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{{BioPsy}}
An '''antiandrogen''', or '''androgen antagonist''', is any of a group of [[hormone]] [[receptor antagonist]] compounds that are capable of preventing or inhibiting the biologic effects of [[androgen]]s, [[male]] sex [[hormone]]s, on normally responsive tissues in the body (see [[androgen insensitivity syndrome]]). Antiandrogens usually work by blocking the appropriate [[receptor (biochemistry)|receptor]]s, competing for binding sites on the [[cell (biology)|cell's]] surface, obstructing the androgens' pathway.
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'''Antiandrogens''', or '''androgen antagonists''', first [[discovery and development of antiandrogens|discovered]] in the 1960s, prevent [[androgen]]s from expressing their biological effects on responsive tissues.<ref>{{cite web |url=http://medical-dictionary.thefreedictionary.com/Anti-androgen |title=Medical Dictionary: Anti-androgen}}</ref> Antiandrogens alter the androgen pathway by blocking the appropriate [[androgen receptor|receptors]], competing for binding sites on the cell's surface, or affecting androgen production.<ref name=Mowszowicz>{{Cite journal |author=Mowszowicz I. |title=Antiandrogens. Mechanisms and paradoxical effects |journal=Ann Endocrinol (Paris) |pages=50(3):189–99 |year=1989 |pmid=2530930 |volume=50 |issue=3}}</ref> Antiandrogens can be prescribed to treat an array of diseases and disorders. In men, antiandrogens are most frequently used to treat prostate cancer.<ref name=Gillatt>{{Cite journal |author=Gillatt D. |title=Antiandrogen treatments in locally advanced prostate cancer: are they all the same? |journal=J Cancer Res Clin Oncol. |volume=1 |pages=S17-26 |year=2006 |pmid=16845534 |doi=10.1007/s00432-006-0133-5}}</ref> In women, antiandrogens are used to decrease levels of male hormones causing symptoms of [[hyperandrogenism]].<ref name=hyperandrogenism>{{cite web |url=http://medical-dictionary.thefreedictionary.com/Hyperandrogenism |title=Medical Dictionary: Hyperandrogenism}}</ref> Antiandrogens present in the environment have become a topic of concern. Many industrial chemicals, [[pesticides]] and [[insecticides]] exhibit antiandrogenic effects.<ref name=Gray>{{Cite journal |author= Gray LE, Ostby J, Furr J, Wolf CJ, Lambright C, Parks L, Veeramachaneni DN, Wilson V, Price M, Hotchkiss A, Orlando E, Guillette L. |title=Effects of environmental antiandrogens on reproductive development in experimental animals |journal=Human Reproduction Update |volume=2 |pages=248–64 |year=2001 |pmid=11392371 |issue=3 |doi=10.1093/humupd/7.3.248}}</ref><ref name=Rider>{{Cite journal |author= Rider CV, Furr JR, Wilson VS, Gray LE Jr. |title=Cumulative effects of in utero administration of mixtures of reproductive toxicants that disrupt common targe tissues via diverse mechanisms of toxicity |journal=International Journal of Andrology |volume=33 |pages=443–62 |year=2010 |month=Apr |pmid=20487044 |doi=10.1111/j.1365-2605.2009.01049.x |issue=2 |pmc=2874988}}</ref> Certain plant species have also been found to produce antiandrogens. Environmental antiandrogens can have harmful effects on reproductive organ development in fetuses exposed in utero as well as their offspring.<ref name=Gray/>
   
Antiandrogens are often indicated to treat severe male sexual disorders, such as [[hypersexuality]] (excessive [[sexual desire]]) and [[sexual deviation]], specifically [[paraphilia]]s, as well as use as an [[antineoplastic]] agent and [[palliative]], [[adjuvant]] or [[neoadjuvant]] [[hormone therapy|hormonal therapy]] in [[prostate cancer]].
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== Mechanism of action ==
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Antiandrogens are classified as [[steroidal]] or nonsteroidal. [[Discovery and development of antiandrogens#Steroidal antiandrogens|Steroidal]] antiandrogens not only counter androgens, but also affect [[secondary sex characteristic]]s. Steroidal antiandrogens directly affect gene expression due to their fat-soluble nature that allows them to diffuse through the [[plasma membrane]]’s [[phospholipid bilayer]] and prevent the binding of testosterone and dihydrotestosterone (DHT) to the androgen receptor.<ref>{{cite web |url=http://healthandprostate.com/prostate-cancer/steroidal-antiandrogens |title=Steroidal Antiandrogens |work= Health and Prostate |accessdate=9 December 2011}}</ref> [[Discovery and development of antiandrogens#Non-steroidal antiandrogens|Non-steroidal]] antiandrogens, or “pure” antiandrogens, such as [[nilutamide]] and [[flutamide]], counter androgens and have no steroidal effects. Antiandrogens inhibit circulating androgens by blocking androgen receptors, suppressing androgen synthesis, or acting in both those ways.<ref name=Zouboulis>{{Cite journal |author =Zouboulis CC, Rabe T. |title=Hormonal antiandrogens in acne treatment |journal=Journal of the German Society of Dermatology |year=2010 |month=March |pmid=20482693 |doi=10.1111/j.1610-0387.2009.07171.x |volume=8 Suppl 1 |pages=S60–74}}</ref> The most common antiandrogens are [[androgen receptor]] (AR) antagonists which act on the target cell level and competitively bind to [[androgen receptors]].<ref name=Mowszowicz/>
   
