Estrogen

Estrogen (chiefly estradiol, E2) is a steroid of reproduction and growth. Brief, opposed pulses of estrogen serve fertility and tissue repair. Trouble comes when estrogen tone stays high relative to progesterone and thyroid, for months and years, in men as well as women.

Estrogen
Abbreviation	E2 (estradiol, dominant form)
Molecular formula	C₁₈H₂₄O₂ (estradiol)
Type	Steroid hormone class (estrane steroids: estradiol, estrone, estriol)
Administration	Oral, transdermal, vaginal, injection (as pharmaceutical estrogens)
Bioavailability	Oral first-pass heavy; transdermal bypasses liver
Synonyms	Oestrogen
Source	Ovaries, adipose tissue (aromatization), placenta
Ray's verdict	Depends on context Brief opposed pulses serve fertility and repair; chronic high tone relative to progesterone and thyroid drives the chemistry of aging

In that unbalanced state estrogen creates the chemistry of aging: less complete oxidation, more stress signals, leaky vessels, and tissue that divides under deprivation rather than under full energy.

Estrogen, at least when it is not opposed by a very large concentration of progesterone, creates all of the conditions known to be involved in the aging process.

— Ray Peat

Dosing

The body's own daily production of estrogen is on the order of a small fraction of a microgram, and one microgram a day is an effective estrogenic dose, illustrating how little estrogen it takes to have an effect.

History

Etymology

The name combines "estr-" (see Estradiol) with "-gen" ("producing"), describing the hormone class that produces estrus and female sexual characteristics.

Edward Doisy and colleagues coined the term in 1927 as the first members of the class, estrone and estriol, were being isolated and characterized.

Estradiol, the dominant human estrogen, was isolated and characterized in 1935 by Edward Doisy's laboratory, six years after Doisy and Adolf Butenandt had each independently isolated the weaker estrogen estrone. "Estrogen" itself, from the Greek oistros ("frenzy"/estrus) plus "-gen" ("producing"), was coined for the class as a whole once it became clear that estradiol, estrone, and estriol were related molecules with overlapping, "estrus-producing" activity, rather than a single substance.

Structure/Chemical properties

"Estrogen" refers to a class of related steroids sharing an aromatic A-ring, the structural feature that distinguishes estrogens from other steroid hormones. The three main human forms interconvert readily: estradiol (the most potent, dominant in reproductive years), estrone (weaker, dominant after menopause and with higher body fat), and estriol (weakest, dominant in pregnancy). See Estrone for the shared structural chemistry in more detail.

Function/Mechanism of Action

Estrogen is both a product of stress and a cause of more stress. A male runner's estrogen can double after a race. Serious illness raises estrogen in both sexes.

Besides causing stress, estrogen levels are increased by stress. For example, a male runner's estrogen is often doubled after a race. Men and women who are hospitalized for serious sickness typically have greatly increased estrogen levels.

— Ray Peat

Estrogen raises HPA axis output at every level: it increases corticotropin-releasing hormone (CRH) expression in the hypothalamus, and both the CRH gene and its receptor gene carry estrogen-responsive elements, priming a larger cortisol response to the same stressor. Estrogen imitates the shock reaction in Hans Selye's shock model. This is understood in the literature as heightened stress sensitivity, not a moral defect in the hormone: reproduction shuts down when a more reactive stress axis signals a poor environment. See Hans Selye.

Beyond the HPA axis, estrogen produces a background of generalized cellular excitation. When that excitatory tone runs very high, it can show up as epilepsy, tetany, or psychosis.

The specific kinds of excitation produced by estrogen that relate to reproduction occur against a background of very generalized cellular excitation, that includes increased sensitivity of sensory nerves, increased activity of motor nerves, changes in the EEG, and, if the estrogen effect is very high, epilepsy, tetany, or psychosis.

— Ray Peat

Estrogen will accelerate the verbalization of women. The number of words per minute simply is faster in general in women. That's the excitatory effect. But when you compare the information transmitted by fast talkers and slow talkers, the information per word is much higher in the slow talkers.

— Ray Peat

In a menstrual-cycle study, women scored higher on articulatory and fine motor tests in the late follicular phase, when estradiol peaks, than during menses. Recordings of American English speakers point the other way on raw speed: in spontaneous talk, men spoke faster than women.

