What Causes Estrogen Dominance: The Big Drivers, In Proportion

Most articles on this topic go straight to plastics and skincare, which makes the whole subject sound like a conspiracy and lets the genuinely large causes go unmentioned.

The causes divide cleanly into two groups, and knowing which group applies to you determines whether anything you do will help. Either estrogen is genuinely elevated, or estrogen is normal and progesterone has fallen — producing the same unopposed state by a completely different route.

In women over 38, the second is far more common. That single fact explains why so much estrogen-reduction advice disappoints.

Group one: progesterone falling

Not a cause of high estrogen at all, and the dominant reason for the pattern in your forties.

Progesterone is only made after ovulation, by the corpus luteum. As the follicle pool depletes, cycles where no egg is released become more frequent. You still bleed — estrogen continues building a lining that eventually sheds — but no corpus luteum formed, so no meaningful progesterone was produced.

Estrogen has not risen. The counterweight has gone. The full mechanism is in what low progesterone actually does.

Chronic stress belongs here too. Progesterone and cortisol both derive from pregnenolone, and under sustained demand the body prioritises cortisol. This is substrate allocation, not a metaphor, and it lands on a supply that is already shrinking.

Group two: estrogen genuinely elevated

Body fat

The largest single cause and the least discussed, presumably because it is uncomfortable.

Adipose tissue is an endocrine organ. It contains aromatase, the enzyme converting androgens into estrogens, so body fat produces estrogen independently of the ovaries. More adipose tissue means more aromatase activity means more circulating estrone.

This creates a loop: higher estrogen favours fat storage, and more fat produces more estrogen. It is also why the pattern often worsens through the forties even as ovarian output declines — the mechanism described in why the old diet approach stops working.

Impaired clearance in the liver

Estrogen is deactivated in two phases: hydroxylation, then conjugation for excretion. Both require liver capacity and specific cofactors.

Alcohol is the big one. It raises circulating estrogen and occupies the liver capacity that would otherwise clear it, and the effect appears at moderate intakes rather than only heavy ones. Detail in what alcohol does to estrogen.

B vitamins, magnesium and sulphur-containing compounds participate in these pathways, so genuine deficiency slows clearance.

Reabsorption from the gut

Once conjugated, estrogen leaves in bile into the intestine — and should exit in stool. Certain gut bacteria produce beta-glucuronidase, which un-conjugates it and frees it to be reabsorbed. That bacterial population is the estrobolome.

Constipation is therefore an estrogen problem, not only a comfort problem. Slow transit means more time for reabsorption. Low fibre intake compounds it, since fibre binds conjugated estrogen and speeds transit.

Insulin resistance

High insulin lowers sex hormone binding globulin, the protein that carries sex hormones in blood. Less binding protein means more free, biologically active estrogen — without total estrogen changing at all. Signs before a blood test are covered in the insulin resistance article.

Exogenous sources

Now the plastics, in proportion.

Some compounds — BPA, certain phthalates, some pesticides — do bind estrogen receptors. The mechanism is real. The magnitude relative to the causes above is generally smaller, and the discourse is disproportionate.

Where it is worth attention: not heating food in plastic, since heat increases leaching, and using glass for hot liquids. Those are cheap and sensible. Buying a €60 “hormone detox” kit is not.

The genuinely significant exogenous source is hormonal medication — some contraceptives and hormone therapy formulations — which is a conversation with your prescriber rather than an environmental issue.

Which group is yours

The distinguishing questions:

Are you over 38 with cycles that have shortened, spotting before your period, or new premenstrual anxiety? Group one — progesterone falling. Estrogen-lowering strategies will underdeliver because they address the wrong half.

Are you under 38 with regular ovulatory cycles, or do you have significant central weight, constipation, regular alcohol intake or signs of insulin resistance? Group two — clearance and production. These are genuinely modifiable.

Most women in their forties have some of both, which is why single-lever approaches disappoint. And confirming any of it requires progesterone measured seven days before your period is due, not on a fixed day 21.

What is overstated

“Xenoestrogens are why women have hormonal problems.” They contribute. Body fat, alcohol, constipation, insulin resistance and anovulation contribute more, and all five are addressable.

Soy. Phytoestrogens bind estrogen receptors weakly and can act as partial antagonists — competing with your stronger endogenous estrogen. The evidence does not support the fear, and populations with high soy intake do not show the predicted problems.

“Estrogen detox” products. Your liver is not failing for want of a supplement. It is occupied — usually by alcohol. Reducing what occupies it does more than adding something alongside.

The short version

Unopposed estrogen arrives two ways: estrogen genuinely rising, or progesterone falling while estrogen stays put. After 38 the second dominates, driven by cycles where no egg is released and by cortisol competing for the same precursor. Where estrogen is genuinely elevated, the real drivers are body fat producing it through aromatase, alcohol occupying liver clearance, constipation allowing reabsorption from the gut, and insulin resistance freeing more of it from binding protein. Plastics are a real but comparatively small contributor, and the marketing around them is disproportionate to the mechanism.