Antiandrogens can also be used for treatment of [[benign prostatic hyperplasia]] (prostate enlargement), [[acne vulgaris]], androgenetic alopecia ([[male pattern baldness]]), and [[hirsutism]] (excessive [[hair]]iness). They are also occasionally used as a [[male contraceptive]] agent, to purposefully prevent or counteract masculinisation in the case of [[transwomen]] undergoing [[gender reassignment therapy]], and to prevent the symptoms associated with reduced [[testosterone]], such as [[hot flush]]es, following [[castration]].
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Inhibition of androgen production occurs through a unique mechanism for each antiandrogen. For example, [[ketoconazole]] not only competes with androgens such as testosterone and DHT for androgen receptor binding, but also suppresses androgen synthesis by inhibiting [[cytochrome P450]] and [[CYP17A1|17,20-lyase]], which partake in synthesizing and degrading steroids, including the precursors of testosterone. The result is a decrease in the overall [[testosterone]] production of the adrenal cortex.<ref name="pmid2652864">{{cite journal |author=Witjes FJ, Debruyne FM, Fernandez del Moral P, Geboers AD |title=Ketoconazole high dose in management of hormonally pretreated patients with progressive metastatic prostate cancer. Dutch South-Eastern Urological Cooperative Group |journal=Urology |volume=33 |issue=5 |pages=411–5 |year=1989 |month=May |pmid=2652864 |doi= 10.1016/0090-4295(89)90037-X|url=}}</ref> [[Gonadotrophins]], pituitary hormones capable of altering androgen synthesis, are also affected by antiandrogens. Antiandrogens can have suppressive effects on gonadotropin secretion by down-regulating [[gonadotropin-releasing hormone receptor]]s (GnRHR) in the [[pituitary gland]]. A decreased amount of GnRHRs results in [[gonadotropin-releasing hormone]] (GnRH) not being able to bind sufficiently. GnRH is responsible for the release of the gonadotropins [[luteinizing hormone]] (LH) and [[follicle-stimulating hormone]] (FSH). LH stimulates the [[Leydig cells]] of the [[testes]] and the [[theca cells]] of the [[ovaries]] to produce testosterone (and indirectly [[estradiol]]). Therefore, if GnRH cannot bind, testosterone synthesis is not induced in the testes or ovaries.<ref name=gonadotropin>{{cite web|url=http://medical-dictionary.thefreedictionary.com/gonadotropin |title=Gonadotropin |accessdate=9 December 2011}}</ref>
   
The administration of antiandrogens in males can result in slowed or halted development or reversal of male [[secondary sex characteristic]]s, reduced activity or function of the accessory male [[sex organs]], and hyposexuality (diminished [[sexual desire]] or [[libido]]).
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== Medical applications ==
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Antiandrogenic pharmaceuticals are used to treat an array of medical conditions that are dependent on the androgen pathway. Antiandrogens are often prescribed for men with [[prostate cancer]], [[benign prostatic hyperplasia]], [[hypersexuality]], [[male contraception]], and for those that are undergoing [[gender reassignment]]. For women, antiandrogens are often prescribed for severe cases of [[acne vulgaris|acne]], [[amenorrhea]], [[seborrhea]], [[hirsutism]], [[androgenic alopecia]], [[hidradenitis suppurativa]], and [[hyperandrogenism]].
   
The term ''antiandrogen withdrawal response'' (AAWR) describes the medical course taken when cancer cells adapt to feed on the antiandrogens rather than androgen, so that treatment must be halted in order to starve those cells thriving on the antiandrogens.
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=== Pharmaceuticals for men ===
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Antiandrogens in males can result in hyposexuality (diminished [[sexual desire]] or [[libido]]), reduced activity or function of the accessory male [[sex organs]], and slowed or halted development or reversal of male [[secondary sex characteristic]]s.<ref name=Antiandrogendrugs>{{cite web |url=http://medical-dictionary.thefreedictionary.com/Antiandrogen+Drugs |title=Antiandrogen Drugs}}</ref>
   
Currently available antiandrogen drugs (brand names in parentheses) include:
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Antiandrogenic drugs are often indicated to treat severe male sexual disorders, such as [[hypersexuality]] (excessive [[sexual desire]]) and [[sexual deviation]] such as [[paraphilia]], a disorder involving intense recurrent sexual urges), since lowering male hormone levels decreases libido.<ref name=Canadian>{{Cite journal |title=Anti-androgens for sex offenders |journal=Canadian Medical Association Journal |volume=109 |pages=257 |year=1973 |pmid=20312137|pmc=1946843 |issue=4}}</ref> As a part of a program for registered sex offenders recently released from prisons, the offender is sometimes administered antiandrogen drugs to reduce the likelihood of repeat offenses by reducing sexual drive.<ref name=Canadian/> On occasion, antiandrogens are used as a [[male contraceptive]] agent.
   
* [[Spironolactone]] (Aldactone, Spiritone), a synthetic 17-spirolactone [[corticosteroid]], which is a renal competitive [[aldosterone]] antagonist in a class of [[pharmaceutical]]s called [[potassium]]-sparing [[diuretic]]s, used primarily to treat low-[[renin]] [[hypertension]], [[hypokalemia]], and [[Conn's syndrome]].
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==== Prostate cancer ====
* [[Cyproterone acetate]] (Androcur, Climen, Diane 35, Ginette 35), a [[chemical synthesis|synthetic]] [[steroid]], a potent antiandrogen that also possesses [[progestagen|progestational]] properties.
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Decreasing the body’s response to androgen can have beneficial effects in treating [[prostate cancer]]. Prostate cancer is the most commonly diagnosed form of cancer found in men.<ref name=Gillatt/> Some prostate cancer cells require androgens for growth. To counteract cancer cell proliferation, antiandrogenic drugs are used for hormone therapy called [[androgen deprivation therapy]] (ADT). Some antiandrogenic drugs suppress androgen production while others inhibit androgens from binding to the cancer cells’ androgen receptors. These two classes of drugs can be prescribed separately or can be used together for a complete/combined androgen blockade (CAB). When the body is deprived of androgens, the therapy is termed castration-based therapy as the lack of androgens mimics castration. By competing with circulating androgens for binding sites on prostate cell receptors, antiandrogens promote apoptosis and inhibit prostate cancer growth.<ref name=Gillatt/> Hormone therapy antiandrogen drugs can be prescribed as monotherapy or in addition to radical radiotherapy or prostatectomy.<ref name=Gillatt/> Antiandrogen monotherapy generally causes fewer side effects in males although it may block androgen less effectively than combined therapies. Monotherapy is often preferred by men as it is less likely than combined therapies to diminish libido or cause tenderness of the breasts, diarrhea, and nausea.<ref>{{[http://www.medicinenet.com/script/main/art.asp?articlekey=50534 "Hormone Therapy for Prostate Cancer"]}}</ref>
* [[Flutamide]] (Eulexin), [[nilutamide]] (Anandron, Nilandron) and [[bicalutamide]] (Casodex), nonsteroidal, pure antiandrogens. Flutamide is the oldest and has more unwanted side effects than the others. Bicalutamide is the newest and has the least side effects.
 
