Lab Reference Library / Estrone (E1) Hormones & Reproductive

Estrone (E1)

E1 · Estrone · Postmenopausal Dominant Estrogen

Reference range, optimal functional medicine levels, and why estrone becomes the dominant circulating estrogen after menopause through adipose aromatase conversion of androstenedione, how obesity and alcohol drive estrone elevation, and why the estradiol-to-estrone ratio matters clinically for hormone therapy optimization and cancer risk assessment.

Estrogen PanelPostmenopausal Estrogen

Premenopausal FM10 to 60 pg/mL

Postmenopausal FMBelow 30 pg/mL

On HRT (transdermal)10 to 40 pg/mL

Unitspg/mL

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Category: Hormones & Reproductive | Also known as: E1, Estrone, Oestrone, Postmenopausal Estrogen

1. What This Test Measures

Estrone (E1) is one of the three primary endogenous estrogens, biosynthesized from androstenedione through aromatization catalyzed by the CYP19A1 enzyme (aromatase). Unlike estradiol, which is primarily produced by granulosa cells in the ovarian follicle, estrone production is distributed across multiple tissues: adipose tissue, liver, skeletal muscle, adrenal cortex, breast tissue, and bone marrow all express aromatase and contribute to peripheral estrone production from circulating androstenedione. This distributed peripheral production pattern means estrone levels are influenced by total body fat mass, androstenedione availability from the adrenals, and the activity of aromatase in each tissue compartment.

The clinical significance of estrone shifts profoundly at menopause. Before menopause, estradiol is the dominant circulating estrogen (typically 50 to 400 pg/mL depending on cycle phase) while estrone is lower (typically 20 to 80 pg/mL). After menopause, ovarian estradiol production ceases and estradiol falls to below 20 pg/mL in most women, while estrone persists at measurable levels (typically 10 to 60 pg/mL) driven by adipose and adrenal androstenedione aromatization. This shift makes estrone the dominant postmenopausal estrogen, and adipose tissue mass the primary determinant of postmenopausal estrogen exposure.

Estrone interconverts bidirectionally with estradiol through 17-beta-hydroxysteroid dehydrogenase (17-beta-HSD) enzymes expressed in breast, uterine, liver, and other tissues. The type 1 isoform converts estrone to estradiol (estrogenic direction); the type 2 isoform converts estradiol back to estrone (anti-estrogenic direction). This intracellular interconversion means that circulating estrone, even at concentrations too low to produce significant direct ER binding, can be converted to potent estradiol locally within target tissues, amplifying its clinical importance beyond what serum estrone levels alone suggest.

2. Reference Range and Optimal Levels

Clinical State	Standard Reference	FM Optimal	Interpretation
Premenopausal (follicular)	17 to 200 pg/mL	20 to 60 pg/mL	Rises through cycle; context-dependent; check day of cycle
Premenopausal (luteal)	30 to 120 pg/mL	30 to 80 pg/mL	Should be paired with adequate progesterone to prevent estrogen dominance
Postmenopausal (no HRT)	7 to 40 pg/mL	Below 30 pg/mL	Primarily from adipose aromatization; elevation correlates with obesity
Postmenopausal (transdermal E2)	Variable with dose	10 to 40 pg/mL	Transdermal produces favorable E2:E1 ratio; monitor alongside estradiol
Postmenopausal (oral E2)	Variable with dose	40 to 80 pg/mL	First-pass hepatic conversion elevates E1 relative to E2; favors transdermal

Estrone levels vary significantly by assay methodology, laboratory, and specimen handling. LC-MS/MS provides superior accuracy over immunoassay, particularly at low postmenopausal concentrations. Always interpret estrone in the context of concurrent estradiol, progesterone, and SHBG measurements. The E2:E1 ratio (estradiol divided by estrone) is a more clinically useful metric than either value in isolation; a ratio above 1.0 indicates estradiol dominance (premenopausal pattern); a ratio below 0.5 indicates estrone dominance (postmenopausal or obese pattern).

3. Adipose Aromatase: The Obesity-Estrone-Cancer Link

The relationship between obesity, elevated estrone, and postmenopausal breast and endometrial cancer risk is one of the most robustly established links between metabolic health and cancer biology.

Adipose tissue is the largest extra-gonadal site of aromatase expression, and aromatase activity per unit adipose tissue increases with inflammation, insulin, and aging. In postmenopausal women, the total adipose aromatase mass determines the majority of circulating estrone: women with obesity (BMI above 30) typically have postmenopausal estrone levels two to three times higher than lean postmenopausal women. This excess estrone is converted intracellularly to estradiol in breast and endometrial tissue, where it drives ER-alpha-mediated proliferation. The Women's Health Initiative confirmed that postmenopausal obesity significantly increases breast cancer risk through this mechanism. Aromatase inhibitors (anastrozole, letrozole, exemestane) work partly by blocking this peripheral adipose aromatization, explaining their efficacy in hormone receptor-positive postmenopausal breast cancer.

