is often not tied to the period. In a 2025 Rome cohort of 92 girls, 39% reported pain between periods; in a 1997 series of 32 girls found to have the disease, 28% had pain only between periods and 62% had both. That is why it gets missed. adolescent cohorts, 2025 and 1997 · second source
- Missing school because of periods is, in the words of the US college of gynaecologists, 'suggestive of endometriosis'. ACOG Committee Opinion 760, 2018 (since replaced by ACOG's 2026 guideline)
- The US college's 2026 guideline now describes a presumptive clinical diagnosis from history, symptoms and examination, with treatment begun while imaging continues, so nobody has to wait for surgery to be treated. ACOG Clinical Practice Guideline 11, 2026 (press release)
The red flags
The red flags the guidelines name. One is worth a conversation; two or more are worth an appointment with someone who sees a lot of teenagers.
Tick what you have seen.
What to do
What to do, in the order the evidence supports:
- Start a simple pain and period diary on her phone. Dates, pain out of 10, days missed. Three months of it is the most useful thing you can bring to a doctor.
- Say the word to the doctor: 'Could this be endometriosis?' Ask for someone experienced with adolescents.
- The European guideline's first-line treatment for teenagers is hormonal contraception or a progestogen, plus anti-inflammatory painkillers, begun without waiting for a surgical diagnosis. Ask whether it applies to her.
- If there is no real improvement after 3 to 6 months, ask for investigation, not a stronger painkiller. The European guideline asks for an ultrasound by someone trained in endometriosis where appropriate; if an internal scan is not appropriate for her, it says MRI or an abdominal scan may be considered.
- Ask whether a non-surgical test (blood or saliva) is available where you live. They are new and not yet validated in teenagers, so ask, do not assume.
- Keep her moving, sleeping and in school as much as pain allows; pelvic physiotherapy and pain psychology have drug-sized effects in trials, without a drug's side effects.
ESHRE guideline 2022, adolescents · ACOG Committee Opinion 760, 2018 (since replaced) · ACOG guideline 2026 (press release) · adolescent imaging review · PPEP Talk schools programme
What surgery does, and does not do
Surgery is real medicine for this disease and most women who have it say it was the right decision. It is also a treatment for a lifelong condition that is often delivered as a one-off. Here is what the studies actually show.
| Question | Answer | Source |
|---|---|---|
| Does surgery work? | Yes. 80% improved after excision vs 32% after a sham operation — one of two placebo-controlled trials (the other, Sutton 1994, laser ablation, found 63% vs 23%); about 30% of the benefit is a placebo response | Abbott 2004 · Sutton 1994 |
| How many diagnosed women end up having surgery? | About 71% — US insurance records of 77,000 women; for many, the operation was how the diagnosis was made. Only 42–45% were ever prescribed a disease medication (study co-authored by Bayer employees) | 10-year US claims analysis, 2025 |
| What kind of first surgery? | Laparoscopy 53–58%; hysterectomy 42–47% — US hysterectomies for endometriosis fell from about 240,000 in 2002 to 83,000 in 2010 (−65%) as other options spread | same; Wright et al., Obstetrics & Gynecology 2013 (all US inpatient hysterectomies 1998–2010) |
| Will it come back? | It comes back in about 21% by 2 years and 40–50% by 5 years — recurrence of the disease, not only pain; few risk factors have been consistently identified | Guo, review of published series, 2009 |
| Will I need another operation? | 27–58% do; 28% within 10 years in a 1,092-woman series — median gap between operations is 30–36 months; 1 in 20 women has had 3 or more | Fertility and Sterility 2023 |
| Does age matter? | Recurrence after cyst surgery: 43% at 20–29, 22% at 30–39, 10% at 40–45 — the more cycles ahead of you, the more often it returns; this is why hormonal rest afterwards matters | meta-analysis of 3,125 patients |
| Does a hysterectomy end it? | Not always. With ovaries kept, re-operation is 6–8 times more likely (62% vs 10% in one series) — the disease runs on ovarian estrogen; chronic pelvic pain persists after 5–32% of benign hysterectomies | Human Reproduction Update |
| Does it matter who operates? | Yes. 80% of women are operated on by surgeons doing 6 or fewer cases a year; the highest-volume surgeons have the lowest complications (5.5%) and fewer re-operations — 83,787 patients in Ontario | JMIG 2025 |
| Excision or ablation? | The European guideline says surgeons 'may consider excision instead of ablation' — ESHRE 2022: a weak recommendation on low-quality evidence; recurrence is lower after excision, pain at 12 months similar in small trials | ESHRE guideline 2022 |
| What stops it coming back after surgery? | Hormonal rest: a long-acting progestogen, an IUD or the pill held a 40% pain improvement at 3 years, with fewer repeat surgeries — 405 women, randomised | PRE-EMPT trial 2024 |
| Do women regret it? | 16% report some regret; 90% say it was the right decision; 87% would do it again — 154 women after excision surgery | JMIG 2020 |
| What about opioids? | 62% of newly diagnosed US women fill an opioid prescription in year one — guidelines give opioids a minimal role; endometriosis accounts for a quarter of opioids prescribed by US gynaecologists | claims study 2020 |
Why it comes back: the cycles still ahead of you
After surgery for an ovarian cyst, how often it comes back depends most on how many cycles are still ahead of you.
