Estrogen hormones promote the development and maintenance of female characteristics in the body. The quantity and type of estrogen hormone produced in a woman's body depends greatly upon the reproductive stage in which she finds herself.
Because there are a variety of bodily systems, glands, and receptors involved with estrogen production, this makes understanding estrogen's proper functioning all the more necessary.
Why is Estrogen Produced?
In essence, estrogen contributes to the well-functioning of a woman's body.
In regards to the menstrual cycle, estrogen is needed to make the lining of the uterus grow and thicken in preparation for a possible pregnancy during the follicular phase, which begins on the first day of menstruation and ends with ovulation. If conception occurs, estrogen is the hormone that causes milk ducts in the breast to widen and prepare for milk production among other functions.
Where is Estrogen Produced?
The majority of the female body's estrogen - estradiol - is produced in the ovaries; it is formed from the corpus luteum and developing egg follicles. Smaller concentrations are produced by the breasts, liver, adrenal glands, and other non-endocrine tissues.
When ovarian function officially stops with the menopausal transition, small levels of estrogens are produced by converting adrenal precursors into estrone and estradiol.
Moreover, estriol - the predominant circulating estrogen during pregnancy - is produced in the placenta from estrogen precursors. These precursors are made by the fetal adrenal gland and liver.
Furthermore, recent studies have proven the brain can produce and release estrogen, which may lead to a better understanding of the hormonal changes experienced before birth and throughout life.
How is Estrogen Produced?
Estrogen in the ovaries is produced during the follicular phase of a woman's menstrual cycle, which begins on the first day of menstruation and ends with ovulation.
The first day of menses is identified as cycle day one, which is when estrogen is at a low point.
At the start of each menstrual cycle, the hypothalamus prompts the pituitary gland to make follicle stimulating hormone, or FSH. FSH is responsible for beginning follicle development and for the initial phase of estrogen production. As the follicle matures, the cells around the egg produce estrogen.
Once the follicle has produced sufficient estrogen, the high estrogen signals the pituitary gland to release luteinizing hormone (LH) to trigger ovulation - the release of the mature egg inside of the follicle - within a couple of days.
If the egg is not fertilized, estrogen levels drop sharply until the beginning of the next cycle.
Estrogen is produced in a variety of glands, from which it is secreted for use within the same glands or other areas of the body. The major glands are the ovaries, adrenal glands, and adipose tissues.
Ovaries are the estrogen glands for estradiol, the most common estrogen hormone in women of childbearing age. During the follicular phase, cells around the developing egg will produce and secrete estrogen. This estrogen will be used to initiate ovulation of the mature egg and further reproductive functions.
Adipose tissues, or body fat, also acts as glands that produce and secrete estrone. This is done by the conversion of androgen precursors with the help of certain enzymes. Estrone is also formed from estradiol in organs, such as the liver, but adipose tissue is its major tissue site of conversion.
Estrone is not considered as potent as estradiol produced by ovaries, but it performs the same functions and behaves in the same way. It is the most common circulating hormone after menopause.
In pregnant women, the placenta produces and secretes the majority of estriol. This estrogen originates from androgenic precursors in the fetal liver, which is processed by the placenta. Due to the membrane that develops between mother and developing fetus, more than 90% of estriol enters the maternal circulation.
Flow of Estrogen in the Body
Once produced and secreted, estrogen is transported throughout the body in the bloodstream, looking for target cells.
Estrogens vary in their range of targets. In general, the hormones regulate function by binding to special estrogen receptor sites.
Moreover, because estrogen circulates in the bloodstream and binds to estrogen receptors on cells in targeted tissues, improper amounts affect not only a woman's breasts and uterus, but the brain, bones, liver, heart, and other important tissues as well.
In general, once estrogens find a target cell in an organ, they penetrate and enter the cell to directly influence the cell's behavior. These effects will then produce a variety of responses in order to adequately function as instructed by the amount of estrogen needed.
Moreover, the effect on the organ receiving the estrogen will feed back to the original signal to control the release of more estrogen. The pituitary gland is well-known for these “feedback loops.”
Estrogens are metabolized and eliminated from the body by metabolic conversion to inactive metabolites in the liver and then excreted through the bowels in urine or feces.
If this process is not working properly, this can cause high estrogen levels or reabsorption of estrogen back into the body. This, consequently, invokes a hormonal imbalance, bringing about a plethora of other symptoms.
Estrogen is also produced to help with the proper functioning of a myriad of other bodily systems and organs.
Continue reading to learn more about estrogen's multiple, transcendent roles and effects throughout the body.
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