* [[Ketoconazole]] (Nizoral), an [[imidazole]] derivative used as a [[broad-spectrum]] antifungal agent effective against a variety of fungal infections, side effects include serious [[liver]] damage and reduced levels of androgen from both the [[testicle]]s and [[adrenal gland]]s. Ketoconazole is a relatively weak antiandrogen.
 
* [[Finasteride]] (Proscar, Propecia) and [[dutasteride]] (Avodart), inhibitors of the [[5-alpha reductase|5-α-reductase]] [[enzyme]] that prevent the conversion of testosterone into [[dihydrotestosterone]] (DHT). Finasteride blocks only 5-α-reductase type II, dutasteride also blocks type I. They are not general antiandrogens in that they don't counteract the effects or production of other androgens than DHT.
 
   
==See also==
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Androgen-deprivation therapy (ADT) has been shown to cause initial reduction of prostate tumors.<ref name=Massard>{{Cite journal |author= Massard, C. |title=Targeting Continued Androgen Receptor Signaling in Prostate Cancer |journal= Clinical Cancer Research |volume=17(12) |pages=3876–883 |year=2011 |month=Jun}}</ref> However, antiandrogenic drugs can cause prostate cancer tumors to become androgen independent. Androgen independence occurs when cells that are not reliant on androgen proliferate and spread while cells that require androgen for survival undergo [[apoptosis]]. The cells that do not require androgen become the basis of the tumors, causing reoccurring tumors a few years after the initial disappearance of the prostate cancer. Once prostate cancer becomes androgen independent, hormone therapy will most likely no longer benefit the individual and a new treatment approach will be needed.<ref name=Massard/>
   
