Oestrogen Explained: What It Is, What It Does, And How It Changes

What you need to know about oestrogen:

• Oestrogen is one of the body's main sex hormones, supporting reproductive health as well as bone, heart, brain and skin health throughout different stages of life.
• Oestrogen levels naturally change during puberty, the menstrual cycle, pregnancy, perimenopause and menopause, with fluctuations influencing how you feel.
• Signs of low or high oestrogen can vary from person to person and may include changes to mood, sleep, periods, bone health and overall wellbeing.
• Healthy lifestyle habits, including regular movement, a balanced diet, quality sleep and stress management, can help support your overall hormonal health and wellbeing.

Oestrogen is one of those hormones you've probably heard about, but you might not know exactly what it does.  

Oestrogen is often talked about in relation to periods and menopause, but its role in the body goes much further than that. This hormone helps support many everyday functions, from reproductive health and bone health to brain function and overall wellbeing¹. 

A balanced level of oestrogen across life is important for women's health, but its reach extends far past that, into the liver, heart, muscles, bones, and brain¹. Consider this your guide to what oestrogen is, where it's made, what it does, and what happens when levels rise and fall.

What is oestrogen?

Oestrogen is one of the body's main sex hormones and plays an important role in women's health throughout life. While it's best known for its role in the menstrual cycle and reproductive system, oestrogen also supports many other functions throughout the body, including bone health, brain function and heart health¹.

Oestrogen is part of the endocrine system, the network of glands that produces hormones to help regulate different processes throughout the body. It belongs to a group of hormones called steroid hormones and acts as a chemical messenger, helping different organs and tissues communicate with one another².

Although oestrogen is often described as a "female hormone", it's produced by both females and males. In females, however, it plays a particularly important role in puberty, the menstrual cycle, fertility, pregnancy and bone development².

Oestrogen function extends well beyond reproductive health. It helps regulate the menstrual cycle, supports bones, contributes to healthy cholesterol levels and influences the brain, heart, skin and bladder³.

The three types of oestrogen

There are three main types of oestrogen, and each is most active at different stages of life:

• Oestradiol (E2): The main form of oestrogen during the reproductive years.
• Oestriol (E3): Produced in large amounts by the placenta during pregnancy.
• Oestrone (E1): The main form of oestrogen after menopause¹⁶.

Although each type has a different role, they all belong to the same family of hormones and work together to support your health at different stages of life.

Where is oestrogen produced?

The main source of oestrogen is your ovaries, specifically the follicles and the corpus luteum (the structure left behind after an egg is released each cycle). 

Smaller amounts of oestrogen are also produced by other parts of the body, including the adrenal glands, adipose tissue, and during pregnancy, the placenta. Some organs like the brain, skin, heart and liver can also produce small amounts of oestrogen for local use⁴.

As you move through different stages of life, where oestrogen is produced changes too. After menopause, the ovaries produce much less oestrogen, and adipose tissue becomes the body's main source of this hormone⁴.

Oestrogen is made from cholesterol through a series of chemical reactions involving an enzyme called aromatase. There are three main forms of oestrogen: oestradiol, oestrone and oestriol, with each playing a different role at different stages of life⁴.

What does oestrogen do in the body?

The function of oestrogen extends far beyond reproductive health. While it's best known for its role in the menstrual cycle, oestrogen also helps support the health of your bones, brain, heart, skin and other tissues throughout the body⁵.

Because oestrogen is involved in so many different processes, it's normal for changing hormone levels to influence how you feel at different stages of life.

Here are some of the key ways oestrogen supports your body.

Reproductive system

Oestrogen plays an important role in reproductive health. It helps regulate the menstrual cycle, supports the growth of the uterine lining, influences cervical mucus, and contributes to the development and release of an egg during ovulation⁵.

Bone health

Oestrogen helps support bone health by slowing the natural process of bone breakdown⁵. As oestrogen levels decline after menopause, bone loss can happen more quickly, which is why maintaining bone health becomes increasingly important during this stage of life. 

