RESEARCH STARTER

Estrogen

Estrogen is a class of hormones crucial for female reproductive and sexual development, with three primary types: estradiol, estriol, and estrone. These hormones are produced by females in varying amounts throughout different life stages, notably increasing during puberty and pregnancy, while declining after menopause. Estradiol, the most significant estrogen in reproductive-age women, is essential for the development of secondary sex characteristics, regulation of the menstrual cycle, and maintenance of bone health. Estriol serves a role during pregnancy and may alleviate menopause symptoms, while estrone is primarily associated with menopausal women and is linked to breast cancer risk. Although estrogen is predominantly recognized as a female hormone, males also produce it in smaller amounts, where it contributes to their overall health. Variations in estrogen levels can lead to various symptoms and conditions in both sexes, necessitating hormone management or replacement therapies in some cases. This complex hormone is also involved in psychological aspects, potentially influencing mood and emotional states. Understanding estrogen's multifaceted roles is essential for grasping its impact on health and development.

Full Article

Estrogen is a class of hormones that plays an important role in female reproductive and sexual development. The estrogen class includes three specific hormones with related functions: estradiol, estriol, and estrone. Women produce these substances in varying amounts throughout their lives, with average levels of some estrogens rising during reproductive age and others being more prevalent after menopause. Puberty and pregnancy also affect the average production levels of particular estrogen hormones. Although estrogen is considered a class of female sex hormones, males produce small amounts of estrogen, and studies have shown that it plays a relatively limited but significant set of functions in their overall health. The main purpose of estrogen hormones is to regulate the growth, maintenance, and repair of the elements of the female reproductive system. It also helps develop female secondary sex characteristics and supports other sexual and reproductive functions. The estrogen hormone estradiol plays a key role in bone health. Scientists have identified several estrogen receptors, including estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G protein–coupled estrogen receptor (GPER), in different tissues. These receptors help explain why estrogen affects the reproductive system, bones, the brain, and other organs in different ways.

Background

Hormones are chemicals that are produced by the human body. They are commonly described as “chemical messengers,” meaning that their production and presence in specific quantities trigger a natural reaction or tell the body to do something specific. For example, production of the hormone melatonin rises after nightfall, signaling to the body that the time to go to sleep is approaching. Melatonin plays a major role in regulating the sleep-waking cycle. Its presence prompts a series of physiological and psychological responses, including drowsiness. During daylight hours, melatonin levels decline, and the responses it triggers recede.

Some hormones are found in roughly equal quantities in males and females, while others are usually found in far greater amounts in one sex or the other. Although males naturally produce estrogen in small quantities, it is strongly associated with the female body due to its origins in the ovaries and role in the female aspects of reproduction and sexuality. The male equivalent of estrogen is androgen. Androgen hormones are mainly produced in the testicles. Like estrogen in females, average androgen levels are much higher in males than in females. Like estrogen in males, females also naturally produce small quantities of androgen hormones, and they play a limited but significant role in female health.

Under normal circumstances, the body releases estrogen hormones in short pulses, and the amount of estrogen active in the body at any given time differs from hour to hour throughout the day. In both males and females, abnormally high or abnormally low estrogen levels can cause symptoms and medical conditions. Treatments known as hormone management or hormone replacement therapy may be necessary to bring symptoms and conditions under control.

Overview

Estradiol is the major estrogen hormone found in females of reproductive age. Its production and secretion begin when ovarian follicles develop and become active, a process that usually accelerates with the onset of puberty. In females, estradiol is responsible for breast development and maintenance, and other physiological changes that occur during puberty and the period after puberty, including expansion of the hips, curvature of the lower back, and fat distribution patterns that give the buttocks a rounded profile. These features are known as secondary sex characteristics, meaning that they are not present at birth. In addition, estradiol governs the growth and development of the cervix, endometrium, fallopian tubes, and vagina. It also regulates the ovulation cycle and strengthens the myometrium, which is the layer of muscles found in the womb.