Insulin and IGF-1 directly upregulate aromatase gene (CYP19A1) expression in adipose stromal cells, creating a mechanistic link between insulin resistance and elevated estrone. This is why the metabolic syndrome, obesity, and type 2 diabetes create a compounding estrone elevation that goes beyond adipose mass alone. Addressing insulin resistance through dietary intervention, exercise, and metabolic optimization reduces aromatase-driven estrone production through multiple mechanisms simultaneously.

4. Estrone and HRT: The Oral vs Transdermal Distinction

Why Oral Estradiol Elevates Estrone Disproportionately

First-pass hepatic metabolism: oral estradiol undergoes extensive first-pass metabolism in the liver and intestinal wall before reaching systemic circulation; hepatic 17-beta-HSD type 2 converts much of the absorbed estradiol to estrone during this first pass; the result is a serum E1:E2 ratio of 3:1 to 5:1 on oral estradiol, meaning estrone dominates the circulating estrogen pool even though estradiol was administered
Clinical consequence of high oral estrone: elevated estrone from oral HRT produces higher hepatic protein synthesis (including SHBG, clotting factors, CRP, and triglycerides) through the portal circulation, explaining why oral HRT is associated with higher thromboembolism risk than transdermal delivery; high SHBG from oral HRT binds free estradiol and testosterone, reducing bioavailable sex hormones
Monitoring oral estradiol therapy: serum estrone alongside estradiol and SHBG at 6 to 8 weeks after initiation or dose change confirms the estrogen profile achieved; an E1:E2 ratio above 4:1 on oral therapy suggests the patient is being exposed primarily to estrone rather than estradiol and may benefit from switching to transdermal delivery

Transdermal Estradiol and the Favorable E2:E1 Ratio

Transdermal pharmacokinetics: patches, gels, and creams applied to non-scrotal skin deliver estradiol directly into systemic venous circulation, bypassing first-pass hepatic metabolism; serum E2:E1 ratios on transdermal therapy approximate the premenopausal pattern of roughly 1:1 to 2:1, representing a more physiological estrogen exposure than oral delivery
Clinical advantages of favorable E1:E2 ratio: lower hepatic first-pass exposure reduces SHBG elevation (preserving free testosterone), reduces CRP induction, reduces clotting factor production (explaining lower VTE risk vs oral HRT), and reduces triglyceride elevation; these differences are particularly relevant in women with obesity, elevated baseline SHBG, or cardiovascular risk factors
Estrone on transdermal therapy: serum estrone rises moderately on transdermal estradiol as the administered estradiol equilibrates with peripheral tissue interconversion; target estrone below 60 pg/mL on transdermal therapy for most postmenopausal women, with estradiol above 50 pg/mL to confirm adequate estrogenic activity at a favorable ratio
Compounded transdermal in bioidentical protocols: estrogen creams and gels from compounding pharmacies vary significantly in absorption efficiency; serum monitoring is essential with compounded preparations because inter-patient absorption can differ two to three fold at the same nominal dose; never rely on dose alone without laboratory confirmation of serum levels achieved

5. Estrone and Estrogen Dominance in Perimenopausal Women

The perimenopausal estrone surplus: in the 5 to 10 years before menopause, ovarian estradiol production becomes erratic while adrenal androstenedione (and therefore adipose aromatase-derived estrone) continues relatively unabated; simultaneously, progesterone production declines sharply as anovulatory cycles increase; the result is a period of relative estrogen excess relative to progesterone even as total estrogen production is declining, producing the classic estrogen dominance symptom cluster
Clinical presentation of estrone-driven estrogen dominance: breast tenderness (particularly premenstrual), heavy or prolonged menstrual bleeding, uterine fibroids (which are ER-alpha sensitive and grow in response to elevated estrone), fluid retention, hip and thigh fat redistribution, mood changes and irritability, sleep disruption, and fatigue; symptoms that wax and wane with cycle phase suggest hormonal cycling as the driver
Laboratory pattern of estrogen dominance: estrone in the upper range or above for cycle phase, estradiol variable, progesterone low (below 5 ng/mL in the luteal phase), progesterone-to-estradiol ratio below 100 (in pg/mL units); SHBG often low from insulin resistance, increasing free estrogen burden; thyroid function should be assessed as hypothyroidism amplifies estrogen dominance through impaired hepatic estrogen clearance
Treatment priorities: progesterone repletion (oral or topical bioidentical progesterone timed to the luteal phase or given continuously) is the most direct intervention; weight management and insulin resistance correction reduce adipose aromatase-driven estrone production; DIM and I3C support hepatic estrogen 2-hydroxylation; reducing alcohol eliminates a significant aromatase upregulator

