Estrone (E1), also spelled oestrone, is a steroid, a weak estrogen, and a minor female sex hormone. It is one of three major endogenous estrogens, the others being estradiol and estriol. Estrone, as well as the other estrogens, are synthesized from cholesterol and secreted mainly from the gonads, though they can also be formed from adrenal androgens in adipose tissue. Relative to estradiol, both estrone and estriol have far weaker activity as estrogens. Estrone can be converted into estradiol, and serves mainly as a precursor or metabolic intermediate of estradiol. It is both a precursor and metabolite of estradiol.
Methyltestosterone, sold under the brand names Android, Metandren, and Testred among others, is an androgen and anabolic steroid (AAS) medication which is used in the treatment of low testosterone levels in men, delayed puberty in boys, at low doses as a component of menopausal hormone therapy for menopausal symptoms like hot flashes, osteoporosis, and low sexual desire in women, and to treat breast cancer in women. It is taken by mouth or held in the cheek or under the tongue.
Fluoxymesterone, sold under the brand names Halotestin and Ultandren among others, is an androgen and anabolic steroid (AAS) medication which is used in the treatment of low testosterone levels in men, delayed puberty in boys, breast cancer in women, and anemia. It is taken by mouth.
Mestranol, sold under the brand names Enovid, Norinyl, and Ortho-Novum among others, is an estrogen medication which has been used in birth control pills, menopausal hormone therapy, and the treatment of menstrual disorders. It is formulated in combination with a progestin and is not available alone. It is taken by mouth.
Testolactone is a non-selective, irreversible, steroidal aromatase inhibitor which is used as an antineoplastic drug to treat advanced-stage breast cancer. The drug was discontinued in 2008 and is no longer available for medical use.
Methallenestril, also known as methallenoestril and as methallenestrol, as well as Horeau's acid, is a synthetic nonsteroidal estrogen and a derivative of allenolic acid and allenestrol that was formerly used to treat menstrual issues but is now no longer marketed. It is a seco-analogue of bisdehydrodoisynolic acid, and although methallenestril is potently estrogenic in rats, in humans it is only weakly so in comparison. Vallestril was a brand of methallenestril issued by G. D. Searle & Company in the 1950s. Methallenestril is taken by mouth. By the oral route, a dose of 25 mg methallenestril is approximately equivalent to 1 mg diethylstilbestrol, 4 mg dienestrol, 20 mg hexestrol, 25 mg estrone, 2.5 mg conjugated estrogens, and 0.05 mg ethinylestradiol.
An estrogen ester is an ester of an estrogen, most typically of estradiol but also of other estrogens such as estrone, estriol, and even nonsteroidal estrogens like diethylstilbestrol. Esterification renders estradiol into a prodrug of estradiol with increased resistance to first-pass metabolism, slightly improving its oral bioavailability. In addition, estrogen esters have increased lipophilicity, which results in a longer duration when given by intramuscular or subcutaneous injection due to the formation of a long-lasting local depot in muscle and fat. Conversely, this is not the case with intravenous injection or oral administration. Estrogen esters are rapidly hydrolyzed into their parent estrogen by esterases once they have been released from the depot. Because estradiol esters are prodrugs of estradiol, they are considered to be natural and bioidentical forms of estrogen.
A nonsteroidal estrogen is an estrogen with a nonsteroidal chemical structure. The most well-known example is the stilbestrol estrogen diethylstilbestrol (DES). Although nonsteroidal estrogens formerly had an important place in medicine, they have gradually fallen out of favor following the discovery of toxicities associated with high-dose DES starting in the early 1970s, and are now almost never used. On the other hand, virtually all selective estrogen receptor modulators (SERMs) are nonsteroidal, with triphenylethylenes like tamoxifen and clomifene having been derived from DES, and these drugs remain widely used in medicine for the treatment of breast cancer among other indications. In addition to pharmaceutical drugs, many xenoestrogens, including phytoestrogens, mycoestrogens, and synthetic endocrine disruptors like bisphenol A, are nonsteroidal substances with estrogenic activity.
Conjugated estrogens (CEs), or conjugated equine estrogens (CEEs), sold under the brand name Premarin among others, is an estrogen medication which is used in menopausal hormone therapy and for various other indications. It is a mixture of the sodium salts of estrogen conjugates found in horses, such as estrone sulfate and equilin sulfate. CEEs are available in the form of both natural preparations manufactured from the urine of pregnant mares and fully synthetic replications of the natural preparations. They are formulated both alone and in combination with progestins such as medroxyprogesterone acetate. CEEs are usually taken by mouth, but can also be given by application to the skin or vagina as a cream or by injection into a blood vessel or muscle.
Broparestrol, also known as α-bromo-α,β-diphenyl-β-p-ethylphenylethylene (BDPE), is a synthetic, nonsteroidal selective estrogen receptor modulator (SERM) of the triphenylethylene group that has been used in Europe as a dermatological agent and for the treatment of breast cancer. The drug is described as slightly estrogenic and potently antiestrogenic, and inhibits mammary gland development and suppresses prolactin levels in animals. It is structurally related to clomifene and diethylstilbestrol. Broparestrol is a mixture of E- and Z- isomers, both of which are active, and are similarly antiestrogenic but, unlike broparestrol, were never marketed.