Beyond these primary functions, estradiol assists the growth and maintenance of bones and joints. Declining estradiol levels are one of the main reasons women are at elevated risk for osteoporosis after menopause. The brain also can make small amounts of estradiol locally, and researchers believe that it helps protect neurological function. Researchers study whether estrogen affects cognitive aging and the risk of Alzheimer’s disease, but the evidence is mixed.

Estriol is produced in small amounts outside pregnancy and in much larger amounts during pregnancy, mainly through the placenta using hormones from the fetus. However, studies suggest that estriol can help ease some of the symptoms associated with menopause, such as vaginal dryness and hot flashes. Because it is active in the placenta, estriol levels tend to rise sharply during pregnancy. In nonpregnant females, estriol levels can be so low that they are functionally undetectable.

Estrone is the main estrogen hormone produced by menopausal women. It is thought to signal a decline in reproductive function, and higher estrogen exposure after menopause is associated with increased breast cancer risk. Females with unusually high estrone levels are considered to be at elevated risk for developing breast cancer.

In addition to their physiological functions, estrogen hormones also have psychological and emotional effects. They are thought to play a major role in the mood disturbances that can accompany the premenstrual period in females, and they are also believed to boost the brain’s production of serotonin and endorphins. However, researchers have yet to definitively identify estrogen’s exact mechanisms of action with regard to mood and emotions.

Unusually low or high estrogen levels can produce symptoms in both sexes. In females, low estrogen levels are associated with diminished sex drive, dry skin, hot flashes, insomnia, interruptions in the menstrual cycle, mood swings, and vaginal dryness. Men with unusually low estrogen levels may report diminished sex drive and accumulation of fat in the stomach area. Low levels may also contribute to the development of osteoporosis in older males. Females with abnormally high estrogen levels can experience anxiety, depression, fatigue, weight gain, unusually light or heavy menstrual bleeding, and the development of noncancerous growths in the breasts and/or uterus. In males, elevated estrogen levels are associated with a condition known as gynecomastia, or male breast development, impotence, and infertility.

Beyond its natural production in the human body, estrogen hormones can be manufactured. Synthetic estrogen is used in hormone management and hormone replacement therapy, which may be offered to members of either sex who have unusually low estrogen levels. Transgender women may elect to undergo hormone therapy to develop some of the physical characteristics associated with women. Manufactured estrogen is a key component of birth control pills, which mainly work by preventing ovulation through hormonal feedback.

Estrogen is also linked to certain diseases, including cancer (mainly breast cancer) and endometriosis, a medical condition in which tissue that normally lines the inside of the uterus instead grows on the outside. In breast cancer, doctors often test tumor cells for estrogen receptors because cancers with these receptors may respond to hormone-blocking treatment. Endometriosis can be treated by artificially reducing estrogen levels in the body, but this carries risks and potential side effects, including a decline in fertility and reproductive function. Researchers also describe endometriosis as a condition shaped by immune and inflammatory processes, not only by estrogen.


Bibliography

Bradford, Alina. “What is Estrogen?” Live Science, 3 May 2017, www.livescience.com/38324-what-is-estrogen.html. Accessed 1 Apr. 2026.

Bruce, Debra Fulghum, and Lorna Collier. “Normal Testosterone and Estrogen Levels in Women.” WebMD, 23 July 2024, www.webmd.com/women/guide/normal-testosterone-and-estrogen-levels-in-women. Accessed 1 Apr. 2026.

Coleman, E., et al. “Standards of Care for the Health of Transgender and Gender Diverse People, Version 8.” International Journal of Transgender Health, vol. 23, suppl. 1, 6 Sept. 2022, pp. S1–S259. doi:10.1080/26895269.2022.2100644. Accessed 1 Apr. 2026.

“Endometriosis.” Mayo Clinic, 30 Aug. 2024, www.mayoclinic.org/diseases-conditions/endometriosis/symptoms-causes/syc-20354656. Accessed 1 Apr. 2026.

“Family Planning: A Global Handbook for Providers. 4th ed.” World Health Organization, 1 Jan. 2022, www.who.int/publications/m/item/family-planning--a-global-handbook-for-providers--4th-ed. Accessed 1 Apr. 2026.