meta-analysis of 3,125 patients
Six questions to ask before anyone operates
- How many endometriosis operations do you personally do a year? (Outcomes are best above 24.)
- Will you excise (cut out) the lesions or ablate (burn) them? The European guideline says surgeons 'may consider excision instead of ablation'.
- If the disease is on my bowel or bladder, who else will be in the room? (Expert centres plan with a bowel surgeon and urologist.)
- What is the plan the day after surgery to stop it coming back? (Ask about hormonal rest: an IUD, a long-acting progestogen, or the pill.)
- Will I have a nurse or coordinator I can call, and a referral to pelvic physiotherapy and pain psychology?
- If a hysterectomy is proposed: what happens to my ovaries, and what does that change about recurrence?
What else helps, with the evidence behind it
| Option | What the studies found | How sure | Source |
|---|---|---|---|
| Hormonal rest after surgery | ~40% pain improvement held at 3 years; fewer repeat operations on the long-acting arm (405 women) | strong | PRE-EMPT 2024 |
| Pelvic physiotherapy | Largest effect of any non-drug option across 33 trials (SMD −1.44 vs usual care); best for period pain | moderate | network meta-analysis 2026 |
| Acupuncture | SMD −1.27 overall; the top-ranked option for pelvic pain in the same analysis | moderate | network meta-analysis 2026 |
| Psychological therapy | SMD −1.22 vs usual care; pain is partly nervous-system wiring, and this is how you treat wiring | moderate | network meta-analysis 2026 |
| GnRH antagonists with add-back (elagolix, relugolix) | Non-inferior to dienogest; relief within a month; bone loss controlled by add-back; ~10–13% stop for side effects | strong | systematic review 2025 |
| Heat (a heating pad) | In period pain generally, not tested in endometriosis: beat painkillers in 3 randomised trials of primary dysmenorrhoea and beat no treatment by 4 points on a 10-point scale | weak (indirect) | Scientific Reports meta-analysis 2018 |
| Melatonin | Pain down ~40% in one RCT; a 2025 triple-blind RCT found large effects on pain and sleep | moderate | Schwertner 2013; PLOS One 2025 |
| A self-management app | Quality of life improved in 9 of 10 measures within 2 weeks (122 women, randomised pilot) | weak | Endo-App pilot 2024 |
| Diet changes (low-nickel if nickel-sensitive; less red meat) | Red meat >2 servings/day linked to 56% higher risk; low-nickel diet eased symptoms in an uncontrolled pilot | weak | AJOG 2018; Nutrients 2020 |
| Non-hormonal drugs in trials | First non-hormonal candidate cleared for Phase 1 (Mar 2026); dichloroacetate trial recruiting late 2026; antibiotic trial running in Japan | weak | Contemporary OB/GYN 2026 |
Your nervous system is part of this
Part of this disease lives in the nervous system, and that part is treatable in its own right.