6. How to Optimize Estrone Levels

Reduce Excess Estrone

Weight management: each unit reduction in BMI measurably reduces adipose aromatase mass and circulating estrone; even 5 to 10% body weight reduction produces clinically meaningful estrone reduction in postmenopausal women; this is the single most impactful lifestyle intervention for estrone normalization
Insulin resistance correction: insulin directly upregulates CYP19A1 aromatase expression; time-restricted eating, carbohydrate reduction, resistance training, and berberine or metformin for insulin sensitization reduce aromatase-driven estrone production independently of weight change
Reduce alcohol intake: alcohol inhibits hepatic estrogen clearance and upregulates aromatase; even moderate consumption (one drink daily) measurably elevates estrone and shifts estrogen metabolite ratios toward proliferative pathways; elimination during active estrone optimization is recommended
DIM (100 to 200mg daily) and cruciferous vegetables: shift hepatic estrogen metabolism toward protective 2-hydroxylation and away from 16-alpha-hydroxylation, reducing estrone contribution to proliferative metabolite pools
Optimize thyroid function: hypothyroidism impairs hepatic estrogen conjugation and biliary clearance; correcting hypothyroidism accelerates estrogen clearance and reduces estrone accumulation; Free T3 optimization is particularly relevant

Balance Estrone With Progesterone

Bioidentical progesterone: oral micronized progesterone (100 to 200mg at bedtime, days 14 to 28 of cycle in premenopausal women, or continuously in postmenopausal women on estrogen therapy) directly counterbalances estrone-driven ER-alpha stimulation; progesterone downregulates ER-alpha expression, promotes endometrial differentiation, reduces breast cellular proliferation, and reduces fluid retention
Progesterone-to-estradiol ratio target: in functional medicine, a luteal phase progesterone-to-estradiol ratio above 100 (both in pg/mL units; progesterone conversion: ng/mL x 1000 = pg/mL) indicates adequate progesterone relative to estrogen; below 100 indicates relative estrogen dominance regardless of absolute estrone level
Address SHBG suppression: low SHBG from insulin resistance increases free estrone and free estradiol, amplifying estrogen dominance; correcting insulin resistance raises SHBG and reduces free estrogen burden without any change in total estrogen production
Magnesium glycinate (400 to 600mg daily): supports hepatic phase II conjugation of estrogen metabolites; magnesium deficiency impairs glucuronidation, the primary estrogen excretion pathway; adequate magnesium improves total estrogen clearance including estrone

Monitoring Protocol

Premenopausal baseline panel: estrone, estradiol, progesterone (days 19 to 22 of cycle for luteal phase assessment), SHBG, testosterone; cycle day documentation is essential for meaningful interpretation
Postmenopausal baseline: estrone, estradiol, progesterone, SHBG; timing is flexible as cyclic variation is absent; morning draw for hormonal consistency
On HRT follow-up: recheck estrone and estradiol at 6 to 8 weeks after any initiation or dose change; earlier if symptoms suggest under- or over-replacement; E2:E1 ratio guides delivery method decisions
DUTCH Complete for metabolite depth: serum estrone and estradiol measure circulating hormone; DUTCH urine testing adds 2-OHE1, 4-OHE1, 16-OHE1, and methylated metabolites for the complete estrogen metabolism picture that informs DIM, I3C, and COMT support decisions
Annual surveillance: stable postmenopausal women on HRT should have annual estrone and estradiol alongside comprehensive metabolic panel, CBC, and lipid panel; mammography with density reporting annually for all women on estrogen-containing therapy

7. Related Lab Tests

Estradiol (E2)Primary Active Estrogen; Estrone Is Its Weaker Peripheral Metabolite

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Estriol (E3)Third Estrogen; Estrogen Metabolism Pathway Endpoint

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ProgesteroneEstrone Balance Partner; Progesterone Deficiency Drives Estrogen Dominance

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SHBGModulates Free Estrone and Estradiol; Low SHBG Amplifies Estrogen Dominance

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Fasting InsulinInsulin Upregulates Aromatase and Elevates Estrone Production

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DHEA-SAndrostenedione Precursor for Aromatase-Driven Estrone Synthesis

