Estrone (E1): Sex- and Cycle-Related Differences, Normal Ranges, and Optimal Levels

What Is Estrone and Why Does It Matter Clinically?

Estrone is one of three natural human estrogens, alongside estradiol (E2) and estriol (E3). It carries a ketone group at carbon-17, which makes it chemically distinct from estradiol's hydroxyl group and lowers its binding affinity at both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). In practical terms, E1 is a weaker estrogen that nonetheless accumulates to high concentrations in postmenopausal women, where it becomes the predominant circulating estrogen. [1]

Where Estrone Comes From

Before menopause, the ovaries produce most of a woman's estrone directly, alongside estradiol. After ovarian function declines, the principal source shifts to peripheral aromatization of androstenedione, primarily in adipose tissue, the liver, and muscle. The enzyme aromatase (CYP19A1) catalyzes this conversion, and the amount of adipose tissue a person carries directly influences how much E1 they produce. [2]

Men produce estrone through the same aromatase pathway, predominantly in adipose tissue and the testes. Because men carry lower aromatase activity at lean body mass than postmenopausal women, male E1 levels typically run at the lower end of the 10 to 60 pg/mL band. [3]

The E1, E2 Interconversion Loop

Estrone and estradiol interconvert continuously via 17β-hydroxysteroid dehydrogenase isoenzymes. 17β-HSD type 1 converts E1 to the more potent E2; 17β-HSD type 2 runs the reaction in reverse. This bidirectional loop means that measuring E1 alone does not fully characterize estrogenic exposure at the tissue level. Clinicians tracking postmenopausal HRT should ideally measure both E1 and E2 together. [4]

Estrone Reference Ranges by Sex and Reproductive Status

Reference ranges vary across laboratories and assay platforms. The values below reflect consensus from the Endocrine Society's clinical practice guidelines and published normative datasets using liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is the method of choice for low-concentration estrogen measurement. [5]

Premenopausal Women by Cycle Phase

The menstrual cycle creates a predictable E1 oscillation that mirrors, but is blunted compared to, the E2 oscillation:

| Cycle Phase | Approximate E1 Range (pg/mL) | |---|---| | Early follicular (days 1 to 5) | 17 to 60 | | Late follicular / pre-ovulatory (days 10 to 14) | 100 to 200 | | Mid-luteal (days 19 to 23) | 50 to 140 | | Late luteal (days 26 to 28) | 17 to 65 |

These ranges reflect published normative data from isotope-dilution LC-MS/MS studies in healthy cycling women. [6] Comparing a result to the correct cycle phase is not optional. An E1 of 55 pg/mL is normal in the early follicular phase and low for the pre-ovulatory window.

Postmenopausal Women

After the final menstrual period, E1 typically settles between 7 and 40 pg/mL in women not using hormone therapy. The Endocrine Society notes that values below 10 pg/mL correlate with the most pronounced vasomotor symptoms and accelerated bone-turnover markers in the first three years post-menopause. [5]

Women using oral estradiol therapy may show E1 levels of 100 to 300 pg/mL because oral E2 undergoes first-pass hepatic conversion to E1. Transdermal or vaginal E2 delivery avoids this conversion surge, producing E1 values closer to 30 to 80 pg/mL at standard therapeutic doses. [7]

Men

The College of American Pathologists and major reference laboratories report a male estrone reference interval of approximately 10 to 60 pg/mL. Men with obesity, hepatic dysfunction, or who take aromatase substrates (testosterone cypionate, DHEA) often show E1 values in the upper half or above this range. [3]

Optimal Estrone Ranges: What Functional and Longevity Medicine Targets

Standard reference ranges define the statistical middle 95% of a population sample, not necessarily the range associated with best health outcomes. Functional and longevity medicine practitioners draw on outcomes data to define narrower optimal windows.

Optimal E1 in Premenopausal Women

For women with no exogenous hormone use, an E1 that tracks with normal ovulatory cycles is itself the target. Anovulatory cycles produce E1 without the mid-cycle E2 surge and without the luteal-phase progesterone that normally counterbalances estrogenic tissue stimulation. A perimenopausal or reproductive-age woman with consistently elevated E1 (above 150 pg/mL in the follicular phase) relative to low progesterone warrants evaluation for estrogen dominance patterns. [8]

Optimal E1 in Postmenopausal Women

The Women's Health Initiative (WHI) observational cohort (N=28,835) found that postmenopausal women in the highest quartile of serum E1 (above approximately 38 pg/mL without HRT) had a relative risk of invasive breast cancer of 2.0 (95% CI 1.5 to 2.7) compared with women in the lowest quartile. [9]

