Estrone (E1)

What Estrone Measures

Estrone belongs to the same estrogen family as estradiol and estriol.^[1] What sets it apart is where it comes from. Estradiol is made mostly by growing follicles in the ovary, so it dominates the reproductive years. Estrone's main source sits outside the ovaries. Fat tissue carries aromatase, an enzyme that converts androgens into estrogens, and when aromatase acts on androstenedione the product is estrone.^[2]

The two hormones aren't sealed off from each other. Estradiol converts to estrone as the body metabolizes it, and the conversion runs in both directions.^[1]

How It's Measured

Estrone is measured from a blood draw, usually on an extended estrogen panel, and results are reported in pg/mL. Standard estrogen testing covers the three main forms, and labs can measure them in blood, urine, or saliva depending on the test.^[3]

Estrone also lends its name to E3G, or estrone-3-glucuronide, the urine marker that at-home fertility monitors read. Our estradiol entry covers the E3G story.

Why People Track Estrone

Estrone matters most in the years when estradiol matters least. After menopause, the ovaries stop producing estrogen, and estrogen synthesis shifts to peripheral sites like fat tissue.^[4] Fat tissue becomes the predominant source of estrogen production, and because its aromatase turns androstenedione into estrone, estrone tends to become the predominant estrogen in circulation.^[2] That's why estrone belongs to the menopause research story rather than to cycle tracking.

For what actually changes in the years after the final period, see our guide to postmenopause.

How Go Go Gaia Tracks Estrone

Go Go Gaia doesn't run lab tests itself, but you can upload results from any panel that includes Estrone (E1), and the app stores each value in pg/mL and charts it over time. Panels that also include estradiol or FSH land on the same timeline, so repeat tests stay in one place instead of scattered across PDFs.

What the Research Shows

A 2025 review in Frontiers in Endocrinology found fat tissue becomes the predominant source of estrogen production after menopause, with its aromatase converting androstenedione mainly into estrone.^[2]

A 2013 review in Trends in Molecular Medicine traced estrone's larger postmenopausal role to synthesis in adipose tissue from adrenal precursors, with the kidney, skin, and brain also contributing estrogen.^[5]

Work on estrogen sources shows the shift also changes how the hormone behaves: after menopause it's produced at extragonadal sites and acts locally in the tissue that made it, rather than traveling through blood as a classic ovarian signal.^[4]

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

What's the difference between estrone and estradiol?

Both are estrogens, but they come from different places at different life stages. Estradiol (E2) is made mostly by growing follicles in the ovary during the reproductive years. Estrone (E1) is made largely in peripheral tissue, mostly fat, from the androgen androstenedione. The two hormones also convert back and forth into each other.

Why is estrone the main estrogen after menopause?

After menopause, the ovaries stop producing estrogen, so ovarian estradiol falls away. Estrogen production shifts to peripheral sites, and fat tissue becomes the predominant source. Since aromatase in fat tissue converts androstenedione into estrone rather than estradiol, estrone tends to become the predominant circulating estrogen at the population level.

Is estrone related to the E3G urine marker?

By name, yes. E3G stands for estrone-3-glucuronide, a form the body excretes in urine. At-home fertility monitors read E3G as an indirect signal of estradiol, since estradiol converts to estrone as the body breaks it down. A serum estrone test is different: it measures the estrone hormone itself, directly from blood.