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8. Clinical Perspective

Clinical Perspective

Estrone is the estrogen that connects metabolic health, body composition, and cancer risk in a single molecule, and understanding this connection changes how I counsel patients about weight management. When a postmenopausal woman with a BMI of 34 asks why her estrone is 68 pg/mL despite not being on any hormone therapy, the explanation is a biology lesson: her adipose tissue is an endogenous estrogen factory running on adrenal androstenedione substrate, and every unit of fat she carries is producing estrone that is being converted locally to estradiol in her breast and uterine tissue without the counterbalancing progesterone she had during her reproductive years. The estrone number gives her something concrete to connect to her metabolic goals. And when she asks why her doctor recommended oral estradiol rather than a patch and her estrone came back at 140 pg/mL versus the 35 pg/mL it is on transdermal delivery, the first-pass hepatic conversion explanation makes a compelling case for the delivery method switch. These numbers translate complex pharmacology into actionable, patient-understandable clinical decisions. That is what evidence-forward hormone medicine looks like in practice.

Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma

9. Frequently Asked Questions

What is estrone and how does it differ from estradiol?

Estrone (E1) is one of the three primary endogenous estrogens alongside estradiol (E2) and estriol (E3). It is significantly weaker than estradiol, with approximately one third the ER-alpha binding affinity. Before menopause, estrone is produced primarily by peripheral aromatization of androstenedione in adipose tissue, liver, and muscle, with ovarian production playing a secondary role. After menopause, when ovarian estradiol production ceases, estrone derived from adrenal androstenedione aromatization in adipose tissue becomes the dominant circulating estrogen. This is why adipose tissue and its aromatase activity become particularly clinically significant in postmenopausal women.

Why does estrone elevation matter clinically?

Elevated estrone relative to estradiol or progesterone is clinically significant for several reasons. Estrone can be converted back to estradiol intracellularly via 17-beta-hydroxysteroid dehydrogenase (17-beta-HSD), meaning high estrone represents a reservoir of potential estradiol activity in breast and uterine tissue even when circulating estradiol is low. Obesity drives estrone elevation through increased adipose aromatase activity; this is one mechanism linking obesity to breast and endometrial cancer risk in postmenopausal women. High estrone relative to progesterone contributes to estrogen dominance symptoms in perimenopausal women including breast tenderness, fluid retention, mood changes, and heavy menstrual bleeding.

What causes high estrone in postmenopausal women?

The primary driver of elevated estrone after menopause is adipose tissue aromatase activity converting adrenal androstenedione to estrone. Obesity is the most significant modifiable cause: adipose tissue mass directly correlates with estrone production, which is why postmenopausal obesity is associated with higher circulating estrogen despite absent ovarian function. Alcohol intake upregulates CYP19A1 (aromatase) and impairs hepatic estrogen clearance, further elevating estrone. Certain medications including some antidepressants and antipsychotics increase aromatase expression. Adrenal androgen excess from subclinical Cushing's or adrenal hyperplasia provides more androstenedione substrate for conversion.

How is estrone monitored during hormone replacement therapy?

On conventional HRT with estradiol (patches, gels, or oral), estrone rises as a metabolite of administered estradiol. Oral estradiol produces higher estrone-to-estradiol ratios than transdermal delivery because first-pass hepatic metabolism converts significant amounts of oral estradiol to estrone before it reaches systemic circulation. This is one reason transdermal estradiol is generally preferred for HRT: it produces more physiological estradiol-to-estrone ratios similar to those seen in premenopausal women. Monitoring serum estrone alongside estradiol during HRT optimization allows delivery method and dose adjustments to achieve a favorable E2-to-E1 ratio.

What is estrogen dominance and how does estrone contribute to it?

Estrogen dominance refers to a state where estrogenic activity is disproportionately high relative to progesterone, producing a clinical syndrome of breast tenderness, bloating, heavy or irregular periods, mood changes, and fat accumulation around hips and thighs. Estrone contributes to estrogen dominance through two mechanisms: directly through its own estrogenic activity at ER-alpha, and indirectly through intracellular conversion to estradiol via 17-beta-HSD in breast and uterine tissue. In perimenopausal women, progesterone production declines more sharply than estrone production, creating a window of unopposed estrogenic effect that produces many classic perimenopausal symptoms. Addressing estrogen dominance requires both reducing estrone production (through weight management and aromatase inhibition) and supporting progesterone production or supplementation.

Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.

Estrone is the dominant postmenopausal estrogen and the link between adipose aromatase activity, obesity, and hormone-sensitive cancer risk. Its ratio to estradiol guides HRT delivery method decisions.

Estrone is measured as part of every comprehensive hormone panel at The Lamkin Clinic. Schedule a consultation for a complete estrogen assessment and personalized hormone optimization plan.

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Medical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.