Fat tissue and gut aromatase (the enzyme that makes estrogen from androgens) add load when PUFA, endotoxin, and low thyroid are present. The same conditions that make estrogen also make the body worse at clearing it. See Endotoxin, PUFA, Stress.

Estrogen stimulation does not produce the normal amount of CO2. The tissue experiences a kind of oxygen and energy deprivation, swells, and is pushed toward cell division. Lipid peroxidation rises with that incomplete respiration.

Chronic estrogen keeps capillaries open and water moving into cells. Tissues stay leaky. Cytochrome oxidase is impaired. Fuel shifts toward fat oxidation. Serotonin rises with estrogen and deepens the "not fully alive" defensive state that appears in learned helplessness and related suppressions. See Tissue leakiness, Mitochondria, Serotonin, Learned helplessness.

By raising circulating free fatty acids, especially PUFA, estrogen pushes cells further away from glucose oxidation and toward lactic acid production, and away from full, organ-specific differentiation. In Ray Peat's framework, this shared metabolic shift underlies both heart failure and cancer, putting the two on the same biological basis.

Estrogen, by increasing the concentration of free fatty acids, especially polyunsaturated fatty acids, contributes to the metabolic shift away from glucose oxidation, toward the formation of lactic acid, and away from the full organ-specific differentiation. This perspective puts heart failure, cancer, and the other degenerative diseases onto the same biological basis, and shows why certain conditions and therapies can be appropriate for all of them.

— Ray Peat

This is not a cartoon where "estrogen is always evil." Brief, progesterone-opposed estrogen is part of healthy cycles. Unopposed, continuous estrogen tone is the problem this site tracks.

Clinical significance

Progesterone opposes estrogen at the receptor, in vessels, in brain energy, and in inflammatory tone. Thyroid lowers estrogen production and blunts its effects. Adequate salt protects against excess estrogen and pregnancy toxemia in the same writing line. Lower seed-oil load, moving bowels, and lower endotoxin cut both production and reabsorption of estrogen from the gut.

Estradiol increases Candida albicans growth, heat-shock survival, and virulence-linked hsp90/cdr1 expression, induces germ-tube morphogenesis at physiological concentrations, and promotes complement evasion through Factor H coating of the fungus. Experimental vaginal candidiasis models depend on estrogen dosing. See Candida.

The practical arc is one arc: restore oxidation (thyroid, glucose, CO2), restore progesterone relative to estrogen, clear the gut source of endotoxin and reabsorbed steroids, and stop adding unnecessary estrogen drugs when the goal is metabolic recovery. See Progesterone, Thyroid, Salt, Harm reduction.

Obesity and clotting

In premenopausal women, obesity and estrogen-based medications (hormone therapy, oral contraceptives) act together to lower Protein S, a natural anticoagulant, through HIF1alpha-mediated suppression. Studying plasma from 157 women stratified by BMI and contraceptive use, alongside 40 mice, researchers found protein S fell with either estrogen or obesity alone and that the combination increased thrombin generation, a laboratory measure of clotting potential. In liver-cell experiments, the same suppression appeared under 1-10% oxygen (mimicking the low-oxygen state of obese tissue), whether or not estradiol was present, pointing to a shared hypoxia-driven pathway.

Aromatization and menopausal memory decline

In ovariectomized rats, androstenedione (the main circulating ovarian hormone after menopause) impairs spatial reference and working memory; blocking its conversion to estrone with the aromatase inhibitor anastrozole prevents the memory deficit, while blocking the androgen receptor directly does not. The impairment traces to estrone itself, not to androgen signaling.

Trauma exposure

In 113 trauma-exposed premenopausal women (56.5% with PTSD), higher circulating estradiol and progesterone were associated with higher subclinical inflammation, a composite score across eleven cytokines (IL-1α, IL-1β, IL-1ra, IL-6, IL-8, IL-17E, MCP-1, IFN-γ, TNF-α, IL-6R, TNF-R2). Researchers had hypothesized the opposite, that estradiol would be anti-inflammatory and cardioprotective in this group. See PTSD.

Estrogen, histamine, and addiction vulnerability

Estrogen raises brain histamine, and high gonadal estrogen during the menstrual cycle is proposed to facilitate drug-seeking behavior, one contributor to women's greater addiction vulnerability relative to men. See Histamine, Alcohol#Histamine and craving.

