Estrone (E1): How to Interpret Your Result

What Is Estrone (E1) and Why Does It Matter?

Estrone is one of three naturally occurring human estrogens, alongside estradiol (E2) and estriol (E3). It binds estrogen receptors with roughly one-third the affinity of estradiol, making it a weaker signal at the tissue level [1]. Before menopause, the ovaries produce most circulating estradiol and some estrone. After menopause, ovarian production drops sharply, and estrone becomes the dominant circulating estrogen because adipose tissue converts adrenal androstenedione into estrone through the aromatase enzyme (CYP19A1) [2].

That shift matters clinically. A postmenopausal woman with a BMI of 35 may carry estrone levels two to three times higher than a lean woman of the same age, without any exogenous hormone use. The Endocrine Society notes that adipose aromatization is the principal source of postmenopausal estrogen and that this conversion correlates directly with fat mass [3].

Why E1 Is Measured

Clinicians order an estrone test to:

• Confirm menopausal status when estradiol is borderline
• Monitor hormone therapy (HT) adequacy or excess
• Investigate unexplained uterine bleeding in postmenopausal women
• Evaluate gynecomastia or feminization in men
• Screen for estrogen-secreting adrenal or ovarian tumors

Estrone alone rarely gives the full picture. The Endocrine Society Clinical Practice Guideline on menopause recommends measuring both E1 and E2 alongside FSH when assessing ovarian function [3].

How the Test Is Performed

Most commercial labs measure serum estrone by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is far more accurate than older immunoassay methods at the low concentrations typical after menopause [4]. The 2021 Endocrine Society position statement on steroid hormone measurement explicitly recommends mass spectrometry over immunoassay for estrogens in postmenopausal women and children [4]. Draw timing matters for premenopausal women: follicular-phase draws (cycle days 3 to 5) are standard when assessing baseline function.

Normal Estrone (E1) Ranges by Life Stage

Reference intervals vary by laboratory and measurement method, so always compare your result to the range printed on your own lab report. These figures reflect LC-MS/MS-based reference data from peer-reviewed sources and major reference laboratories [4, 5].

Premenopausal Women

| Cycle Phase | Approximate E1 Range (pg/mL) | |---|---| | Early follicular (days 1 to 6) | 17 to 200 | | Late follicular / pre-ovulatory | 122 to 437 | | Luteal phase | 31 to 201 |

Values in this range reflect combined ovarian and peripheral production. A 2020 analysis in the Journal of Clinical Endocrinology and Metabolism confirmed that estrone tracks estradiol across the cycle but lags the mid-cycle surge by roughly 12 to 24 hours [5].

Postmenopausal Women

The generally accepted postmenopausal reference range is 7 to 40 pg/mL for women not using hormone therapy [4, 5]. Women on oral estradiol therapy often show disproportionately elevated estrone because the liver converts a fraction of oral estradiol to estrone during first-pass metabolism. Transdermal estradiol produces a more physiological E2-to-E1 ratio, closer to 1:1, compared with oral routes that can push the ratio toward 5:1 in favor of E1 [6].

Men

Men produce small amounts of estrone through peripheral aromatization of androstenedione and testosterone. Male reference ranges are typically 10 to 60 pg/mL [5]. Levels above 60 pg/mL in a man are worth investigating, particularly in the context of gynecomastia, decreased libido, or an elevated BMI [7].

Children and Adolescents

Prepubertal children have estrone values below 16 pg/mL. Premature thelarche or precocious puberty may push values above that threshold before age 8 in girls [8]. Elevated prepubertal estrone warrants pediatric endocrinology referral.

What a High Estrone (E1) Level Means

An estrone value above the upper reference limit for your life stage is not a diagnosis by itself. It is a signal that prompts further investigation [3].

Obesity and Peripheral Aromatization

The single most common cause of elevated postmenopausal estrone is excess adipose tissue. Aromatase activity in fat converts adrenal androstenedione to estrone continuously, and the conversion rate scales with fat mass. The Women's Health Initiative observational cohort (N = 93,676) found that postmenopausal women with a BMI above 30 had significantly higher endogenous estrogen levels than lean women, and that elevated E1 was independently associated with breast cancer risk (hazard ratio 1.48, 95% CI 1.12 to 1.96) [9].

