Oestrogen (oestradiol, E2)

On this page

1. What is oestrogen?
2. Where is oestrogen produced?
3. Function of oestrogen
4. Oestrogen across the menstrual cycle
5. Normal oestradiol levels
6. Causes of high oestrogen and oestrogen dominance
7. Causes of low oestrogen
8. Xenoestrogens and phytoestrogens
9. When and how to test oestradiol
10. Oestrogen in traditional Chinese medicine
11. Acupuncture and oestrogen
12. Chinese herbal medicine and oestrogen
13. Diet, supplements and lifestyle
14. Related pages

1. What is oestrogen?

Oestrogens (also spelled estrogens) are a group of three steroid hormones — oestradiol (E2), oestrone (E1) and oestriol (E3). The most abundant and biologically active is oestradiol, often abbreviated to E2 or 17β-oestradiol. Oestradiol is the dominant oestrogen during the reproductive years; oestrone takes over after the menopause; and oestriol is produced in large amounts by the placenta during pregnancy.

Oestrogens are essential for female reproductive function — they build the uterine lining, produce cervical mucus, maintain libido, regulate the menstrual cycle and support bone, brain and cardiovascular health. They also have important roles in male physiology.

Reference ranges vary from country to country and between laboratories. Always interpret your own result against the reference range provided by the laboratory that performed your test.

2. Where is oestrogen produced?

The main site of oestradiol production is the granulosa cells of the developing ovarian follicle. Smaller amounts of oestrogens are produced in the adrenal glands, in adipose (fat) tissue (where androgens are converted to oestrogens by the enzyme aromatase), in the placenta during pregnancy and in the testes in men.

3. Function of oestrogen

Oestrogens have many functions, including:

1. Building and maintaining the uterine lining each cycle.
2. Producing fertile-quality cervical mucus around ovulation.
3. Maintaining vaginal lubrication and elasticity.
4. Supporting libido (alongside testosterone).
5. Triggering the LH surge and ovulation through positive feedback on the pituitary.
6. Maintaining bone density.
7. Supporting cardiovascular and cognitive function.
8. Regulating mood and skin quality.

4. Oestrogen across the menstrual cycle

Oestradiol levels vary dramatically across the menstrual cycle:

1. Early follicular phase (days 1–5): low — typically 100–200 pmol/L.
2. Late follicular phase (days 6–13): rising rapidly as the dominant follicle matures.
3. Pre-ovulatory peak (day 13–14): 800–1500 pmol/L — triggers the LH surge.
4. Mid-luteal phase (days 19–22): a smaller secondary peak from the corpus luteum, alongside high progesterone.
5. Late luteal phase: falling oestradiol and progesterone trigger menstruation.

5. Normal oestradiol levels

Typical reference ranges for oestradiol in the early follicular phase are approximately 45–850 pmol/L (or 12–230 pg/mL). Higher than 290 pmol/L (80 pg/mL) on day 2–3 is considered elevated and may artificially suppress FSH, masking diminished ovarian reserve. Reference ranges vary from country to country and between laboratories.

6. Causes of high oestrogen and oestrogen dominance

"Oestrogen dominance" describes a state in which oestrogen is high relative to progesterone, even when absolute oestrogen levels are within the reference range. Causes include:

1. Excess body fat — adipose tissue produces oestrogens via aromatase.
2. Anovulatory cycles — without ovulation there is no corpus luteum to produce progesterone, so oestrogen acts unopposed.
3. Liver dysfunction — the liver clears oestrogens from the body; impaired liver function leads to oestrogen build-up.
4. Exposure to xenoestrogens — synthetic oestrogen-mimicking chemicals from plastics, cosmetics, pesticides and household products.
5. Excessive phytoestrogen intake — soya products, especially in concentrated form.
6. Hormone replacement therapy or oral contraceptives.
7. Endometriosis, fibroids and PCOS — can both cause and be aggravated by high oestrogen.

