Summary
Oestradiol (E2) is the most potent and important form of oestrogen. In women it regulates the menstrual cycle, supports fertility, maintains bone density, and protects cardiovascular and brain health. In men, smaller amounts (made by aromatisation of testosterone) are essential for bone health, libido, and fertility. Oestradiol levels vary dramatically across the menstrual cycle, so timing matters for interpretation.
In premenopausal women, oestradiol is produced mainly by the developing ovarian follicles. Levels are lowest during menstruation, rise to a peak just before ovulation, dip, then rise again in the luteal phase. This is why the day of the cycle on which the test is taken is essential for interpretation.
After menopause, ovarian oestradiol production falls dramatically, causing hot flushes, night sweats, vaginal dryness, mood changes, and accelerated bone loss. Oestradiol is measured to assess ovarian function, investigate fertility, monitor IVF, confirm menopause, and monitor hormone replacement therapy.
In men, oestradiol is produced by aromatisation of testosterone. Too little impairs bone health and libido; too much (often from obesity) causes gynaecomastia and can suppress testosterone.
What It Is
Oestradiol (17β-estradiol) is a C18 steroid and the most biologically active of the three human oestrogens (oestradiol, oestrone, oestriol). It is synthesised from androgens — testosterone and androstenedione — by the enzyme aromatase, found in the ovaries, testes, adipose tissue, brain, and bone.
Oestradiol acts via nuclear oestrogen receptors (ERα and ERβ) to regulate gene transcription across reproductive tissues, bone, the cardiovascular system, and the brain. It exerts negative and positive feedback on the hypothalamic-pituitary axis, controlling FSH and LH secretion.
Reference ranges vary by sex and, in women, cycle phase: follicular 70–500 pmol/L, mid-cycle peak 400–1500 pmol/L, luteal 200–800 pmol/L, postmenopausal < 130 pmol/L. Men: 40–160 pmol/L.
Functions
Menstrual cycle and fertility
Drives follicle development, the LH surge that triggers ovulation, and preparation of the uterine lining for implantation.
Bone density maintenance
Oestradiol inhibits bone resorption — its decline at menopause is the main cause of postmenopausal osteoporosis in women.
Mood and cognition
Modulates serotonin and other neurotransmitters; fluctuations contribute to PMS, perimenopausal mood changes, and cognitive symptoms.
Cardiovascular protection
Supports healthy blood vessel function and favourable lipid profiles — its loss after menopause increases cardiovascular risk in women.
Reference Ranges
Oestradiol (E2)
Measured in pmol/L| Status | Range (pmol/L) | Range (pg/mL) | What it means |
|---|---|---|---|
| Postmenopausal / low | < 130 | < 35 | Low oestradiol — consistent with menopause, ovarian failure, or hypothalamic suppression. |
| Follicular | 70–500 | 19–136 | Normal early/mid follicular phase range in cycling women. |
| Mid-cycle peak | 400–1500 | 109–409 | Pre-ovulatory peak — triggers the LH surge and ovulation. |
| High | > 1500 | > 409 | Very high — ovarian stimulation, oestrogen therapy, or (rarely) an oestrogen-producing tumour. |
Female reference ranges depend entirely on menstrual cycle phase, menopausal status, and pregnancy. Always record cycle day. Male ranges are much lower (40–160 pmol/L). Interpret with FSH, LH, and clinical context.
Symptoms of Imbalance
Oestradiol symptoms differ by sex and by whether levels are too low or too high.
- Hot flushes and night sweats
- Vaginal dryness and discomfort
- Irregular or absent periods
- Low mood, anxiety, and irritability
- Reduced libido
- Bone loss and increased fracture risk
- Poor concentration and sleep disturbance
- Breast tenderness and swelling
- Fluid retention and bloating
- Heavy or irregular periods
- Mood swings
- Headaches
- Gynaecomastia in men
Causes of Imbalance
- Menopause and perimenopause
- Premature ovarian insufficiency
- Hypothalamic amenorrhoea (low body weight, excessive exercise, stress)
- Hyperprolactinaemia
- Pituitary dysfunction
- Anorexia nervosa
- Ovarian stimulation (IVF treatment)
- Oestrogen-containing medications and HRT
- Obesity (peripheral aromatisation in fat tissue)
- Oestrogen-secreting ovarian tumours (rare)
- Liver disease (reduced oestrogen clearance)
FAQs
It depends on the question. For a baseline assessment of ovarian reserve, oestradiol is measured on days 2–5 of the cycle, alongside FSH. To confirm ovulation or assess the luteal phase, it is tested later in the cycle. Because levels change dramatically across the month, always note your cycle day so the result can be interpreted correctly.
Low oestradiol most commonly reflects menopause or perimenopause, but it can also result from premature ovarian insufficiency, very low body weight, excessive exercise, stress, or pituitary problems. Symptoms include hot flushes, irregular periods, vaginal dryness, mood changes, and accelerated bone loss. The cause is clarified by measuring FSH and LH alongside oestradiol.
Although present in much smaller amounts, oestradiol is essential for male bone health, libido, and fertility. It is made by converting testosterone via aromatase. Too little oestradiol impairs bone density and sexual function, while too much — often driven by excess body fat — can cause gynaecomastia (breast tissue growth) and suppress testosterone. Oestradiol is therefore an important marker when monitoring testosterone replacement therapy.
Low oestradiol together with persistently high FSH supports a diagnosis of menopause, especially when periods have stopped for 12 months. However, in perimenopause, hormone levels fluctuate widely, so a single test can be misleading. Diagnosis is usually clinical, based on age and symptoms, with blood tests used as supporting evidence — particularly in younger women or uncertain cases.
References
- Burger HG, et al. A review of hormonal changes during the menopausal transition. Endocr Rev. 2007;28(6):e1–e26. View source
- Khosla S, et al. Estrogen and the skeleton. Trends Endocrinol Metab. 2012;23(11):576–581. View source
- Schulster M, et al. The role of estradiol in male reproductive function. Asian J Androl. 2016;18(3):435–440. View source