By Leila Martyn, Founder of MyOva

"Oestrogen dominance" is one of those terms that divides rooms.

In integrative and functional medicine circles, it's used frequently — to describe heavy periods, PMS, breast tenderness, mood instability, and perimenopausal symptoms. In conventional medicine, it's treated with scepticism, because it doesn't exist as a formal ICD-10 diagnosis and isn't measured by a single definitive test.

Both positions contain something true. And the gap between them is where most women get left without useful information.

This article navigates that gap honestly. It explains what oestrogen dominance actually describes as a biological concept, what the evidence says about the mechanisms behind it, what drives the oestrogen-progesterone imbalance pattern in the first place, and what — practically — can support healthier oestrogen metabolism.

No oversimplification. No dismissal. Just the clearest possible picture of what we actually know.

The phrase "oestrogen dominance" was popularised in the 1990s by Dr John Lee, an American physician who proposed that many women's symptoms stemmed from having too much oestrogen relative to progesterone [1]. The concept spread rapidly — it gave a name to a cluster of symptoms that many women recognised immediately.

The term is not recognised as a formal diagnosis by major medical organisations, and some clinicians argue it doesn't align with what peer-reviewed research tells us about how hormones actually work.

The clinical scepticism has a legitimate basis. "Oestrogen dominance" as a label can be:

• Imprecise — oestrogen levels vary dramatically across the cycle, between women, and across life stages
• Untestable by a single blood draw — because the ratio fluctuates daily
• Commercially exploited — used to sell unregulated supplements that make sweeping claims without clinical evidence

So when a GP raises an eyebrow at the term, they're not necessarily wrong to do so.

But here's the problem with dismissing the concept entirely: the oestrogen dominance hypothesis is supported by a growing body of evidence linking imbalanced oestrogen-progesterone signalling to clinical disorders such as fibrocystic breast disease, endometrial hyperplasia, and endometriosis — conditions in which progesterone resistance and local oestrogen excess in lesions are well-documented, and treatment strategies often aim to restore hormonal balance.

In other words: the term may be imperfect, but the underlying biology is real. The question isn't whether oestrogen-progesterone imbalance causes symptoms — it demonstrably can. The question is what's driving it in any individual woman, and what can be done about it.

The most clinically useful definition is this: oestrogen dominance refers to a hormonal pattern where oestrogen levels are unopposed by progesterone. Importantly, oestrogen levels do not have to be high for this imbalance to occur — if progesterone is low, oestrogen will be left unopposed, meaning its effects are magnified.

This is the distinction that matters most and is most frequently missed.

Oestrogen dominance does not necessarily mean that oestrogen levels are high. Rather, it describes a state where the ratio between oestrogen and progesterone has shifted — and this can happen even when both hormones are declining, as they do during the menopausal transition.

To understand why this matters, consider what these two hormones do in opposition to each other. Oestrogen thickens the uterine lining, while progesterone thins it. Oestrogen stimulates the brain, while progesterone calms it. Oestrogen increases cell division inside the breasts, while progesterone slows it. Oestrogen increases the release of histamine, while progesterone has an antihistamine effect.

When this balance is disrupted — for any reason — the effects of unopposed oestrogen become clinically apparent.

Oestrogen dominance can result from three distinct mechanisms: excessive oestrogen production, low progesterone even with normal oestrogen levels, or xenoestrogen exposure. Understanding which mechanism is primary for any individual woman determines the most useful approach.

Progesterone is produced by the corpus luteum — the structure that forms in the ovary after ovulation. This means progesterone production is entirely dependent on ovulation occurring. No ovulation means no corpus luteum means no progesterone.

Anovulatory cycles — cycles in which no egg is released — are far more common than most women realise. They produce oestrogen through follicular development without the progesterone counterbalance of the luteal phase. The result is an oestrogen-dominant hormonal environment even with entirely normal oestrogen levels.

Anovulatory cycles become increasingly frequent as perimenopause approaches — progesterone production falls considerably faster than oestrogen as the hormonal decline of the menopausal transition commences, resulting in a widened gap between the levels of these two hormones.

Chronic stress also suppresses ovulation through HPA axis activation — cortisol signals to the hypothalamus that the body is under threat, which deprioritises the reproductive axis. High amounts of cortisol due to stress can deplete the body's ability to make progesterone, causing an imbalance of oestrogen. This is the mechanism by which stress directly contributes to PMS severity, heavy periods, and cycle irregularity — not through oestrogen levels, but through progesterone suppression.

Even when oestrogen production is normal, inadequate clearance allows it to accumulate — effectively creating the same downstream effect as excess production.

Oestrogen is metabolised primarily in the liver through a two-phase process. Oestrogen dominance may be the result of overproduction of oestrogen by the body, changes in oestrogen metabolism and excretion, or an imbalance in the oestrogen-to-progesterone ratio.