Estrogen and serotonin synthesis

Estrogen directly raises the brain's capacity to synthesize serotonin, a connection that gets less attention than SSRIs and serotonin itself:

Estrogen increases the brain's capacity to synthesize serotonin... Drug company manipulation of information about estrogen has been more extreme than its treatment of serotonin. Activated by stress, along with serotonin, it is one of the major activators of the corticotropin release hormone, CRH.

— Ray Peat

A primary rat study found that estrogen increased TPH2 messenger RNA in specific dorsal and median raphe subregions, while combined estrogen and progesterone did not change TPH2 messenger RNA relative to ovariectomized controls. The effect was therefore region-specific rather than a uniform increase across the serotonin system.

Capillary leakiness and prolactin

Estrogen makes capillaries leaky and promotes excess fibrin formation, so its effects show first in the organs where it concentrates. Prolactin, promoted by estrogen and inhibited by progesterone, rises with stress and age.

Menopausal hormone therapy trials

In the Women's Health Initiative trials of 27,347 postmenopausal women, conjugated equine estrogens plus medroxyprogesterone raised invasive breast cancer and added stroke and pulmonary embolism risk. In 25 postmenopausal women given conjugated estrogens alone, cyclic or continuous, endometrial hyperplasia appeared at a rate of about 4 per 100 woman-months, which the authors judged unacceptably high. The observational Million Women Study followed over a million British women aged 50 to 64. Women then using estrogen alone were diagnosed with breast cancer more often than never users, the excess was larger with an added progestin, and past users carried no extra risk.

Varicose veins in men and women

Excess estrogen relative to androgen associates with varicose veins in men as well as women, not a female-only condition. Men with primary varicose veins show a higher serum estradiol-to-testosterone ratio than healthy controls. In menopausal women, higher endogenous estradiol tracks with increased venous distensibility and clinically evident varicose veins. Oestradiol in blood drawn from varicose leg veins runs higher when pelvic vein incompetence is also present. In animal studies, direct estrogen receptor activation enhances venous relaxation, a proposed mechanism for the sex-related pattern in varicose vein prevalence. See Varicose veins.

Oral contraceptives and liver mitochondria

Women taking oral contraceptives for 12 to 30 months showed liver-cell mitochondrial shape change, enlargement, and crystalline inclusions on electron microscopy; 1 to 6 months of use showed mainly increased smooth endoplasmic reticulum without those mitochondrial changes. Mitochondrial change did not track liver-function test abnormalities. See Birth control, Liver, Mitochondria.

Endometriosis

Prolonged excessive estrogen without interruption from progesterone drives endometriosis. Estrogen is the most important known factor stimulating lesion growth, including local aromatase activity that normal endometrium lacks. Cutting that local supply with oral aromatase inhibition (1 mg/day) extinguished pain by month two and shrank a 30 x 30 x 20 mm vaginal implant to a 3 mm gray remnant in a severe postmenopausal case. Estrogen promoted as therapy for endometriosis sits among claims called at best dubious in the same writing that warns against estrogen for nervousness, depression, or "restoring youthfulness."

Pomegranate juice

Lyophilized fresh pomegranate juice reduced 17β-estradiol estrogenic activity by 55% in a yeast estrogen screen. Fermented-juice, pericarp, and seed-oil polyphenols inhibited aromatase by 60-80% and 17β-HSD1 by 34-79% in vitro. Preclinical assays only. Detail on Pomegranate and Aromatase.

Estrogen and osteoporosis

Mainstream endocrinology promotes estrogen as bone-protective, yet age-corrected osteoporotic fracture rates have risen for decades even as estrogen use became more common; estrogen is closer to a stress- and age-promoting hormone while progesterone is the bone-protective one. Estrogen produces a positive calcium balance, but the retained calcium accumulates in soft tissue rather than bone; researchers settled on "estrogen prevents bone loss" after finding it suppresses osteoclasts without activating osteoblasts, while estrogen's rise in circulating endotoxin and TNF drives calcium into cells, blocks respiration, and causes tissue wasting. Bone loss in women begins around age 23, during the years estrogen is rising rather than falling; a year-long study of premenopausal women found spinal bone density fell 2.0% per year on average with normal estrogen, and women with anovulatory (progesterone-deficient) cycles lost bone more than twice as fast, 4.2% per year. Standard x-ray bone density scans cant distinguish bone mineral from estrogen-driven changes in soft-tissue fat and water content, an artifact that has flattered estrogens apparent effect on "bone density." See Osteoporosis, Estrogen dominance.