* [[GnRH antagonist]]
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In one study, the efficacy of reducing prostate cancer cells by castration was compared to combined androgen blockade (CAB) in which castration is combined with an antiandrogenic drug. [[Flutamide]] (brand name Eulexin), [[nilutamide]] (brand names Anandron and Nilandron) and [[bicalutamide]] (brand name Casodex) are nonsteroidal, “pure” antiandrogens. Flutamide has several side effects that the newer bicalutamide does not. Used in combination with castration, [[nilutamide]] and [[flutamide]] were found to have a minimal effect on prolonging survival while [[bicalutamide]] significantly prolonged life in prostate cancer patients.<ref name=Akaza>{{Cite journal |author= Akaza H. |title=Combined androgen blockade for prostate cancer: review of efficacy, safety, and cost-effectiveness |journal=Cancer Science |volume=102 |pages=51–6 |year=2011 |month=Jan |pmid=21091846 |doi=10.1111/j.1349-7006.2010.01774.x |issue=1}}</ref> As a result of these conclusions, since 2007 combined androgen blockade with bicalutamide has been used as an effective, safe, and cost-efficient treatment of prostate cancer.<ref name=Akaza/>
* [[GnRH agonist]]
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* [[Baldness treatments]]
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[[5-alpha-reductase inhibitor]]s such as [[finasteride]] (brand names Proscar and Propecia), [[dutasteride]] (brand name Avodart), [[bexlosteride]], [[izonsteride]], [[turosteride]], and [[epristeride]] are antiandrogenic as they prevent the reduction of [[testosterone]] to [[dihydrotestosterone]] (DHT).<ref name=Flores>{{Cite journal |author= Flores E, Bratoeff E, Cabeza M, Ramirez E, Quiroz A, Heuze I. |title=Steroid 5alpha-reductase inhibitors |journal=Mini-Reviews in Medicinal Chemistry |volume=3 |pages=225–37 |year=2003 |month=May |pmid=12570838 |issue=3}}</ref> DHT is 3-5 times more potent than testosterone or other androgens (except in skeletal muscle tissue, where testosterone is the main androgen). They are unique because they do not counteract the effects or production of other androgens other than DHT. Dihydrotestosterone is necessary for development of both external male sex organs and the prostate. 5α-reductase inhibitors are most often used to treat [[benign prostatic hyperplasia]] since the resulting decrease in dihydrotestosterone inhibits proliferation of prostate cells.<ref name=Flores/>
* [[Estrogens]]
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=== Pharmaceuticals for women ===
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Hyperandrogenism is a condition found in women where ovaries overproduce androgens, which are typically considered male hormones as they are important for the development of male reproductive organs and secondary male characteristics.<ref name=hyperandrogenism/> Antiandrogenic drugs can help to counteract male hormones that cause skin and hair problems in women. [[Gonadotrophin]], a pituitary hormone, is involved in ovarial androgen production and its suppression can result in reduced testosterone production. Antiandrogens can inhibit the release of the gonadotropic hormone, [[luteinizing hormone]] (LH), suppressing testosterone synthesis in the ovaries.<ref name=gonadotropin/> [[Androgenic alopecia]] (a type of hair loss and pattern baldness), [[acne vulgaris]], [[seborrhea]], [[amenorrhea]] (absence of menstrual periods), [[hirsutism]] (excessive facial and bodily hair in women), and [[hidradenitis suppurativa]] can all be caused by an excess of male hormones.<ref name=Dermnet>{{cite web |url=http://dermnetnz.org/treatments/antiandrogens.html |author=Dr. Amanda Oakley |title=Hormonal treatment}}</ref>
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Hormonal antiandrogen treatment is given to female patients that suffer from multiple symptoms of hyperandrogenism.<ref name=Zouboulis/> Acne is the most common of all the skin disorders that result from male hormones overproduction. Fewer androgens present in a female’s tissues results in a reduction of oil ([[sebum]]) production and bumps ([[comedone]]).<ref name=Dermnet/> Also, antiandrogenic drugs are often combined with topical and oral pharmaceuticals to treat acne. In women that suffer from overproduction of hair due to high testosterone levels (hirsutism), antiandrogenic drugs are used to slow hair growth, lighten hair color, and thin the hair. For females with pattern hair loss (androgenic alopecia), antiandrogens can assist in reducing hair shedding and thinning.<ref name=Dermnet/>
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The most common antiandrogenic drugs used to treat women with hyperandrogenism are [[spironolactone]] and [[cyproterone acetate]]. [[Spironolactone]] (brand names Aldactone and Spirotone), a synthetic 17-spirolactone [[corticosteroid]] is used primarily to treat low-[[renin]] [[hypertension]], [[hypokalemia]], and [[Conn's syndrome]]. [[Cyproterone acetate]] (brand names Androcur, Climen, Diane 35, and Ginette 35) is a [[chemical synthesis|synthetic]] [[steroid]], a potent antiandrogen that also possesses [[progestagen|progestational]] properties. Oral contraceptives that mediate progesterone have no effect on androgens but may be combined with spironolactone and cyproterone acetate for the purpose of correcting menstrual irregularities.<ref name=Dermnet/>
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Also used to purposefully prevent or counteract masculinisation in the case of [[transwomen|transsexual women]] undergoing [[sex reassignment therapy]], and to prevent the symptoms associated with reduced [[testosterone]], such as [[hot flash]]es, following [[castration]].<ref name=Antiandrogendrugs/>
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== Environmental exposure ==
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Exposure to antiandrogens can occur unintentionally due to natural or anthropogenic compounds in the environment. Environmental compounds affecting the endocrine system, termed [[endocrine disruptor]]s, that antagonistically affect androgen receptors and androgen production can negatively affect individuals that come in contact with the compounds as well as their future generations.<ref name=Gray/> Certain pesticides and insecticides as well as in industrial chemicals contain antiandrogenic chemicals. Some species of plants produce phytochemicals with antiandrogenic effects. Exposure to these environmental antiandrogens has resulted in adverse effects on animals that allude to human health risks.
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=== Pesticides and insecticides ===
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Exposure to pesticides and insecticides with antiandrogenic properties has been found to negatively affect humans and laboratory animals. Androgens are important in fetal development as well as in pubertal development. Exposure during critical periods of development can cause reproductive malformations in males while exposure after birth and before puberty can delay pubertal development.<ref name=Gray/>
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Animal studies with [[vinclozolin]], [[procymidone]], linuron, and the [[DDT]] metabolite [[dichlorodiphenyldichloroethylene]] (p.p’-DDE) show irregular reproductive development due to their function as androgen receptor antagonists that inhibit androgen-activated gene expression.<ref name=Gray/><ref name=Curtis>{{Cite journal |author= Curtis LR. |title=Organophosphate antagonism of the androgen receptor |journal=Toxicological Sciences |volume=60 |pages=1–2 |year=2001 |month=Mar |pmid=11222865 |issue=1}}</ref> Even with low doses of antiandrogenic pesticides, developmental effects such as reduced anogenital distance and induction of areolas were seen in male rats.<ref name=Gray/>
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Animal studies show that deformities result in offspring exposed to antiandrogens.<ref name=Gray/> Male mice can display malformations that resemble the reproductive organs of females as in the case of exposure to [[vinclozolin]] or proymidone. Exposure to vinclozolin or procymidone in utero feminized male offspring, as seen in abnormalities of anogenital distance, small or absent sex accessory glands, [[hypospadias]], undescended testes, retained nipples, cleft [[phallus]], and presence of a vaginal pouch. Male mice exposed before puberty to vinclozolin experienced delayed pubertal development visualized by delayed onset of androgen-dependent [[foreskin|preputial]] separation.<ref name=Gray/>
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[[Ketoconazole]]'s [[imidazole]] derivative is used as a [[broad-spectrum]] antifungal agent effective against a variety of fungal infections. Although ketoconazole is a relatively weak antiandrogen, side-effects seen as a result of exposure include serious [[liver]] damage and reduced levels of androgens from both the [[testicle]]s and [[adrenal gland]]s.<ref name=Gray/>
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Organophostphate insecticides such as fenitrothion can also behave as androgen receptor antagonists. Fenitrothion was found to completely inhibit dihydrotestosterone-dependent human androgen receptor activation, resulting in reduced weights of seminal vesicles and the ventral prostate. Structural similarity of fenitrothion with linuron further supports the findings of antiandrogenic activity.<ref name=Curtis/>
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=== Industrial chemicals ===
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Industrial chemicals with antiandrogenic effects are ubiquitous in the environment. Consumer products such as toys and cosmetics may contain phthalates or parabens, which disrupt androgen synthesis.<ref name=Gray/><ref name=Rider/>
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Phthalates are mainly found in plastics. Fetuses that are exposed to a mixture of pthalates in utero may show signs of disrupted reproductive development.<ref name=Rider/><ref name=Darbre>{{Cite journal |author= Darbre PD, Harvey PW. |title=Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks |journal=Journal of Applied Toxicology |volume=28 |pages=561–78 |year=2008 |month=Jul |pmid=18484575 |doi=10.1002/jat.1358 |issue=5}}</ref> When [[Di-n-butyl phthalate]] (DBP), [[diisobutyl phthalate]] (DiBP), [[benzyl butyl phthalate]] (BBP), [[Bis(2-ethylhexyl) phthalate]] (DEHP) and di-n-pentyl phthalate (DPP) were combined, reductions in both testosterone synthesis and gene expression of steroidogenic pathway proteins were seen. The result in male rats was undescended testes and abnormal development of reproductive tissues.<ref name=Rider/>
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Parabens are commonly found in cosmetics and pharmaceuticals. Paraben esters, such as [[Butylparaben#Antiandrogenic|butylparaben]], have been found to mimic androgen antagonist activity. Antiandrogenic endocrine disruption has been shown in aquatic species but the mechanism is unknown. Researchers believe parabens have the ability to bind to human androgen receptors but it still remains unclear.<ref name=Darbre/>
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=== Phytochemicals ===
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Antiandrogenic chemicals can also occur naturally in plants.
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The best known plant-derived anti-androgen is [[3,3'-Diindolylmethane]](DIM)<ref name="example web reference">[http://www.ncbi.nlm.nih.gov/pubmed/12665522 Plant-derived 3,3'-Diindolylmethane is a strong androgen antagonist in human prostate cancer cells.]</ref>
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Spearmint tea has antiandrogenic properties in females with [[hirsutism]].,<ref>Grant P. 'Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial [[Phytotherapy Research]] 2010 24:2 (186-188)</ref><ref>Akdogan M. Tamer MN. Cure E. Cure MC. Koroglu BK. Delibas N."Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism." '' Phytotherapy Research''. 21(5):444-7, 2007 May.</ref>
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''[[Scutellaria baicalensis]]'' may also have antiandrogenic properties.<ref>Bonham M., Posakony J., Coleman I., Montgomery B., Simon J., Nelson P.S."Characterization of chemical constituents in Scutellaria baicalensis with antiandrogenic and growth-inhibitory activities toward prostate carcinoma" [[Clinical Cancer Research]] 2005 11:10 (3905-3914)</ref>
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The compound N-butylbenzene-sulfonamide (NBBS) isolated from ''[[Pygeum africanum]]'' is a specific [[androgen antagonist|androgen antagonis]]t.,<ref>Papaioannou M. Schleich S. Roell D. Schubert U. Tanner T. Claessens F. Matusch R. Baniahmad A. ,"NBBS isolated from Pygeum africanum bark exhibits androgen antagonistic activity, inhibits AR nuclear translocation and prostate cancer cell growth.",''Investigational New Drugs''. 28(6):729-43, 2010 Dec.</ref><ref>Schleich S. Papaioannou M. Baniahmad A. Matusch R.,"Extracts from Pygeum africanum and other ethnobotanical species with antiandrogenic activity.", [[Planta Medica]]. 72(9):807-13, 2006 Jul.</ref>
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''[[Glycyrrhiza glabra]]'' has shown antiandrogenic activity in male rats<ref>Zamansoltani F. Nassiri-Asl M. Sarookhani MR. Jahani-Hashemi H. Zangivand AA. "Antiandrogenic activities of Glycyrrhiza glabra in male rats.", International Journal of Andrology. 32(4):417-22, 2009 Aug</ref>
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A herbal formula (termed KMKKT) containing Korean ''[[Angelica gigas]]'' Nakai (AGN) root and nine other oriental herbs has shown ''in vitro'' anti-androgen activity.<ref>Jiang C., Lee H.-J., Li G.-X., Guo J., Malewicz B., Zhao Y., Lee E.-O., Lee H.-J., Lee J.-H., Kim M.-S., Kim S.-H., Lu J. "Potent antiandrogen and androgen receptor activities of an Angelica gigas-containing herbal formulation: Identification of decursin as a novel and active compound with implications for prevention and treatment of prostate cancer" '' Cancer Research'' 2006 66:1 (453-463)</ref>
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''[[Pygeum africanum]]'' contains an antiandrogenic compound atraric acid.<ref>Schleich S. Papaioannou M. Baniahmad A. Matusch R.,"Activity-guided isolation of an antiandrogenic compound of Pygeum africanum." [[Planta Medica]]. 72(6):547-51, 2006 May.</ref>
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[http://www.ars-grin.gov/duke/activity.html Duke's database (enter 'antiandrogenic' in search field)] lists several more herbs that have antiandrogenic properties.
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== Future research ==
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Currently, further research is being conducted on the effects of antiandrogens. In the pharmaceutical industry, researchers continue to experiment with antiandrogenic drugs and other treatments in the hope of finding cures to diseases such as prostate cancer. Greater insight into the mechanisms and pathways of antiandrogens would provide more effective treatment that might decrease the likelihood of recurrent prostatic tumors.
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The future of antiandrogenic drugs is believed to be peptide antagonists. Current androgen receptor antagonist drugs bind to the ligand binding domain on the receptors and inhibit receptor function. Androgen receptor peptide antagonists act in an alternative manner. A peptide antagonist interrupts androgen receptor protein interactions from the surface of the receptor.<ref name=Gao>{{Cite journal |author= Gao W. |title=Peptide antagonist of the androgen receptor |journal=Current Pharmaceutical Design |volume=16 |pages=1106–113 |year=2010 |pmid=20030610 |issue=9}}</ref> This approach is “mechanism-based” and has greater potential for blocking receptor activity than the traditional ligand-receptor binding approach. Researchers are trying to target the ligand-binding domain and N-terminal domain of androgen receptors.<ref name=Gao/>
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== See also ==
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* [[Androgen]]
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* [[Antiestrogen]]
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* [[Antiprogestin]]
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* [[Estrogen]]
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* [[Selective androgen receptor modulator|SARM]]
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* [[5α-reductase inhibitor]]
 
