Why are both oestrogens measured together?

Measuring both reveals the balance between ovarian and peripheral oestrogen production. The estrone-to-estradiol ratio helps identify increased peripheral aromatisation in obesity, postmenopausal bleeding, or polycystic ovary syndrome, and guides hormone-replacement formulation.

Does the test require fasting?

No fasting is required, but documenting menstrual-cycle day or menopausal status is essential because estradiol fluctuates markedly across the cycle.

When in the menstrual cycle should the test be drawn?

Early follicular phase (days 2–5) is standard for baseline ovarian assessment; mid-luteal phase (days 19–23 of a 28-day cycle) is used to confirm ovulation when paired with progesterone. The clinical question determines timing.

Can oral contraceptives affect the result?

Yes. Oral contraceptives suppress endogenous production but the assay measures total circulating oestrogen, including the exogenous hormone. Oral routes elevate estrone more than transdermal due to first-pass liver metabolism.

What does a high estrone-to-estradiol ratio indicate?

An elevated ratio suggests increased peripheral aromatisation, seen in obesity, polycystic ovary syndrome, and postmenopausal states. It reflects oestrogen production outside the ovaries, predominantly in adipose tissue.

Are these oestrogens measured in men?

Yes. Men produce estradiol through peripheral aromatisation of testosterone. Elevated estradiol or an abnormal testosterone-to-estradiol ratio may explain gynaecomastia, and low estradiol in hypogonadal men can impair bone density.

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Estradiol and Estrone

Q: What is the difference between estradiol and estrone?

Estradiol is the most potent oestrogen and the dominant form during reproductive years, synthesised mainly by the ovaries. Estrone is a weaker oestrogen produced by peripheral aromatisation of androgens; it becomes the primary circulating oestrogen after menopause.

Q: How accurate are oestrogen assays at low concentrations?

Immunoassays can lack precision at postmenopausal or male concentrations; liquid chromatography-tandem mass spectrometry is preferred for accuracy in these ranges and to avoid cross-reactivity with other steroids.

The Estradiol and Estrone test measures the two principal circulating oestrogens, evaluating ovarian function, peripheral aromatisation, and oestrogen exposure. Estradiol is the dominant bioactive oestrogen premenopausally; estrone predominates postmenopausally via adipose conversion. Together they guide diagnosis of menstrual disorders, infertility, menopause, and hormone-replacement monitoring.

Biomarkers

Blood (serum)

Sample

2–3 business days

Turnaround

Fasting

What is the E2 + E1 test?

The Estradiol and Estrone test measures serum concentrations of the two principal circulating oestrogens, providing complementary information about ovarian function, peripheral aromatisation, and oestrogen exposure across the reproductive lifespan. Estradiol is the predominant bioactive oestrogen in premenopausal women and the primary target in fertility and menstrual-disorder evaluation, while estrone becomes more significant postmenopausally and in states of increased peripheral conversion. Ordering both analytes together is particularly valuable when the clinical picture suggests dissociation between ovarian and peripheral oestrogen production — for instance, in obesity-related anovulation, postmenopausal bleeding, or suspected aromatase-excess syndromes. The estrone-to-estradiol ratio offers insight into the source and metabolism of oestrogen, complementing gonadotrophin and androgen results to build a complete hormonal profile. Practitioners rely on this dual measurement to guide diagnosis, to tailor hormone-replacement therapy, and to monitor treatment response in both women and men.

What does the E2 + E1 test measure?

E2(Estradiol)

Range: Follicular 19–144 pg/mL; mid-cycle 64–357 pg/mL; luteal 56–214 pg/mL; postmenopausal <31 pg/mL; male 10–40 pg/mL. Highly cycle- and assay-dependent.Optimal: Functional practitioners sometimes target mid-follicular estradiol around 50–100 pg/mL for symptom optimisation during hormone therapy, though these thresholds are not universally validated.pg/mL / pmol/L

Estradiol is the predominant and most potent oestrogen during reproductive years, synthesised primarily by ovarian granulosa cells under FSH and LH control via aromatisation of testosterone. In men, peripheral aromatisation of testosterone accounts for most circulating estradiol. The hormone acts through oestrogen receptors alpha and beta to regulate the menstrual cycle, support endometrial proliferation, maintain bone density, modulate lipid metabolism, and influence mood and cognition. Estradiol exhibits marked cyclical variation in menstruating women, peaking just before ovulation and rising again in the luteal phase.