Aromatase

Aromatase (CYP19) is the enzyme that converts androgens to estrogen. It is present in fat tissue and elsewhere in both sexes.

Stress and aging raise it

Stress, hypothyroidism, and aging increase aromatase activity in various tissues, producing estrogen locally; this tissue-bound estrogen stays elevated in postmenopausal women even when serum estrogen is low. PUFA and their prostaglandins stimulate aromatase expression, which is one reason aspirin (by blocking prostaglandin formation) lowers estrogen production.

Beyond prostaglandin block, aspirin also irreversibly inhibits adenylate cyclase in human ovarian granulosa cells, cutting aromatase expression and estrogen synthesis via AKT/mTOR and CREB; mouse PCOS models improved on androgen, insulin, and cystic follicles.

Lowering PUFA and stress load and improving thyroid status are the upstream levers. Pharmaceutical aromatase inhibitors are oncology tools, not casual supplements.

Local estrogen and aggression

A cross-species review of hormone-manipulation studies in birds, mammals, and humans found local, brain-produced estrogen (from aromatase converting circulating androgens) modulates aggression, and that social experience itself, especially reproductive/territorial encounters, changes brain aromatase activity, creating a feedback loop between social context and aggressive behavior rather than a fixed hormone-to-behavior wiring.

Nicotinic alkaloids

In human choriocarcinoma cell cultures and term placental microsomes, nicotine, cotinine, and anabasine each inhibited androgen-to-estrogen conversion in a dose-dependent, reversible way; kinetic analysis showed competitive inhibition with respect to substrate, and a high androstenedione concentration (73 µM) blocked the cell-culture inhibition.

Testicular Leydig cells and azoospermia

In 76 men with nonobstructive azoospermia (NOA), including 4 who received anastrozole for 3 months before microdissection testicular sperm extraction (micro-TESE), versus 18 men with obstructive azoospermia (OA) and preserved spermatogenesis, aromatase was mainly located in Leydig cells, and both transcript and protein expression were higher in NOA than in OA.

Serum testosterone and estradiol did not correlate with intratesticular testosterone (ITT) or intratesticular estradiol (ITE2). Across NOA graded by testicular aromatase intensity (+, ++, +++), higher aromatase tracked with lower ITT (means about 42,590 to 25,774), higher ITE2 (about 3,177 to 5,856), and a lower ITT/ITE2 ratio (15.7 to 4.6).

High aromatase (+++) was independently associated with failed sperm retrieval on micro-TESE. In the 4 men pretreated with anastrozole, the ITT/ITE2 ratio rose and aromatase expression fell (small n).

Pomegranate polyphenols (in vitro)

Polyphenols from fermented pomegranate juice, pericarp, and seed oil inhibited aromatase activity by 60-80% in vitro. The same fractions, plus whole seed oil, inhibited 17β-hydroxysteroid dehydrogenase type 1 by 34-79% at 100-1,000 µg/ml (seed oil strongest). Enzyme assays only. See Pomegranate.

Early puberty

Age at menarche has fallen sharply since the 19th century. The median age at first menstrual period in the United States dropped from 12.1 in 1995 to 11.9 in 2013-2017. Early menarche (onset before age 13) raises the risk of breast cancer, obesity, diabetes, liver disease, depression, eating disorders, and substance abuse, and is a risk factor for autism in offspring when it marks the mother's own early puberty. These outcomes track elevated estrogen, growth hormone, and prolactin released in response to perceived environmental stress and resource scarcity.

The population trends toward greater obesity and earlier puberty, both of which are associated with a higher risk of breast cancer, suggest that the war against cancer is far from over. In the 19th century when the incidence of breast cancer was much lower than it is now, puberty usually occurred around the age of 17. In countries with a low incidence of breast cancer, puberty still occurs in the middle to late teens.

