What is oestrogen?

Oestrogen is one of the main female sex hormones. While both females and males produce oestrogen, it plays a more important role in the female body.

Oestrogen is part of the hormonal (endocrine) system.

In the female body, oestrogen is needed for:

• puberty and breast development
• the menstrual cycle
• fertility and pregnancy
• bone strength
• maintaining healthy cholesterol levels

Oestrogen also has other health benefits such as:

• helping with brain function
• protecting from heart disease
• protecting your skin from the effects of ageing
• helping with bladder control

How do oestrogen levels change over time?

Your oestrogen levels differ depending on where you are in your menstrual cycle and your stage of life. Oestrogen levels are highest in the middle of your cycle, before you ovulate.

Levels are lowest during your period. At menopause, your oestrogen levels fall and remain at a lower level.

There are 3 types of oestrogen found in females, produced at different phases of your life:

• oestradiol — the main type produced before menopause, mostly by your ovaries
• oestriol — the main type produced during pregnancy, mostly by the placenta
• oestrone — the main type produced after menopause, mainly by your adrenal glands and fatty tissue

What are some common health conditions linked with oestrogen?

There are some health conditions linked to oestrogen.

Too much oestrogen can increase your risk of some health conditions including:

• adenomyosis — This is when cells that normally line the inside of your uterus (womb) also grow inside its muscular walls. These cells need oestrogen to grow, therefore, adenomyosis usually goes away after menopause, when oestrogen levels are lower.
• fibroids (also called myomas) — These are lumps of muscle tissue that grow inside the wall of your uterus. It is suspected oestrogen and progesterone stimulate the growth of fibroids. They usually go away after menopause.
• blood clots and stroke
• gallstones

Not enough oestrogen can increase your risk of:

• osteoporosis — Your bones become fragile and may break more easily. Oestrogen helps to keep your bones strong. You are at a higher risk of osteoporosis after menopause because of lower oestrogen levels.
• symptoms of menopause — These include vaginal dryness, hot flushes, mood swings and sleep changes.

When should I see my doctor?

Speak to your doctor if you are concerned about any of the health conditions listed above, as treatments are available for many conditions.

Your doctor may refer you for a blood test to check your oestrogen levels.

How is oestrogen used in medicines?

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

Oestrogen in contraception

In Australia, the combined oral contraceptive pill ('the pill') and the vaginal ring contain an artificial version of oestrogen. These contraceptives work mainly by preventing the release of eggs from your ovaries.

Oestrogen in menopause hormone therapy (MHT) or hormone replacement therapy (HRT)

MHT for menopause symptoms

If you are struggling with your menopause symptoms, including hot flushes and mood swings, you can take menopause hormonal therapy (MHT). This is also known as hormone replacement therapy (HRT).

MHT includes oestrogen and can be taken in different forms. Oral tablets, topical gels or skin patches can be used to reduce menopausal symptoms. Creams, pessaries or tablets used vaginally can help relieve vaginal dryness.

MHT for bone health

Some people experience early menopause before 40 years of age due to some health conditions, cancer treatment or surgery to remove the ovaries.

If you go through early menopause, your doctor may recommend MHT or the oral contraceptive pill. MHT replaces the oestrogen your ovaries would normally produce and helps you keep the protective benefits of oestrogen.

Progesterone in MHT

If you are taking MHT and still have a uterus, your treatment should include progesterone together with oestrogen. High levels of oestrogen without progesterone can cause dangerous changes to the lining of your uterus. Progestogen is added to lower your risk of cancer of your uterus.

If your uterus has been removed (known as a hysterectomy), it is safe for you to take oestrogen by itself.

Does oestrogen cause breast cancer?

One of the many causes of breast cancer can be high levels of oestrogen in your body. This is because oestrogen can help breast cancer cells grow.

Oestrogen can increase your risk of breast cancer if:

• You have been exposed to higher than usual levels of oestrogen throughout your life. If you got your period at a very young age or went through menopause late, your body would have been producing oestrogen for longer amounts of time.
• You take medicines containing oestrogen, such as MHT or the oral contraceptive pill.

Medicines containing oestrogen only increase your risk of breast cancer by very small amounts.

However, there are a few important things to remember:

• Breast cancer is common and affects about 1 in 8 females. The added risk from taking MHT or the oral contraceptive pill is very small.
• To put it in perspective, for every 1000 females using MHT each year, there's one extra case of breast cancer.
• The risk increases the longer you take the medicine and goes down after you stop taking it.
• Medicines for MHT can also lower your risk of other health problems and relieve symptoms of menopause.

It is also important to know that MHT and oral contraceptives have other health benefits. They can lower your risk of other cancers, such as ovarian cancer. Every person's health is different. Your doctor can help you decide which medicines are right for you. Talk to your doctor if you are concerned about your risk of breast cancer.

Resources and support

• Pathology Tests Explained has more information about the role of oestrogen in your body.
• If you are going through menopause, the Australian Menopause Society factsheet explains 'What is Menopause Hormone Therapy (MHT) and is it safe?'
• The Royal Women's Hospital Melbourne has a fact sheet about Menopause Hormone Therapy.

Do you prefer to read in languages other than English?

Jean Hailes for Women's Health has a wide variety of fact sheets about women's health in a variety of community languages.

Looking for information for Aboriginal and/or Torres Strait Islander people?

Cancer Australia has a guide Aboriginal and Torres Strait Islander people and their families going through breast cancer.