Estrone (E1)

After menopause, estrogen production continues in fat and other tissues even as ovarian production falls. Estrone becomes the main circulating estrogen, and higher blood levels are consistently associated with higher breast cancer risk. Urinary estrone offers a different view of this biology: how the hormone is excreted.

This 24-hour urine measurement can describe estrogen excretion, but its use for predicting your cancer risk or choosing a hormone dose remains exploratory. Studies of blood estrone establish important biological relationships. They do not establish treatment targets for this urine result.

What This Urine Result Represents

The test measures estrone in urine collected over a full day using LC-MS/MS. This method separates compounds and identifies them by their mass and characteristic fragments. Results are reported in micrograms per gram of creatinine. Creatinine is a waste product used to adjust for urine concentration.

Your body attaches chemical groups to much of the estrone it sends into urine. These forms are called conjugates. Urinary estrogen analysis releases those groups before measuring estrone, so the result includes estrone excreted in conjugated forms.

Although the collection spans 24 hours, the reported value is a ratio to creatinine, not the total amount produced or excreted in a day. Production, conversion into other hormones, metabolism, and kidney handling all influence the result. It cannot identify how much estrogen came from your fat tissue or how much reached your breast, uterus, or brain.

Where Estrone Comes From

Estrone, estradiol, and estriol are three major natural estrogens. Estradiol is more potent and is the principal ovarian estrogen during the reproductive years. Estriol becomes especially abundant during pregnancy. Estrone is less potent than estradiol, but there is no single activity ratio that applies across every tissue and biological effect.

An enzyme called aromatase converts androstenedione into estrone. Androstenedione is a hormone made by the adrenal glands and reproductive organs. After menopause, conversion outside the ovaries becomes a major source of estrogen, including conversion in fat tissue. Men also make estrone through this process.

Tissues can convert estrone into estradiol and back again. Human uterine tissue studies show that local estrogen concentrations can differ substantially from blood concentrations. Neither blood nor urinary estrone directly measures estrogen activity inside a particular organ.

Age, Menopause, and Body Fat

Studies measuring serum estrone by LC-MS/MS show low concentrations in childhood, increases around puberty, and variation across the menstrual cycle. After menopause, estradiol falls more sharply and estrone generally exceeds it in circulation. These blood patterns provide biological context, not numerical targets for urine testing.

Body fat is an important influence. In a study of more than 4,000 postmenopausal women, women with obesity had substantially higher average serum estrone than leaner women. BMI was the strongest predictor among the characteristics examined, but all measured characteristics together explained only a minority of the variation. Your weight cannot reliably predict your individual result.

Breast Cancer Risk

Higher naturally occurring estrogen exposure is associated with higher breast cancer risk after menopause. The evidence is strongest for circulating hormones. Urine studies support investigating estrogen excretion and metabolism, but the collection method and the hormones being compared matter.

The Chinese urine study also found lower risk among women with a greater proportion of estrogen broken down through the 2-hydroxylation pathway. Those associations weakened and were no longer statistically significant after accounting for the combined estrone and estradiol level. The findings do not establish a protective urine ratio or show that changing the ratio prevents cancer.

These studies establish associations across groups. They have not validated this 24-hour urine result as a personal breast cancer risk score, a screening test, or a target whose reduction improves outcomes.

Uterine and Colorectal Cancer

Blood studies in postmenopausal women also connect higher estrogen exposure with endometrial cancer. This cancer starts in the lining of the uterus. Research from the Women's Health Initiative supports a role for conversion of adrenal hormones into estrogens, but it does not establish a urinary estrone test for detecting or predicting the disease.

For colorectal cancer, a prospective study and meta-analysis found no clear association with circulating estrone or estradiol. Estrogen findings from one cancer cannot be applied automatically to another.

Heart and Brain Research

In a study of 222 midlife women, higher serum estrone was associated with fewer white matter abnormalities on brain MRI, including after adjustment for cardiovascular risk factors. These abnormalities can reflect small-vessel injury. The study did not show that raising estrone prevents dementia or that urinary estrone measures brain protection.

A study of people with rheumatoid arthritis found that the relationship with coronary plaque differed by reproductive stage. Higher serum estrone was associated with less plaque before menopause, while both estrone and estradiol were associated with more plaque after menopause. This study used a blood antibody-based assay and does not establish a cardiovascular target for urinary estrone.

Liver Disease and PCOS

Liver disease can alter estrogen metabolism and clearance. An older study comparing 33 men with alcohol-related liver disease with 17 controls found higher blood and urinary estrogens in the liver disease group. It used older laboratory methods and measured several estrogens. An isolated urinary estrone result cannot diagnose liver disease or establish its severity.

Polycystic ovary syndrome, or PCOS, can involve irregular ovulation and excess androgen activity. In a small study of 74 women with PCOS and 31 controls, serum estrone and free testosterone distinguished the groups well. This was blood research. Urinary estrone has not been established as a diagnostic test for PCOS.

When Results Can Be Misleading

• Incomplete or mistimed collection: missed urine, an incorrect collection interval, poor storage, or inadequate mixing can change the result. Creatinine adjustment does not make an incomplete collection reliable.
• Menstrual timing and contamination: estrogen excretion changes across the cycle. Menstrual blood or other blood in the sample can also interfere with interpretation.
• Kidney function and creatinine: kidney disease can affect urinary hormone handling. Because the result is divided by creatinine, differences in creatinine excretion, including those related to muscle mass, can change the ratio independently of estrone production.
• Hormone products: prescribed hormones can change estrogen metabolism and excretion. The route and formulation matter, and the estrone result does not capture the effects of every estrogen-containing drug.
• Serious illness: studies of severe brain injury found altered blood estrone during acute illness. Those blood findings cannot be translated into a urinary risk estimate, and a collection during serious illness may not represent your usual physiology.
• Analytical limits: LC-MS/MS distinguishes compounds more specifically than many antibody-based assays, but sample preparation, other substances in urine, and the assay's measurement limits still affect accuracy. A result below a measurement limit does not mean that your body contains no estrone.