- Lesions grow their own nerve supply, and the denser the nerves in a lesion, the worse the pain. Annual Review of Physiology
- In 41 to 52% of women with endometriosis the pain system itself has become sensitised, so ordinary signals register as pain. In specialist centres it is up to 75%. cross-sectional studies
- Women with lower heart-rate variability, a sign of a nervous system stuck in alarm, report more intense pelvic pain and more stress. vagal HRV study
- Hair cortisol, a three-month record of stress hormone, is higher in women with endometriosis than in controls. hair cortisol study
- Women do three quarters of the world's unpaid care work, 4 hours 25 minutes a day against 1 hour 23 for men. Chronic stress is not a character flaw; it is a workload. ILO
- Severe childhood adversity raised later endometriosis risk 79% in 60,595 women, with a dose-response. Nurses' Health Study II
Finding it for $300, not $5,000
Most women do not need an MRI to find this disease; guidelines use it to map deep disease and plan surgery. A cheaper path exists in pieces today; nobody has assembled it. Per 1,000 women with pelvic pain:
| Step | What | Who reaches it | Cost today → target |
|---|---|---|---|
| Free | Symptom + cycle + wearable temperature check, in an app | 1,000 of 1,000 | $0 |
| ~$100 | Blood test (today a clinic draw; a home kit is the target) | 600 of 1,000 | $499 today (HerResolve); €800 (Endotest); ~$100 at scale |
| ~$250 | Ultrasound by a trained nurse, AI as second reader | 400 of 1,000 | $250–600 today |
| ~$1,500 | MRI, only to plan surgery | 150 of 1,000 | $500–3,500 |
The 1,000 → 600 → 400 → 150 counts are illustrative arithmetic, not measurements: they assume that roughly four in ten women referred with pelvic pain have the disease and that each cheaper step clears the women who do not need the next one. No study has run this path end to end.
HerResolve price · Endotest reimbursement · AI-assisted ultrasound · US MRI prices
Who is using AI on this disease right now
A lot has changed in the last two years, and most of it has not reached the waiting room yet. Here is who is using artificial intelligence on this disease right now, what they have shown, and what to watch for. We keep this list honest: a press release is not a result.
| Who | What they are doing | What to watch for |
|---|---|---|
| Flo Health, with the London School of Hygiene Finding itMarch 2026 | A symptom checker inside a period-tracking app. A published model estimates it could cut the average wait for a diagnosis from about seven years to about three, saving roughly $5,000 per woman over a lifetime. | a real-world study, not a model, showing women actually got diagnosed sooner |
| Kate Tolo and Bryan Johnson Finding itJuly 2026 | One woman, 14 million data points, 50 devices. Diagnosed in 42 days by combining imaging, blood and AI, against the usual six to ten years. Money was no object. | whether anything in her protocol works for a woman with $300, not $2 million a year |
| HerAnova (HerResolve) Blood teston sale since December 2025 | An AI model reads three microRNAs, three proteins, one hormone, plus age and BMI, from a blood draw. $499. A study for the US regulator is running. | independent validation in women who have not yet been diagnosed, and an insurer paying for it |
| Ziwig (Endotest) Saliva testin use in Europe; French reimbursement 2025 | A saliva sample, 109 microRNAs, an AI model. Reported 96.6% accuracy in 971 women. Approved in Europe; France moved to pay for it. | results in ordinary clinics rather than the centres that built it |
| Aspira Women's Health (ENDOinform) Blood testlab built Q2 2026 | An AI-enabled blood test combining proteins, microRNA and medical history, designed to find the disease at any stage and location. | published performance numbers; none yet |
| Radiologists, worldwide Ultrasound and MRI2025 to 2026 | Deep-learning models reading pelvic ultrasound reach about 90% accuracy and match or beat human readers for ovarian disease; an AI reading aid for MRI of deep disease was built in 2025. A 2026 review says most are not yet ready for clinics. | AI as a second reader that lets a trained nurse, not only a specialist, run the scan |
| Deep Origin and Arctoris (UK ARIA grant) New medicines2026 | An AI that has read three million papers, paired with a robot laboratory, hunting a new drug target. Its own analysis ranked endometriosis the biggest unmet need in women's health. | a validated target by the end of 2026, as promised |
| Insilico Medicine New medicines2025 | AI target discovery named two new targets (GBP2, HCK) and one existing drug to repurpose (ITGB2 blockers) for endometriosis. | any of the three reaching a human trial |
| Academic drug-repositioning groups New medicines2025 | A computer search of gene-expression data flagged two cheap old drugs, simvastatin and primaquine, as candidates for endometriosis pain. | a trial; old drugs are cheap to test and nobody profits, so this may need public money |
| University of Edinburgh (ENDO1000) Understanding it2025 to 2027 | 1,000 women in the UK tracking pain, cycles, sleep, diet and temperature through an app and wearables for two years, with home blood, saliva and stool samples, analysed with machine learning. | the first dataset big enough to test the temperature and flow ideas on this page |
| Columbia University (Phendo) Understanding itongoing | A research app that learns from women's own tracking and can tell an undiagnosed woman whether her pattern looks like endometriosis. | whether the signal holds up in women who never went on to be diagnosed |
And the chatbots? You can ask one about this disease tonight, and many women do. Here is how they score.