— Ray Peat

A study of over 9,000 Louisiana schoolchildren (the Bogalusa Heart Study) found the secular trend toward earlier menarche tracked rising childhood obesity in both black and white girls.

Causes

Declining core body temperature

Core body temperature has fallen steadily since the Industrial Revolution, tracking a broader metabolic slowdown. Lower thyroid function and higher stress hormone output accompany this drop and accelerate puberty.

Environmental stress

Historical records show large gaps in menarche age by living conditions: 17th-to-19th-century townspeople reached menarche around 13-15 years old, while peasants in the same era reached it at 17-22. Stressful, resource-limited environments raise estrogen and prolactin, hastening puberty and correlating with worse long-term health outcomes.

Father absence

A meta-analysis of 33 studies (n=70,403) found father absence in childhood significantly correlated with earlier daughter menarche (weighted mean r=0.14).

High PUFA diet

A longitudinal cohort study found childhood PUFA intake was prospectively associated with earlier puberty timing, independent of dietary protein.

Vitamin D deficiency

Vitamin D deficiency accelerates menarche; sufficiency delays it by about a year. A prospective study of 242 girls in Bogotá, Colombia found lower 25(OH)D concentrations predicted earlier menarche onset.

Impaired light perception

Blindness advances menarche, and total loss of light perception advances it further still. A 2022 review of visually impaired girls found consistent evidence for earlier menarche, hypothesized to run through light-dark cycle disruption on the hypothalamic-pituitary-gonadal axis.

Prevention and delay

The energy frame treats delaying early menarche as a matter of raising metabolism and reducing perceived stress, rather than targeting any single hormone in isolation.

• Thermogenic diet: frequent meals, roughly half of calories from carbohydrate, with moderate protein and fat, to raise metabolism and thyroid activity and counter the downward trend in core temperature. Start with small amounts of saturated fat (about 1 teaspoon coconut oil) building to 1-2 tablespoons a day, paired with 200-400 g of carbohydrate a day from fruit and juice.
• Vitamin D: sufficient levels delay menarche by about a year.
• Light exposure: 15-30 minutes of morning sunlight; avoid artificial light and blue light at night to keep circadian rhythm aligned.
• Reduce environmental stress: lower perceived stress and resource scarcity, which otherwise drive the estrogen/prolactin shift that hastens puberty.
• Iron management: avoid excess iron intake, including iron-fortified foods; consider blood donation where applicable.

Estriol

Estriol (E3) is a weak estrogen in some laboratory tests. Serum E3 rises sharply in pregnancy as the placenta converts estradiol. Mainstream endocrinology measures urinary estriol in prenatal screening. Typical baseline levels in a third-trimester study of women at risk for preterm delivery ran around 5-6 ng/mL, illustrating the magnitude of normal late-pregnancy serum E3 compared to the low single digits it runs at outside pregnancy.

The three main estrogens in our bodies are estradiol, estrone, and estriol, though there are many other minor variants on the basic molecule.

— Ray Peat

A full article addresses estriol alongside DES and DDT. See Estrogen, Estradiol.

Dosing (Estriol)

Hormone protocols belong on Estrogen, Progesterone, and Harm reduction. This page does not list doses.

History (Estriol)

Etymology (Estriol)

The name combines "estr-" (see Estradiol) with "tri-" (for its three hydroxyl groups) and the alcohol suffix "-ol."

Guy Marrian isolated estriol in 1930, identifying it as a weaker estrogen than estradiol and estrone, and notable for rising sharply during pregnancy.

Estriol was characterized in the 1930s as a pregnancy-dominated estrogen metabolite. The name marks three hydroxyl groups on the steroid ring system.

Structure/Chemical properties (Estriol)

Estriol is C₁₈H₂₄O₃. It binds estrogen receptors with lower affinity than estradiol or estrone.

Estriol is a little more water soluble than estrone, so it interacts with every body system in a slightly different way, entering oily environments with slightly less ease, etc.

— Ray Peat

Function/Mechanism of Action (Estriol)

Mainstream physiology: fetal-placental unit produces large E3 output in normal pregnancy. Outside pregnancy, E3 is a minor circulating estrogen.

By some tests, estriol is a "weak estrogen," by others it is a powerful estrogen.