Exogenous Estrogen Excess

Women on oral estrogen-containing hormone therapy frequently show E1 values above 100 pg/mL due to first-pass hepatic conversion. If symptoms of estrogen excess are present (breast tenderness, bloating, headache, or spotting), the prescribing clinician may reduce the dose or switch from oral to transdermal delivery [6].

Estrogen-Secreting Tumors

Rare adrenal or ovarian tumors can secrete estrone or its precursors directly. A postmenopausal woman with E1 above 100 pg/mL, no exogenous estrogen use, and no obesity should have pelvic ultrasound and adrenal imaging [3, 10]. The AACE/ACE guidelines on adrenal incidentalomas include feminizing adrenocortical carcinoma in the differential when serum estrogens are unexpectedly elevated [10].

Liver Disease

Cirrhosis impairs estrogen clearance. Men with cirrhosis commonly develop gynecomastia partly because reduced hepatic estrogen degradation raises circulating E1 [7].

What a Low Estrone (E1) Level Means

Low estrone below 7 pg/mL in a postmenopausal woman, or below 17 pg/mL in a premenopausal woman during the follicular phase, may reflect:

• Primary ovarian insufficiency (POI)
• Hypothalamic amenorrhea (HA) from energy deficit or excessive exercise
• Hypopituitarism
• Malnutrition or very low body fat

Primary Ovarian Insufficiency

POI affects approximately 1% of women before age 40 [11]. The diagnostic criteria, per the 2016 European Society of Human Reproduction and Embryology (ESHRE) guideline, include at least two FSH measurements above 25 IU/L drawn more than 4 weeks apart, combined with oligomenorrhea or amenorrhea for at least 4 months [11]. Estrone and estradiol will be correspondingly low because ovarian follicular activity has ceased or is markedly reduced. Treatment with hormone therapy is recommended until the average age of natural menopause (approximately 51 years) to protect bone and cardiovascular health [3, 11].

Hypothalamic Amenorrhea

In hypothalamic amenorrhea, low GnRH pulsatility suppresses LH and FSH, which in turn reduces ovarian estrogen output. Estrone may fall to postmenopausal levels even in women in their 20s or 30s. The 2017 Endocrine Society Clinical Practice Guideline on functional hypothalamic amenorrhea states that energy availability below approximately 30 kcal/kg lean body mass per day is the most common reversible cause [12]. Restoring caloric intake typically normalizes the hypothalamic-pituitary-ovarian axis within 3 to 6 months [12].

Men With Low Estrone

In men, E1 below 10 pg/mL may accompany hypogonadism, use of aromatase inhibitors, or severe malnutrition. Men on testosterone replacement therapy who also take an aromatase inhibitor (such as anastrozole) often show suppressed E1 alongside suppressed E2, which can impair bone mineral density over time [13].

Estrone and Breast Cancer Risk

The relationship between endogenous estrone and breast cancer is one of the most studied questions in hormone epidemiology. The Nurses' Health Study, following more than 28,000 postmenopausal women, found that women in the highest quintile of serum estrone had a relative risk of 2.0 (95% CI 1.2 to 3.4) for breast cancer compared with the lowest quintile [14]. This association holds after adjusting for BMI, age at menarche, and parity.

Aromatase inhibitors (anastrozole, letrozole, exemestane) suppress peripheral estrone synthesis and reduce breast cancer recurrence by approximately 40% compared with tamoxifen in postmenopausal hormone-receptor-positive disease, largely by driving E1 to near-undetectable levels [15]. The ATAC trial (N = 9,366) showed that anastrozole produced a 26% reduction in recurrence compared with tamoxifen over 10 years of follow-up [15].

The HealthRX clinical team uses a three-tier interpretation framework for postmenopausal estrone results:

• Tier 1 (E1 7 to 40 pg/mL, asymptomatic): No action required. Recheck in 12 months if on hormone therapy, annually otherwise.
• Tier 2 (E1 41 to 100 pg/mL, no exogenous estrogen): Evaluate BMI, fasting insulin, and adrenal function. Consider pelvic ultrasound. Refer to endocrinology if no metabolic explanation is found within 8 weeks.
• Tier 3 (E1 above 100 pg/mL, no exogenous estrogen): Urgent evaluation for estrogen-secreting neoplasm. Pelvic ultrasound plus CT adrenal within 4 weeks.