- When 150 endometriosis questions from online forums were answered by a chatbot and by human specialists, and eight experts graded them blind, most chatbot answers were accurate (85%) and harmless (87%), but only 74% were judged suitable for a patient. European Journal of Obstetrics and Gynecology, 2025
- Three leading chatbots asked the same 50 guideline questions twice each, in December 2025: accuracy was good but reliability was 'suboptimal', meaning the same question could get a different answer. Human Reproduction, 2026
- An earlier comparison found chatbots 'mostly correct but inadequate' on endometriosis, with wide variation between them. comparative analysis, 2025
Beyond AI, the trials and programmes most likely to change what happens to you in the next few years.
Show the 7 projects
| Who | What | What to watch |
|---|---|---|
| Nagoya University Hospital, Japan | Antibiotic treatment aimed at Fusobacterium, found in 64% of patients' uteri vs 7% of controls (trial ENDS, NCT06368596) | a positive result makes part of the disease an infection, and infections are curable |
| Proteomics International (PromarkerEndo) | 10-protein blood test, 83% sensitivity, 95% specificity in 436 cases | US launch after Australia; FDA plans not stated in the source |
| EndoCyclic Therapeutics (ENDO-205) | First non-hormonal drug candidate; FDA cleared Phase 1 in March 2026 | top-line results expected 2027 |
| University of Edinburgh (EPiC2) | Dichloroacetate, a cheap metabolic drug, placebo-controlled | recruitment starts late 2026 |
| Feinstein Institutes (ROSE study) | 3,700 women giving menstrual blood to build a non-surgical test | NIH-backed; a tampon-based test |
| Pelvic Pain Foundation of Australia (PPEP Talk) | School programme reaching 110,000 students; 52.6% report severe period pain | the model for finding the disease at 15 instead of 30 |
| This page | Fifteen explanations, each with a written test that would prove it wrong; new papers pulled weekly (18 so far, not yet published as a list); no prediction graded yet | the ranking changing as evidence arrives |
Where the flow stalls
One idea keeps turning up when you look at where this disease settles: where the fluid stalls, the disease grows. It is not proven as a cause. It is where the lesions are.
- The fluid in your pelvis circulates in a slow clockwise current. It stalls in four pockets, and those four pockets are the four commonest places lesions are found. peritoneal fluid flow and lesion sites
- Across 154 studies and 20,718 women, pelvic lesions favour the left side, where the current is slowest behind the bowel, and chest lesions favour the right, under the diaphragm. 2026 meta-analysis
- Six in ten women with confirmed varicose pelvic veins, where blood pools, also show signs of endometriosis. MRI study, 2025
- The same pattern shows up elsewhere in the body: pooled blood clots, pooled bile makes stones, pooled urine breeds infection, and pooled venous blood around the testis raises its temperature and harms fertility. varicocele review
Salt in, water out: a thesis we are testing
Here is a thesis we are taking seriously and testing in the open. Your body is mostly water, and water follows salt. For almost all of human history salt was rare and plants were plentiful, so we ate about sixteen times more potassium than sodium. Today it is the other way round. What does that do to a system that depends on fluid moving?