— Ray Peat

since the placenta produces hormones, and during pregnancy converts estradiol to estriol. Since estradiol in excess kills the fetus, its conversion by the placenta to estriol is in accord with the evidence showing that estriol is the more quickly excreted form.

— Ray Peat

Estriol is slightly weaker, in terms of milligrams required to cause a certain rate of uterine enlargement, than estradiol.

— Ray Peat

an increased intake of salt is highly protective against the effects of excess estrogen and toxemia of pregnancy.

— Ray Peat

Medical uses/Effects

Topical estriol appears in some menopausal and urogenital prescriptions (mainstream gynecology).

"Estriol, the forgotten estrogen?" is being circulated to promote the use of estriol, or the phytoestrogens.

— Ray Peat

Counterweights: Progesterone, Thyroid, salt, adequate Glucose.

Side/Adverse effects

Whether weak or strong, the estrogenic response of a chemical, if not overcome, will add extra estrogenic burden to the system.

— Ray Peat

When added to long-term culture of human breast cancer cells, estriol stimulated their growth, and overcame the antiestrogenic effects of tamoxifen, even at concentrations hundreds of times lower than that of tamoxifen.

— Ray Peat

Pharmaceutical estrogens carry cancer and thrombosis risks in epidemiological studies cited on the Estrogen page.

Estrogen dominance

Estrogen dominance is shorthand for excess Estrogen activity relative to protective Progesterone and Thyroid function. It is common in Peat community writing, not a single ICD diagnosis. Associated patterns include PMS, fibroids, mood instability, water retention, and metabolic slowdown.

Mainstream endocrinology measures estradiol and progesterone separately. "Dominance" here means tissue-level imbalance, not only lab ratios.

Common drivers

Cells in the most cancer-susceptible tissues proliferate in proportion to the ratio of estrogen to progesterone, and long uninterrupted estrogen dominance progressively distorts the responsive organs. Estrogen dominance also promotes division of the prolactin-secreting cells of the pituitary, and by age 50 most people have some enlargement of that part of the gland.

• Stress and hypoglycemia (raises cortisol, estrogen, prolactin)
• PUFA storage and lipolysis (estrogen-mimetic effects in Peat's writing)
• Gut Endotoxin (estrogen synergy with LPS in Peat's endotoxin writing)
• Impaired Liver clearance of estrogen
• Low Progesterone / Thyroid

When estrogen is given to an animal, it almost instantly causes capillaries to become leaky, allowing water to move out of the blood stream, and at the same time, estrogen causes cells to take up water.

— Ray Peat

Intense interval training raised estradiol about 45% acutely in male athletes (human study).

Opposing estrogen

Progesterone is Peat's primary tissue antagonist to estrogen. Thyroid, lower PUFA, gut endotoxin reduction, Aspirin, niacinamide, and CO₂ retention also appear often. See Harm reduction before Progesterone supplementation.

Reducing xenoestrogen exposure

Beyond internal hormone balance, environmental estrogen sources are a compounding load. Two categories he singled out directly:

Other chemicals used in the sun screen lotions, such as PABA derivatives, also react dangerously with light, and are easily absorbed in significant quantities into the deeper layers of the skin, where they can cause mutations.

— Ray Peat

Opaque zinc oxide or titanium oxide sunscreens sit on the skin surface rather than absorbing into it, avoiding this problem.

The water, birth control pills getting into the sewage, much of it ends up in the water of, of rivers and recycles. And there are natural sources of estrogens, but just the tremendous flow of estrogen down the sewers is a tremendous polluting source.

— Ray Peat

Synthetic estrogens from oral contraceptives pass through municipal sewage treatment largely unchanged; a point-of-use carbon-block filter is the practical response, since treatment plants don't remove them. Soy is Peat's most-discussed dietary estrogen source; see that page for the case against it. Plasticizers (soft PVC, thermal receipt paper, canned-food linings) and synthetic fragrance in personal-care products are the other categories most often raised in Peat's writing and interviews.

Aspirin, coffee, quercetin, vitamin D, zinc, and vitamin C are commonly cited as partial or selective aromatase inhibitors, useful on pregnenolone days; this is a compiled folk-protocol claim rather than one study testing the combination, so treat individual mechanisms (each has some independent evidence) more confidently than the specific combined list.

Estrone

Estrone is an estrogen produced in fat tissue and elsewhere. Levels rise with body fat and aromatase activity. Weaker than estradiol at many receptors; still part of estrogen load.