Triphenylethylene (TPE) is a simple aromatic hydrocarbon that possesses weak estrogenic activity. Its estrogenic effects were discovered in 1937. TPE was derived from structural modification of the more potent estrogen diethylstilbestrol, which is a member of the stilbestrol group of nonsteroidal estrogens.
Estradiol stearate (E2-17-St), also known as estradiol octadecanoate and sold under the brand name Depofollan, is a naturally occurring estrogen and an estrogen ester – specifically, the C17β stearate ester of estradiol. It occurs in the body as a very long-lasting metabolite and prohormone of estradiol. The compound is one of the components that collectively constitute lipoidal estradiol, another of which is estradiol palmitate. It is extremely lipophilic and hydrophobic. Estradiol stearate has no affinity for the estrogen receptor, requiring transformation into estradiol via esterases for its estrogenic activity. The compound does not bind to sex hormone-binding globulin or α-fetoprotein, instead being transported by lipoproteins such as high-density lipoprotein and low-density lipoprotein.
Bisdehydrodoisynolic acid (BDDA), as the (Z)-isomer ( -BDDA), is a synthetic, nonsteroidal estrogen related to doisynolic acid that was never marketed. It is one of the most potent estrogens known, although it has more recently been characterized as a selective estrogen receptor modulator (SERM). BDDA and other doisynolic acid derivatives display relatively low affinity accompanied by disproportionately high estrogenic potency in vivo, which was eventually determined to be due to transformation into metabolites with greater estrogenic activity. The drug was discovered in 1947 as a degradation product of the reaction of equilenin or dihydroequilenin with potassium hydroxide. It is the seco-analogue of equilenin, while doisynolic acid is the seco-analogue of estrone. These compounds, along with diethylstilbestrol, can be considered to be open-ring analogues of estradiol. The methyl ether of BDDA, doisynoestrol, is also an estrogen, and in contrast to BDDA, has been marketed.
Allenolic acid, or allenoic acid, is a synthetic, nonsteroidal estrogen discovered in 1947 or 1948 that, although studied clinically, was never marketed. It is an open-ring or seco-analogue of steroidal estrogens like estrone and equilenin. The compound was named after Edgar Allen, one of the pioneers in estrogen research. Although described as an estrogen, allenolic acid probably is totally inactive at the receptor, whereas a derivative, allenestrol, is reported to be a potent estrogen. Another derivative of allenolic acid, methallenestril, is also a potent estrogen and, in contrast to allenolic acid and allenestrol, has been marketed.
Estriol glucuronide (E3G), or oestriol glucuronide, also known as estriol monoglucuronide, as well as estriol 16α-β-D-glucosiduronic acid, is a natural, steroidal estrogen and the glucuronic acid conjugate of estriol. It occurs in high concentrations in the urine of pregnant women as a reversibly formed metabolite of estriol. Estriol glucuronide is a prodrug of estriol, and was the major component of Progynon and Emmenin, estrogenic products manufactured from the urine of pregnant women that were introduced in the 1920s and 1930s and were the first orally active estrogens. Emmenin was succeeded by Premarin, which is sourced from the urine of pregnant mares and was introduced in 1941. Premarin replaced Emmenin due to the fact that it was easier and less expensive to produce.
Allenestrol, or allenoestrol, also known as α,α-dimethyl-β-ethylallenolic acid or as methallenestrilphenol, is a synthetic, nonsteroidal estrogen and a derivative of allenolic acid that was never marketed. A methyl ether of allenestrol, methallenestril (methallenestrol), is also an estrogen, but, in contrast to allenestrol, has been marketed.
A sex-hormonal agent, also known as a sex-hormone receptor modulator, is a type of hormonal agent which specifically modulates the effects of sex hormones and of their biological targets, the sex hormone receptors. The sex hormones include androgens such as testosterone, estrogens such as estradiol, and progestogens such as progesterone. Sex-hormonal agents may be either steroidal or nonsteroidal in chemical structure and may serve to either enhance, inhibit, or have mixed effects on the function of the sex hormone systems.
Estriol (E3), sold under the brand name Ovestin among others, is an estrogen medication and naturally occurring steroid hormone which is used in menopausal hormone therapy. It is also used in veterinary medicine as Incurin to treat urinary incontinence due to estrogen deficiency in dogs. The medication is taken by mouth in the form of tablets, as a cream that is applied to the skin, as a cream or pessary that is applied in the vagina, and by injection into muscle.
Estrone sulfate (E1S) is an estrogen medication and naturally occurring steroid hormone. It is used in menopausal hormone therapy among other indications. As the sodium salt, it is the major estrogen component of conjugated estrogens (Premarin) and esterified estrogens. In addition, E1S is used on its own as the piperazine salt estropipate. The compound also occurs as a major and important metabolite of estradiol and estrone. E1S is most commonly taken by mouth, but in the form of Premarin can also be taken by parenteral routes such as transdermal, vaginal, and injection.
