Estradiol (E2)
E2· also: Estradiol
Clinical Overview
Estradiol (E2) is the most potent and predominant form of estrogen in reproductive-age women, produced primarily by ovarian follicles. It drives secondary sexual development, menstrual cycle regulation, bone maintenance, and cardiovascular protection. Estradiol is also present in men, derived from testosterone conversion in adipose tissue.
Why This Test Matters
Estradiol is essential in fertility evaluation — measuring it alongside FSH on cycle day 2–3 helps assess ovarian reserve and IVF response potential. Low estradiol causes hot flashes, bone loss, and vaginal atrophy (menopause or premature ovarian insufficiency). High estradiol in women with regular cycles may not be clinically significant; in men, high estradiol from obesity or testosterone aromatization causes gynecomastia and reproductive dysfunction.
Reference RangesWHO/IFCC standards
| Age Group | Sex | Reference Range | Unit | Notes |
|---|---|---|---|---|
| Adults (18–64) | Female | 30 – 400 | pg/mL | Follicular phase |
| Adults (18–64) | Female | 0 – 30 | pg/mL | Post-menopause |
| Adults (18–64) | Male | 10 – 50 | pg/mL | — |
Also reported in: pmol/L.
What Causes Abnormal Results?
High E2 Causes
- Ovarian follicular cysts
- Ovarian stimulation during IVF
- Obesity (peripheral aromatization of testosterone to estradiol)
- Estrogen-secreting ovarian tumors
- Cirrhosis (impaired estrogen metabolism)
- Exogenous estrogen therapy
- In men: gynecomastia workup
Low E2 Causes
- Menopause (natural or surgical)
- Premature ovarian insufficiency (POI)
- Hypothalamic amenorrhea (exercise, eating disorders, stress)
- Hypopituitarism
- Turner syndrome
- Hypogonadotropic hypogonadism
Signs & Symptoms to Watch For
How to Prepare for This Test
In women, document the day of the menstrual cycle when the test is drawn — values vary markedly throughout the cycle. No fasting required.
Factors That Can Affect Results
- Cycle phase (estradiol peaks dramatically at ovulation)
- Exogenous estrogen (oral contraceptives, HRT)
- Biotin supplements (can interfere with immunoassay)
- Obesity (higher baseline estradiol from peripheral aromatization)
Related Topics
Frequently Asked Questions
What estradiol level indicates menopause?
In post-menopausal women, estradiol is typically below 30 pg/mL. A high FSH (>40 mIU/mL) combined with low estradiol (<30 pg/mL) and absent periods for 12 months confirms menopause in women over 45. In women under 40 with these findings, premature ovarian insufficiency should be considered.