Medical Article

Functions of Estrogens

Estrogen is one of two main sex hormones that women have which includes Estrone (E1), Estradiol(E2) and Estriol (E3). Estrogen is produced by the ovaries and smaller amounts by the adrenal cortex, testicles and fetoplacental unit. Testosterone is considered to be male hormone. However, both hormones are present in both sexes. 

Estrogen hormones support the development and growth of secondary sexual hormones of female like breasts, pubic and armpit hair, endometrium, regulation of the menstrual cycle and the reproductive system. 

In case of male, estrogen plays the role in normal reproductive processes. Now it is recognized that pubertal development in boys attributed to the actions of androgens are mediated in part by estrogen. The final steps of spermatid maturation spermiogenesis, appear to be sensitive and dependent upon estrogen.

Estrone (E1)

It is a weaker form of estrogen and is the major estrogenic form found in naturally-menopausal women who are not taking hormone replacement therapy (HRT). Estrone is the least abundant of the three hormones. Small amount of estrone are made in tissues, especially fat and muscle. 

Estradiol (E2)

It is the most potent form of estrogenic steroids produced by the ovaries. Reaching the tissues estradiol conncects with estrogen receptors to trigger specific activities in those tissues and cells. It is also produced by conversion from a number of precursors in the adrenal glands and the placenta. It is thought to trigger problems like endometriosis, fibroids and even female cancers.

Estriol (E3)

It is a metabolic waste product of estradiol metabolism .  Estriol is made by the placenta.

Works of estrogen

Estrogen binding fractions of cells called estrogen receptors. These receptors are protein molecules inside those cells that are targets for estrogen action. Other organs and tissues in the body don’t contain such receptors. So the estrogen molecules only exert effects on cells contain estrogen receptors while circulating throughout the body. It exists in the cell’s nucleus together with DNA molecules.  In the absence of estrogen molecules, the receptors are inactive and have no influence on DNA. 

When an estrogen molecule enters a cell and passes into the nucleus, the estrogen binds to its receptor, it causes shape change of receptor. This estrogen-receptor complex then binds to specific DNA sites, called estrogen response elements, located near genes that are controlled by estrogen.

After the attachment of estrogen-receptor to DNA, this element binds with co activator proteins and then activates genes nearby. The active genes produce molecules of messenger ribonucleic acid (RNA), which support the synthesis of specific protein. These proteins influence the cell behaviours, in different ways, depending on the cell type involved.

Estrogens’ Sources

The prime locations for estrogen are the ovaries. It is released from the ovarian follicles and also secreted by the corpus luteum following the release of an egg from the follicle and the placenta. Follicle-stimulating hormone (FSH) causes the release of estrogen and estrogens inhibit FSH as part of a negative feedback loop. In the brain the FSH are produced by the pituitary gland. The other sources of estrogens production in human are adrenal cortex, placenta, liver, breasts, fat cells, testes.

Key functions of these hormones:

FSH: It causes the egg to mature in an ovary and stimulates the ovaries to release estrogens.

Estrogen: It encourages the growth of the uterine lining. Stimulates the pituitary gland to release the luteinising hormone (LH) and inhibits in it after ovulation. It inhibits FSH production to ensure that only one egg matures in a cycle.

LH: It stimulates egg release (ovulation) and stimulates estrogen and progesterone production.

Role of estrogen

Estrogen is a crucial component that contributes to the estrus cycle, which influences female reproductive capacity. 

Effects of estrogen in females

Ovaries : It stimulates the growth of the egg follicle.

Vagina : It stimulates the growth of the vagina to its adult size, thickens vagina wall and increases the vaginal acidity, which helps to reduce the bacterial infections. 

Fallopian tubes: Estrogen develops a thick muscular wall in the fallopian tubes, and supports the contractions that transport the egg and sperm cells.

Uterus : Estrogen enhances and maintains the endometrium, the mucous membrane that lines the uterus. The endometrium’s size and weight are increased in addition to cell number, cell types, blood flow, protein content, and enzyme activity. The uterus muscles develop and contract according to the stimulation of estrogen. Contraction supports in the delivery of a child and placenta, and help the uterine wall to cast off dead tissue during menstruation.

Cervix :  Estrogen is thought to regulate the flow and thickness of uterine mucous secretion to enhance sperm transport.

Mammary glands : Estrogen forms unique complexes joining other hormones in the breast and is responsible for growth of the breasts during adolescence. 

Estrogen effect on physical structure

The structural difference of male and female bodies has the influences of Estrogen.

Female structure

Bones : Female bones are smaller and shorter. The shoulders are narrower and the pelvis is broader.

Body : Estrogen increases fat storage around the hips and thighs, so body is curved and contoured. During puberty estrogen helps decelerate height increase in females and increases sensitivity to insulin.

Body hair is less pronounced and the scalp hair is permanent.

Voice box : The female voice box is smaller and the vocal cords shorter.

Sebaceous gland (oil-producing gland): estrogens suppress sebaceous gland activity and thereby reduce acne in females.

Estrogen effect on the brain 

Estrogen helps to maintain body temperature. May delay memory loss and helps to regulate parts of the brain that prepare the body for sexual and reproductive development. It increases serotonin and the number of serotonin receptors in the brain. It modifies production and the effect of endorphins, the chemical in the brain that protects nerves from damage and possibly stimulates nerve growth.

Estrogen’s effect on hormones

It increases cortisol and sex hormone binding globulin. Estrogen also increases the serum concentrations of binding proteins that transport other substances, including the binding proteins for cortisol, thyroxine and iron.  It increases the melanin and pheomelanin, and increase in sensitivity to insulin. 

Estrogen’s effect on skin

The estrogen receptors quantity varies in different parts of the body. Estrogen receptors levels are highest in the facial skin and skin over the thight and breasts.  It is an important factor in the maintenance of human skin. It has factors like improved collagen content and quality, increased skin thickness, improved blood supply to the skin. 

Estrogen effect on bones

The actions of estrogen are related to bone development and bone maintenance. It preserves bone strength along with the bone formation and the closure of bone epiphyses, which causes linear growth to cease at the end of puberty, maintaining bone throughout the reproductive years. It prevents bone loss by working together with calcium, vitamin D and other hormones and mineral to build bones.  Once estrogen levels start to decline, this process of bone-building slows, and at the age of 30-35, the breakdown of bone begins to outstrip the rate at which new bone is built.

Estrogen’s effect on heart and liver

It helps to regulate the liver’s production of cholesterol by decreasing the serum cholesterol concentrations. It can also increases serum triglyceride concentrations. 

The menstrual cycle and estrogen

The menstrual cycle is controlled by female sex hormones. This cycle repeats itself every 28 days on average and estrogen plays a leading role in this cycle. 

Uses of estrogen as a drug

The most common an notable uses of estrogen are in birth control pills or contraceptives and in hormone replacement therapy. It also used for advanced prostate or postmenopausal breast carcinoma treatment and in Osteoporosis prophylaxis.


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