What does oestrogen do

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Last updated: April 4, 2026

Quick Answer: Oestrogen is a group of hormones, primarily female sex hormones, that play a crucial role in the development and regulation of the female reproductive system and secondary sex characteristics. It also influences various other bodily functions, including bone health, mood, and cardiovascular health.

Key Facts

Oestrogen is a key hormone in female sexual development, leading to the maturation of reproductive organs and the development of secondary sex characteristics like breast growth and hip widening.
It regulates the menstrual cycle, preparing the uterus for potential pregnancy each month.
Oestrogen is vital for maintaining bone density, helping to prevent osteoporosis.
It plays a role in cardiovascular health by helping to keep blood vessels flexible.
Oestrogen levels fluctuate throughout a woman's life, with significant changes occurring during puberty, pregnancy, and menopause.

What is Oestrogen?

Oestrogen, also spelled estrogen, is a group of steroid hormones that are the primary female sex hormones. While most commonly associated with females, males also produce oestrogen, albeit in much smaller quantities. The main types of oestrogen found in humans are oestradiol, oestriol, and oestrone. Oestradiol is the most potent and abundant form during reproductive years.

Functions of Oestrogen

Oestrogen has a wide range of functions throughout the body, impacting numerous systems:

Reproductive Health and Development:

This is perhaps the most well-known role of oestrogen. During puberty, rising oestrogen levels are responsible for:

The development of primary sexual characteristics, including the growth and maturation of the ovaries, uterus, fallopian tubes, and vagina.
The development of secondary sexual characteristics such as breast development, widening of the hips, and the growth of pubic and axillary hair.

Throughout a woman's reproductive life, oestrogen is central to regulating the menstrual cycle. It causes the thickening of the uterine lining (endometrium) in the first half of the cycle, preparing it to receive a fertilized egg. It also plays a role in ovulation.

Bone Health:

Oestrogen is crucial for maintaining bone density and strength in both men and women. It works by:

Inhibiting bone resorption (the breakdown of bone tissue).
Promoting the formation of new bone tissue.

This protective effect is why women are at a higher risk of osteoporosis after menopause, when oestrogen levels decline significantly.

Cardiovascular Health:

Oestrogen has beneficial effects on the cardiovascular system. It is thought to:

Help keep blood vessels flexible and dilated, promoting healthy blood flow.
Positively influence cholesterol levels by increasing HDL ('good') cholesterol and decreasing LDL ('bad') cholesterol.

The decline in oestrogen after menopause is believed to contribute to the increased risk of heart disease in older women.

Brain Function and Mood:

Oestrogen receptors are present in the brain, suggesting a role in cognitive function and mood regulation. Fluctuations in oestrogen levels, particularly during the menstrual cycle, perimenopause, and postpartum period, have been linked to mood changes, irritability, and even depression in some individuals.

Skin and Hair:

Oestrogen can influence skin elasticity and hydration, contributing to a more youthful appearance. It may also play a role in hair growth cycles.

Other Functions:

Oestrogen also affects:

Fat distribution, often leading to a more 'pear-shaped' body in women.
Energy metabolism.
The development and function of other organs.

Oestrogen Levels and Changes

Oestrogen levels are not constant; they change significantly throughout a person's life:

Childhood: Levels are low.
Puberty: Levels rise, initiating sexual development.
Reproductive Years: Levels fluctuate in a cyclical pattern with the menstrual cycle. They peak around ovulation and are lower during menstruation. Levels are also elevated during pregnancy.
Perimenopause and Menopause: Oestrogen production gradually declines, leading to symptoms like hot flashes, vaginal dryness, and mood swings. After menopause, oestrogen levels are significantly lower than during reproductive years.

Understanding the multifaceted roles of oestrogen is key to comprehending female physiology and the health changes that occur throughout a woman's life, particularly around reproductive milestones.