Catechol estrogen

A catechol estrogen is a steroidal estrogen that contains catechol (1,2-dihydroxybenzene) within its structure.[1] The catechol estrogens are endogenous metabolites of estradiol and estrone and include the following compounds:[1][2]

  • 2-Hydroxylated:
  • 4-Hydroxylated:
    • 4-Hydroxyestradiol
    • 4-Hydroxyestrone
    • 4-Hydroxyestriol
Structure of 2-hydroxyestradiol, a catechol estrogen.

The most abundant catechol estrogen in serum and urine is 2-hydroxyestrone, with 2-hydroxyestradiol and 2-hydroxyestriol also being formed, while the principal 4-hydroxy catechol estrogen, 4-hydroxyestrone, is present in only small amounts in urine.[1] 4-Hydroxyestriol has been detected in the urine of pregnant women.[3] The catechol estrogens are formed from estradiol and estrone by cytochrome P450 enzymes predominantly in the liver but also in extrahepatic tissues, and are metabolized by catechol O-methyltransferase (COMT) into methoxylated estrogens such as 2-methoxyestradiol and 4-methoxyestrone as well as by conjugation via other phase II enzymes.[1][2] Under poor conditions of inactivation by phase II enzymes, catechol estrogens can undergo oxidation to reactive quinones and semiquinones, and this has been hypothesized to contribute to estrogen-induced carcinogenesis.[2]

Similarly to estradiol and estrone, catechol estrogens possess estrogenic activity.[1] 2-Hydroxylated catechol estrogens are weak and possibly antiestrogenic estrogens, whereas their 4-hydroxylated counterparts are more potent in their estrogenic activity.[1] For instance, 2-hydroxyestrone reportedly shows negligible uterotrophic effect in animals, whereas 4-hydroxy catechol estrogens show moderate changes in stimulating uterine weight.[1] In addition to being substrates for COMT similarly to catecholamines like dopamine, norepinephrine, and epinephrine, catechol estrogens are potent competitive inhibitors of COMT as well as of tyrosine hydroxylase, and may affect both catecholamine biosynthesis and metabolism.[1][2]

