PCOS and Endometriosis: Can They Occur Together?

Yes, polycystic ovary syndrome (PCOS) and endometriosis can occur together, though they represent distinct conditions with different underlying pathophysiology. Studies have documented their coexistence in clinical practice.

In a laparoscopic study, pelvic endometriosis was observed in 16.5% of women with confirmed PCOS.  Women with both conditions more frequently presented with regular menses (40% vs 14.5%) and less frequently with secondary amenorrhea compared to those with PCOS alone, though hormonal profiles (LH, FSH, testosterone, DHEA-S) were similar between groups. This suggests endometriosis may be a coincidental finding that modifies menstrual patterns but does not significantly alter the core biochemical features of PCOS.

Recent genetic analyses provide additional evidence for their coexistence. A genome-wide association (GWAS) study identified positive genetic correlation and 12 shared pleiotropic loci between endometriosis and PCOS.  Mendelian randomization analysis (an epidemiologic technique) suggests potential bidirectional causal relationships between the conditions, with genetic associations particularly enriched in uterine, endometrial, and fallopian tube tissues.  So, it is likely not clinically associated disease that is random. 

While some researchers have proposed that PCOS and endometriosis represent "diametric" or opposite phenotypes based on differences in prenatal testosterone exposure and hormonal profiles, this theoretical framework does not preclude their clinical coexistence.   This is kind of an old school way to think about it but will often be mentioned to patients, potentially delaying diagnosis of endometriosis.

The bottom line is that the two conditions can overlap in individual patients despite having contrasting pathophysiologic mechanisms.

The results is that living with polycystic ovarian syndrome (PCOS), endometriosis, or both can feel like juggling two different problems at once: irregular ovulation and hormone patterns on the PCOS side, and inflammation-driven pain and fertility challenges on the endometriosis side. Many patients searching “polycystic ovarian syndrome endometriosis” are really asking a practical question: If I have one (or both), what does that mean for my fertility treatment choices—and for my health beyond the pelvis?

Recent research doesn’t offer a single, simple answer, but it does give a clearer map. Evidence from large population datasets, IVF frozen embryo transfer (FET) outcomes, and multiple mechanistic reviews (on inflammation, oxidative stress, mitochondria, and hormone signaling “amplifiers”) points to a consistent theme: PCOS and endometriosis can affect reproduction through different pathways, and your best plan often depends on which pathway is most active for you (ovulation issues, uterine environment, ovarian reserve, inflammation/pain, or metabolic/cardiovascular risk).

Below is a patient-focused synthesis of what the combined evidence suggests—especially if you’re trying to conceive or planning IVF.

First: Are PCOS and endometriosis both common causes of infertility?

Yes—and on a global scale, they’re major contributors, but in different ways. Global Burden of Disease (GBD) 2021 estimates suggest both conditions contribute substantially to disability and infertility worldwide, with PCOS-attributed infertility burden exceeding endometriosis-attributed infertility burden in most regions. That doesn’t mean PCOS is “worse” for an individual; it means that at the population level, ovulation-related infertility is extremely prevalent, and PCOS is widely under-diagnosed and under-treated in many settings.

At the same time, the GBD analysis also highlights why patients often feel dismissed: reported endometriosis rates can underestimate reality because diagnosis frequently requires specialized imaging, expert evaluation, or laparoscopy, and delays are common. In other words, “how common” a condition looks on paper may reflect access to diagnosis, not just biology.

How do PCOS and endometriosis affect fertility differently?

A helpful way to think about the overlap is that *PCOS more often interferes with getting an egg released*, while endometriosis more often interferes with the environment where fertilization and implantation happen**—though either condition can affect ovaries, hormones, and inflammation.

PCOS: cycle and ovulation disruption (and sometimes egg quality)

PCOS is commonly associated with irregular or absent ovulation, androgen excess, and metabolic features like insulin resistance. While the papers provided here focus more on population burden and environmental exposures than on PCOS-specific treatments, the take-home message is still relevant: PCOS is a dominant driver of infertility burden, which fits what many patients experience—difficulty timing ovulation, needing ovulation induction, or moving to IVF due to inconsistent cycles.

Endometriosis: inflammation, implantation environment, and ovarian effects

Several lines of evidence converge on endometriosis as a condition shaped by inflammation and cellular stress:

• A review spanning gynecologic endocrine disorders emphasizes oxidative stress findings across many human sample types in endometriosis (peritoneal fluid, follicular fluid, tissue, serum), often correlating with severity or stage in published studies. That pattern supports a “whole microenvironment” story: inflammation and reactive oxygen species may affect pelvic tissues, eggs, and implantation conditions.
• Mechanistic reviews propose that cellular “survival programs” may help lesions persist. One review highlights steroid receptor coactivators (SRCs)—proteins that can amplify estrogen/progesterone receptor signaling—and describes experimental findings where SRC-related changes appear to help endometriotic cells resist cell death and become more invasive.
• Another review discusses mitophagy (mitochondrial quality control). In preclinical models, the PINK1–Parkin pathway is described as suppressing migration/invasion and promoting apoptosis in endometrial stromal cells—suggesting that when mitochondrial quality control is impaired, lesion persistence may be easier.

None of these mechanisms are yet routine clinical tests. But together they help explain why endometriosis can affect fertility even when ovulation seems normal.

If I’m doing IVF, does endometriosis change the best frozen embryo transfer protocol?

This is where one of the most clinically actionable studies comes in.