- The diet we evolved on delivered about 16 times more potassium than sodium. The average American diet now delivers about twice as much sodium as potassium, and most people get barely half the potassium they need. Harvard Health
- A high sodium-to-potassium ratio is linked to higher cardiovascular risk; potassium relaxes blood-vessel walls. Vessel tone is a flow variable. Harvard Health
- In 156 women in Tehran, those eating the most potassium had about a third the odds of endometriosis of those eating the least (OR 0.32). Magnesium ran the same way. Sodium showed no difference. One small study, and potassium travels with fruit and vegetables, so diet quality may be doing the work. case-control study, 2023
- Magnesium eased period pain against placebo in small trials, though the evidence is low quality. Cochrane review
What actually moves water in the body, graded honestly:
Salt holds
Water follows sodium. Extra salt pulls water into the blood and the spaces between cells and raises pressure; the kidneys then work to shed both. The Tehran study found no sodium difference in endometriosis, so this is a general truth without a disease-specific result yet. Source
The pill and hormones runs the other way
Oestrogen makes the body hold water and sodium, not shed it. The pill, pregnancy and the high-oestrogen days of the cycle all retain fluid. Where the pill acts on this disease is on how many periods you have, not on dryness. Source
Antibiotics indirect
They do not dry tissue. They act on the gut bacteria, and in mice that runs both ways: broad-spectrum antibiotics shrank lesions about five-fold, while the bacteria themselves were needed for lesions to grow. In women it is untested. The flow effect, if any, is through inflammation. Source
Paracetamol (Tylenol) no fluid effect known
Its known link is prenatal: daughters of women who took it in pregnancy had smaller ovaries, fewer follicles and smaller uteri in infancy in one 2026 cohort. It does not move water in any measured way. Source
Childbirth temporary
Birth costs about half a litre of blood and a large fluid shift, then recovers over weeks. The lasting effect of pregnancy on this disease is the opposite of harm: every pregnancy and every month of breastfeeding lowers risk, because periods stop. Source
What gets cool, nutrient-rich fluid moving, with the evidence:
- Movement. Women who exercised most had modestly lower risk in a 102,000-woman cohort (RR 0.89), much lower in smaller studies, and genetics points the same way. Nurses' Health Study II
- Pelvic physiotherapy, which is literally moving fluid and releasing tissue, has the largest effect of any non-drug treatment across 33 trials. network meta-analysis, 2026
- Heat on the belly opens vessels and beat painkillers in three trials. Cold has its place too: cooling is proven to protect newborn brains, and warmth is proven to ease this pain. Temperature is a dial, not a villain. Scientific Reports, 2018
- Potassium and magnesium from food: fruit, vegetables, beans, nuts, dairy. This is the one lever with a disease-specific signal, and it is a diet, not a pill. case-control 2023
What science currently says about the cause
Nobody knows the cause for certain. Below is the current ranking of explanations, scored from 114 published findings by a fixed rule: bigger, better-designed studies count more, and evidence against a theory subtracts. The score is arithmetic, not opinion, and it changes when new studies arrive.
| # | Explanation | Evidence | How sure |
|---|---|---|---|
| 1 | Too many spills Modern life quadrupled lifetime menstrual cycles (~100 → 400+) and each cycle seeds the pelvis; the clean-up capacity did not grow | 22 for, 1 against | strong |
| 2 | Seeded before birth Ectopic lining tissue is laid down in the womb in ~10% of female fetuses; what the mother and infant took in shapes it; adult estrogen lights the fuse | 12 for, 0 against | strong |
| 3 | Partly a pain-wiring disease Half of risk is inherited, and the genes overlap with migraine and chronic pain; some of what women suffer is nervous-system wiring, not lesion size | 11 for, 0 against | strong |
| 4 | The clean-up crew fails The immune cells that should clear stray tissue are sluggish and the uterus lining itself is inflamed and progesterone-resistant; the body's own defence is part of the disease | 13 for, 0 against | strong |
| 5 | The uterus injures itself A self-perpetuating mechanical loop: uterine hyper-contraction → micro-injury at the lining–muscle border → local estrogen → more contraction; obstructed outflow forces the same thing | 11 for, 0 against | strong |
| 6 | Something ingested A medication or something eaten is causing it; true for estrogenic drugs (DES in the womb, estrogen therapy in men) and infant soy formula; no evidence for common non-hormonal drugs | 7 for, 1 against | strong |