Estradiol measurement is central to the evaluation of menstrual irregularities, hypogonadism, infertility, and menopausal status. Levels guide ovulation induction, distinguish hypothalamic-pituitary from primary ovarian failure, and monitor hormone-replacement regimens. In men, estradiol may be assessed when gynaecomastia or aromatase-excess syndromes are suspected. Because values fluctuate throughout the cycle, interpretation demands knowledge of cycle day or menopausal status.

E1(Estrone)

Range: Follicular 37–138 pg/mL; mid-cycle 60–229 pg/mL; luteal 45–214 pg/mL; postmenopausal 11–95 pg/mL; male 10–60 pg/mL. Assay-specific.Optimal: No widely accepted optimal range; interpretation is context-dependent and influenced by body composition and aromatase activity.pg/mL / pmol/L

Estrone is a weaker oestrogen synthesised by ovarian and peripheral aromatisation of androstenedione, with adipose tissue and liver contributing substantially after menopause. It serves as a reservoir for estradiol via reversible conversion by 17-beta-hydroxysteroid dehydrogenase. Postmenopausally, estrone becomes the dominant circulating oestrogen, maintained by peripheral aromatisation in fat and muscle. The estrone-to-estradiol ratio shifts across reproductive life and can reflect the degree of peripheral aromatase activity.

Estrone measurement is less commonly ordered than estradiol but is useful in evaluating postmenopausal bleeding (where peripheral aromatisation may drive endometrial proliferation), androgen-secreting tumours that aromatise peripherally, and polycystic ovary syndrome, in which elevated estrone-to-estradiol ratios may be observed. The test adds diagnostic value when oestrogen exposure is suspected despite low estradiol, particularly in obesity or when assessing postmenopausal hormone-replacement formulations.

Why is the E2 + E1 test ordered?

Evaluation of irregular menses, amenorrhoea, or anovulation, interpreted with FSH, LH, and progesterone to distinguish hypothalamic, pituitary, and ovarian causes
Infertility work-up to confirm ovulation, assess ovarian reserve, and time intercourse or assisted-reproduction procedures
Investigation of suspected premature ovarian insufficiency or perimenopausal transition, where declining estradiol and rising gonadotrophins establish the diagnosis
Postmenopausal bleeding or unexplained endometrial proliferation, where elevated estrone from peripheral aromatisation may be implicated
Monitoring of hormone-replacement therapy to ensure physiological oestrogen levels and minimise adverse effects such as venous thromboembolism or breast stimulation
Assessment of gynaecomastia or hypogonadism in men, where elevated estradiol or an abnormal testosterone-to-estradiol ratio may point to aromatase excess or exogenous androgen use
Polycystic ovary syndrome evaluation, in which an elevated estrone-to-estradiol ratio reflects increased peripheral conversion and anovulatory cycles
Suspected oestrogen-secreting tumour (rare), where autonomous production causes inappropriately elevated oestrogen independent of gonadotrophin drive

Sample collection and turnaround

Sample type

Blood (serum)

Fasting required

Collection method

Venipuncture at patient service centre

Turnaround

2–3 business days

Collection notes

Phlebotomy via Quest; no special preparation. Document menstrual-cycle day (day 1 = first day of bleeding) or menopausal status and any exogenous hormone use. Early follicular-phase (days 2–5) sampling is conventional for baseline ovarian assessment; mid-luteal (day 19–23 of a 28-day cycle) confirms ovulation. Avoid collection during pregnancy.