Affinities of estrogen receptor ligands for the ERα and ERβ
LigandOther namesRelative binding affinities (RBA, %)aAbsolute binding affinities (Ki, nM)aAction
ERαERβERαERβ
EstradiolE2; 17β-Estradiol1001000.115 (0.04–0.24)0.15 (0.10–2.08)Estrogen
EstroneE1; 17-Ketoestradiol16.39 (0.7–60)6.5 (1.36–52)0.445 (0.3–1.01)1.75 (0.35–9.24)Estrogen
EstriolE3; 16α-OH-17β-E212.65 (4.03–56)26 (14.0–44.6)0.45 (0.35–1.4)0.7 (0.63–0.7)Estrogen
EstetrolE4; 15α,16α-Di-OH-17β-E24.03.04.919Estrogen
Alfatradiol17α-Estradiol20.5 (7–80.1)8.195 (2–42)0.2–0.520.43–1.2Metabolite
16-Epiestriol16β-Hydroxy-17β-estradiol7.795 (4.94–63)50 ? ?Metabolite
17-Epiestriol16α-Hydroxy-17α-estradiol55.45 (29–103)79–80 ? ?Metabolite
16,17-Epiestriol16β-Hydroxy-17α-estradiol1.013 ? ?Metabolite
2-Hydroxyestradiol2-OH-E222 (7–81)11–352.51.3Metabolite
2-Methoxyestradiol2-MeO-E20.0027–2.01.0 ? ?Metabolite
4-Hydroxyestradiol4-OH-E213 (8–70)7–561.01.9Metabolite
4-Methoxyestradiol4-MeO-E22.01.0 ? ?Metabolite
2-Hydroxyestrone2-OH-E12.0–4.00.2–0.4 ? ?Metabolite
2-Methoxyestrone2-MeO-E1<0.001–<1<1 ? ?Metabolite
4-Hydroxyestrone4-OH-E11.0–2.01.0 ? ?Metabolite
4-Methoxyestrone4-MeO-E1<1<1 ? ?Metabolite
16α-Hydroxyestrone16α-OH-E1; 17-Ketoestriol2.0–6.535 ? ?Metabolite
2-Hydroxyestriol2-OH-E32.01.0 ? ?Metabolite
4-Methoxyestriol4-MeO-E31.01.0 ? ?Metabolite
Estradiol sulfateE2S; Estradiol 3-sulfate<1<1 ? ?Metabolite
Estradiol disulfateEstradiol 3,17β-disulfate0.0004 ? ? ?Metabolite
Estradiol 3-glucuronideE2-3G0.0079 ? ? ?Metabolite
Estradiol 17β-glucuronideE2-17G0.0015 ? ? ?Metabolite
Estradiol 3-gluc. 17β-sulfateE2-3G-17S0.0001 ? ? ?Metabolite
Estrone sulfateE1S; Estrone 3-sulfate<1<1>10>10Metabolite
Estradiol benzoateEB; Estradiol 3-benzoate10 ? ? ?Estrogen
Estradiol 17β-benzoateE2-17B11.332.6 ? ?Estrogen
Estrone methyl etherEstrone 3-methyl ether0.145 ? ? ?Estrogen
ent-Estradiol1-Estradiol1.31–12.349.44–80.07 ? ?Estrogen
Equilin7-Dehydroestrone13 (4.0–28.9)13.0–490.790.36Estrogen
Equilenin6,8-Didehydroestrone2.0–157.0–200.640.62Estrogen
17β-Dihydroequilin7-Dehydro-17β-estradiol7.9–1137.9–1080.090.17Estrogen
17α-Dihydroequilin7-Dehydro-17α-estradiol18.6 (18–41)14–320.240.57Estrogen
17β-Dihydroequilenin6,8-Didehydro-17β-estradiol35–6890–1000.150.20Estrogen
17α-Dihydroequilenin6,8-Didehydro-17α-estradiol20490.500.37Estrogen
Δ8-Estradiol8,9-Dehydro-17β-estradiol68720.150.25Estrogen
Δ8-Estrone8,9-Dehydroestrone19320.520.57Estrogen
EthinylestradiolEE; 17α-Ethynyl-17β-E2120.9 (68.8–480)44.4 (2.0–144)0.02–0.050.29–0.81Estrogen
MestranolEE 3-methyl ether ?2.5 ? ?Estrogen
MoxestrolRU-2858; 11β-Methoxy-EE35–435–200.52.6Estrogen
Methylestradiol17α-Methyl-17β-estradiol7044 ? ?Estrogen
DiethylstilbestrolDES; Stilbestrol129.5 (89.1–468)219.63 (61.2–295)0.040.05Estrogen
HexestrolDihydrodiethylstilbestrol153.6 (31–302)60–2340.060.06Estrogen
DienestrolDehydrostilbestrol37 (20.4–223)56–4040.050.03Estrogen
Benzestrol (B2)–114 ? ? ?Estrogen
ChlorotrianiseneTACE1.74 ?15.30 ?Estrogen
TriphenylethyleneTPE0.074 ? ? ?Estrogen
TriphenylbromoethyleneTPBE2.69 ? ? ?Estrogen
TamoxifenICI-46,4743 (0.1–47)3.33 (0.28–6)3.4–9.692.5SERM
Afimoxifene4-Hydroxytamoxifen; 4-OHT100.1 (1.7–257)10 (0.98–339)2.3 (0.1–3.61)0.04–4.8SERM