7. Causes of low oestrogen

Low oestrogen is seen in:

1. Menopause and perimenopause.
2. Premature ovarian failure.
3. Hypothalamic amenorrhoea — caused by stress, low body fat or excessive exercise.
4. Hyperprolactinaemia.
5. Anorexia or chronic undereating.
6. Use of GnRH agonists or aromatase inhibitors.

8. Xenoestrogens and phytoestrogens

The modern environment exposes us to enormous quantities of oestrogen-mimicking chemicals — collectively called xenoestrogens. Sources include plastics (BPA, BPS, phthalates), pesticides, cosmetics (parabens, phthalates), household products and hormones in non-organic meat and dairy. The cumulative effect is to disturb the natural oestrogen balance, contributing to the rise of fertility problems, endometriosis, fibroids and oestrogen-related cancers. Reducing exposure is one of the most important fertility-supportive lifestyle changes.

Phytoestrogens are naturally occurring plant compounds with weak oestrogen-like activity. They include lignans (in flaxseed, sesame seeds), isoflavones (in soya, especially genistein) and coumestans (in clover, alfalfa). In small amounts these are generally beneficial; in large amounts (concentrated soya products, soya protein isolates, supplements) they can disrupt fertility.

9. When and how to test oestradiol

Oestradiol is usually measured on day 2 or 3 of the menstrual cycle alongside FSH, LH and prolactin. Oestradiol can also be measured at mid-cycle to confirm a pre-ovulatory peak, and in the mid-luteal phase alongside progesterone to assess corpus luteum function.

Reference ranges vary from country to country. Always interpret your own result against the laboratory's reference range and discuss it with your doctor.

10. Oestrogen in traditional Chinese medicine

In traditional Chinese medicine, oestrogen most closely corresponds to Kidney Yin and Blood — the cooling, nourishing, building substances that support the follicular phase of the menstrual cycle. Low oestrogen typically reflects Kidney Yin and Blood deficiency. High oestrogen, particularly with Liver Qi stagnation, often produces a pattern of Damp-Heat with Blood stasis — typical of endometriosis, fibroids and PMS.

11. Acupuncture and oestrogen

Research has shown that acupuncture can regulate oestrogen levels — increasing them where they are too low and reducing them where they are too high. Acupuncture works by acting on the hypothalamic-pituitary-ovarian axis and by improving liver function (in TCM terms, smoothing Liver Qi and supporting Kidney Yin and Blood).

12. Chinese herbal medicine and oestrogen

For low oestrogen, formulae that nourish Kidney Yin and Blood are used — such as Liu Wei Di Huang Wan, Zuo Gui Wan and Er Zhi Wan. For high oestrogen with Liver Qi stagnation, Xiao Yao San and its variants are first-line. Treatment is individualised after a full TCM assessment.

13. Diet, supplements and lifestyle

To support healthy oestrogen balance:

1. Reduce exposure to xenoestrogens — avoid plastics 3, 6 and 7; limit cosmetics; choose organic produce and meat where possible.
2. Limit concentrated soya products such as soya isolates, soya milk and tofu in excess. Whole organic edamame in moderation is fine.
3. Maintain a body fat percentage of 22–28% — both very low and very high body fat disturb oestrogen.
4. Eat plenty of cruciferous vegetables (broccoli, cauliflower, cabbage) — they support liver clearance of oestrogens.
5. Take 1 tablespoon of ground flaxseed daily — its lignans support healthy oestrogen metabolism.
6. Limit alcohol — alcohol impairs liver clearance of oestrogens.
7. Reduce psychological stress, which can increase oestrogen-related symptoms.

14. Related pages

• Fertility hormones directory
• Progesterone
• Follicle stimulating hormone (FSH)
• Luteinising hormone (LH)
• Anti-Müllerian hormone (AMH)
• Endometriosis
• Fibroids
• PCOS
• My Fertility Guide