Estrone (E1) Test · Dried Urine

After menopause, your ovaries largely stop making estrogen, but your body does not stop producing it. Fat tissue, skin, and other organs convert adrenal hormones into estrone, which then becomes the dominant estrogen circulating in your blood. Knowing your estrone level tells you how much of this background estrogen activity your body is generating, which is information a standard estradiol test usually cannot give you once you are past menopause.

This matters because estrogen exposure does not end at menopause. It shifts. Higher estrone reflects more peripheral conversion, often driven by body fat, and has been linked in research cohorts to hormone-sensitive cancers and to overall estrogen burden. Lower estrone reflects a quieter estrogen environment. Both have implications for breast health, bone health, and how you think about hormone therapy.

What Estrone Actually Is

E1 (estrone) is one of the three main estrogens your body makes, alongside E2 (estradiol) and E3 (estriol). Before menopause, the ovaries produce mostly estradiol, and estrone sits in the background. After menopause, the pattern flips. Estrone becomes the principal circulating estrogen, while estradiol drops below 15 picograms per milliliter (a unit measuring very small concentrations in blood) in most women.

Estrone is made mainly from androstenedione, a precursor hormone produced by the adrenal glands. An enzyme called aromatase, found in fat tissue, breast tissue, and other peripheral organs, converts androstenedione into estrone. Estrone can then be converted into estradiol, the more biologically active form. This is why estrone levels strongly predict estradiol levels in older women: in one study of 5,325 women aged 70 and older, estrone was detectable in nearly all participants while estradiol was below the detection limit in about two-thirds of them.

Why Estrone Matters After Menopause

In premenopausal women, ovarian estradiol drives most estrogen signaling, and a routine estradiol test gives a useful read. Once the ovaries quiet down, that test loses sensitivity. Many postmenopausal women have estradiol levels too low for standard assays to measure accurately, leaving a blind spot. Estrone fills that gap. Typical postmenopausal estrone values range from about 7 to 40 picograms per milliliter, and these levels are reliably measurable using modern mass spectrometry methods.

This makes estrone the better window into postmenopausal estrogen status. It reflects how active your peripheral estrogen production is, which is largely a function of how much fat tissue you carry and how active your aromatase enzymes are. In adult men, estrone is also often higher than or equal to estradiol, because men derive most of their estrogen from peripheral aromatization of androgens rather than from gonadal production.

Breast Cancer Risk

Higher circulating estrogens, including estrone, are implicated in breast cancer risk. In estrogen receptor positive breast cancer, estrone and its conjugated form estrone sulfate serve as important hormone sources for tumor cells. Breast tissue contains the enzymes needed to convert estrone sulfate back into estrone and then into estradiol, locally fueling cancer growth even when blood levels look modest.

Research has also found that the way your body metabolizes estrone matters. More extensive 2-hydroxylation, one of the routes by which estrone is broken down, has been associated with lower postmenopausal breast cancer risk in several cohorts. Less efficient methylation of 4-hydroxylation pathway products has been linked with higher risk. These patterns suggest that both how much estrone you make and how you process it shape your long-term risk.

Endometrial Cancer Risk

Postmenopausal women with elevated circulating estrogens, including estrone, have shown increased endometrial cancer risk in large prospective cohorts. The uterine lining is exquisitely sensitive to estrogen, and unopposed estrogen exposure (estrogen without progesterone) drives proliferation. In women with intact uteruses who are not taking progesterone, sustained higher estrone levels are part of the broader estrogenic picture that raises risk.

Body Fat and Estrogen Production

Fat tissue is not inert. It is one of your body's largest estrogen-producing organs after menopause. Higher BMI consistently tracks with higher estrone in postmenopausal women. In the MAP.3 breast cancer prevention trial of 4,068 postmenopausal women, women with a BMI below 25 had average estrone levels around 19 picograms per milliliter, while women with a BMI over 30 averaged around 31 picograms per milliliter, roughly 60% higher.

Visceral fat (the fat around your organs) is particularly active. It contains higher concentrations of estrone and the enzymes that convert it. This is one mechanism by which carrying extra weight, especially around the midsection, raises hormone-sensitive cancer risk after menopause. It is also why some women see meaningful drops in estrone after sustained weight loss.

Reference Ranges

Estrone is a Tier 2 marker. Published reference ranges exist from well-conducted studies, but cutpoints are not standardized across labs the way they are for cholesterol or HbA1c. The values below come from large LC-MS/MS studies, which use the most accurate measurement method. They are illustrative orientation, not universal targets. Your lab may report different units or slightly different ranges.

Compare your results within the same lab over time for the most meaningful trend. Different assays can produce different numbers for the same blood sample, so a value from one lab is not directly comparable to a value from another.

Why One Reading Is Not Enough

A single estrone measurement is a snapshot. Estrogen levels shift with body composition changes, medications, and aging. The most useful information comes from tracking your trend over time, not from agonizing over a single number. Establish a baseline. If you are starting hormone therapy, changing your body composition, or entering menopause, retest in 3 to 6 months to see how the trajectory is moving. Once you have a stable picture, annual monitoring is reasonable for most people focused on prevention.

Serial tracking also matters because estrone correlates strongly with estradiol in older women. Watching the trend gives you a more reliable read on your overall estrogen environment than any one reading. If estrone is rising over years without a clear explanation, that pattern deserves attention. If it is stable within your personal range, a single number that looks high or low is less alarming.

When Results Can Be Misleading

A few factors can distort a single reading or make interpretation harder:

• Assay differences: older immunoassays are less accurate at the low concentrations seen after menopause. Modern mass spectrometry methods (LC-MS/MS) are the standard and produce the most reliable numbers.
• Recent hormone therapy or oral contraceptives: combined oral contraceptives containing ethinyl estradiol can lower free urinary estrone while shifting how the body metabolizes it. Vaginal estriol at low doses does not appear to raise serum estrone meaningfully.
• Acute weight changes: rapid weight loss or gain shifts peripheral aromatization, which can move estrone before a new steady state is reached.
• Timing within the menstrual cycle: for premenopausal women, estrone varies across the cycle, so the timing of the draw matters for interpretation.

What to Do If Your Result Is Unexpected

If your estrone comes back higher than expected for your menopausal status, the practical next step is to look at the bigger hormonal picture. Order estradiol, sex hormone binding globulin (SHBG), and depending on your situation, testosterone and DHEA-S (dehydroepiandrosterone sulfate, an adrenal precursor hormone). These together let you see whether the elevation reflects increased peripheral conversion (often tied to body fat), exogenous hormone exposure, or a less common pattern that warrants a closer look with an endocrinologist.

If your estrone is low and you are postmenopausal, that is generally expected. If you are premenopausal and have low estrone alongside low estradiol, fatigue, irregular cycles, or fertility concerns, pair this result with FSH, LH, and AMH to assess ovarian function. A reproductive endocrinologist is the right person to involve. For anyone considering or already on hormone therapy, tracking estrone alongside estradiol gives a more complete picture of total estrogen exposure than estradiol alone.