Estrogen Dominance in Women With PCOS

Estrogen is an important hormone produced by the ovaries and in small quantities by the adrenal glands. It's responsible for the development of female sex characteristics. Estrogen is required for the development of female sexual organs, maintenance of the skeletal system, regulation of the menstrual cycle, and maintenance of pregnancy.

A woman patient talking with her doctor
 David P. Hall / Getty Images

Estrogen levels normally fluctuate throughout the menstrual cycle and throughout a lifetime.

  • During the menstrual cycle, estrogen levels fluctuate throughout the month. Secreted by the developing egg follicle, this hormone aids in thickening the endometrium for ovulation and possible pregnancy.
  • Also one of the major hormones of pregnancy, estrogen supports the production of fluid in the reproductive tract that enhances the survival of sperm by modifying cervical secretions.
  • Toward the end of pregnancy, estrogen promotes the growth of milk ducts within the mother's breasts and enhances the effect of prolactin, the hormone responsible for lactation.

Some women experience a condition known as estrogen dominance, where they have higher than normal levels of estrogen.

Estrogen Dominance in Women With PCOS

High levels of estrogen are known as estrogen dominance and can occur in women with polycystic ovary syndrome (PCOS). This condition is a hormone imbalance that can cause irregular periods, unwanted hair growth, and acne. It is characterized by multiple fluid-filled, cyst-like sacs on the ovaries, although this does not have to be present for a diagnosis of this condition.

PCOS is the most common cause of ovulatory infertility and it’s believed that estrogen dominance plays a part, along with other hormonal imbalances, including elevated testosterone.

Lack of ovulation results in continuous high levels of estrogen and insufficient progesterone.

Unopposed by progesterone, constant estrogen exposure may cause the endometrium to become excessively thickened, which can lead to heavy and/or irregular bleeding or anovulatory uterine bleeding (periods without ovulation).

Heavy Menstrual Bleeding and PCOS

For women with menorrhagia (excessively prolonged or heavy menstruation), the administration of estrogen in combination with progesterone may be recommended to temporarily stop the bleeding and stabilize the endometrial lining. 

Synthetic estrogen is one of the main hormones found in birth control pills, which usually contain both estrogen and progestin (synthetic progesterone).

Alternatively, progestins alone may be administered orally to control bleeding. 

Low-dose oral contraceptive pills or intrauterine devices (IUD), such as Mirena (a levonorgestrel-releasing intrauterine system), are also options to reduce heavy bleeding.

In some cases, an endometrial ablation, a surgical procedure that removes most of the endometrial lining, is recommended.

Environmental Causes of Estrogen Dominance

Hormone dysfunction is a major factor in the estrogen dominance seen in women with PCOS. Environmental factors can also play a role. Chemicals in our environment, known as xenoestrogens, can mimic naturally occurring estrogen in our bodies and act as endocrine disruptors.

Some sources of endocrine disruptors include pesticides, Bisphenol A (BPA) and phthalates (found in plastic containers, water bottles, and paper receipts), and parabens (often found in skin and hair care products).

It is thought that BPA disrupts signaling pathways, perhaps by interfering with estrogen receptors. BPA levels have been shown in studies to be higher in women with PCOS.

To minimize your exposure to environmental disruptors, follow these tips:

  • Choose glass containers to heat and store food.
  • Drink beverages from glass bottles or those marked “BPA-free.”
  • Buy canned goods marked “BPA-free.”
  • Eat organic and hormone-free foods.
  • Wash hands well after handling paper receipts.
  • Check ingredients in skin and hair care products, and buy paraben-free products.
  • Eating a diet rich in antioxidants can also help to protect your estrogen receptors from environmental damage.​
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Delgado BJ, Lopez-Ojeda W. Estrogen. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Available from:

  2. Reed BG, Carr BR. The Normal Menstrual Cycle and the Control of Ovulation. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA):, Inc. Available from:

  3. Rasquin Leon LI, Mayrin JV. Polycystic Ovarian Disease (Stein-Leventhal Syndrome) In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Available from:

  4. Dennett CC, Simon J. The role of polycystic ovary syndrome in reproductive and metabolic health: overview and approaches for treatmentDiabetes Spectr. 2015;28(2):116–120. doi:10.2337/diaspect.28.2.116

  5. Hickey M, Higham J, Fraser IS. Progestogens versus oestrogens and progestogens for irregular uterine bleeding associated with anovulation. Cochrane Database Syst Rev. 2000;(2):CD001895.

  6. Maybin JA, Critchley HO. Medical management of heavy menstrual bleedingWomens Health (Lond). 2016;12(1):27–34. doi:10.2217/whe.15.100

  7. Villavicencio J, Allen RH. Unscheduled bleeding and contraceptive choice: increasing satisfaction and continuation ratesOpen Access J Contracept. 2016;7:43–52. doi:10.2147/OAJC.S85565

  8. De Leo V, Musacchio MC, Cappelli V, Massaro MG, Morgante G, Petraglia F. Genetic, hormonal and metabolic aspects of PCOS: an updateReprod Biol Endocrinol. 2016;14(1):38. doi:10.1186/s12958-016-0173-x

  9. Diamanti-Kandarakis E, Bourguignon JP, Giudice LC, et al. Endocrine-disrupting chemicals: an Endocrine Society scientific statementEndocr Rev. 2009;30(4):293–342. doi:10.1210/er.2009-0002

  10. Monneret C. What is an endocrine disruptor? C R Biol. 2017 Sep-Oct;340(9-10):403-405. doi:10.1016/j.crvi.2017.07.004

  11. Rutkowska AZ, Diamanti-kandarakis E. Polycystic ovary syndrome and environmental toxins. Fertil Steril. 2016;106(4):948-58.

Additional Reading

By Nicole Galan, RN
Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book."