Phase 1 liver metabolism converts oestradiol and oestrone into one of three metabolite pathways — and this is where the distinction between "good" and "bad" oestrogen metabolites becomes relevant:

The principal hydroxylation products from oestradiol and oestrone are 2-hydroxyoestrone, 4-hydroxyoestrone, and 16-alpha-hydroxyoestrone. Individuals who metabolise oestradiol and oestrone to unbalanced ratios of 4-hydroxyoestrone and 16-alpha-hydroxyoestrone may be at increased risk of serious health issues. The 16-alpha-hydroxyoestrone metabolites retain potent hormonal activity and are associated with symptoms of oestrogen excess.

The gut plays a critical secondary role through a bacterial enzyme called beta-glucuronidase. After the liver packages oestrogen metabolites for excretion via bile into the gut, beta-glucuronidase — produced by certain gut bacteria in excess — can cleave those packages and release the oestrogen back into circulation. Too few digestive enzymes and too many unhealthy gut bacteria — dysbiosis — can contribute to oestrogen build-up. The collection of gut bacteria involved in oestrogen recirculation is sometimes called the "oestrobolome" — and its composition directly affects how much oestrogen is cleared versus recycled.

Factors that impair oestrogen clearance include: compromised liver function, alcohol consumption, gut dysbiosis, constipation (reducing transit time for oestrogen excretion), nutrient deficiencies affecting phase 2 liver conjugation (including B vitamins and magnesium), and genetic variants affecting CYP450 enzyme activity.

Xenoestrogens are chemicals in the environment that act like oestrogen once they're inside the body — a type of hormone-disrupting chemical. They include compounds found in certain plastics (BPA, BPS), pesticide residues on food, some personal care product ingredients (parabens, phthalates), and industrial chemicals.

Xenoestrogens bind to oestrogen receptors — sometimes with greater affinity than endogenous oestrogen — adding to the total oestrogenic load the liver must process and clear. They are not a fringe concept: the World Health Organisation recognises endocrine-disrupting chemicals as a global public health concern, and their accumulation in adipose tissue is well-documented.

Reducing xenoestrogen exposure — through food choices, switching to glass or stainless steel food storage, and choosing personal care products without parabens and phthalates — is a practical and evidence-consistent strategy, even where absolute elimination is impossible.

The symptom cluster most associated with relative oestrogen excess — whether from low progesterone, impaired clearance, or xenoestrogen load — includes:

Cycle-related symptoms:

• Heavy or prolonged periods (unopposed oestrogen stimulates endometrial thickening without progesterone to oppose it)
• Spotting before periods
• Worsening PMS — mood changes, irritability, fluid retention, breast tenderness
• Painful periods (oestrogen promotes prostaglandin production and histamine release)
• Irregular cycles or anovulatory cycles

Mood and neurological symptoms:

• Anxiety and low mood in the luteal phase
• Difficulty sleeping — particularly in the second half of the cycle
• Brain fog and concentration difficulties
• Worsening PMDD symptoms (oestrogen excess amplifies the neurological sensitivity already present)

Physical symptoms:

• Breast tenderness or fibrocystic breasts
• Bloating and fluid retention
• Weight gain — particularly around hips and thighs
• Headaches or migraines that worsen around the cycle
• Fatigue disproportionate to sleep

In perimenopause specifically: As progesterone declines faster than oestrogen in early perimenopause, many women experience an intensification of these symptoms before vasomotor symptoms begin — heavier periods, worsening PMS, increased breast tenderness, and mood instability that feels cyclically driven but without the classic "menopause" associations.

This is one of the most important things to understand about early perimenopause: when the hormonal decline commences, progesterone production falls considerably faster than oestrogen — resulting in a widened gap in the levels of these two hormones which does not right itself until hormone levels finally stabilise in the years following the menopause.

→ Read: Perimenopause — The Complete Guide to What's Happening, Why It Matters, and What You Can Do

PCOS is a complex disorder with many moving parts. Even though oestrogen imbalance isn't part of the diagnostic criteria, it's seen clinically. Oestrogen dominance can occur when oestrogen levels are normal, but progesterone is low.

In PCOS, anovulation is frequently the primary driver of low progesterone — cycles without ovulation produce oestrogen without the progesterone counterbalance. Insulin resistance amplifies the problem by increasing ovarian androgen production, which further disrupts ovulatory function. And chronic stress — common in women managing a complex hormonal condition — compounds progesterone suppression through the cortisol mechanism described above.

For women with PCOS, addressing oestrogen metabolism support alongside insulin regulation and stress management addresses the whole hormonal picture rather than individual symptoms in isolation.

→ Read: Why Your Hormones Feel Off — And What to Do About It

This is where the article moves from mechanism to strategy — and where the nuance between "has clinical evidence" and "is frequently claimed" matters enormously.