* [[Steroids]]
 
* [[Steroids]]
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==References==
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{{Reflist}}
   
   
{{Sex hormones}}
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{{Androgens}}
{{Hormone antagonists}}
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{{Androgenics}}
   
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[[Category:Antiandrogens]]
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[[CAtegory:Drugs]]
 
[[Category:Hormonal agents]]
 
[[Category:Hormonal agents]]
[[Category:Drugs]]
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[[Category:Sex hormones]]
   
:cs:Antiandrogeny
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Antiandrogens, or androgen antagonists, first discovered in the 1960s, prevent androgens from expressing their biological effects on responsive tissues.[1] Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting androgen production.[2] Antiandrogens can be prescribed to treat an array of diseases and disorders. In men, antiandrogens are most frequently used to treat prostate cancer.[3] In women, antiandrogens are used to decrease levels of male hormones causing symptoms of hyperandrogenism.[4] Antiandrogens present in the environment have become a topic of concern. Many industrial chemicals, pesticides and insecticides exhibit antiandrogenic effects.[5][6] Certain plant species have also been found to produce antiandrogens. Environmental antiandrogens can have harmful effects on reproductive organ development in fetuses exposed in utero as well as their offspring.[5]

Mechanism of action

Antiandrogens are classified as steroidal or nonsteroidal. Steroidal antiandrogens not only counter androgens, but also affect secondary sex characteristics. Steroidal antiandrogens directly affect gene expression due to their fat-soluble nature that allows them to diffuse through the plasma membrane’s phospholipid bilayer and prevent the binding of testosterone and dihydrotestosterone (DHT) to the androgen receptor.[7] Non-steroidal antiandrogens, or “pure” antiandrogens, such as nilutamide and flutamide, counter androgens and have no steroidal effects. Antiandrogens inhibit circulating androgens by blocking androgen receptors, suppressing androgen synthesis, or acting in both those ways.[8] The most common antiandrogens are androgen receptor (AR) antagonists which act on the target cell level and competitively bind to androgen receptors.[2]