Heart health

Oestrogen also supports cardiovascular health. It helps maintain healthy cholesterol levels and supports the normal function of blood vessels⁵. As oestrogen levels decline after menopause, this protective effect becomes less pronounced, contributing to changes in cardiovascular health over time. 

Brain and mood

Oestrogen interacts with several brain chemicals involved in mood, memory, sleep and the body's response to stress, including serotonin, dopamine and noradrenaline⁵. This may help explain why changing hormone levels during life stages such as perimenopause can influence mood, concentration or sleep for some people. 

Skin and hair

Oestrogen helps support healthy skin by contributing to collagen production, skin hydration and elasticity. It also plays a role in the hair growth cycle⁶. As oestrogen levels decline with age, many people notice gradual changes to their skin and hair, including reduced skin elasticity⁶. 

What are normal oestrogen levels?

Oestrogen levels naturally change throughout life and even across a single menstrual cycle. That means there's no single "normal" oestrogen level that applies to everyone. Your age, stage of life, and where you are in your menstrual cycle all influence how much oestrogen your body produces⁷.

During the reproductive years, oestradiol, the main form of oestrogen, typically rises as you approach ovulation before falling again later in the cycle. However, the exact levels can vary, both throughout the month and between individuals⁷.

To give you an idea of how oestrogen levels change across the menstrual cycle, typical reference ranges (measured in pmol/L) include⁷.

If you have questions about your hormone levels or menstrual cycle, speak with your healthcare professional8.

Signs of low oestrogen

Oestrogen deficiency symptoms can vary depending on your age, stage of life and the underlying cause of lower hormone levels. Common signs may include hot flushes, vaginal dryness, mood changes, disrupted sleep, difficulty concentrating, joint discomfort and reduced bone density^{9 10}.

These changes are most commonly associated with perimenopause and menopause, when oestrogen levels naturally decline. However, lower oestrogen levels can also occur at other stages of life for a range of reasons⁹.

Research suggests that sleep disturbance, joint discomfort, muscle aches and changes in mood are among the symptoms commonly reported by people with lower oestrogen levels¹¹. 

Signs of high oestrogen

Higher oestrogen levels may be associated with symptoms such as heavy or irregular periods, bloating, breast tenderness, mood changes and headaches¹². However, these symptoms can have many possible causes and don't necessarily mean your oestrogen levels are high.

You may also come across the term "oestrogen dominance", which is sometimes used to describe a situation where oestrogen levels are higher relative to progesterone. Some healthcare professionals use this term when discussing hormonal balance, but symptoms should always be assessed in the context of your overall health and menstrual cycle¹³.

How do oestrogen levels change over time?

Oestrogen levels naturally change throughout life. From puberty to menopause, it's normal for hormone levels to rise and fall at different stages, supporting your body's changing needs over time¹⁴.

Here's what those changes typically look like:

• Puberty: Oestrogen levels begin to rise, supporting sexual development and the start of the menstrual cycle.
• Reproductive years: Oestrogen levels naturally fluctuate throughout each menstrual cycle, rising towards ovulation before falling again.
• Pregnancy: Oestrogen levels increase significantly to help support pregnancy.
• After birth: Oestrogen levels drop rapidly following childbirth.
• Perimenopause: Hormone levels become more variable, which can contribute to changes in the menstrual cycle and other symptoms.
• Menopause and beyond: Oestrogen levels remain lower than during the reproductive years as the ovaries produce much less oestrogen¹⁴.

These changes are a normal part of ageing, and everyone's experience will be different.

Supporting healthy oestrogen levels naturally

While oestrogen levels naturally change throughout life, healthy lifestyle habits can help support your overall hormonal health and wellbeing. Many of these are the same everyday habits that support your health more broadly¹⁵.

