Estradiol: definition and meaning
Estradiol, also written oestradiol or E2, is the strongest and most common form of estrogen during the reproductive years. It's made mainly by the growing follicles in the ovaries. Estradiol builds the uterine lining, triggers the LH surge that leads to ovulation, and affects bones, skin, brain and mood. Levels rise and fall across the menstrual cycle.
How it works in your cycle
| Phase | Estradiol level | What it does |
|---|---|---|
| Menstrual | Low | Lining sheds |
| Follicular | Rising fast | Rebuilds the lining, makes mucus slippery |
| Just before ovulation | Peak | Triggers the LH surge |
| Luteal | Second smaller rise, then falls | Works with progesterone; the fall precedes your period |
Estradiol and mood
Estradiol supports serotonin and dopamine signaling in the brain. Many people feel brighter, more energetic and more social as it climbs toward ovulation. The drop before your period, and the bigger, bumpier swings of perimenopause, are linked to irritability, low mood and poor sleep in people sensitive to these changes. See serotonin.
Why it matters
Estradiol is one of three main estrogens: estradiol (reproductive years), estrone (main type after menopause) and estriol (pregnancy). Doctors test E2 to check ovary function, monitor fertility treatment and IVF, and assess menopause. It's also the hormone in most modern HRT. Learn about the whole family on the estrogen page.
Ask a doctor about hormone tests if your periods stop, become very irregular, or you have hot flashes or other menopause symptoms before 40.
Frequently asked questions
What is the difference between estrogen and estradiol?
Estrogen is a group of hormones. Estradiol is the main one during your reproductive years, so the words are often used interchangeably.
When should estradiol be tested?
It depends on the question. For fertility checks it's often tested on cycle day 2 to 5, along with FSH.
Sources
This page is for information only and isn鈥檛 medical advice. If something worries you, please talk to a doctor.
Keep reading
Estrogen: definition and meaningEstrogen (oestrogen) is the hormone that builds the uterine lining and drives ovulation. How it rises and falls in your cycle and how it affects mood.Follicular phase: definition and meaningThe follicular phase runs from your period to ovulation, as follicles grow and estrogen rises. How long it lasts and how it tends to feel for mood and energy.Menstrual cycle hormones: a simple chart of what rises and fallsMenstrual cycle hormones explained simply: how estrogen, progesterone, LH and FSH rise and fall through each phase, and how they shape mood and energy.
Hormone replacement therapy (HRT): what it meansHormone replacement therapy (HRT) tops up estrogen, often with progestogen, to ease menopause symptoms. Types, benefits, risks and how mood can respond.Reproductive hormones: definition and meaningReproductive hormones are the chemical messengers that run your menstrual cycle. Meet GnRH, FSH, LH, estrogen and progesterone, and how they shape your mood.