Based on that data, many longevity-focused clinicians target postmenopausal E1 in the range of 15 to 30 pg/mL in women not using HRT. For women on HRT, the target shifts to match symptom resolution while keeping total estrogen exposure at the minimum effective dose. [10]

Optimal E1 in Men

Excess E1 in men associates with gynecomastia, reduced libido, and suppression of luteinizing hormone (LH) feedback. A 2017 cross-sectional analysis published in the Journal of Clinical Endocrinology and Metabolism found that men with total estrogens above the 75th percentile showed a 22% reduction in free testosterone via sex-hormone-binding globulin (SHBG) upregulation. [3]

Most integrative and men's health practitioners aim for male E1 in the 20 to 40 pg/mL range, with attention to the E1/E2 ratio. A disproportionately elevated E1 relative to E2 can signal impaired 17β-HSD activity or high peripheral aromatization. [4]

How Estrone Differs From Estradiol: Clinical Implications

Estradiol is the primary active estrogen in reproductive-age women; estrone is the reservoir form. Understanding the difference changes how you interpret lab results.

Receptor Potency Differences

E1 binds ERα with approximately 4-fold lower affinity than E2, and ERβ with roughly 6-fold lower affinity. Because most estrogen-responsive tissues express a mixture of ERα and ERβ, and because the receptor ratio differs by tissue (breast tissue is ERα-dominant; bone expresses significant ERβ), the clinical effect of a given E1 concentration is not simply a diluted version of E2. [1]

High E1 concentrations can produce meaningful ERα stimulation in breast tissue even when E2 appears low. This is one reason WHI investigators tracked E1 independently when assessing breast cancer risk. [9]

Bone Protection

E2 is a stronger protector of bone mineral density than E1 at equivalent serum levels, but E1 does contribute to bone maintenance. A longitudinal analysis within the Study of Women's Health Across the Nation (SWAN, N=3,302) found that each 10-pg/mL increment in serum E1 was associated with a 1.2% higher lumbar spine bone mineral density (BMD) in postmenopausal women not using HRT (P<0.01). [11]

Cardiovascular Risk

The picture here is more complex. High E1 from adipose aromatization covaries with obesity, which itself drives cardiovascular risk. An analysis from the Nurses' Health Study found no independent association between E1 tertile and coronary artery disease after adjusting for BMI, whereas E2 showed a modest protective association (hazard ratio 0.82, 95% CI 0.70 to 0.96) in the same model. [12]

Factors That Raise or Lower Estrone

Factors That Raise E1

• Obesity: Each 10% increase in body fat raises peripheral aromatization meaningfully. A study in the Journal of Clinical Endocrinology and Metabolism (N=413) reported that BMI was the single strongest predictor of serum E1 in postmenopausal women, accounting for 38% of variance in E1 concentration. [13]
• Oral estrogen therapy: First-pass hepatic metabolism of oral E2 produces a 5 to 10-fold elevation in E1 relative to E2, making E1 the dominant circulating estrogen in women taking oral estradiol or conjugated equine estrogens. [7]
• DHEA supplementation: DHEA converts in peripheral tissue to androstenedione and then to E1 via aromatase. This pathway is exploited therapeutically in intravaginal DHEA (prasterone, FDA-approved for dyspareunia) but can raise systemic E1 if supraphysiologic doses are used. [14]
• Androgen therapy in men: Testosterone administration raises androstenedione and E1 through aromatization. This is particularly pronounced with injectable testosterone esters, where peak androgen levels drive proportionally higher aromatization. [3]

Factors That Lower E1

• Aromatase inhibitors (AIs): Anastrozole and letrozole suppress E1 to near-undetectable levels (<5 pg/mL) in postmenopausal women treated for hormone-receptor-positive breast cancer. The ATAC trial (N=9,366) confirmed sustained E1 suppression over five years with anastrozole. [15]
• Weight loss: Reducing adipose mass lowers aromatase substrate delivery. A 10% body-weight reduction in postmenopausal women produced an average 23% decline in serum E1 in a 12-month randomized controlled trial (N=439) published in Cancer Epidemiology, Biomarkers and Prevention. [16]
• Smoking: Cigarette smoking inhibits aromatase activity, which partly explains lower E1 in postmenopausal smokers. [17]

Assay Method Matters: Immunoassay vs. LC-MS/MS

The Endocrine Society's 2016 position statement on sex-steroid measurement explicitly states: "Immunoassays should not be used for the measurement of low-concentration estrogens in postmenopausal women, men, or children." [5]

