Estradiol
Synonyms: BETA-ESTRADIOL-16,16,17-D3
CAS: 50-28-2
MF: C18H24O2
MW: 272.38
Content: 99%
Properties: white crystalline powder
Description
----------------------------------------------Estradiol, or more precisely, 17β-estradiol, is a human sex hormone and steroid, and the primary female sex hormone. It is named for and is important in the regulation of the estrous and menstrual female reproductive cycles. Estradiol is essential for the development and maintenance of female reproductive tissues but it also has important effects in many other tissues including bone. While estrogen levels in men are lower compared to women, estrogens have essential functions in men as well. Estradiol is found in most vertebrates as well as many crustaceans, insects, fish, and other animal species.
Estradiol or oestradiol (American or British English usages), derives from estra-, and -diol, a chemical name and suffix indicating that this form of steroid and sex hormone is a type of alcohol bearing two hydroxyl groups.
Estradiol is produced especially within the follicles of female ovaries, but also in other endocrine (i.e., hormone-producing) and non-endocrine tissues (e.g., including fat, liver, adrenal, breast, and neural tissues). Estradiol is biosynthesized from progesterone (arrived at in two steps from cholesterol, via intermediate pregnenolone).One principle pathway then converts progesterone to its 17-hydroxy-derivative, and then to androstenedione via sequential cytochrome P450-catalyzed oxidations.[citation needed] Action of aromatase on this dione generates estrone, and action of a dehydrogenase on this gives the title compound, 17β-estradiol.
Application
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Female reproduction
In the female, estradiol acts as a growth hormone for tissue of the reproductive organs, supporting the lining of the vagina, the cervical glands, the endometrium, and the lining of the fallopian tubes. It enhances growth of the myometrium. Estradiol appears necessary to maintain oocytes in the ovary. During the menstrual cycle, estradiol produced by the growing follicle triggers, via a positive feedback system, the hypothalamic-pituitary events that lead to the luteinizing hormone surge, inducing ovulation. In the luteal phase, estradiol, in conjunction with progesterone, prepares the endometrium for implantation. During pregnancy, estradiol increases due to placental production. In baboons, blocking of estrogen production leads to pregnancy loss, suggesting estradiol has a role in the maintenance of pregnancy. Research is investigating the role of estrogens in the process of initiation of labor. Actions of estradiol are required before the exposure of progesterone in the luteal phase.
Sexual development
The development of secondary sex characteristics in women is driven by estrogens, to be specific, estradiol. These changes are initiated at the time of puberty, most are enhanced during the reproductive years, and become less pronounced with declining estradiol support after the menopause. Thus, estradiol enhances breast development, and is responsible for changes in the body shape, affecting bones, joints and fat deposition. Fat structure and skin composition are modified by estradiol.
Male reproduction
The effect of estradiol (and estrogens) upon male reproduction is complex. Estradiol is produced by action of aromatase mainly in the Leydig cells of the mammalian testis, but also by some germ cells and the Sertoli cells of immature mammals. It functions (in vitro) to prevent apoptosis of male sperm cells.
Several studies have noted sperm counts have been declining in many parts of the world, and estrogen exposure in the environment has been postulated to be the cause.Suppression of estradiol production in a subpopulation of subfertile men may improve the semen analysis.
Males with sex chromosome genetic conditions, such as Klinefelters syndrome, will have a higher level of estradiol.
Bone
Estradiol has a profound effect on bone. Individuals without it (or other estrogens) will become tall and eunuchoid, as epiphyseal closure is delayed or may not take place. Bone structure is affected also, resulting in early osteopenia and osteoporosis.Also, women past menopause experience an accelerated loss of bone mass due to a relative estrogen deficiency.
Liver
Estradiol has complex effects on the liver. It can lead to cholestasis. It affects the production of multiple proteins, including lipoproteins, binding proteins, and proteins responsible for blood clotting.
Brain
Estrogens can be produced in the brain from steroid precursors. As antioxidants, they have been found to have neuroprotective function.
The positive and negative feedback loops of the menstrual cycle involve ovarian estradiol as the link to the hypothalamic-pituitary system to regulate gonadotropins.
Recently, the volumes of sexually dimorphic brain structures in phenotypical males were found to change and approximate typical female brain structures when exposed to estradiol over a period of months,suggesting estradiol has a significant part to play in sex differentiation of the brain, both prenatally and throughout life.
There is also evidence the programming of adult male sexual behavior in many vertebrates is largely dependent on estradiol produced during prenatal life and early infancy. It is not yet known whether this process plays a significant role in human sexual behavior, although evidence from other mammals tends to indicate a connection.
Blood vessels
Estrogen affects certain blood vessels. Improvement in arterial blood flow has been demonstrated in coronary arteries.
OncogeneEstrogen is suspected to activate certain oncogenes, as it supports certain cancers, notably breast cancer and cancer of the uterine lining. In addition, several benign gynecologic conditions are dependent on estrogen, such as endometriosis, leiomyomata uteri, and uterine bleeding.
Pregnancy
The effect of estradiol, together with estrone and estriol, in pregnancy is less clear. They may promote uterine blood flow, myometrial growth, stimulate breast growth and at term, promote cervical softening and expression of myometrial oxytocin receptors.
Medical uses
---------------------------------------Hormonal contraception:A chemical derivative of estradiol, ethinyl estradiol with maximum dosage 200 μg, is a major component of hormonal contraceptive devices.
Hormone replacement therapy:If severe side effects of low levels of estradiol in a woman's blood are experienced (commonly at the beginning of menopause or after oophorectomy), hormone replacement therapy may be prescribed. Such therapy is usually combined with a progestin to reduce the risk of endometrial cancer.
Hormone replacement therapy in transgender women:Estrogen therapy is also used as part of the hormone replacement therapy for trans women. Either oral or transdermal estradiol is used in higher concentrations during initial treatment and transition; estradiol is continued in lower doses to maintain female-level hormones following gender reassignment surgery
Blocking estrogens:Inducing a state of hypoestrogenism may be beneficial in certain situations where estrogens are contributing to unwanted effects, e.g., certain forms of breast cancer, gynecomastia, premature closure of epiphyses, and inhibiting feminization in female-to-male transsexual hormone treatment. Estrogen levels can be reduced by inhibiting production using gonadotropin-releasing factor agonists (GnRH agonists) or blocking the aromatase enzyme using an aromatase inhibitor, such as anastrozole, or with an estrogen receptor antagonist, such as tamoxifen.
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