Two components in cruciferous vegetables — indole-3-carbinol (I3C) and diindolylmethane (DIM) — have been shown to inhibit the formation of the 16-alpha-hydroxyoestrone oestrogen metabolite. One study found that DIM had the ability to decrease its production by 50% while increasing production of the 2-hydroxyoestrone metabolite by 75%.

I3C is found in cruciferous vegetables including cabbage, cauliflower, broccoli, and brussels sprouts, and is a potent inducer of cytochrome P-450 metabolism of oestrogen, which results in 2-hydroxylation of oestradiol.

Adding 500g per day of broccoli to a standard diet shifts the 2:16 ratio upward in humans — a finding from a peer-reviewed study in Cancer Epidemiology, Biomarkers & Prevention.

In practical terms: regularly eating cruciferous vegetables — broccoli, kale, cauliflower, brussels sprouts, cabbage — provides I3C and the DIM it converts to in the gut, supporting the liver's Phase 1 conversion of oestrogen toward the less proliferative 2-hydroxylation pathway.

For supplemental support, broccoli extract standardised to sulforaphane — as found in the MyOva Cycle Support Supplement — provides a concentrated, bioavailable source of the glucosinolate compounds that support this metabolic pathway.

Indole-3-carbinol significantly increased the 2:16α-OHE1 ratio at doses ranging from 200–800mg in clinical intervention studies, though interpretation is limited by heterogeneity between studies. The evidence is consistent in direction — the limitation is study quality, not biological plausibility.

Phase 2 liver metabolism conjugates oestrogen metabolites for excretion — and this phase is highly dependent on nutrient cofactors. B vitamins (B6, B12, folate in their active forms), magnesium, and methionine are all required for efficient oestrogen conjugation through methylation pathways.

Active B6 (Pyridoxal-5'-Phosphate) directly supports oestrogen clearance through its role in steroid hormone receptor modulation and methylation pathway function — as well as its neurotransmitter synthesis roles relevant to the mood symptoms that accompany oestrogen-progesterone imbalance.

→ Read: Why Vitamin B6 Keeps Coming Up in PMS Research

Reducing beta-glucuronidase activity — and therefore oestrogen recirculation — requires supporting a healthy gut microbiome. Practically:

• Adequate dietary fibre (oestrogen metabolites bind to fibre for excretion — inadequate fibre slows clearance)
• Fermented foods to support microbiome diversity
• Reducing alcohol — consuming excessive alcohol can reduce the body's ability to break down oestrogen
• Probiotic support where gut dysbiosis is a factor

Because cortisol and progesterone share the same biochemical precursor (pregnenolone), chronic cortisol demand directly reduces progesterone availability. Supporting HPA axis regulation — through adaptogenic botanical support and stress management — addresses one of the most important upstream drivers of relative oestrogen excess.

→ Read: Holy Basil for Hormones: The Adaptogen You've Never Heard Of

→ Read: Ashwagandha for Hormones — What the Research Actually Says

Practical reduction strategies that are evidence-consistent if not individually RCT-proven:

• Switch to glass, stainless steel, or ceramic food and drink storage — particularly avoiding heating food in plastic
• Choose organic produce for the highest-pesticide crops where possible
• Review personal care products for parabens and phthalates
• Use fragrance-free cleaning products where feasible

Beyond cruciferous vegetables, rosemary — Rosmarinus officinalis — contains carnosic acid and rosmarinic acid, compounds with demonstrated activity on the CYP1A2 and CYP1B1 enzyme pathways that govern oestrogen hydroxylation in the liver. Consuming rosemary, cruciferous vegetables, soy, flaxseed, and sufficient fibre may aid in maintaining a healthy balance of oestrogens and oestrogen metabolites to reduce the risk of a variety of health conditions.

The MyOva Hormone Balance Supplement includes a 10:1 Rosemary leaf extract specifically for its hepatic oestrogen metabolism support — alongside Turmeric (which reduces the systemic inflammation that impairs oestrogen clearance), active B6 (P5P) for methylation pathway support, and the full botanical formula addressing the cortisol and progesterone suppression mechanisms upstream.

For women where the PMDD or severe PMS angle is primary — and oestrogen metabolism support is part of a broader luteal phase strategy — the Cycle Support Supplement includes Broccoli Extract (5% Sulforaphane) alongside Turmeric and P5P for a formula specifically oriented toward the oestrogen metabolism and neurotransmitter support relevant to cycle-related mood symptoms.

→ Explore the MyOva Hormone Balance Supplement

→ Explore the MyOva Cycle Support Supplement

A practical, sequenced approach:

1. Track your cycle and symptoms. Two to three months of daily symptom tracking — noting cycle day, symptom type, and severity — helps identify whether your symptoms follow a pattern consistent with the oestrogen-progesterone imbalance picture (typically worse in the second half of the cycle, particularly the week before your period).

