Treatments and Recovery | Diagnosis and Symptoms | Reproductive Endocrinology
Endometriosis Makes Its Own Estrogen
Where the Disease Gets Its Fuel, and Why It’s So Hard to Suppress
Yes, endometriosis makes its own estrogen. Beyond the ovary, the disease draws estrogen from fat, the adrenal gland, and the lesion itself, which is why suppressing the ovary and the birth-control pill never quite finish the job. A guide to the four sources of estrogen, why suppression is incomplete, and what actually reaches the estrogen the others miss.
Medically reviewed by Andrea Vidali, MD – Reproductive Endocrinologist, Reproductive Immunologist, and Endometriosis and Adenomyosis Excision Surgeon, ESSI. Estimated reading time: 14 minutes.
Quick Answer – Does Endometriosis Make Its Own Estrogen?
Yes. Endometriotic lesions switch on aromatase, the enzyme that produces estrogen, which normal endometrial tissue does not have, so the disease manufactures estrogen locally, inside the lesion. Overall, endometriosis is fed by estrogen from four sources: the ovary, fat and skin, the adrenal gland, and the lesion itself. Because the ovary is only one of the four, silencing it, or taking the birth-control pill, lowers only part of the supply, which is why endometriosis is so hard to suppress and so often returns.
- The lesion expresses aromatase and makes its own estradiol; normal endometrium does not.
- Four estrogen sources: ovary, fat/skin, adrenal gland (precursor), and the lesion itself.
- The birth-control pill contains estrogen and misses the local supply, so it manages symptoms, not the disease.
- Only aromatase inhibitors block local/peripheral estrogen; no hormonal therapy removes the disease.
Endometriosis runs on estrogen. Lower estrogen or block its action, and the disease quiets; raise it, and the disease grows, inflames, and hurts. That single fact is the engine behind nearly every hormonal treatment for the condition. But it raises a question patients are rarely asked to think about: where, exactly, does that estrogen come from?
The answer explains the most frustrating things about the disease, why silencing the ovary is not enough, why the birth-control pill so often disappoints, and why endometriosis keeps coming back. Estrogen, it turns out, comes from more than one place, and the disease has learned to make its own.
Part 1: Endometriosis Runs on Estrogen
Endometriosis is an estrogen-dependent, inflammatory disease. Estrogen drives the growth of the misplaced tissue, feeds the inflammation around it, and amplifies the pain. This is why the disease tends to quiet after menopause, and why almost every medical therapy works by one of two routes: lowering the amount of estrogen the tissue sees, or blocking estrogen’s action at the tissue. In principle, then, the cure is simple, take the estrogen away. The problem is that you cannot fully take it away, and understanding why begins with knowing where it comes from.
Part 2: Where Does the Estrogen Come From? The Four Sources
Most people assume the ovary is the whole story. It is the biggest single source, but it is one of four, and the other three are exactly why suppression leaks.
| Source | When It Dominates | What It Contributes | Can Ovarian Suppression Stop It? |
|---|---|---|---|
| The ovary | Reproductive years | Direct estradiol, released cyclically | Yes – this is what the pill and GnRH drugs target |
| Peripheral tissue (fat and skin) | After menopause or ovarian suppression | Aromatizes adrenal androgen into estrogen | No – only an aromatase inhibitor blocks this step |
| The adrenal gland | Always present; unmasked when the ovary is off | Androstenedione, the raw material for estrogen | No – not suppressed by ovary-directed therapy |
| The lesion itself | Throughout the disease | Its own aromatase makes and traps estradiol locally | No – only aromatase inhibition reaches it |
The lesion is its own estrogen factory
The most important of the four is the least known. Normal endometrium contains no aromatase, the enzyme that makes estrogen, but endometriotic lesions switch it on, along with the enzyme that converts weak estrogen into potent estradiol. Worse, the lesion runs a self-amplifying loop: its estrogen drives inflammation (prostaglandin E2), and that prostaglandin is the most powerful known trigger of aromatase, which makes more estrogen. At the same time, the enzyme that would normally dispose of estrogen is missing (part of the progesterone-resistance story). So the lesion manufactures estrogen, amplifies it, and fails to clear it, all locally, inside the tissue you are trying to starve.