Girling, Jane E. “Harnessing the Inflammatory Processes in Endometriosis.” Nature Reviews Endocrinology, vol. 20, Feb. 2024, pp. 69–70, doi:10.1038/s41574-023-00937-x. Accessed 1 Apr. 2026.

Hoffman, Matthew, and Alyson Powell Key. “The Effects of Estrogen on Women’s Emotions and Mood.” WebMD, 5 Aug. 2024, www.webmd.com/women/guide/estrogen-and-womens-emotions. Accessed 1 Apr. 2026.

“Hormones.” National Cancer Institute, 29 Apr. 2015, www.cancer.gov/about-cancer/causes-prevention/risk/hormones. Accessed 1 Apr. 2026.

Lampen, Claire. “Do Men Have Estrogen? Yes, and It’s Critical to Their Health.” Mic, 15 Feb. 2016, mic.com/articles/135096/do-men-have-estrogen-yes-and-it-s-critical-to-their-health. Accessed 1 Apr. 2026.

Mandal, Ananya. “What Does Estradiol Do?” News-Medical.net, 17 June 2023, www.news-medical.net/health/What-does-Estradiol-do.aspx. Accessed 1 Apr. 2026.

Martinez, LaQuita. “Quadruple Screen Test.” MedlinePlus, 31 Mar. 2024, www.medlineplus.gov/ency/article/007311.htm. Accessed 1 Apr. 2026.

Mervosh, Nicholas, and Gayatri Devi. “Estrogen, Menopause, and Alzheimer’s Disease: Understanding the Link to Cognitive Decline in Women.” Frontiers in Molecular Biosciences, vol. 12, 30 June 2025, doi:10.3389/fmolb.2025.1634302. Accessed 1 Apr. 2026.

Seibel, Mache. The Estrogen Window: The Breakthrough Guide to Being Healthy, Energized, and Hormonally Balanced through Perimenopause, Menopause, and Beyond. Rodale, 2016.

Simpson, Evan R., and Susan R. Davis. “Minireview: Aromatase and the Regulation of Estrogen Biosynthesis—Some New Perspectives.” Endocrinology, vol. 142, no. 11, 2001, pp. 4589–94, doi:10.1210/endo.142.11.8547. Accessed 1 Apr. 2026.

Prossnitz, Eric R., and Matthias Barton. “The G Protein-Coupled Oestrogen Receptor GPER in Health and Disease: An Update.” Nature Reviews Endocrinology, vol. 19, 2023, pp. 407–24, doi:10.1038/s41574-023-00822-7. Accessed 1 Apr. 2026.

Full Article

Estrogen is a class of hormones that plays an important role in female reproductive and sexual development. The estrogen class includes three specific hormones with related functions: estradiol, estriol, and estrone. Women produce these substances in varying amounts throughout their lives, with average levels of some estrogens rising during reproductive age and others being more prevalent after menopause. Puberty and pregnancy also affect the average production levels of particular estrogen hormones. Although estrogen is considered a class of female sex hormones, males produce small amounts of estrogen, and studies have shown that it plays a relatively limited but significant set of functions in their overall health. The main purpose of estrogen hormones is to regulate the growth, maintenance, and repair of the elements of the female reproductive system. It also helps develop female secondary sex characteristics and supports other sexual and reproductive functions. The estrogen hormone estradiol plays a key role in bone health. Scientists have identified several estrogen receptors, including estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G protein–coupled estrogen receptor (GPER), in different tissues. These receptors help explain why estrogen affects the reproductive system, bones, the brain, and other organs in different ways.

Background

Hormones are chemicals that are produced by the human body. They are commonly described as “chemical messengers,” meaning that their production and presence in specific quantities trigger a natural reaction or tell the body to do something specific. For example, production of the hormone melatonin rises after nightfall, signaling to the body that the time to go to sleep is approaching. Melatonin plays a major role in regulating the sleep-waking cycle. Its presence prompts a series of physiological and psychological responses, including drowsiness. During daylight hours, melatonin levels decline, and the responses it triggers recede.