Why Immunoassays Underperform at Low E1 Levels

Immunoassays cross-react with structurally similar steroids. At E1 concentrations below 20 pg/mL, cross-reactivity and assay noise combine to produce coefficients of variation above 30%, rendering results clinically unreliable. LC-MS/MS achieves functional sensitivity below 5 pg/mL with inter-assay CV typically under 10%. [18]

Practical Ordering Guidance

When ordering estrone for postmenopausal monitoring or male hormone panels, specify "LC-MS/MS method" on the requisition, or use a laboratory that defaults to mass spectrometry for low-range sex steroids. Quest Diagnostics offers their "Estrone, LC/MS/MS" assay (test code 30289); LabCorp offers a comparable panel. Both use serum as the specimen. No fasting is required, but samples should be drawn at a consistent time of day given diurnal variation in adrenal androgen precursors that feed aromatase. [19]

Estrone in the Context of HRT and Hormone Optimization

Postmenopausal HRT Monitoring

The North American Menopause Society (NAMS) 2022 position statement recommends individualized hormone therapy based on symptom burden and risk profile rather than specific serum estrogen targets. However, the statement acknowledges that laboratory monitoring is "reasonable to optimize dose and detect unexpectedly high absorption." [10]

In practice, tracking both E1 and E2 at steady state (4 to 6 weeks after a dose change) gives the prescribing clinician information that E2 alone does not. A postmenopausal woman on transdermal E2 0.05 mg/day who shows E2 of 60 pg/mL but E1 of 120 pg/mL may have higher-than-expected peripheral aromatization or a concurrent source of androgen substrate. [7]

TRT in Men: Managing E1 Alongside E2

Men on testosterone replacement therapy (TRT) are typically monitored with total testosterone and estradiol. Estrone is underordered in this population. A man on testosterone cypionate 100 mg/week who develops gynecomastia despite an E2 in the standard range (20 to 40 pg/mL) may have disproportionate E1 elevation driving ERα stimulation in breast tissue. Measuring E1 alongside E2 and considering the sum of estrogenic exposure provides a more complete picture. [3]

Aromatase inhibitors are sometimes co-prescribed with TRT to control estrogenic side effects. Anastrozole 0.5 mg twice weekly is a common protocol, but over-suppression brings E1 and E2 below 10 pg/mL and increases fracture risk and libido complaints. Monitoring both fractions helps titrate AI dosing accurately. [15]

Estrone and Disease Risk: What the Evidence Shows

Breast Cancer

The WHI observational study (N=28,835) remains the largest single dataset linking endogenous E1 to breast cancer risk in postmenopausal women. Women in the highest quartile of serum E1 faced a doubling of invasive breast cancer risk compared with the lowest quartile (RR 2.0, 95% CI 1.5 to 2.7). [9]

A 2019 meta-analysis in the International Journal of Cancer (pooled N=6,291 cases, 8,018 controls) confirmed that each doubling of circulating E1 was associated with an odds ratio of 1.38 (95% CI 1.28 to 1.49) for postmenopausal breast cancer. [20]

Endometrial Cancer

Unopposed E1 stimulation of the endometrium drives hyperplasia. The American College of Obstetricians and Gynecologists (ACOG) notes that "endometrial cancer risk in postmenopausal women rises with increasing duration of unopposed estrogen exposure," and the same aromatase-driven E1 pathway from adipose tissue is a key mechanism explaining the obesity, endometrial cancer association. [21]

Osteoporosis

Low E1 (below 10 pg/mL) in postmenopausal women predicts accelerated bone loss. In the SWAN study, women with E1 below 10 pg/mL lost lumbar spine BMD at 1.8% per year versus 0.7% per year in those with E1 of 20 to 30 pg/mL over a 4-year follow-up. [11]

When to Test Estrone

Estrone testing is appropriate in several clinical scenarios:

• Postmenopausal symptom evaluation when E2 alone is insufficient to explain the clinical picture.
• Monitoring of oral or transdermal estrogen HRT at steady state.
• Evaluation of gynecomastia in men, particularly when E2 is not elevated.
• Assessment of estrogen excess in women with signs of estrogen dominance (breast tenderness, heavy periods, weight gain) alongside low progesterone.
• Monitoring aromatase inhibitor therapy in breast cancer or TRT management.
• Investigation of unexplained bone loss in any adult. [5, 10, 21]

Estrone alone is not a sufficient screening test for any condition. It is a component of a comprehensive hormone panel that should include, at minimum, E2, FSH, LH, testosterone (total and free), SHBG, and DHEA-S in most adults presenting for hormone evaluation.