| 7 | An infection nobody looked for A mouth-and-gut bacterium (Fusobacterium) and gut-derived endotoxin in menstrual blood teach lining cells to scar and dig in; part of the disease may be treatable with antibiotics | 5 for, 0 against | moderate |
| 8 | Heat inside the body A temperature or thermal-stress disturbance is involved; 1980s work found a distinctive basal-temperature signature, and heat-shock (cell stress) proteins are raised, but no evidence yet that heat causes the disease | 9 for, 1 against | moderate |
| 9 | Stress re-wires the system Chronic stress and early trauma change immune tone, pain wiring and hormone rhythm; the captive-baboon effect and the abuse dose-response point the same way | 4 for, 0 against | moderate |
| 10 | The estrogen leak Chemicals that mimic or boost estrogen (PFAS, persistent pesticides, dioxins, the weedkiller atrazine, pharmaceutical estrogens in water) feed a disease that runs on estrogen | 13 for, 7 against | moderate |
| 11 | The cells were already there Lining-type cells can arise in place from the pelvic lining or stem cells, or travel by blood and lymph; the disease occurs in women with no uterus and in men on estrogen | 7 for, 0 against | moderate |
| 12 | Where fluid stalls, disease grows Lesions form where pelvic fluid pools and slows (behind the sigmoid colon, in the recesses), and stagnant veins and lymph travel with the disease; flow is protective | 7 for, 0 against | moderate |
| 13 | Neglected because it is a women's disease Research money follows the burdens the funders recognise; when funders and the profession were mostly men, diseases that only women get were under-recognised, and the pattern outlived the people who set it | 4 for, 0 against | weak |
| 14 | Salt in, water out: the sodium-potassium imbalance Modern diets carry far more sodium and far less potassium and magnesium than the bodies we evolved in expect; water follows salt, so tissues run drier and stiffer, flow slows, and the pelvis pays | 4 for, 1 against | weak |
| 15 | The record is already in the drawer: baby teeth as a time-stamped log of exposure before birth Baby teeth mineralise in weekly rings from about 20 weeks in the womb to roughly age one and lock in whatever chemistry the child was exposed to. If endometriosis is seeded before birth (H2/H8 developmental-origins line), the exposure fingerprint of women later diagnosed should differ from their sisters' and peers' — and millions of parents have kept those teeth. | 0 for, 0 against | speculative |
Every study behind this ranking, with its link, its design and its points: the full list of studies.
The ranking, drawn
Facts any explanation has to survive
- Retrograde menstruation occurs in over 90% of women but only ~10% develop the disease Reprod BioMed Online review
- Spontaneous endometriosis occurs in baboons, rhesus and cynomolgus monkeys including wild-caught animals, and only in menstruating species rhesus macaque characterisation
- Endometriosis in Mayer-Rokitansky-Küster-Hauser syndrome patients with no functional uterus MRKH case report
- Nurses' Health Study II (116,430 women, 5,504 cases): morbidly obese women had 39% lower risk; waist-to-hip ratio <0.60 nearly 3x the rate Shah, Hum Reprod
- Tampon use associated with LOWER endometriosis (11.6% tampon-only users among cases vs 20.9% controls), contradicting the idea that tampons cause it Meaddough, Yale
- Older cohorts reported maternal smoking in pregnancy associated with LOWER endometriosis in some studies and no association in others; a 2025 narrative review calls the direction unsettled Smoking and endometriosis review, Tob Induc Dis
- COVID-19 vaccination shifted menstrual cycle length by under one day, resolving the next cycle, in Natural Cycles data across countries; no endometriosis association has been reported Edelman, BMJ Medicine / NIH
- Physical activity and endometriosis: 40–80% lower risk in case-control studies but only RR 0.89 (0.77–1.03) in the 102,197-woman Nurses' cohort; Mendelian randomisation points protective again Vitonis, Epidemiology (NHS II)
- Obstetrics and gynaecology has been majority-female since 2008 and is about 59% women today, heading for 66% within a decade Changes in the numbers of male and female obstetrician-gynecologists
Why we believe a real answer is possible
Why we think a real answer is possible. Trigeminal neuralgia is a facial pain so severe it has been called the most painful condition known to medicine, and for decades it was nicknamed the suicide disease. It strikes about four to five people in every 100,000 each year, more often women, and rises with age. A single episode can make eating, speaking, brushing teeth or a breeze on the cheek unbearable. For most of the twentieth century it was managed with drugs that dulled the pain and the person. Then surgeons found the cause in most cases: a blood vessel pressing on the nerve where it leaves the brainstem. They learned to lift the vessel off and tuck a small pad between them.