Inhibition of androgen production occurs through a unique mechanism for each antiandrogen. For example, ketoconazole not only competes with androgens such as testosterone and DHT for androgen receptor binding, but also suppresses androgen synthesis by inhibiting cytochrome P450 and 17,20-lyase, which partake in synthesizing and degrading steroids, including the precursors of testosterone. The result is a decrease in the overall testosterone production of the adrenal cortex.[9] Gonadotrophins, pituitary hormones capable of altering androgen synthesis, are also affected by antiandrogens. Antiandrogens can have suppressive effects on gonadotropin secretion by down-regulating gonadotropin-releasing hormone receptors (GnRHR) in the pituitary gland. A decreased amount of GnRHRs results in gonadotropin-releasing hormone (GnRH) not being able to bind sufficiently. GnRH is responsible for the release of the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH stimulates the Leydig cells of the testes and the theca cells of the ovaries to produce testosterone (and indirectly estradiol). Therefore, if GnRH cannot bind, testosterone synthesis is not induced in the testes or ovaries.[10]

Medical applications

Antiandrogenic pharmaceuticals are used to treat an array of medical conditions that are dependent on the androgen pathway. Antiandrogens are often prescribed for men with prostate cancer, benign prostatic hyperplasia, hypersexuality, male contraception, and for those that are undergoing gender reassignment. For women, antiandrogens are often prescribed for severe cases of acne, amenorrhea, seborrhea, hirsutism, androgenic alopecia, hidradenitis suppurativa, and hyperandrogenism.

Pharmaceuticals for men

Antiandrogens in males can result in hyposexuality (diminished sexual desire or libido), reduced activity or function of the accessory male sex organs, and slowed or halted development or reversal of male secondary sex characteristics.[11]

Antiandrogenic drugs are often indicated to treat severe male sexual disorders, such as hypersexuality (excessive sexual desire) and sexual deviation such as paraphilia, a disorder involving intense recurrent sexual urges), since lowering male hormone levels decreases libido.[12] As a part of a program for registered sex offenders recently released from prisons, the offender is sometimes administered antiandrogen drugs to reduce the likelihood of repeat offenses by reducing sexual drive.[12] On occasion, antiandrogens are used as a male contraceptive agent.

Prostate cancer

Decreasing the body’s response to androgen can have beneficial effects in treating prostate cancer. Prostate cancer is the most commonly diagnosed form of cancer found in men.[3] Some prostate cancer cells require androgens for growth. To counteract cancer cell proliferation, antiandrogenic drugs are used for hormone therapy called androgen deprivation therapy (ADT). Some antiandrogenic drugs suppress androgen production while others inhibit androgens from binding to the cancer cells’ androgen receptors. These two classes of drugs can be prescribed separately or can be used together for a complete/combined androgen blockade (CAB). When the body is deprived of androgens, the therapy is termed castration-based therapy as the lack of androgens mimics castration. By competing with circulating androgens for binding sites on prostate cell receptors, antiandrogens promote apoptosis and inhibit prostate cancer growth.[3] Hormone therapy antiandrogen drugs can be prescribed as monotherapy or in addition to radical radiotherapy or prostatectomy.[3] Antiandrogen monotherapy generally causes fewer side effects in males although it may block androgen less effectively than combined therapies. Monotherapy is often preferred by men as it is less likely than combined therapies to diminish libido or cause tenderness of the breasts, diarrhea, and nausea.[13]

Androgen-deprivation therapy (ADT) has been shown to cause initial reduction of prostate tumors.[14] However, antiandrogenic drugs can cause prostate cancer tumors to become androgen independent. Androgen independence occurs when cells that are not reliant on androgen proliferate and spread while cells that require androgen for survival undergo apoptosis. The cells that do not require androgen become the basis of the tumors, causing reoccurring tumors a few years after the initial disappearance of the prostate cancer. Once prostate cancer becomes androgen independent, hormone therapy will most likely no longer benefit the individual and a new treatment approach will be needed.[14]

In one study, the efficacy of reducing prostate cancer cells by castration was compared to combined androgen blockade (CAB) in which castration is combined with an antiandrogenic drug. Flutamide (brand name Eulexin), nilutamide (brand names Anandron and Nilandron) and bicalutamide (brand name Casodex) are nonsteroidal, “pure” antiandrogens. Flutamide has several side effects that the newer bicalutamide does not. Used in combination with castration, nilutamide and flutamide were found to have a minimal effect on prolonging survival while bicalutamide significantly prolonged life in prostate cancer patients.[15] As a result of these conclusions, since 2007 combined androgen blockade with bicalutamide has been used as an effective, safe, and cost-efficient treatment of prostate cancer.[15]

5-alpha-reductase inhibitors such as finasteride (brand names Proscar and Propecia), dutasteride (brand name Avodart), bexlosteride, izonsteride, turosteride, and epristeride are antiandrogenic as they prevent the reduction of testosterone to dihydrotestosterone (DHT).[16] DHT is 3-5 times more potent than testosterone or other androgens (except in skeletal muscle tissue, where testosterone is the main androgen). They are unique because they do not counteract the effects or production of other androgens other than DHT. Dihydrotestosterone is necessary for development of both external male sex organs and the prostate. 5α-reductase inhibitors are most often used to treat benign prostatic hyperplasia since the resulting decrease in dihydrotestosterone inhibits proliferation of prostate cells.[16]

Pharmaceuticals for women

Hyperandrogenism is a condition found in women where ovaries overproduce androgens, which are typically considered male hormones as they are important for the development of male reproductive organs and secondary male characteristics.[4] Antiandrogenic drugs can help to counteract male hormones that cause skin and hair problems in women. Gonadotrophin, a pituitary hormone, is involved in ovarial androgen production and its suppression can result in reduced testosterone production. Antiandrogens can inhibit the release of the gonadotropic hormone, luteinizing hormone (LH), suppressing testosterone synthesis in the ovaries.[10] Androgenic alopecia (a type of hair loss and pattern baldness), acne vulgaris, seborrhea, amenorrhea (absence of menstrual periods), hirsutism (excessive facial and bodily hair in women), and hidradenitis suppurativa can all be caused by an excess of male hormones.[17]

