Anatomy And Physiology

Estradiol Role in the Human Body

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Estradiol also known as E2, oestradiol or 17β-estradiol is a naturally occurring hormone synthesized in large quantities in women and low amounts in men. In women, it is the predominant sex hormone while in men it is formed as an active metabolic product of testosterone (predominant male sex hormone).

Estradiol is among Estriol (E3) and Estrone (E1) that make up Estrogens also referred to as oestrogens (BE), œstrogens or estrogens (AmE). Among the three types of estrogens, Estradiol is prevalent in normal reproductive women who are not pregnant or postmenopausal. Estriol is found in pregnant women while Estrone is found in postmenopausal women.

Role of Estradiol in the female body

Although Estradiol is referred to as the female sex hormone, it is necessary for other body functions that are not tied to reproductive and sexual functions.

Sexual development

Being the predominant female sex hormone, Estradiol is responsible for development of secondary female sex traits that include: widening of hips, onset of menstrual cycle, growth of bodily hair, breast enlargement and nipple erection, distribution of weight and fat, and expansion of thigh muscles.

Female reproduction

Estradiol is responsible for production of growth hormones responsible for the female reproductive organs, lining the vagina, fallopian tubes, cervical glands and the endometrium. It also maintains oocytes found in the ovaries and promotes myometrium growth (middle layer of the uterine wall). Estradiol stimulates ovulation and used with progesterone to get the endometrium ready for implantation during pregnancy.

Bone, Liver and coronary arteries

In the liver, Estradiol influences production and binding of proteins such as lipoproteins and blood clotting proteins. In bones, it affects bone mineralization and the lack of Estradiol especially in menopausal women leads to osteoporosis. A study by (U.S. National Library of Medicine - National Institutes of Health) showed a connection between low levels of Estradiol and coronary artery disease.

Estradiol's role in males

In men, Sertoli cells located in the testes produce Estradiol. It helps prevent sperm cell apoptosis (death of sperm cells). Higher levels of Estradiol and estrogen in general are believed to lead to low sperm count in men and development of female-like characteristics.

Estradiol and menopause Although Estradiol can be produced by other organs such as arterial walls, adrenal cortex, brain and fat cells, the highest percent in women is produced in the ovaries. When a woman stops ovulating, Estradiol levels are greatly affected leading to drop in functions that it is required for. Postmenopausal women can undergo hormone replacement therapy to keep their estrogen levels in check.

17β-estradiol should not be confused with 17α-estradiol. 17β-estradiol is used to alleviate symptoms associated with low estrogen levels while 17α-estradiol is used to treat hair loss in men and women.

Sources: – Estradiol - 17 beta-Estradiol attenuates acetylcholine-induced coronary arterial constriction in women but not men with coronary heart disease. - Actions of Estradiol

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