A 2025 retrospective study of 1,454 frozen embryo transfer cycles compared standard hormone replacement therapy (HRT) endometrial preparation to a protocol that adds GnRH agonist (GnRHa) pretreatment (“downregulation”) before HRT. Overall live birth rates were similar across all patients—but the details matter:

• In the endometriosis subgroup, pregnancy and live birth rates were higher with GnRHa–HRT than HRT alone (live birth about 46% vs 28% in the subgroup analysis).
• The apparent benefit was clearest in single-embryo transfer cycles, where live birth rates were higher with GnRHa–HRT than HRT.
• Age still mattered strongly: increasing age reduced odds of live birth in the endometriosis subgroup model.

What this means in real life

If you have endometriosis and are planning frozen embryo transfer, this body of evidence supports a common clinical approach: temporary ovarian/pituitary suppression (downregulation) before building the lining may help some patients, especially when transferring a single embryo.

But it’s not a guarantee. Because the study was retrospective (not randomized), it can’t fully control for differences between groups (for example, who was selected for which protocol, subtle embryo differences, or other unmeasured factors). Even within the endometriosis subgroup, the most adjusted analysis showed a trend toward benefit rather than a definitive conclusion.

The tradeoff: time and treatment burden

GnRHa pretreatment typically adds weeks before transfer (often around a month of downregulation). That can mean more injections, more waiting, and sometimes more side effects (hot flashes, mood changes, headaches). So the decision becomes a values-based conversation: Is a possible improvement in implantation/live birth worth extra time and medication for me?

What about adenomyosis?

In the materials provided, adenomyosis isn’t directly analyzed in the FET protocol study and isn’t specifically developed in the mechanistic reviews summarized. So, based on these papers alone, we can’t responsibly generalize the FET protocol findings to adenomyosis—even though, clinically, adenomyosis is often discussed alongside endometriosis and sometimes managed with similar suppression strategies.

If adenomyosis is part of your diagnosis, it’s reasonable to ask your fertility specialist whether they tailor FET preparation differently (for example, based on ultrasound features, uterine size, symptoms, or prior transfer outcomes).

Beyond fertility: does endometriosis affect heart health?

This is an area patients often don’t hear about until later. A 2025 review connecting gynecologic endocrine disorders to cardiovascular risk summarizes epidemiologic evidence linking endometriosis with higher cardiovascular disease risk (for example, ischemic heart disease and cerebrovascular disease in large cohort data). The proposed bridge is chronic inflammation + oxidative stress → endothelial dysfunction, including disruption of nitric oxide signaling.

Important nuance: this is largely association, not proof that endometriosis directly causes heart disease. But it’s meaningful enough that patients—especially those with additional risks (high blood pressure, smoking, diabetes, strong family history)—may want to discuss cardiovascular prevention with their primary care clinician.

Environmental exposures: are they relevant to PCOS and endometriosis?

A 2025 review of endocrine-disrupting chemicals (EDCs) summarizes observational links between certain exposures and reproductive outcomes, including endometriosis and assisted reproduction results:

• Phthalates: case–control evidence cited suggests higher urinary metabolites in women with endometriosis (association, not causation).
• BPA: summarized associations with poorer assisted reproduction measures in some studies (e.g., ovarian response, implantation outcomes).
• PFAS: evidence suggests possible longer time-to-pregnancy and altered reproductive outcomes, though findings vary by compound and population.

For patients, the most practical takeaway is this: environmental exposures are one of many factors under study. If you work in a high-exposure setting or have concerns, it’s reasonable to mention it during fertility or gynecology visits. The research is not yet at a point where a clinician can say, “This exposure caused your endometriosis,” but it does support including environment in a full reproductive history.

What about ovarian “scarring” and long-term ovarian function?

A newer mechanistic review (2026) focuses on ovarian fibrosis—a wound-healing-like process where excess extracellular matrix (like collagen) accumulates and tissue becomes stiffer. The review links fibrosis to ovarian aging and notes associations with conditions including ovarian endometriosis. It highlights pathways like TGF-β/Smad as central drivers and describes antifibrotic strategies as experimental.

Patient-level importance: if you have an endometrioma or have had ovarian surgery for this or other reasons, you may hear concerns about ovarian reserve. This review doesn’t provide clinical thresholds or a proven anti-fibrosis therapy, but it supports why clinicians pay attention to ovarian tissue health over time and why minimizing repeated ovarian injury can matter.

Practical takeaways: how to use this evidence in your next appointment

• If you have endometriosis and are planning FET: Ask whether GnRH agonist pretreatment before HRT is appropriate for you, especially if you’re doing single-embryo transfer or have had a prior failed transfer.
• If you have PCOS and endometriosis together: Ask your clinician to clarify which factor is currently most limiting—ovulation, uterine/implantation environment, tubal/pelvic anatomy, or ovarian reserve—because the best strategy depends on the bottleneck.
• If you’re concerned about whole-body health: Consider discussing cardiovascular risk screening (blood pressure, lipids, glucose) as part of long-term care, particularly if you have endometriosis plus other risk factors.

What we still don’t know

Many of the “why” explanations—oxidative stress, SRC signaling, mitophagy, fibrosis pathways—come from preclinical or observational research. They are valuable for understanding the disease, but they don’t automatically translate into proven treatments.

Even the most directly clinical paper here (FET protocol comparison) is retrospective, meaning:

• people weren’t randomized to one or another treatment and compared (the Randomized Controlled Trial research gold standard),
• unmeasured differences between groups may influence outcomes,
• and results may not generalize to every clinic, embryo strategy, or patient phenotype (including adenomyosis).

That’s why two patients with the same labels—PCOS, endometriosis—can have very different experiences. The diagnosis names matter, but your specific pattern of symptoms, imaging, labs, prior response to treatment, and reproductive goals matter more. The more information that you have which supports your having both PCOS and endometriosis, the more it is prudent to get very specialized consultations. This might be through a reproductive endocrinologist (REI) or an endometriosis specialist who is more than an excision surgeon.