Specimen requirements

Minimum 1 mL serum (gel separator acceptable). Separate from cells and freeze if not assayed within 48 hours. Note performing laboratory for serial comparability.

What can affect E2 + E1 results?

variableMenstrual-cycle phase

Estradiol fluctuates markedly across the cycle, peaking pre-ovulation and in the luteal phase; estrone shows similar but less pronounced variation. Cycle day must be documented for meaningful interpretation.

elevatesOral contraceptives and hormone-replacement therapy

Exogenous oestrogens suppress endogenous production via negative feedback but the assay measures total circulating oestrogen, including the administered hormone; oral routes elevate estrone more than transdermal due to first-pass hepatic conversion.

elevatesObesity and increased adipose tissue

Adipose aromatase converts androgens to oestrogens, raising estrone disproportionately and shifting the estrone-to-estradiol ratio; this peripheral production is gonadotrophin-independent.

elevatesPregnancy

Placental and ovarian production elevates both oestrogens by orders of magnitude; the test is not useful during pregnancy.

elevatesLiver disease and cirrhosis

Impaired hepatic clearance and increased sex-hormone-binding globulin raise total oestrogen levels; altered oestrogen metabolism may produce feminisation in men.

reducesAromatase inhibitors and selective oestrogen-receptor modulators

Aromatase inhibitors (letrozole, anastrozole) block peripheral conversion, lowering both oestrogens; SERMs (tamoxifen, raloxifene) do not alter circulating levels but modulate receptor signalling.

What do E2 + E1 results mean?

Elevated

In premenopausal women: mid-cycle surge (physiological), oestrogen-secreting ovarian tumour (rare), or exogenous hormone use. Postmenopausally: peripheral aromatisation in obesity, exogenous therapy, or ovarian/adrenal androgen-secreting tumour with peripheral conversion. In men: aromatase excess (congenital or obesity-related), exogenous testosterone with aromatisation, liver disease, or testicular/adrenal tumour.

Normal

A mid-follicular or luteal-phase estradiol in the reference range supports normal ovarian function if the cycle is regular and ovulatory; postmenopausal values below 31 pg/mL confirm oestrogen deficiency. Normal estrone with low estradiol postmenopausally reflects residual peripheral aromatisation.

Reduced

In premenopausal women: primary ovarian insufficiency, hypothalamic amenorrhoea (functional hypothalamic suppression from stress, low weight, or excessive exercise), hypopituitarism, Turner syndrome, or recent menopause. In men: primary or secondary hypogonadism with low testosterone substrate for aromatisation. Markedly low estradiol in either sex may impair bone density and lipid metabolism.

Note: Cycle phase, menopausal status, and exogenous hormone use must be documented. A single random value can be misleading; serial measurements or correlation with LH surge may be needed in fertility contexts. The estrone-to-estradiol ratio is most informative when peripheral versus ovarian sources are in question. Assay interference can occur with cross-reacting steroids or heterophile antibodies; liquid chromatography-tandem mass spectrometry is preferred for accuracy at low concentrations.

Frequently asked questions

Estradiol is the most potent oestrogen and the dominant form during reproductive years, synthesised mainly by the ovaries. Estrone is a weaker oestrogen produced by peripheral aromatisation of androgens; it becomes the primary circulating oestrogen after menopause.

How to access the E2 + E1 test

The E2 + E1 reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

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About this page

Published: October 7, 2026

Last reviewed: October 7, 2026

References:

ACOG Committee Opinion No. 698: Hormone therapy in primary ovarian insufficiency. Obstet Gynecol. (2017)
Endocrine Society clinical practice guideline: evaluation and treatment of adult growth hormone deficiency (oestrogen-metabolism section). (2019)
National Institute for Health and Care Excellence (NICE) guideline NG23: Menopause — diagnosis and management. (2015)
Santoro N, et al. The menopause transition: signs, symptoms, and management options. J Clin Endocrinol Metab. (2021)
Simpson ER. Sources of estrogen and their importance. J Steroid Biochem Mol Biol. (2003)

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.

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