Estradiol
Also called: estradiol level, E2 test
What it means
Estradiol (E2) is the main form of estrogen measured in a blood test. It plays a central role in protecting bone in both women and men, and doctors check it when bone loss seems unusual for someone's age or sex.
Low estradiol - whether from menopause, hormone therapy side effects, or low body weight - speeds up bone loss, so checking it helps explain why bones may be thinning faster than expected.
Estradiol is a type of estrogen, and it's the hormone most responsible for keeping your skeleton strong. In women, estradiol drops sharply at menopause, and that drop is the main reason bone loss speeds up in the years that follow. In men, estradiol is made by converting testosterone through an enzyme called aromatase, and some research suggests estradiol may play a larger role than testosterone in restraining bone breakdown in men as well.
An estradiol blood test (sometimes called an E2 test) measures how much of this hormone is circulating. It's used to help understand menopause status, investigate unexplained bone loss, or check hormone levels in men being treated with testosterone therapy or medications that block estrogen production, like aromatase inhibitors used in some breast cancer treatments. Low estradiol in either sex is linked to faster bone resorption (breakdown) because estrogen normally calms down the cells that dissolve bone and helps the body absorb calcium.
If your estradiol comes back low or your bone density is changing faster than expected, that's a conversation for your doctor, not something to self-treat. Decisions about hormone replacement therapy, aromatase inhibitor adjustments, or testosterone therapy involve weighing benefits and risks specific to your health history, and should always be made with your prescriber.
How sure is this?
Graded Strong Clinical Evidence: Supported by multiple well-designed clinical studies in humans. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
Estradiol is the main estrogen doctors check to explain unexpectedly fast bone loss.
Where this leads
WordLow estradiol often starts with menopause. Curious why the years around menopause speed up bone loss so much?
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Related words
Estrogen is a hormone that protects bone by keeping bone-removing cells in check. Falling estrogen, especially at…
Menopause is when your periods stop and estrogen levels drop sharply, which speeds up bone loss because the cells…
Testosterone is a male hormone that supports bone formation directly and indirectly, partly by being converted into…
Hormone replacement therapy (HRT) replaces oestrogen, often with a progestin, after menopause and has been shown to…
An aromatase inhibitor is a medication that blocks the enzyme aromatase, which the body uses to make estrogen. It's…
Estrogen deficiency is a drop in estrogen levels — from menopause, ovary removal, or other causes — that speeds up…
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