Some hormones are found in roughly equal quantities in males and females, while others are usually found in far greater amounts in one sex or the other. Although males naturally produce estrogen in small quantities, it is strongly associated with the female body due to its origins in the ovaries and role in the female aspects of reproduction and sexuality. The male equivalent of estrogen is androgen. Androgen hormones are mainly produced in the testicles. Like estrogen in females, average androgen levels are much higher in males than in females. Like estrogen in males, females also naturally produce small quantities of androgen hormones, and they play a limited but significant role in female health.

Under normal circumstances, the body releases estrogen hormones in short pulses, and the amount of estrogen active in the body at any given time differs from hour to hour throughout the day. In both males and females, abnormally high or abnormally low estrogen levels can cause symptoms and medical conditions. Treatments known as hormone management or hormone replacement therapy may be necessary to bring symptoms and conditions under control.

Overview

Estradiol is the major estrogen hormone found in females of reproductive age. Its production and secretion begin when ovarian follicles develop and become active, a process that usually accelerates with the onset of puberty. In females, estradiol is responsible for breast development and maintenance, and other physiological changes that occur during puberty and the period after puberty, including expansion of the hips, curvature of the lower back, and fat distribution patterns that give the buttocks a rounded profile. These features are known as secondary sex characteristics, meaning that they are not present at birth. In addition, estradiol governs the growth and development of the cervix, endometrium, fallopian tubes, and vagina. It also regulates the ovulation cycle and strengthens the myometrium, which is the layer of muscles found in the womb.

Beyond these primary functions, estradiol assists the growth and maintenance of bones and joints. Declining estradiol levels are one of the main reasons women are at elevated risk for osteoporosis after menopause. The brain also can make small amounts of estradiol locally, and researchers believe that it helps protect neurological function. Researchers study whether estrogen affects cognitive aging and the risk of Alzheimer’s disease, but the evidence is mixed.

Estriol is produced in small amounts outside pregnancy and in much larger amounts during pregnancy, mainly through the placenta using hormones from the fetus. However, studies suggest that estriol can help ease some of the symptoms associated with menopause, such as vaginal dryness and hot flashes. Because it is active in the placenta, estriol levels tend to rise sharply during pregnancy. In nonpregnant females, estriol levels can be so low that they are functionally undetectable.

Estrone is the main estrogen hormone produced by menopausal women. It is thought to signal a decline in reproductive function, and higher estrogen exposure after menopause is associated with increased breast cancer risk. Females with unusually high estrone levels are considered to be at elevated risk for developing breast cancer.

In addition to their physiological functions, estrogen hormones also have psychological and emotional effects. They are thought to play a major role in the mood disturbances that can accompany the premenstrual period in females, and they are also believed to boost the brain’s production of serotonin and endorphins. However, researchers have yet to definitively identify estrogen’s exact mechanisms of action with regard to mood and emotions.

Unusually low or high estrogen levels can produce symptoms in both sexes. In females, low estrogen levels are associated with diminished sex drive, dry skin, hot flashes, insomnia, interruptions in the menstrual cycle, mood swings, and vaginal dryness. Men with unusually low estrogen levels may report diminished sex drive and accumulation of fat in the stomach area. Low levels may also contribute to the development of osteoporosis in older males. Females with abnormally high estrogen levels can experience anxiety, depression, fatigue, weight gain, unusually light or heavy menstrual bleeding, and the development of noncancerous growths in the breasts and/or uterus. In males, elevated estrogen levels are associated with a condition known as gynecomastia, or male breast development, impotence, and infertility.

Beyond its natural production in the human body, estrogen hormones can be manufactured. Synthetic estrogen is used in hormone management and hormone replacement therapy, which may be offered to members of either sex who have unusually low estrogen levels. Transgender women may elect to undergo hormone therapy to develop some of the physical characteristics associated with women. Manufactured estrogen is a key component of birth control pills, which mainly work by preventing ovulation through hormonal feedback.

Estrogen is also linked to certain diseases, including cancer (mainly breast cancer) and endometriosis, a medical condition in which tissue that normally lines the inside of the uterus instead grows on the outside. In breast cancer, doctors often test tumor cells for estrogen receptors because cancers with these receptors may respond to hormone-blocking treatment. Endometriosis can be treated by artificially reducing estrogen levels in the body, but this carries risks and potential side effects, including a decline in fertility and reproductive function. Researchers also describe endometriosis as a condition shaped by immune and inflammatory processes, not only by estrogen.