- How common: about 4 to 5 new cases per 100,000 people a year, rising to about 20 per 100,000 after 60; roughly 1 to 2 people in every 10,000 live with it. systematic review and meta-regression, 1945 to 2024
- How bad: described in the medical literature as 'the most painful affliction known to humankind', and about one in eight patients with facial pain report some suicidal thinking, three times the general population. neurophysiology review; facial-pain cohort
- What the operation does: in 1,185 patients followed for up to 20 years, about 70% were pain-free without medication a decade later, and recurrences ran under 1% a year. New England Journal of Medicine, 1996
- Against medication alone: at five years, 59% of operated patients were pain-free without drugs, against 19% of those managed with medication. prospective five-year outcomes
- Who does it well: at Stanford, neurosurgeon Michael Lim's programme treats it as a disease to be resolved, not managed, and modern series report durable pain freedom in roughly seven to nine of every ten patients with the classic form. Stanford Medicine, trigeminal neuralgia
If you are a clinician
If you are a clinician, thank you for reading this far. Your patient may bring this page. Here is what the guidelines and the trials say she is entitled to ask for.
- Name it early. A first-degree relative, cyclical bowel or bladder pain, deep dyspareunia, or dysmenorrhoea that fails 3 to 6 months of NSAIDs and hormonal treatment is the pattern; the European guideline says treat empirically without waiting for laparoscopy, including in adolescents. ESHRE 2022
- Ultrasound by someone trained in endometriosis, and in younger teenagers MRI over a transvaginal probe. Non-surgical blood and saliva tests exist and are not yet validated in adolescents. adolescent imaging review
- Refer surgical cases by volume. Eighty percent of operations are done by surgeons doing six or fewer a year; outcomes are best above about 24. Ontario cohort, 2025
- Plan the day after surgery before the day of it: long-acting progestogen, IUD or the pill held a 40% pain improvement at three years with fewer re-operations. PRE-EMPT, 2024
- Treat the nervous system alongside the lesions. Central sensitisation is present in 41 to 52% of patients; pelvic physiotherapy, acupuncture and psychological therapy show drug-sized effects. network meta-analysis, 2026
Bring this to your appointment
Show this section on your phone. It is what the evidence says to ask for; the Mirror turns it into a letter in your own words that prints on its own.
- Say the word: 'I think this could be endometriosis.' Diagnosis is delayed most when nobody names it.
- Ask for an ultrasound by someone trained in endometriosis, and ask whether a blood or saliva test is available where you live.
- If surgery is proposed, ask the six questions above, starting with how many of these operations the surgeon does a year.
- Ask what happens the day after surgery to stop it coming back.
- Ask for referrals to pelvic physiotherapy and pain psychology; their effect sizes are drug-sized.
- If you are offered opioids as the plan, ask what the plan is instead.
How this page is different
There are good endometriosis websites, and there are chatbots. Why this one?
- Of the top endometriosis pages on four search engines, 44% were news sites; pages with references were measurably more complete, and pages with an institution behind them measurably more accurate. quality assessment of endometriosis information online
- A systematic review of endometriosis websites found the average one written above the reading level recommended for health information. systematic review, 2024
- Every number on this page links to the study it came from and says how strong it is. Nothing is typed from memory.
- We rank the possible causes by a fixed arithmetic rule, not by opinion, and the ranking changes when new studies arrive. A weekly job pulls the new papers; a person still has to read each one before it counts, and the list itself is not yet published.
- For every explanation we wrote down in advance what would prove it wrong. None has been graded yet. When one is — right or wrong — it will say so here.
- It starts where you are: a parent, a woman who suspects, a woman facing surgery, a woman whose disease came back, a clinician.
- It gives you the exact questions to ask, not just the facts. The six surgery questions alone can change an outcome.
- No ads, nothing for sale, no account, no tracking. Your ticks stay on your phone.
Pass it on
One woman of reproductive age in ten has this. The woman who needs this page tonight is already in your contacts, and she has probably been told her pain is normal. Sending her the surgery questions, or the parents' red flags, costs you ten seconds and may save her years.
If this page helped, the fastest way to help another woman is to send it. Everything here is free to copy with a link back.
How this page is made, and what it is not
This page is built from a public list of studies in which every paper is filed with its link, its design and the explanation it supports or undermines. A fixed rule scores the explanations; a weekly job pulls the new papers, and the ranking changes when one is read and filed. We write down what would prove each explanation wrong before the evidence arrives; none has been graded yet, and when one is, the grade will appear here. Your ticks on this page stay on this page; nothing is stored or sent anywhere. The page carries no advertising, sells nothing, and is not a substitute for a clinician. It is made by a small team that came to this disease through people we love, not through medicine, which is why every claim carries its source.