Estrogen is a hormone that plays various roles in the body. In females, it helps develop and maintain both the reproductive system and female characteristics, such as breasts and pubic hair.

Estrogen contributes to cognitive health, bone health, the function of the cardiovascular system, and other essential bodily processes.

However, most people know it for its role alongside progesterone in female sexual and reproductive health.

The ovaries, adrenal glands, and fat tissues produce estrogen. Both female and male bodies have this hormone, but females create more of it.

In this article, we look at estrogen in more detail, including how it works, what happens when the levels fluctuate, and medical uses.

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Estrogen plays an important role in many bodily functions.

There are different types of estrogen:

Estrone

This type of estrogen is present in the body after menopause. It is a weaker form of estrogen and one that the body can convert to other forms of estrogen, as necessary.

Estradiol

Both males and females produce estradiol, and it is the most common type of estrogen in females during their reproductive years.

Too much estradiol may result in acne, loss of sex drive, osteoporosis, and depression. Very high levels can increase the risk of uterine and breast cancer. However, low levels can result in weight gain and cardiovascular disease.

Estriol

Levels of estriol rise during pregnancy, as it helps the uterus grow and prepares the body for delivery. Estriol levels peak just before birth.

Estrogen enables the following organs to function:

Ovaries: Estrogen helps stimulate the growth of the egg follicle.

Vagina: In the vagina, estrogen maintains the thickness of the vaginal wall and promotes lubrication.

Uterus: Estrogen enhances and maintains the mucous membrane that lines the uterus. It also regulates the flow and thickness of uterine mucus secretions.

Breasts: The body uses estrogen in the formation of breast tissue. This hormone also helps stop the flow of milk after weaning.

Estrogen levels vary among individuals. They also fluctuate during the menstrual cycle and over a female’s lifetime. This fluctuation can sometimes produce effects such as mood changes before menstruation or hot flashes in menopause.

Factors that can affect estrogen levels include:

  • pregnancy, the end of pregnancy, and breastfeeding
  • puberty
  • menopause
  • older age
  • overweight and obesity
  • extreme dieting or anorexia nervosa
  • strenuous exercise or training
  • the use of certain medications, including steroids, ampicillin, estrogen-containing drugs, phenothiazines, and tetracyclines
  • some congenital conditions, such as Turner’s syndrome
  • high blood pressure
  • diabetes
  • primary ovarian insufficiency
  • an underactive pituitary gland
  • polycystic ovary syndrome (PCOS)
  • tumors of the ovaries or adrenal glands

Learn more about high estrogen levels and low estrogen levels here.

An imbalance of estrogen leads to:

  • irregular or no menstruation
  • light or heavy bleeding during menstruation
  • more severe premenstrual or menopausal symptoms
  • hot flashes, night sweats, or both
  • noncancerous lumps in the breast and uterus
  • mood changes and sleeping problems
  • weight gain, mainly in the hips, thighs, and waist
  • low sexual desire
  • vaginal dryness and vaginal atrophy
  • fatigue
  • mood swings
  • feelings of depression and anxiety
  • dry skin

Some of these effects are common during menopause.

Some hereditary and other conditions can lead to high levels of estrogen in males, which can result in:

Males with low estrogen levels may have excess belly fat and low libido.

If a person has low levels of estrogen, a doctor may prescribe supplements or medication.

Estrogen products include:

  • synthetic estrogen
  • bioidentical estrogen
  • Premarin, which contains estrogens from the urine of pregnant mares

Estrogen therapy

Estrogen therapy can help manage menopause symptoms as part of hormone therapy, which people usually refer to as hormone replacement therapy.

The treatment may consist solely of estrogen (estrogen replacement therapy, or ERT), or it may involve a combination of estrogen and progestin, a synthetic form of progesterone.

Hormone treatment is available as a pill, nasal spray, patch, skin gel, injection, vaginal cream, or ring.

It can help manage:

  • hot flashes
  • vaginal dryness
  • painful intercourse
  • mood changes
  • sleep disorders
  • anxiety
  • decreased sexual desire

It may also help reduce the risk of osteoporosis, which increases when people enter menopause.

Side effects include:

  • bloating
  • breast soreness
  • headaches
  • leg cramps
  • indigestion
  • nausea
  • vaginal bleeding
  • fluid retention, leading to swelling

Some types of hormone therapy can also increase the risk of a stroke, blood clots, and uterine and breast cancer. A doctor can advise a person on whether estrogen therapy is suitable for them.

In addition to menopause, estrogen therapy can also help resolve:

  • primary ovarian insufficiency
  • other ovarian issues
  • some types of acne
  • some cases of prostate cancer
  • delayed puberty, for example, in Turner’s syndrome

High levels of estrogen can increase the risk and progression of some types of breast cancer. Some hormone treatments block the action of estrogen as a way of slowing or stopping cancer development.

Hormonal therapy is not for everyone. A family history of breast cancer or thyroid issues may contradict using hormones. People who are unsure can speak to a doctor.

Transitioning to female

A doctor can prescribe estrogen as part of the therapy for a person assigned male at birth who wishes to transition to female. The person may also need anti-androgenic treatment.

Estrogen can help a person develop female secondary sexual characteristics, such as breasts, and reduce male pattern hair formation.

Estrogen therapy will be part of a broader treatment approach. A healthcare professional can advise the individual on the best course of treatment.

Birth control

Birth control pills contain either synthetic estrogen and progestin or progestin only.

Some types prevent pregnancy by stopping ovulation, and they do this by ensuring that hormone levels do not fluctuate throughout the month.

They also make the mucus in the cervix thick so that any sperm cannot reach the egg.

Other uses include decreasing premenstrual symptoms and reducing the severity of hormone-related acne.

Birth control pills may increase the risk of:

Oral birth control presents more risk for women who smoke or are over the age of 35 years. Long-term use may also lead to a higher risk of breast cancer.

Some foods contain phytoestrogens, which are plant-based substances that resemble estrogen.

Some studies suggest that these may affect levels of estrogen in the body. However, there is not enough evidence to confirm this.

Foods that contain phytoestrogens include:

  • cruciferous vegetables
  • soy and some foods containing soy protein
  • berries
  • seeds and grains
  • nuts
  • fruit
  • wine

Some people believe that foods containing phytoestrogens can help manage hot flashes and other effects of menopause, but this does not have scientific backing.

In addition, eating whole soy foods, for example, is unlikely to have the same effect as taking extracts from soy as a supplement.

Some herbs and supplements contain phytoestrogens, which act in a similar way to estrogen. These may help regulate estrogen and treat symptoms of menopause.

Examples are:

However, it is unclear exactly how these compounds affect estrogen and estrogen-related activity in the body, and there is not enough evidence to confirm that they are safe and effective, especially in the long term. Researchers have called for further studies.

In addition, the Food and Drug Administration (FDA) do not regulate herbal and nonmedicinal supplements. As a result, it is not possible to know exactly what a product contains.

People should check with a doctor before taking any supplements or medications.