Estrone in the context of "Estriol"

Estrogen (also spelled oestrogen in British English; see spelling differences) is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal activity: estrone (E1), estradiol (E2), and estriol (E3). Estradiol, an estrane, is the most potent and prevalent. Another estrogen called estetrol (E4) is produced only during pregnancy.

Estrogens are synthesized in all vertebrates and some insects. Quantitatively, estrogens circulate at lower levels than androgens in both men and women. While estrogen levels are significantly lower in males than in females, estrogens nevertheless have important physiological roles in males.

Estrane is a C18 steroid derivative, with a gonane core.

Estrenes are estrane derivatives that contain a double bond, with an example being nandrolone. Estratrienes (estrins) are estrane derivatives that contain three double bonds, for instance estrin (estra-1,3,5(10)-triene). A class of female sex hormones, estrogens, such as estradiol, estrone, and estriol are estratrienes.

Estetrol (E4), or oestetrol, is one of the four natural estrogenic steroid hormones found in humans, along with estrone (E1), estradiol (E2), and estriol (E3). Estetrol is a major estrogen in the body. In contrast to estrone and estradiol, estetrol is a native estrogen of fetal life. Estetrol is produced exclusively by the fetal liver and is found in detectable levels only during pregnancy, with relatively high levels in the fetus and lower levels in the maternal circulation.

In addition to its physiological role as a native hormone, estetrol can be used as a medication, see estetrol (medication). Estetrol, in combination with drospirenone, has recently been approved as a new estrogenic component of a combined oral contraceptive (COC) and estetrol alone is in clinical development for the treatment of menopausal symptoms as well as breast and prostate cancer.

Bioidentical hormone replacement therapy (BHRT), also known as bioidentical hormone therapy (BHT) or natural hormone therapy, is the use of hormones that are identical on a molecular level with endogenous hormones in hormone replacement therapy. It may also be combined with blood and saliva testing of hormone levels, and the use of pharmacy compounding to obtain hormones in an effort to reach a targeted level of hormones in the body. A number of claims by some proponents of BHT have not been confirmed through scientific testing. Specific hormones used in BHT include estrone, estradiol, progesterone, testosterone, dehydroepiandrosterone (DHEA), and estriol.

Custom-compounded BHT is a practice almost wholly restricted to the United States and is a form of alternative medicine. It has been promoted as a panacea for many diseases and for relieving the symptoms of menopause beyond the medical objective of reducing the risk of osteoporosis. There is little evidence to support these incremental claims; the hormones are expected to have the same risks and benefits as comparable approved drugs for which there is evidence based on extensive research and regulation, except for progesterone, which may have an improved safety profile than artificial progestogens, though direct comparisons with progestins have not been made. Risks associated with the less-controlled process of compounding bioidentical hormones are not clearly understood. In addition, the accuracy and efficacy of saliva testing have not been definitively proven, and the long-term effects of using blood testing to reach target levels of hormones have not been researched.