Hormonal antiandrogen treatment is given to female patients that suffer from multiple symptoms of hyperandrogenism.[8] Acne is the most common of all the skin disorders that result from male hormones overproduction. Fewer androgens present in a female’s tissues results in a reduction of oil (sebum) production and bumps (comedone).[17] Also, antiandrogenic drugs are often combined with topical and oral pharmaceuticals to treat acne. In women that suffer from overproduction of hair due to high testosterone levels (hirsutism), antiandrogenic drugs are used to slow hair growth, lighten hair color, and thin the hair. For females with pattern hair loss (androgenic alopecia), antiandrogens can assist in reducing hair shedding and thinning.[17]

The most common antiandrogenic drugs used to treat women with hyperandrogenism are spironolactone and cyproterone acetate. Spironolactone (brand names Aldactone and Spirotone), a synthetic 17-spirolactone corticosteroid is used primarily to treat low-renin hypertension, hypokalemia, and Conn's syndrome. Cyproterone acetate (brand names Androcur, Climen, Diane 35, and Ginette 35) is a synthetic steroid, a potent antiandrogen that also possesses progestational properties. Oral contraceptives that mediate progesterone have no effect on androgens but may be combined with spironolactone and cyproterone acetate for the purpose of correcting menstrual irregularities.[17]

Also used to purposefully prevent or counteract masculinisation in the case of transsexual women undergoing sex reassignment therapy, and to prevent the symptoms associated with reduced testosterone, such as hot flashes, following castration.[11]

Environmental exposure

Exposure to antiandrogens can occur unintentionally due to natural or anthropogenic compounds in the environment. Environmental compounds affecting the endocrine system, termed endocrine disruptors, that antagonistically affect androgen receptors and androgen production can negatively affect individuals that come in contact with the compounds as well as their future generations.[5] Certain pesticides and insecticides as well as in industrial chemicals contain antiandrogenic chemicals. Some species of plants produce phytochemicals with antiandrogenic effects. Exposure to these environmental antiandrogens has resulted in adverse effects on animals that allude to human health risks.

Pesticides and insecticides

Exposure to pesticides and insecticides with antiandrogenic properties has been found to negatively affect humans and laboratory animals. Androgens are important in fetal development as well as in pubertal development. Exposure during critical periods of development can cause reproductive malformations in males while exposure after birth and before puberty can delay pubertal development.[5]

Animal studies with vinclozolin, procymidone, linuron, and the DDT metabolite dichlorodiphenyldichloroethylene (p.p’-DDE) show irregular reproductive development due to their function as androgen receptor antagonists that inhibit androgen-activated gene expression.[5][18] Even with low doses of antiandrogenic pesticides, developmental effects such as reduced anogenital distance and induction of areolas were seen in male rats.[5]

Animal studies show that deformities result in offspring exposed to antiandrogens.[5] Male mice can display malformations that resemble the reproductive organs of females as in the case of exposure to vinclozolin or proymidone. Exposure to vinclozolin or procymidone in utero feminized male offspring, as seen in abnormalities of anogenital distance, small or absent sex accessory glands, hypospadias, undescended testes, retained nipples, cleft phallus, and presence of a vaginal pouch. Male mice exposed before puberty to vinclozolin experienced delayed pubertal development visualized by delayed onset of androgen-dependent preputial separation.[5]

Ketoconazole's imidazole derivative is used as a broad-spectrum antifungal agent effective against a variety of fungal infections. Although ketoconazole is a relatively weak antiandrogen, side-effects seen as a result of exposure include serious liver damage and reduced levels of androgens from both the testicles and adrenal glands.[5]

Organophostphate insecticides such as fenitrothion can also behave as androgen receptor antagonists. Fenitrothion was found to completely inhibit dihydrotestosterone-dependent human androgen receptor activation, resulting in reduced weights of seminal vesicles and the ventral prostate. Structural similarity of fenitrothion with linuron further supports the findings of antiandrogenic activity.[18]

Industrial chemicals

Industrial chemicals with antiandrogenic effects are ubiquitous in the environment. Consumer products such as toys and cosmetics may contain phthalates or parabens, which disrupt androgen synthesis.[5][6]

Phthalates are mainly found in plastics. Fetuses that are exposed to a mixture of pthalates in utero may show signs of disrupted reproductive development.[6][19] When Di-n-butyl phthalate (DBP), diisobutyl phthalate (DiBP), benzyl butyl phthalate (BBP), Bis(2-ethylhexyl) phthalate (DEHP) and di-n-pentyl phthalate (DPP) were combined, reductions in both testosterone synthesis and gene expression of steroidogenic pathway proteins were seen. The result in male rats was undescended testes and abnormal development of reproductive tissues.[6]

Parabens are commonly found in cosmetics and pharmaceuticals. Paraben esters, such as butylparaben, have been found to mimic androgen antagonist activity. Antiandrogenic endocrine disruption has been shown in aquatic species but the mechanism is unknown. Researchers believe parabens have the ability to bind to human androgen receptors but it still remains unclear.[19]

Phytochemicals

Antiandrogenic chemicals can also occur naturally in plants.

The best known plant-derived anti-androgen is 3,3'-Diindolylmethane(DIM)[20]

Spearmint tea has antiandrogenic properties in females with hirsutism.,[21][22]

Scutellaria baicalensis may also have antiandrogenic properties.[23]

The compound N-butylbenzene-sulfonamide (NBBS) isolated from Pygeum africanum is a specific androgen antagonist.,[24][25]

Glycyrrhiza glabra has shown antiandrogenic activity in male rats[26]

A herbal formula (termed KMKKT) containing Korean Angelica gigas Nakai (AGN) root and nine other oriental herbs has shown in vitro anti-androgen activity.[27]

Pygeum africanum contains an antiandrogenic compound atraric acid.[28]

Duke's database (enter 'antiandrogenic' in search field) lists several more herbs that have antiandrogenic properties.

Future research

Currently, further research is being conducted on the effects of antiandrogens. In the pharmaceutical industry, researchers continue to experiment with antiandrogenic drugs and other treatments in the hope of finding cures to diseases such as prostate cancer. Greater insight into the mechanisms and pathways of antiandrogens would provide more effective treatment that might decrease the likelihood of recurrent prostatic tumors.