Dosing (Estrone)

As part of conjugated estrogen products, estrone sulfate is typically present at doses in the 0.3-1.25 mg/day range within combination tablets; it is not dosed independently in standard practice.

History (Estrone)

Etymology (Estrone)

The name combines "estr-" (see Estradiol) with the ketone suffix "-one."

Edward Doisy and Adolf Butenandt independently isolated estrone in 1929, making it the first steroid hormone from the estrogen family to be identified in pure form.

Estrone was the first sex steroid ever isolated in pure form, purified from pregnant women's urine independently by Adolf Butenandt in Germany and Edward Doisy in the United States in 1929. Early researchers called the whole class of ovarian hormones "folliculin," after the ovarian follicle's role in producing them, before "estrogen" (from the Greek oistros, "frenzy" or "gadfly," referring to estrus) became the standard term.

Structure/Chemical properties (Estrone)

Estrone (C₁₈H₂₂O₂) is one of the three main human estrogens, alongside estradiol and estriol. It differs from estradiol by a single functional group: a ketone at the 17-position where estradiol has a hydroxyl. That difference makes estrone somewhat less water soluble than estriol and, in general, weaker-acting at estrogen receptors than estradiol, though the three interconvert readily in the body.

Estriol is a little more water soluble than estrone, so it interacts with every body system in a slightly different way, entering oily environments with slightly less ease, etc.

— Ray Peat

Function/Mechanism of Action (Estrone)

Estrone is produced by the ovaries and adrenal glands directly, and also by aromatization of androstenedione in adipose tissue, a pathway that becomes proportionally more important with age and with higher body fat. It's readily interconverted with estradiol (via 17β-hydroxysteroid dehydrogenase) and further metabolized to estriol and other estrogen metabolites, so blood estrone levels track total estrogen load even though estrone itself is a weaker receptor agonist than estradiol.

Medical uses/Effects (estrone)

Estrone (usually as estrone sulfate, a water-soluble conjugate) is a component of some conjugated estrogen hormone replacement products, including the horse-urine-derived Premarin. It is not typically prescribed as a standalone drug.

Side/Adverse effects (estrone)

Because estrone contributes to overall estrogen load and rises with body fat, elevated estrone is one of the mechanisms linking obesity to estrogen-sensitive conditions. General estrogen-related risks (endometrial and breast tissue stimulation, clotting risk) apply to estrone as a contributor to total estrogen exposure, even though it's individually weaker-acting than estradiol.

Practice

Lower excess body PUFA stress and support progesterone and thyroid. See Estrogen, Estradiol, Estriol, Obesity.

Menopause

Hot flashes are sudden heat and flushing, most common around menopause and with estrogen swings. Ray Peat connected the mechanism to the body's opioid/endorphin system rather than treating it as simple "estrogen deficiency."

The morphine-withdrawal model

Ray Peat's model for hot flashes rests on an established animal research finding: morphine withdrawal produces the same flushing and temperature-drop pattern seen in human hot flashes, and large doses of estrogen can stop both:

One of the animal "models" used to study hot flashes is morphine withdrawal.

— Ray Peat

The model seems relevant to human hot flashes, because estrogen can stop the morphine withdrawal flushing... estrogen's acute and chronic effects on the brain-pituitary-ovary system involve the endorphins and the opioidergic nerves.

— Ray Peat

In this framing, hot flashes reflect estrogen's action on the same opioid/endorphin systems morphine engages during withdrawal, not simply a shortage of estrogen that needs replacing. In the naloxone-induced version of this animal model, morphine-dependent rats showed a tail-skin temperature spike averaging 6.4°C, and a single dose of a brain-targeted estradiol delivery system blunted that spike by 25%. See Morphine for the fuller withdrawal-model discussion.

Practice (menopause)

Progesterone and thyroid support are the general levers in this framework rather than treating hot flashes as requiring estrogen replacement by default. See Menopause, Progesterone, Thyroid.

Menopause is the permanent end of menstrual cycles. Mainstream talk blames "running out of eggs." Reproductive aging work at the University of Oregon and elsewhere showed that story is false as a simple cause: ovaries do not simply empty of eggs, and hormone production is a separate problem from ovulation.