Commentary – Andrea Vidali, MD
“This is the fact that reframes everything for patients. Endometriosis is not a passive tissue waiting for the ovary’s permission to grow, it builds its own supply line. You cannot fully starve a lesion that manufactures its own food. That is not a reason for despair; it is the reason our treatment has to be smarter than ‘just lower the ovarian estrogen and hope.'”
Part 3: Why Suppression Is Never Complete
Silence the ovary, and the adrenal is unmasked
When you shut the ovary down, with a GnRH agonist like leuprolide, or through menopause or surgery, you remove the largest source of estrogen. But the adrenal gland keeps producing androstenedione, and it is not listening to any of the drugs aimed at the ovary. That adrenal androgen is then converted into estrogen by aromatase in fat, skin, and the lesion itself. The adrenal is not revved up by ovarian suppression, it is simply the source left standing. This residual, adrenal-fed estrogen is why pelvic pain recurs in as many as three-quarters of women with severe disease within five years of GnRH-agonist treatment. You lowered the biggest source and the disease found the next one.
| Therapy | Relative Estrogen-Suppression Level | Note |
|---|---|---|
| Combined birth-control pill | Moderate | Deliberately stays above the level that actually quiets the disease, to protect bone and tolerability |
| Progestins (such as dienogest) | Moderate to strong | Estrogen-free; suppresses the lining directly rather than adding estrogen |
| GnRH agonist | Profound (near-total ovarian shutdown) | Crosses the disease-suppression threshold, but leaves adrenal-fed estrogen untouched |
| Aromatase inhibitor | Blocks the conversion step directly | Reaches peripheral and local estrogen that other therapies miss |
Why the birth-control pill doesn’t fully suppress endometriosis
This is the question almost every patient asks, and it has a precise answer with several parts.
First, the pill contains estrogen. A combined pill is built around ethinylestradiol, so you are adding estrogen to an estrogen-driven disease. It is dosed to control the cycle, not to remove estrogen.
Second, it only lowers estrogen a little. Hormonal therapies sit on a scale from mild to profound estrogen suppression. Combined pills deliberately stay in the moderate zone, above the level that actually quiets endometriosis, because driving estrogen lower would cost bone and tolerability. The pill keeps you on the wrong side of the threshold that matters.
Third, it never touches the local supply. The pill suppresses ovulation and thins the lining, which reduces bleeding and eases cramps, real, worthwhile relief. But it does nothing to the lesion’s own aromatase, nothing to the adrenal androgen feeding it, and it cannot overcome the tissue’s resistance to progesterone. The local factory keeps running.
Fourth, it may not stop the disease from progressing. Combined pills reduce period pain but show limited benefit for other symptoms and may not prevent lesion progression. One study even found that oral contraceptives did not suppress, and may have increased, the growth of new blood vessels in endometriotic lesions. And part of the pill’s apparent “protective” effect may simply be that it masks symptoms and postpones diagnosis, not that it treats the disease.
| What the Pill Does | What the Pill Misses |
|---|---|
| Suppresses ovulation | The lesion’s own aromatase-made estrogen |
| Thins the uterine lining | Adrenal androgen feeding local estrogen production |
| Reduces bleeding | The tissue’s underlying resistance to progesterone |
| Eases menstrual cramps | Lesion progression; may not slow disease growth |
The pill quiets the cycle. It does not starve the disease.
