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 proper development of sexual organs, maintenance of the skeletal system, regulation of the menstrual cycle, and maintenance of pregnancy.

A woman patient talking with her doctor
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During the menstrual cycle, estrogen levels fluctuate throughout the month. Secreted by the developing egg follicle, it 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 slightly neutralizing cervical secretions.

Toward the end of pregnancy, estrogen promotes the growth of milk ducts within the breasts and enhances the effect of prolactin, the hormone responsible for lactation.

While estrogen levels fluctuate normally throughout the menstrual cycle and throughout a lifetime, 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). PCOS 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.

PCOS is the most common cause of ovulatory infertility and it’s believed that estrogen dominance plays a part. 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 (dysfunctional or anovulatory uterine bleeding).

Heavy Menstrual Bleeding and PCOS

For women with menorrhagia (excessively prolonged or heavy menstruation), the administration of estrogen may be recommended to temporarily stop the bleeding and stabilize the endometrial lining. Synthetic estrogen is the main hormone found in birth control pills.

Alternatively, progestins may be administered orally to try to achieve a controlled bleeding episode. 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

While high estrogen levels along with a lack of progesterone is a major factor 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, buying “paraben-free” instead.
  • In addition, eating a diet rich in antioxidants can also help to protect your estrogen receptors from environmental damage.​
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  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. Rutkowska AZ, Diamanti-kandarakis E. Polycystic ovary syndrome and environmental toxins. Fertil Steril. 2016;106(4):948-58.

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