When ovaries are x-rayed so ovulation stops, estrogen production can rise. Ovulation and steroid output are different jobs. Measuring hormones does not prove whether ovulation occurred.

Aging and steroids

Aging changes the signals and energy that cells receive. Brain and skin make steroids; loss of active tissue is part of the steroid decline, and a fixed 50-division clock does not explain it. The environment of the cell (signals, substances, energy) governs aging more than a fixed division quota.

Estrogen unopposed by progesterone, low thyroid, high PUFA, and chronic stress load the same chemistry this site tracks in younger people: leakiness, poor oxidation, heat waves, sleep break, and tissue that feels older than the calendar. Menopause concentrates that pattern when ovarian progesterone falls hard.

Framing menopause as simple "estrogen deficiency" doesn't hold up against tissue-level measurement: estrogen concentrations in fat and other tissue run far higher than blood levels, and while circulating estradiol falls after menopause, estrone and its sulfate form largely take over as the dominant circulating estrogens rather than estrogen simply disappearing. Ray Peat also drew a direct parallel between the hormone pattern of menopause and chronic cortisol excess, noting that the two produce a strikingly similar set of symptoms.

Support

Progesterone and thyroid support appear in the broader hormone essays as the protective pair against unopposed estrogen and stress. HRT decisions are medical and personal. Seed oils, stagnant bowel, under-eating, and sleep loss still matter for symptom load after cycles stop. In a 3-month RCT of 133 menopausal women, oral micronized progesterone alone (300 mg at bedtime) cut hot flashes and night sweats by 55% on average, with no rebound after stopping and improved deep sleep, distinct from the safety profile of estrogen-containing hormone therapy. A one-year trial in postmenopausal women found that oral DHEA alone (10 mg/day) lowered cortisol more than standard HRT (transdermal estradiol plus oral progesterone), and adding DHEA to HRT blunted that cortisol-lowering effect compared to DHEA alone. See Progesterone, Estrogen, Thyroid, Sleep, PUFA, Harm reduction.

The menopause essay describes a shift in protective steroids and energy that can be understood and supported, with no need for the story of running out of eggs.

In this account menopause comes from progesterone failing while estrogen production stays normal, producing a functional estrogen excess that typically takes about four years to clear. That excess drives bone loss, depression, insomnia, and flushing. High lifetime estrogen exposure desensitizes the hypothalamic nerves that regulate the pituitary, which is what eventually produces menopause.

In a one-month placebo-controlled trial in postmenopausal women with chronic insomnia, daily vitamin E improved sleep quality and cut the use of sleeping pills.

HRT

HRT (hormone replacement therapy) supplies estrogen, progesterone, thyroid hormone or others when production is low, and formulations differ widely. Bioidentical progesterone and careful thyroid therapy are discussed more favorably in this literature than older high-dose synthetic combinations. Individual risk (clotting, breast tissue) needs medical counseling. See Bioidentical hormones.

Xenoestrogens

Microplastics are tiny plastic particles now found in water, food, air, and human tissue. Long-term human health research is still young, but their small particle size itself is a meaningful concern in Ray Peat's framework.

Microplastics and reactive oxygen

Common microplastics in plain water made reactive oxygen species on their own, more so the more water-repelling the plastic, and this chemistry pulled DNA and proteins onto the surface, clumped proteins and damaged cells in lab tests. On reducing microplastic exposure, and on whether ingested microplastics act like raw starch granules in the gut:

Reverse osmosis is the most effective practical way to filter water. Nanoparticles enter cells more easily than starch granules.

— Ray Peat

Starch granules can themselves be absorbed intact into the bloodstream under some conditions (see Safe starches); plastic nanoparticles enter cells even more readily, according to Peat. Autopsy analysis of human brain, liver, and kidney tissue confirmed plastic particle buildup directly: brain samples carried a higher proportion of polyethylene nanoparticles than liver or kidney, concentrations rose significantly between tissue collected in 2016 and 2024, and decedents with a documented dementia diagnosis showed even greater brain accumulation than the general autopsy cohort, with deposits found in blood vessel walls and immune cells.

Practice (xenoestrogens)

Reverse-osmosis water filtration where practical; avoid heating food in soft plastic, which increases particle and chemical migration into food. See Water, Harm reduction.