Commentary – Andrea Vidali, MD
“The combined pill is usually the first thing prescribed, and for many women it genuinely helps with pain, I don’t want to take that away from anyone it is serving. But it is important to be honest about what it is doing: it is managing the monthly symptom, not treating the disease, and it does so while adding a little estrogen to a disease that runs on estrogen. When a patient tells me the pill ‘stopped working,’ she is usually describing a disease that was never actually being suppressed, only quieted at the surface.”
Part 4: What Actually Reaches the Missed Estrogen
If the ovary is only one source and the pill barely dents the others, what does reach them? The logic of good treatment is to match the tool to the source, and to respect the trade-off between suppressing estrogen enough to help and suppressing it so much that bone and quality of life suffer.
| Therapy | Estrogen Suppression | What It Reaches | What It Misses | Main Trade-Off |
|---|---|---|---|---|
| Combined pill | Moderate; contains estrogen | Ovulation and cyclic bleeding, giving pain relief | Local and peripheral aromatase; progesterone resistance | Adds estrogen; may not halt progression |
| Progestins / dienogest | Moderate to strong; estrogen-free | Suppresses the lining; anti-inflammatory; reaches the suppression window | Doesn’t block aromatase directly | Breakthrough bleeding, mood effects |
| GnRH agonist | Profound (near-total ovarian shutdown) | Ovarian estrogen, almost completely | Adrenal-androgen local aromatization | Bone loss, menopausal symptoms; needs add-back therapy |
| Oral GnRH antagonist | Dose-dependent, tunable | Ovarian estrogen, adjustable depth | Local aromatase | Dose-related bone loss and hot flashes |
| Aromatase inhibitor | Blocks the conversion step itself | Peripheral and local estrogen, the residual source | Needs ovarian co-suppression before menopause | Ovarian stimulation if used alone; bone loss; joint pain |
| Surgery (excision) | Not hormonal; removes tissue | The lesion itself, definitively | Not applicable | Operative; recurrence if incomplete |
The aromatase inhibitor: the tool aimed at the residual source
Aromatase inhibitors (letrozole, anastrozole) are the one class that blocks the conversion step itself, the aromatase that turns adrenal androgen into estrogen in fat, skin, and the lesion. That is exactly the residual source the pill and even GnRH drugs miss. They work: combined with a progestin or the pill, they reduce refractory pain, and after surgery they lower recurrence. The catch is that in a premenopausal woman an aromatase inhibitor alone lowers estrogen enough to trigger the ovary into overdrive, so it must be paired with something that suppresses the ovary, a progestin, the pill, or a GnRH drug. That requirement is itself the proof that the ovary is still the dominant source; the inhibitor cleans up what ovarian suppression leaves behind. This is the rationale for combining a GnRH agonist with an aromatase inhibitor in the hardest cases: one empties the ovary, the other intercepts the adrenal-fed local estrogen.
Why dienogest and weight both matter
Two practical points follow from the same biology. A progestin like dienogest suppresses the lining, opposes estrogen, and calms inflammation without adding estrogen, which is why it out-performs the combined pill for the disease itself, not just the symptom. And because fat tissue is a major site where adrenal androgen is aromatized into estrogen, body weight genuinely influences the disease’s fuel supply; it is one of the few levers a patient can pull herself.
The honest ceiling
No hormonal therapy removes endometriosis. Every option on the table, pill, progestin, GnRH drug, aromatase inhibitor, manages the estrogen supply, and some do it very well. But because the lesion makes and traps its own estrogen and recruits its own nerves, medical suppression manages the disease rather than curing it. When the goal is to actually remove the disease, complete surgical excision is the definitive step, a separate decision, made around each woman’s symptoms and fertility goals.
Commentary – Andrea Vidali, MD
“I want patients to leave this discussion with two true things held at once. Medical therapy is valuable and, chosen well and matched to the sources, can control this disease for years. And it has a ceiling, because the lesion is a self-sustaining, estrogen-making, nerve-recruiting structure that no pill dissolves. Knowing which of those you are being offered, control or cure, is the difference between a plan and a disappointment.”