2. Talk to your GP. Ask specifically about: cycle length and regularity, luteal phase progesterone testing (a day 21 progesterone blood test can indicate whether ovulation is occurring and progesterone is adequate), and a referral if symptoms are significantly affecting quality of life.

3. Consider comprehensive hormone testing. The DUTCH test (Dried Urine Test for Comprehensive Hormones) assesses oestrogen metabolites including the 2:16 ratio — something a standard blood test does not cover. This is available privately through functional medicine practitioners and provides a more complete picture of oestrogen metabolism than serum oestradiol alone.

4. Address the foundational drivers. Blood sugar stability, stress regulation, adequate sleep, regular bowel movements, and reducing xenoestrogen exposure are the non-negotiable foundations on which any supplemental strategy builds.

5. Consider targeted nutritional and botanical support. Cruciferous vegetables daily, active B vitamins, fibre, and botanical support for oestrogen metabolism and HPA axis regulation — as outlined above — form a coherent, evidence-consistent approach to supporting healthier oestrogen clearance.

→ Read: Anti-Inflammatory Eating for Hormonal Health

→ Read: PMDD vs Severe PMS — How to Tell the Difference (And Why It Matters)

→ Read: Red Clover for Menopause: Plant Oestrogen or Overhyped Herb?

"Oestrogen dominance" is an imperfect term for a real biological phenomenon. The oestrogen-progesterone ratio matters. Impaired oestrogen clearance matters. Cortisol-driven progesterone suppression matters. Xenoestrogen accumulation matters.

None of these are fringe concepts. They are documented mechanisms with peer-reviewed evidence — even if the label used to group them isn't a formal diagnostic category.

The most useful response to this information isn't to dismiss the term because clinicians don't use it, or to accept it uncritically because it names your experience. It's to understand the specific mechanisms that drive the imbalance in your particular situation — and address those mechanisms directly.

Your body is trying to tell you something. The pattern is real. Understanding the biology is how you do something useful with it.

Can oestrogen dominance be confirmed by a blood test? Not definitively by a single test. Serum oestradiol and progesterone on day 21 of the cycle can indicate whether ovulation has occurred and progesterone is adequate. For oestrogen metabolism assessment — the 2:16 metabolite ratio — the DUTCH urine test provides more comprehensive information than standard blood panels.

Is oestrogen dominance the same as high oestrogen? No — and this distinction is critical. Oestrogen levels do not have to be high for this imbalance to occur. If progesterone levels are low, oestrogen will be left unopposed, meaning its effects are magnified even at normal levels.

Can men experience oestrogen dominance? Yes — men produce oestrogen in small amounts, and the same clearance mechanisms apply. Elevated aromatase activity (which converts testosterone to oestrogen), liver impairment, and xenoestrogen exposure can all create relative oestrogen excess in men. This is outside the scope of this article but worth noting.

Does the contraceptive pill cause oestrogen dominance? The combined pill introduces synthetic oestrogen and progestin — which is not the same as progesterone. Coming off the pill can temporarily disrupt the body's natural oestrogen-progesterone rhythm, and the B vitamin depletion associated with pill use affects the methylation pathways required for oestrogen clearance. Post-pill oestrogen metabolism support is worth considering.

Are fibroids and endometriosis related to oestrogen dominance? Many conditions are associated with or exacerbated by oestrogen dominance, including fibrocystic breast disease, endometrial hyperplasia, and endometriosis — conditions in which progesterone resistance and local oestrogen excess are well-documented. This doesn't mean oestrogen dominance causes these conditions, but the hormonal environment is a significant driver of their symptom burden and progression.

How long does it take to see changes from supporting oestrogen metabolism? Liver oestrogen metabolism responds relatively quickly to dietary changes — studies on cruciferous vegetable intake have shown measurable 2:16 ratio shifts within weeks. Gut microbiome changes take longer — typically two to three months of consistent intervention. Cycle-level symptom changes are best evaluated after two to three full cycles.

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12. MD Nutritionals. Understanding DIM — Oestrogen Metabolism and Diindolylmethane. Available at: mdnutritionals.com

13. Fowke JH, et al. Brassica vegetable consumption shifts estrogen metabolism in healthy postmenopausal women. Cancer Epidemiol Biomarkers Prev. 2000;9(8):773–779. PMID: 10952093

14. Northern College of Acupuncture. What is the clinical evidence that cruciferous vegetables modulate the potentially harmful effects of oestrogen metabolites? Narrative review. Available at: nca.ac.uk

15. ScienceDirect. 16-Alpha-Hydroxyestrone. Pharmacology and Pharmaceutical Science overview. Available at: sciencedirect.com

This article is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting any new supplement or making changes to existing medical treatment.