Oestrogens are a group of sex hormones that promote the development and maintenance of female characteristics in the human body.
They play an essential role in the growth and development of female secondary sexual characteristics, such as breasts, pubic and armpit hair, and the regulation of the menstrual cycle and reproductive system.
During the menstrual cycle, oestrogen produces an environment suitable for the fertilization, implantation, and nutrition of an early embryo.
An imbalance of these hormones can lead to a range of health problems and unwanted physical changes. This MNT Knowledge Center article will explain what oestrogen is, how it works in the body, its range of medical uses, and the effects of oestrogen imbalance.
Fast facts on oestrogen
- The ovaries are the main location for oestrogen production.
- Oestrogen influences the structural differences between the male and female bodies, such as females having a wider pelvis and more permanent hair on the head.
- Synthetic oestrogen has a range of uses in medicine, including birth control and managing the effects of menopause.
- Oestrogen is involved in the development of a range of health issues.
What is oestrogen?
Hormones are chemical messengers that tell specific tissues to behave in a certain way.
During puberty, the ovaries begin releasing oestrogen hormones in line with each monthly menstrual cycle. The oestrogen level rises suddenly halfway through the cycle, which triggers the release of an egg. This level then quickly decreases after ovulation.
Oestrogens usually travel through the bloodstream in fluids, interact with cells in a variety of tissues in the body, and deliver a message or instruction.
It is one of the most important hormones for women, alongside progesterone. Progesterone helps to maintain pregnancies and implant an egg in the uterus.
The related hormones in the oestrogen family include:
Estrone (E1): This is a weak form of oestrogen and the only type found in women after the menopause. Small amounts of estrone are present in most tissues of the body, mainly fat and muscle. The body can convert estrone to estradiol and estradiol to estrone.
Estradiol (E2): This is the strongest type of oestrogen. Estradiol is a steroid produced by the ovaries. It is thought to contribute to a range of gynecological problems, such as endometriosis, fibroids, and cancers that occur in females, particularly endometrial cancer.
Estriol (E3): This is the weakest of the oestrogens and is a waste product made after the body uses estradiol. Pregnancy is the only time at which significant amounts of estriol are made. Estriol cannot be converted to estradiol or estrone.
Oestrogen is crucial to the reproductive function and cycle of a woman.
In females, oestrogen affects the following areas of the body:
Ovaries: Oestrogen helps stimulate the growth of an egg follicle.
Vagina: It also stimulates the growth of the vagina to its adult size, the thickening of the vaginal wall, and an increase in vaginal acidity that reduces bacterial infections. It also helps lubricate the vagina.
Fallopian tubes: Oestrogen is responsible for the growth of a thick, muscular wall in the fallopian tubes, and for the contractions that transport the egg and sperm cells.
Uterus: Oestrogen enhances and maintains the mucous membrane that lines the uterus. It increases the size of the endometrium as well as enhancing blood flow, protein content, and enzyme activity. Oestrogen also stimulates the muscles in the uterus to develop and contract. Contractions help during the delivery of an infant and placenta, and they also assist the wall of the uterus in getting rid of dead tissue during menstruation.
Cervix: Oestrogen is thought to regulate the flow and thickness of uterine mucous secretions. This enhances the movement of a sperm cell to an egg and enables fertilization.
Mammary glands: Oestrogen forms unique relationships with other hormones in the breast. They are responsible for the growth of the breasts during adolescence, the pigmentation of the nipples, and eventually stopping the flow of milk when an infant is no longer breast-feeding.
Oestrogen is responsible for the differences between male and female bodies. For example, in a female body:
- Oestrogen makes the bones smaller and shorter, the pelvis broader, and the shoulders narrower.
- It increases fat storage around the hips and thighs, meaning that the body is more curved and contoured.
- Oestrogen helps to slow down the growth of females during puberty and increases sensitivity to insulin. Insulin influences the amount of body fat and lean muscle a person can develop.
- It influences body hair to become finer and less pronounced while making the hair on a woman’s head more permanent.
- Oestrogen makes the voice box smaller and the vocal cords shorter, giving females a higher-pitched voice than males.
- Oestrogens suppress the activity of the glands in the skin that produce oily substances. This reduces the likelihood of acne in females.
Other areas on which oestrogen has an impact include:
- The brain: It can help maintain body temperature, regulate the part of the brain linked to sexual development, and enhance the effects of the brain’s “feel-good” chemicals.
- The skin: Oestrogens improve the thickness and quality of the skin as well as the collagen content which prevents aging.
- The bones: Oestrogen helps to preserve bone strength and prevent bone loss.
- The liver and heart: The hormone regulates cholesterol production in the liver, helping to protect the heart and arteries.
Some foods contain phytooestrogens, which may affect levels of oestrogen in the body.
- cruciferous vegetables
- soy and some foods containing soy protein, the most concentrated source
- seeds and grains
Some scientists consider phytooestrogens to be endocrine disruptors. They appear to have dual functions at times, able to increase and decrease oestrogen activity.
It is a common misconception that phytooestrogens can negatively impact health, but some research confirms that the foods containing phytooestrogens listed above can lower cancer risk, reduce hot flashes, improve other menopausal symptoms, and provide other health benefits.
The effects of soy’s phytooestrogens depend on the type of soy being studied at the time, and this has led to inconsistent findings. Soy protein isolate will have a different impact from whole soy foods.
Article by by Hannah Nichols