Take-Home Messages
- Endometriosis runs on estrogen: every hormonal therapy works by lowering estrogen or blocking its action.
- Estrogen comes from four sources, not one: the ovary, peripheral fat and skin, the adrenal gland (as precursor), and the lesion itself.
- The lesion makes and traps its own estrogen through aromatase and a self-amplifying inflammatory loop; you cannot fully starve it.
- Silencing the ovary is incomplete because the adrenal keeps supplying androgen that fat, skin, and the lesion turn into estrogen, hence high recurrence.
- The pill doesn’t fully suppress the disease: it contains estrogen, only lowers it moderately, misses the local supply, and may not stop progression.
- Aromatase inhibitors reach the residual source, but need ovarian co-suppression, and no hormonal therapy removes the disease; surgery is the definitive step.
Frequently Asked Questions
Where does the estrogen that feeds endometriosis come from?
From four places: the ovary (the biggest source in the reproductive years), peripheral tissues like fat and skin (which convert adrenal androgen into estrogen), the adrenal gland (which supplies the raw material), and the lesion itself, which switches on the estrogen-making enzyme aromatase and produces estrogen locally. Silencing the ovary leaves the other three running.
Why doesn’t the birth-control pill cure or fully suppress endometriosis?
Because it contains estrogen, only lowers estrogen moderately, and never touches the lesion’s own estrogen production or the adrenal androgen feeding it. The pill stops ovulation and cyclic bleeding, which eases pain, but it manages the symptom rather than treating the disease, and it can’t overcome the tissue’s resistance to progesterone. It may not prevent the disease from progressing.
If I’ve stopped having periods, why isn’t the endometriosis gone?
Stopping your period means the lining of the uterus isn’t shedding, it doesn’t mean the endometriosis lesions have lost their estrogen. Those lesions make estrogen locally and are fed by adrenal androgen, both of which continue even when menstruation stops. No period is not the same as no disease activity.
Why does endometriosis come back after menopause or after Lupron (a GnRH agonist)?
Because menopause and GnRH agonists shut down the ovary, but not the adrenal gland. The adrenal keeps producing androgen, which fat, skin, and the lesions convert into estrogen, enough to sustain the disease. This is why pelvic pain recurs in a large share of women after these treatments, and why postmenopausal endometriosis exists.
Can estrogen be removed from the body completely?
No. Even with the ovary fully suppressed, the adrenal gland supplies androgen that is converted to estrogen elsewhere, and lesions make their own. The most you can do pharmacologically is block the conversion step with an aromatase inhibitor, which suppresses total-body estrogen production by roughly 97 to 99 percent but still can’t be used alone in premenopausal women.
Do aromatase inhibitors help, and why aren’t they first-line?
They help, they block the enzyme that makes estrogen in fat, skin, and the lesion, which is the source other drugs miss, and they reduce refractory pain and post-surgical recurrence. They aren’t first-line because in premenopausal women they must be combined with ovarian suppression (or they stimulate the ovary), and long-term estrogen deprivation costs bone and causes joint pain, so they’re reserved for resistant disease.
Does losing weight help endometriosis?
It can influence the fuel supply. Fat tissue is a major site where adrenal androgen is converted into estrogen, so body weight affects how much estrogen the body produces outside the ovary. Weight is not a cure and endometriosis affects women of every size, but it is one of the few levers a patient can influence directly.
Is an estradiol-based pill better than an ethinylestradiol one for endometriosis?
Ethinylestradiol has broader effects on metabolism, inflammation, and clotting, so newer pills using natural estradiol may have a milder systemic footprint and a lower clot risk. For suppressing the disease itself, though, the more important shift is usually toward progestin-dominant, estrogen-free therapy rather than swapping one estrogen for another.
Is dienogest better than the pill for suppressing the disease?
