Hormonal Health Hormones Explained
Oestrogen

Oestrogen.
The Master Hormone.

The primary female sex hormone that drives your menstrual cycle, protects your bones, supports your heart and shapes how you feel every day.

Primary female sex hormone
Produced mainly by the ovaries
Regulates the menstrual cycle
Protects bone & heart health
3 main types: E1, E2 & E3
Declines during perimenopause
Hormones Explained Oestrogen Progesterone Testosterone Cortisol Insulin Thyroid Hormones Hormone Interactions

What Is Oestrogen?

Oestrogen is the primary female sex hormone — but it is not a single compound. It is a family of closely related hormones, of which three are clinically important: oestradiol (E2), oestrone (E1) and oestriol (E3). During the reproductive years, oestradiol dominates and drives the monthly menstrual cycle, prepares the uterus for pregnancy, maintains bone density, supports cardiovascular and brain health, and keeps vaginal and urinary tissues healthy. Oestrogen is produced primarily by the ovaries, with smaller contributions from the adrenal glands and fat tissue — and its influence reaches virtually every organ system in the body.

The Three Types of Oestrogen

What each form does, when it dominates, and what happens when levels go wrong

Form Too Low Too High
Oestradiol (E2) Hot flushes, bone loss, vaginal dryness, mood changes Breast tenderness, heavy periods, fibroids, bloating
Oestrone (E1) Less clinically significant in isolation Linked to oestrogen dominance when E2 is low but E1 is elevated
Oestriol (E3) Not clinically significant outside of pregnancy Not a concern at physiological levels

Oestrogen Dominance vs Oestrogen Deficiency

Oestrogen imbalance shows up in two opposite ways — too much relative to progesterone, or too little overall. Both cause significant symptoms and are frequently misdiagnosed or overlooked in standard medical care.

Oestrogen Dominance Too much / imbalanced

Oestrogen is high relative to progesterone — or oestrogen metabolises down harmful pathways. Causes: chronic stress (depletes progesterone), excess body fat, xenoestrogen exposure, perimenopause. Symptoms: heavy periods, breast tenderness, bloating, mood swings, fibroids, endometriosis.

Oestrogen Deficiency Too little

Low oestradiol from menopause, POI, hypothalamic amenorrhoea or surgical removal of ovaries. Symptoms: hot flushes, night sweats, vaginal dryness, painful sex, brain fog, joint pain, accelerated bone loss, mood changes, recurrent UTIs.

Premature Ovarian Insufficiency (POI) Medical condition

Loss of normal ovarian function before age 40 — affects 1% of women. Causes: autoimmune, genetic, iatrogenic. Requires prompt HRT for bone and cardiovascular protection.

Hypothalamic Amenorrhoea Functional pattern

Loss of periods and oestrogen production due to undereating, overtraining or severe stress. The brain shuts down reproduction to conserve energy — GnRH signalling is suppressed.

Oestrogen Metabolism: Why HOW You Clear It Matters

Oestrogen is metabolised in the liver and gut through several pathways — and which pathway predominates significantly affects breast cancer risk and overall hormonal health. This is why oestrogen metabolite testing (via DUTCH panel) is increasingly used in functional medicine.

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2-OH pathway

The 'safe' pathway — produces weak, non-proliferative oestrogen metabolites. Favoured by cruciferous vegetables, DIM, I3C and fibre.

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4-OH pathway

Produces genotoxic metabolites linked to DNA damage and elevated breast cancer risk. Supported by antioxidants and methylation nutrients (B12, folate, B6).

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16-OH pathway

Produces proliferative metabolites — promotes cell growth. Elevated in obesity and poor metabolic health. Cruciferous vegetables help shift away from this pathway.

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Oestrogen and Women's Health: What You Need to Know

Oestrogen is one of the most important hormones in the female body, yet many women know surprisingly little about what it actually does, how it changes across their lifetime, and what happens when levels fall too low or become disproportionately high. Understanding oestrogen is one of the most empowering steps a woman can take for her health.

Produced primarily by the ovaries, oestrogen is not a single hormone but a family of closely related hormones — oestradiol (E2), oestrone (E1) and oestriol (E3). During the reproductive years, oestradiol is the dominant form and the most biologically active. It drives the monthly menstrual cycle, triggering the growth and release of eggs, preparing the uterine lining for potential pregnancy, and regulating the hormonal feedback loop between the brain and the ovaries. Without adequate oestradiol, the menstrual cycle cannot function normally.

Beyond reproduction, oestrogen plays a critical protective role throughout the body. It keeps bones strong by slowing the activity of osteoclasts — the cells responsible for breaking down bone tissue. This is why women experience a dramatic acceleration in bone loss in the years following menopause, when oestrogen levels drop significantly. Without intervention, this bone loss can lead to osteopenia and ultimately osteoporosis, dramatically increasing the risk of fractures.

Oestrogen also supports cardiovascular health by maintaining the flexibility of blood vessel walls, supporting healthy cholesterol ratios — raising HDL (good cholesterol) and lowering LDL (bad cholesterol) — and reducing inflammation. Research consistently shows that women’s rates of cardiovascular disease increase markedly after menopause, reflecting the loss of oestrogen’s protective cardiovascular effects.

For South African women, access to oestrogen testing and treatment through both the public and private healthcare systems is available, though navigating the options can be confusing. Whether you are experiencing symptoms of low oestrogen, concerned about oestrogen dominance, or exploring your options around HRT, speaking with an HPCSA-registered gynaecologist or endocrinologist is the most important first step. HealthLab’s professional directory can help you find the right specialist in your area.