Some areas to focus on include:

• Managing stress. Finding healthy ways to manage stress may help support your overall wellbeing and hormonal health.
• Getting enough sleep. Quality sleep plays an important role in supporting hormone regulation, mood and recovery.
• Staying active. Regular physical activity supports overall health and can be an important part of a healthy lifestyle.
• Eating a balanced diet. A varied diet that includes plenty of whole foods, fibre and nutrient-rich ingredients helps support your overall health. Some people also choose to include foods naturally containing phytoestrogens as part of a balanced diet15.
• Looking after your health over time. As oestrogen production changes with age, maintaining your overall health through balanced nutrition, regular movement and routine healthcare can help support your wellbeing.

Every stage of life brings natural hormonal changes. Rather than trying to change those patterns, focus on habits that help you feel your best and support your health over the long term.

Oestrogen and your health

Oestrogen plays an important role in many functions throughout the body, from reproductive health and the menstrual cycle to bone, heart and brain health. As with all hormones, it's normal for oestrogen levels to change throughout life, and these changes are a natural part of ageing.

Understanding how oestrogen works can help you make sense of the changes your body goes through at different stages of life. While everyone's experience is different, recognising your own patterns can help you make informed decisions about your health and wellbeing.

If you have questions about your hormone levels or notice ongoing changes that concern you, speak with your healthcare professional. They can help determine whether further assessment or testing is appropriate.

Discover more articles on women’s health on the Swisse Wellness Hub. Explore articles like managing the symptoms of menopause and understanding the different stages of your menstrual cycle.

References:

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2. Bartkowiak-Wieczorek J, et al. The Dual Faces of Oestrogen: The Impact of Exogenous Oestrogen on the Physiological and Pathophysiological Functions of Tissues and Organs. Int J Mol Sci. 2024 Jul 26;25(15):8167. doi: 10.3390/ijms25158167. PMID: 39125736; PMCID: PMC11311417. 

3. Zhu J, Zhou Y, Jin B, Shu J. Role of estrogen in the regulation of central and peripheral energy homeostasis: from a menopausal perspective. Ther Adv Endocrinol Metab. 2023 Sep 15;14:20420188231199359. doi: 10.1177/20420188231199359. PMID: 37719789; PMCID: PMC10504839. 

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5. Prior, J. C. (2020). Women's reproductive system as balanced estradiol and progesterone actions — A revolutionary, paradigm-shifting concept in women's health. Drug Discovery Today: Disease Models, 32(Part B), 31–40. https://doi.org/10.1016/j.ddmod.2020.11.005 

6. Stevenson S, Thornton J. Effect of estrogens on skin aging and the potential role of SERMs. Clin Interv Aging. 2007;2(3):283-97. doi: 10.2147/cia.s798. PMID: 18044179; PMCID: PMC2685269. 

7. Sung, V. Y., et al. (2021). Extensive monitoring of the natural menstrual cycle using the serum biomarkers estradiol, luteinizing hormone and progesterone. PMC8042396. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8042396/ 

8. Hardy, C., et al. (2025). The range and variation in serum estradiol concentration in perimenopausal and postmenopausal women treated with transdermal estradiol. Menopause, PMC12147738. https://pmc.ncbi.nlm.nih.gov/articles/PMC12147738/ 

9. Bedell, S., Nachtigall, M., & Naftolin, F. (2014). Cognition, mood and sleep in menopausal transition: The role of menopause hormone therapy. PMC6843314. https://pmc.ncbi.nlm.nih.gov/articles/PMC6843314/ 

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11. Khadilkar, S. S., et al. (2022). Correlation of menopausal symptoms with serum estradiol: A study in urban Indian postmenopausal women. Journal of Obstetrics and Gynaecology of India. https://pmc.ncbi.nlm.nih.gov/articles/PMC9339428/ 

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13. Reed, B. G., & Carr, B. R. (2023). The normal menstrual cycle and the control of ovulation. In StatPearls. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK279054/ 

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