For the disease itself, generally yes. Dienogest is a progestin that suppresses the lining, opposes estrogen, and calms inflammation without adding estrogen, and it shows superior long-term efficacy compared with combined pills. The pill mainly controls the symptom; a progestin like dienogest does more of the disease work.
Does any hormonal treatment cure endometriosis?
No. Hormonal treatments manage the estrogen supply and can control symptoms well, sometimes for years, but they don’t remove the disease, the lesion makes its own estrogen and recruits its own nerves. Definitive removal means surgery. The right plan depends on your symptoms, your fertility goals, and how your disease behaves.
Final Commentary – Andrea Vidali, MD
“The reason endometriosis is so hard to suppress is written into its biology: it doesn’t just borrow estrogen from the ovary, it manufactures and hoards its own, and it draws on the adrenal gland that no ovary-directed drug can silence. Once you see that, the frustrations stop being mysterious. The pill disappoints because it adds estrogen and misses the local supply. GnRH drugs leave a residue because the adrenal keeps feeding the fire.
The way forward is not a single magic suppressant, it is matching the tool to the source, being honest about the ceiling of medicine, and knowing when the answer is to remove the disease rather than to keep starving it. Every patient deserves that clarity, and a team that can offer both the medical and the surgical halves of it.”
The Most Important Step Is the First One
If hormonal therapy has controlled your symptoms but not your disease, ESSI can help you understand what’s driving it, and what your options are.
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Medical disclaimer: This article is for education and is not a substitute for medical advice, diagnosis, or treatment. Speak with a qualified clinician about your individual situation and before changing any medication.
Selected References
- Bulun SE, Zeitoun KM, Takayama K, Sasano H. Estrogen biosynthesis in endometriosis: molecular basis and clinical relevance. J Mol Endocrinol. 2000;25(1):35-42.
- Bulun SE, et al. Role of aromatase in endometrial disease. J Steroid Biochem Mol Biol. (Aromatase absent in normal endometrium, aberrantly expressed and PGE2-stimulated in endometriosis.)
- Zeitoun KM, Bulun SE. Aromatase: a key molecule in the pathophysiology of endometriosis and a therapeutic target. Fertil Steril. 1999;72(6):961-969. (Origin of estrogen; adrenal androstenedione; peripheral and local aromatization.)
- Takayama K, Zeitoun K, Gunby RT, Sasano H, Carr BR, Bulun SE. Treatment of severe postmenopausal endometriosis with an aromatase inhibitor. Fertil Steril. 1998;69(4):709-713.
- Noble LS, et al. Prostaglandin E2 stimulates aromatase expression in endometriosis-derived stromal cells. J Clin Endocrinol Metab. 1997;82(2):600-606.
- Estrogen-threshold modulation framework in endometriosis; hormonal therapies from moderate (COC/progestin) to profound (GnRH) suppression. Expert Opin Pharmacother. 2026.
- Hormonal treatment of endometriosis: a narrative review. Pharmaceuticals (Basel). 2025. (COCs reduce dysmenorrhea but may not prevent disease progression; dienogest superior long-term.)
- Effect of combined oral contraceptive pills on angiogenesis in endometriotic lesions. Hormones (Athens). 2025. (OCs did not inhibit, and may upregulate, lesion angiogenesis.)
- Vercellini P, et al. Oral contraceptives and risk of endometriosis: systematic review and meta-analysis. (Apparent protection may reflect symptom masking.)
- Ferrero S, et al. Aromatase inhibitors combined with progestins or GnRH analogues for endometriosis-related pain: systematic review and RCTs. Reprod Biol Endocrinol. 2011.
- GnRH agonists and the adrenal axis: chronic GnRH-agonist use does not alter the hypothalamic-pituitary-adrenal axis; adrenal androgens are the non-suppressible (dexamethasone-suppressible) fraction. J Clin Endocrinol Metab; Fertil Steril.
- Becker CM, et al. ESHRE guideline: endometriosis. Hum Reprod Open. 2022;2022(2):hoac009.