Toremifene4-Chlorotamoxifen; 4-CT ? ?7.14–20.315.4SERM
ClomifeneMRL-4125 (19.2–37.2)120.91.2SERM
CyclofenilF-6066; Sexovid151–152243 ? ?SERM
NafoxidineU-11,000A30.9–44160.30.8SERM
Raloxifene–41.2 (7.8–69)5.34 (0.54–16)0.188–0.5220.2SERM
ArzoxifeneLY-353,381 ? ?0.179 ?SERM
LasofoxifeneCP-336,15610.2–16619.00.229 ?SERM
OrmeloxifeneCentchroman ? ?0.313 ?SERM
Levormeloxifene6720-CDRI; NNC-460,0201.551.88 ? ?SERM
OspemifeneDeaminohydroxytoremifene0.82–2.630.59–1.22 ? ?SERM
Bazedoxifene– ? ?0.053 ?SERM
EtacstilGW-56384.3011.5 ? ?SERM
ICI-164,384–63.5 (3.70–97.7)1660.20.08Antiestrogen
FulvestrantICI-182,78043.5 (9.4–325)21.65 (2.05–40.5)0.421.3Antiestrogen
PropylpyrazoletriolPPT49 (10.0–89.1)0.120.4092.8ERα agonist
16α-LE216α-Lactone-17β-estradiol14.6–570.0890.27131ERα agonist
16α-Iodo-E216α-Iodo-17β-estradiol30.22.30 ? ?ERα agonist
MethylpiperidinopyrazoleMPP110.05 ? ?ERα antagonist
DiarylpropionitrileDPN0.12–0.256.6–1832.41.7ERβ agonist
8β-VE28β-Vinyl-17β-estradiol0.3522.0–8312.90.50ERβ agonist
PrinaberelERB-041; WAY-202,0410.2767–72 ? ?ERβ agonist
ERB-196WAY-202,196 ?180 ? ?ERβ agonist
ErteberelSERBA-1; LY-500,307 ? ?2.680.19ERβ agonist
SERBA-2– ? ?14.51.54ERβ agonist
Coumestrol–9.225 (0.0117–94)64.125 (0.41–185)0.14–80.00.07–27.0Xenoestrogen
Genistein–0.445 (0.0012–16)33.42 (0.86–87)2.6–1260.3–12.8Xenoestrogen
Equol–0.2–0.2870.85 (0.10–2.85) ? ?Xenoestrogen
Daidzein–0.07 (0.0018–9.3)0.7865 (0.04–17.1)2.085.3Xenoestrogen
Biochanin A–0.04 (0.022–0.15)0.6225 (0.010–1.2)1748.9Xenoestrogen
Kaempferol–0.07 (0.029–0.10)2.2 (0.002–3.00) ? ?Xenoestrogen
Naringenin–0.0054 (<0.001–0.01)0.15 (0.11–0.33) ? ?Xenoestrogen
8-Prenylnaringenin8-PN4.4 ? ? ?Xenoestrogen
Quercetin–<0.001–0.010.002–0.040 ? ?Xenoestrogen
Ipriflavone–<0.01<0.01 ? ?Xenoestrogen
Miroestrol–0.39 ? ? ?Xenoestrogen
Deoxymiroestrol–2.0 ? ? ?Xenoestrogen
β-Sitosterol–<0.001–0.0875<0.001–0.016 ? ?Xenoestrogen
Resveratrol–<0.001–0.0032 ? ? ?Xenoestrogen
α-Zearalenol–48 (13–52.5) ? ? ?Xenoestrogen
β-Zearalenol–0.6 (0.032–13) ? ? ?Xenoestrogen
Zeranolα-Zearalanol48–111 ? ? ?Xenoestrogen
Taleranolβ-Zearalanol16 (13–17.8)140.80.9Xenoestrogen
ZearalenoneZEN7.68 (2.04–28)9.45 (2.43–31.5) ? ?Xenoestrogen
ZearalanoneZAN0.51 ? ? ?Xenoestrogen
Bisphenol ABPA0.0315 (0.008–1.0)0.135 (0.002–4.23)19535Xenoestrogen
EndosulfanEDS<0.001–<0.01<0.01 ? ?Xenoestrogen
KeponeChlordecone0.0069–0.2 ? ? ?Xenoestrogen
o,p'-DDT–0.0073–0.4 ? ? ?Xenoestrogen
p,p'-DDT–0.03 ? ? ?Xenoestrogen
Methoxychlorp,p'-Dimethoxy-DDT0.01 (<0.001–0.02)0.01–0.13 ? ?Xenoestrogen
HPTEHydroxychlor; p,p'-OH-DDT1.2–1.7 ? ? ?Xenoestrogen
TestosteroneT; 4-Androstenolone<0.0001–<0.01<0.002–0.040>5000>5000Androgen
DihydrotestosteroneDHT; 5α-Androstanolone0.01 (<0.001–0.05)0.0059–0.17221–>500073–1688Androgen
Nandrolone19-Nortestosterone; 19-NT0.010.2376553Androgen
DehydroepiandrosteroneDHEA; Prasterone0.038 (<0.001–0.04)0.019–0.07245–1053163–515Androgen
5-AndrostenediolA5; Androstenediol6173.60.9Androgen
4-Androstenediol–0.50.62319Androgen
4-AndrostenedioneA4; Androstenedione<0.01<0.01>10000>10000Androgen
3α-Androstanediol3α-Adiol0.070.326048Androgen
3β-Androstanediol3β-Adiol3762Androgen
Androstanedione5α-Androstanedione<0.01<0.01>10000>10000Androgen