Bibliography

Bradford, Alina. “What is Estrogen?” Live Science, 3 May 2017, www.livescience.com/38324-what-is-estrogen.html. Accessed 1 Apr. 2026.

Bruce, Debra Fulghum, and Lorna Collier. “Normal Testosterone and Estrogen Levels in Women.” WebMD, 23 July 2024, www.webmd.com/women/guide/normal-testosterone-and-estrogen-levels-in-women. Accessed 1 Apr. 2026.

Coleman, E., et al. “Standards of Care for the Health of Transgender and Gender Diverse People, Version 8.” International Journal of Transgender Health, vol. 23, suppl. 1, 6 Sept. 2022, pp. S1–S259. doi:10.1080/26895269.2022.2100644. Accessed 1 Apr. 2026.

“Endometriosis.” Mayo Clinic, 30 Aug. 2024, www.mayoclinic.org/diseases-conditions/endometriosis/symptoms-causes/syc-20354656. Accessed 1 Apr. 2026.

“Family Planning: A Global Handbook for Providers. 4th ed.” World Health Organization, 1 Jan. 2022, www.who.int/publications/m/item/family-planning--a-global-handbook-for-providers--4th-ed. Accessed 1 Apr. 2026.

Girling, Jane E. “Harnessing the Inflammatory Processes in Endometriosis.” Nature Reviews Endocrinology, vol. 20, Feb. 2024, pp. 69–70, doi:10.1038/s41574-023-00937-x. Accessed 1 Apr. 2026.

Hoffman, Matthew, and Alyson Powell Key. “The Effects of Estrogen on Women’s Emotions and Mood.” WebMD, 5 Aug. 2024, www.webmd.com/women/guide/estrogen-and-womens-emotions. Accessed 1 Apr. 2026.

“Hormones.” National Cancer Institute, 29 Apr. 2015, www.cancer.gov/about-cancer/causes-prevention/risk/hormones. Accessed 1 Apr. 2026.

Lampen, Claire. “Do Men Have Estrogen? Yes, and It’s Critical to Their Health.” Mic, 15 Feb. 2016, mic.com/articles/135096/do-men-have-estrogen-yes-and-it-s-critical-to-their-health. Accessed 1 Apr. 2026.

Mandal, Ananya. “What Does Estradiol Do?” News-Medical.net, 17 June 2023, www.news-medical.net/health/What-does-Estradiol-do.aspx. Accessed 1 Apr. 2026.

Martinez, LaQuita. “Quadruple Screen Test.” MedlinePlus, 31 Mar. 2024, www.medlineplus.gov/ency/article/007311.htm. Accessed 1 Apr. 2026.

Mervosh, Nicholas, and Gayatri Devi. “Estrogen, Menopause, and Alzheimer’s Disease: Understanding the Link to Cognitive Decline in Women.” Frontiers in Molecular Biosciences, vol. 12, 30 June 2025, doi:10.3389/fmolb.2025.1634302. Accessed 1 Apr. 2026.

Seibel, Mache. The Estrogen Window: The Breakthrough Guide to Being Healthy, Energized, and Hormonally Balanced through Perimenopause, Menopause, and Beyond. Rodale, 2016.

Simpson, Evan R., and Susan R. Davis. “Minireview: Aromatase and the Regulation of Estrogen Biosynthesis—Some New Perspectives.” Endocrinology, vol. 142, no. 11, 2001, pp. 4589–94, doi:10.1210/endo.142.11.8547. Accessed 1 Apr. 2026.

Prossnitz, Eric R., and Matthias Barton. “The G Protein-Coupled Oestrogen Receptor GPER in Health and Disease: An Update.” Nature Reviews Endocrinology, vol. 19, 2023, pp. 407–24, doi:10.1038/s41574-023-00822-7. Accessed 1 Apr. 2026.

More Like ThisRelated Articles

Related Articles (5)

Related Articles (5)