The future of antiandrogenic drugs is believed to be peptide antagonists. Current androgen receptor antagonist drugs bind to the ligand binding domain on the receptors and inhibit receptor function. Androgen receptor peptide antagonists act in an alternative manner. A peptide antagonist interrupts androgen receptor protein interactions from the surface of the receptor.[29] This approach is “mechanism-based” and has greater potential for blocking receptor activity than the traditional ligand-receptor binding approach. Researchers are trying to target the ligand-binding domain and N-terminal domain of androgen receptors.[29]

See also

References

  1. Medical Dictionary: Anti-androgen.
  2. 2.0 2.1 Mowszowicz I. (1989). Antiandrogens. Mechanisms and paradoxical effects. Ann Endocrinol (Paris) 50 (3): 50(3):189–99.
  3. 3.0 3.1 3.2 3.3 Gillatt D. (2006). Antiandrogen treatments in locally advanced prostate cancer: are they all the same?. J Cancer Res Clin Oncol. 1: S17-26.
  4. 4.0 4.1 Medical Dictionary: Hyperandrogenism.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 Gray LE, Ostby J, Furr J, Wolf CJ, Lambright C, Parks L, Veeramachaneni DN, Wilson V, Price M, Hotchkiss A, Orlando E, Guillette L. (2001). Effects of environmental antiandrogens on reproductive development in experimental animals. Human Reproduction Update 2 (3): 248–64.
  6. 6.0 6.1 6.2 6.3 Rider CV, Furr JR, Wilson VS, Gray LE Jr. (Apr 2010). Cumulative effects of in utero administration of mixtures of reproductive toxicants that disrupt common targe tissues via diverse mechanisms of toxicity. International Journal of Andrology 33 (2): 443–62.
  7. Steroidal Antiandrogens. Health and Prostate. URL accessed on 9 December 2011.
  8. 8.0 8.1 Zouboulis CC, Rabe T. (March 2010). Hormonal antiandrogens in acne treatment. Journal of the German Society of Dermatology 8 Suppl 1: S60–74.
  9. Witjes FJ, Debruyne FM, Fernandez del Moral P, Geboers AD (May 1989). Ketoconazole high dose in management of hormonally pretreated patients with progressive metastatic prostate cancer. Dutch South-Eastern Urological Cooperative Group. Urology 33 (5): 411–5.
  10. 10.0 10.1 Gonadotropin. URL accessed on 9 December 2011.
  11. 11.0 11.1 Antiandrogen Drugs.
  12. 12.0 12.1 (1973). Anti-androgens for sex offenders. Canadian Medical Association Journal 109 (4): 257.
  13. {{"Hormone Therapy for Prostate Cancer"}}
  14. 14.0 14.1 Massard, C. (Jun 2011). Targeting Continued Androgen Receptor Signaling in Prostate Cancer. Clinical Cancer Research 17(12): 3876–883.
  15. 15.0 15.1 Akaza H. (Jan 2011). Combined androgen blockade for prostate cancer: review of efficacy, safety, and cost-effectiveness. Cancer Science 102 (1): 51–6.
  16. 16.0 16.1 Flores E, Bratoeff E, Cabeza M, Ramirez E, Quiroz A, Heuze I. (May 2003). Steroid 5alpha-reductase inhibitors. Mini-Reviews in Medicinal Chemistry 3 (3): 225–37.
  17. 17.0 17.1 17.2 17.3 Dr. Amanda Oakley. Hormonal treatment.
  18. 18.0 18.1 Curtis LR. (Mar 2001). Organophosphate antagonism of the androgen receptor. Toxicological Sciences 60 (1): 1–2.
  19. 19.0 19.1 Darbre PD, Harvey PW. (Jul 2008). Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks. Journal of Applied Toxicology 28 (5): 561–78.
  20. Plant-derived 3,3'-Diindolylmethane is a strong androgen antagonist in human prostate cancer cells.
  21. Grant P. 'Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome. A randomized controlled trial Phytotherapy Research 2010 24:2 (186-188)
  22. Akdogan M. Tamer MN. Cure E. Cure MC. Koroglu BK. Delibas N."Effect of spearmint (Mentha spicata Labiatae) teas on androgen levels in women with hirsutism." Phytotherapy Research. 21(5):444-7, 2007 May.
  23. Bonham M., Posakony J., Coleman I., Montgomery B., Simon J., Nelson P.S."Characterization of chemical constituents in Scutellaria baicalensis with antiandrogenic and growth-inhibitory activities toward prostate carcinoma" Clinical Cancer Research 2005 11:10 (3905-3914)
  24. Papaioannou M. Schleich S. Roell D. Schubert U. Tanner T. Claessens F. Matusch R. Baniahmad A. ,"NBBS isolated from Pygeum africanum bark exhibits androgen antagonistic activity, inhibits AR nuclear translocation and prostate cancer cell growth.",Investigational New Drugs. 28(6):729-43, 2010 Dec.
  25. Schleich S. Papaioannou M. Baniahmad A. Matusch R.,"Extracts from Pygeum africanum and other ethnobotanical species with antiandrogenic activity.", Planta Medica. 72(9):807-13, 2006 Jul.
  26. Zamansoltani F. Nassiri-Asl M. Sarookhani MR. Jahani-Hashemi H. Zangivand AA. "Antiandrogenic activities of Glycyrrhiza glabra in male rats.", International Journal of Andrology. 32(4):417-22, 2009 Aug
  27. Jiang C., Lee H.-J., Li G.-X., Guo J., Malewicz B., Zhao Y., Lee E.-O., Lee H.-J., Lee J.-H., Kim M.-S., Kim S.-H., Lu J. "Potent antiandrogen and androgen receptor activities of an Angelica gigas-containing herbal formulation: Identification of decursin as a novel and active compound with implications for prevention and treatment of prostate cancer" Cancer Research 2006 66:1 (453-463)
  28. Schleich S. Papaioannou M. Baniahmad A. Matusch R.,"Activity-guided isolation of an antiandrogenic compound of Pygeum africanum." Planta Medica. 72(6):547-51, 2006 May.
  29. 29.0 29.1 Gao W. (2010). Peptide antagonist of the androgen receptor. Current Pharmaceutical Design 16 (9): 1106–113.


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