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Oestrogen is a female sex hormone that has many roles in the body, from controlling puberty to strengthening bones. Having too much or too little oestrogen can cause a range of different medical conditions.

What is oestrogen?

Oestrogen is one of the main female sex hormones. While both women and men produce oestrogen, it plays a bigger role in women’s bodies.

Oestrogen is produced by your hormonal (endocrine) system and moves through the bloodstream. In the female body, oestrogen is needed for:

Oestrogen also affects your brain, heart and skin.

How oestrogen levels change

Your oestrogen levels change according to where you are in your menstrual cycle, and also your stage of life. Oestrogen levels are highest in the middle of your cycle, and lowest during your period. At menopause, your oestrogen levels begin to fall.

There are 3 types of oestrogen in women, produced at different phases of a woman’s life:

  • Oestradiol is produced in women of childbearing age, mostly by the ovaries.
  • Oestriol is the main oestrogen produced during pregnancy, mostly in the placenta.
  • Oestrone, produced by the adrenal glands and fatty tissue, is the only type of oestrogen produced after menopause.

Oestrogen in medicines

Oestrogen is used in some medicines, including some contraceptives and menopause medications.

In Australia, the combined oral contraceptive pill (‘the pill’) contains a synthetic version of oestrogen. Another type of contraception, the vaginal ring, also contains oestrogen. These contraceptives work mainly by preventing the release of eggs from the ovaries.

If you are having problems with menopause symptoms, such as hot flushes and mood swings, you may choose to go on hormone replacement therapy (HRT). HRT includes oestrogen taken in the form of a tablet, gel or skin patch, and can be very effective in easing menopausal symptoms.

Common conditions linked with oestrogen

Oestrogen affects many parts of the body, and can cause problems when it is off balance.

Having too much oestrogen can lead to minor problems such as acne and constipation, or more serious conditions such as breast cancer. Having too little oestrogen can cause problems such as poor bone growth and menopausal symptoms.

Some of the common medical conditions linked to oestrogen:

  • Adenomyosis – when cells that normally line the inside of the uterus (womb) also grow inside its muscular walls. Because it needs oestrogen to grow, adenomyosis usually goes away after menopause.
  • Fibroids – lumps of muscle tissue inside the uterus. Fibroids are stimulated to grow by hormones and tend to go away after menopause.
  • Osteoporosis – a condition where your bones become fragile and more easily broken. Because oestrogen helps with bone strength, women are more at risk after menopause.
  • Vaginal dryness – falling oestrogen at menopause can cause the vagina to become dry and thin, causing discomfort and sometimes leading to other problems.

Treatment is available for these conditions, so see your doctor if you have concerns. You can also use Healthdirect’s Symptom Checker.

Oestrogen and breast cancer

The causes of breast cancer are complex, involving many factors. However, it is known that oestrogen can help breast cancer cells grow.

Women who have been exposed to more oestrogen – for example, because they reached puberty early or went through menopause late – have an increased risk of breast cancer. Women who reach menopause at the normal age, but whose bodies have naturally high concentrations of oestrogen, also have an increased risk.

Oestrogen taken in the form of combined hormone-based medicines (that contains both oestrogen and progestogen), including combined HRT and the pill, can lead to an increased risk of breast cancer too.

Often, however, these risks are small, so talk to your doctor if you are concerned about breast cancer. The risk is also reduced if you stop using these medicines.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: February 2020

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