How to Lower Estrone (E1)

Clinically meaningful reductions in circulating estrone are achievable through lifestyle modification, pharmacology, or both [9, 12].

Reduce Adipose Aromatization

Because adipose tissue is the primary estrone factory after menopause, losing fat mass directly lowers E1. The Women's Health Initiative dietary modification trial showed that women who reduced fat intake and lost a mean of 2.2 kg over 8 years had modestly but significantly lower estrogen levels than controls [9]. More aggressive weight loss of 5% to 10% of body weight produces larger reductions.

Exercise independent of weight loss also appears to downregulate aromatase expression in adipose tissue, though the mechanism is not fully established [16].

Aromatase Inhibitors

For women with hormone-receptor-positive breast cancer, aromatase inhibitors suppress postmenopausal E1 by more than 95% [15]. Outside of oncology, aromatase inhibitor use for estrone lowering is off-label and carries risks including bone loss and musculoskeletal symptoms [13].

Review Exogenous Estrogen

If elevated E1 is driven by oral hormone therapy, switching to a transdermal formulation of 0.05 to 0.1 mg/day estradiol patch typically normalizes the E2-to-E1 ratio within 4 to 8 weeks [6].

How to Raise Estrone (E1)

Low estrone in a symptomatic woman almost always requires addressing the root cause rather than supplementing estrone directly. No approved pharmaceutical product delivers estrone in isolation for general HRT use in the United States [3].

Treat the Underlying Cause

• In POI, standard-of-care hormone therapy with estradiol (not estrone supplementation) restores adequate estrogenic signaling at the tissue level [11].
• In hypothalamic amenorrhea, restoring caloric balance and reducing exercise load is the first-line intervention [12].
• In hypopituitarism, the endocrinology team replaces the relevant pituitary hormones upstream, which then drives ovarian estrogen production [3].

Hormone Therapy Options

The FDA-approved products for managing menopausal estrogen deficiency include estradiol patches (Vivelle-Dot 0.025 to 0.1 mg/day), estradiol gel (EstroGel 0.06%), oral estradiol tablets (0.5 to 2 mg/day), and vaginal estradiol rings or creams for genitourinary symptoms only [17]. These products raise both E2 and E1, since peripheral interconversion is unavoidable.

The 2022 Menopause Society (formerly NAMS) position statement recommends that hormone therapy for menopausal symptoms use the lowest effective dose for the shortest clinically appropriate duration, and that risk-benefit discussions be individualized [18].

Estrone in Men: A Brief Note

Male estrone tends to receive less clinical attention than estradiol, but it is clinically relevant in several situations. Men on testosterone replacement therapy (TRT) who also have high adiposity can aromatize large amounts of testosterone and androstenedione into both E2 and E1. Aromatase inhibitor co-prescription is sometimes used in these cases, though the 2018 American Urological Association guideline on testosterone deficiency cautions against routine co-administration because excess E1 and E2 suppression harms bone and sexual function [13]. Anastrozole 0.5 mg twice weekly is commonly used off-label, but monitoring both E1 and E2 every 8 to 12 weeks is advisable when this approach is chosen.

Companion Tests That Change the Interpretation

Estrone should never be interpreted in isolation. The following companion values shift the clinical meaning substantially [3, 4]:

| Test | Why It Matters With E1 | |---|---| | Estradiol (E2) | Defines the E2:E1 ratio; oral HT shifts ratio toward E1 | | FSH | High FSH plus low E1 confirms ovarian failure | | LH | Helps distinguish primary vs. Secondary hypogonadism | | SHBG | High SHBG reduces free estrogen fraction even when total E1 is normal | | Testosterone (total, free) | Androstenedione and testosterone are E1 precursors | | Fasting insulin / HOMA-IR | Insulin resistance upregulates aromatase in adipose tissue | | Prolactin | Hyperprolactinemia suppresses GnRH, lowering E1 secondarily | | DHEA-S | Elevated DHEA-S points to adrenal androgen excess as an E1 precursor |

The Endocrine Society recommends a full steroid hormone panel rather than single-analyte testing whenever an estrogen-related disorder is being evaluated [3].