Etiocholanedione5β-Androstanedione<0.01<0.01>10000>10000Androgen
Methyltestosterone17α-Methyltestosterone<0.0001 ? ? ?Androgen
Ethinyl-3α-androstanediol17α-Ethynyl-3α-adiol4.0<0.07 ? ?Estrogen
Ethinyl-3β-androstanediol17α-Ethynyl-3β-adiol505.6 ? ?Estrogen
ProgesteroneP4; 4-Pregnenedione<0.001–0.6<0.001–0.010 ? ?Progestogen
NorethisteroneNET; 17α-Ethynyl-19-NT0.085 (0.0015–<0.1)0.1 (0.01–0.3)1521084Progestogen
Norethynodrel5(10)-Norethisterone0.5 (0.3–0.7)<0.1–0.221453Progestogen
Tibolone7α-Methylnorethynodrel0.5 (0.45–2.0)0.2–0.076 ? ?Progestogen
Δ4-Tibolone7α-Methylnorethisterone0.069–<0.10.027–<0.1 ? ?Progestogen
3α-Hydroxytibolone–2.5 (1.06–5.0)0.6–0.8 ? ?Progestogen
3β-Hydroxytibolone–1.6 (0.75–1.9)0.070–0.1 ? ?Progestogen
Footnotes: a = (1) Binding affinity values are of the format "median (range)" (# (#–#)), "range" (#–#), or "value" (#) depending on the values available. The full sets of values within the ranges can be found in the Wiki code. (2) Binding affinities were determined via displacement studies in a variety of in-vitro systems with labeled estradiol and human ERα and ERβ proteins (except the ERβ values from Kuiper et al. (1997), which are rat ERβ). Sources: See template page.
Selected biological properties of endogenous estrogens in rats
EstrogenER RBA (%)Uterine weight (%)UterotrophyLH levels (%)SHBG RBA (%)
Control–100–100–
Estradiol (E2)100506 ± 20+++12–19100
Estrone (E1)11 ± 8490 ± 22+++ ?20
Estriol (E3)10 ± 4468 ± 30+++8–183
Estetrol (E4)0.5 ± 0.2 ?Inactive ?1
17α-Estradiol4.2 ± 0.8 ? ? ? ?
2-Hydroxyestradiol24 ± 7285 ± 8+b31–6128
2-Methoxyestradiol0.05 ± 0.04101Inactive ?130
4-Hydroxyestradiol45 ± 12 ? ? ? ?
4-Methoxyestradiol1.3 ± 0.2260++ ?9
4-Fluoroestradiola180 ± 43 ?+++ ? ?
2-Hydroxyestrone1.9 ± 0.8130 ± 9Inactive110–1428
2-Methoxyestrone0.01 ± 0.00103 ± 7Inactive95–100120
4-Hydroxyestrone11 ± 4351++21–5035
4-Methoxyestrone0.13 ± 0.04338++65–9212
16α-Hydroxyestrone2.8 ± 1.0552 ± 42+++7–24<0.5
2-Hydroxyestriol0.9 ± 0.3302+b ? ?
2-Methoxyestriol0.01 ± 0.00 ?Inactive ?4
Notes: Values are mean ± SD or range. ER RBA = Relative binding affinity to estrogen receptors of rat uterine cytosol. Uterine weight = Percentage change in uterine wet weight of ovariectomized rats after 72 hours with continuous administration of 1 μg/hour via subcutaneously implanted osmotic pumps. LH levels = Luteinizing hormone levels relative to baseline of ovariectomized rats after 24 to 72 hours of continuous administration via subcutaneous implant. Footnotes: a = Synthetic (i.e., not endogenous). b = Atypical uterotrophic effect which plateaus within 48 hours (estradiol's uterotrophy continues linearly up to 72 hours). Sources: See template.

See also

References
  1. H.J. Buchsbaum (6 December 2012). The Menopause. Springer Science & Business Media. pp. 65–. ISBN 978-1-4612-5525-3.
  2. Shufeng Zhou (6 April 2016). Cytochrome P450 2D6: Structure, Function, Regulation and Polymorphism. CRC Press. pp. 241–242. ISBN 978-1-4665-9788-4.
  3. Fotsis T, Järvenpää P, Adlercreutz H (1980). "Identification of 4-hydroxyestriol in pregnancy urine". J. Clin. Endocrinol. Metab. 51 (1): 148–51. doi:10.1210/jcem-51-1-148. PMID 6892918.
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