Chemical compound
Equilin
Other names Δ7 -Estrone; 7-Dehydroestrone; Estra-1,3,5(10),7-tetraen-3-ol-17-one
Routes of administration
By mouth
Drug class
Estrogen
(9S ,13S ,14S )-3-hydroxy-13-methyl-9,11,12,14,15,16-hexahydro-6H -cyclopenta[a ]phenanthren-17-one
CAS Number
PubChem
CID
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (
EPA )
ECHA InfoCard
100.006.809
Formula C 18 H 20 O 2
Molar mass 268.356 g·mol−1 3D model (
JSmol )
O=C3CC[C@H]4C/2=C/Cc1c(ccc(O)c1)[C@H]\2CC[C@]34C
InChI=1S/C18H20O2/c1-18-9-8-14-13-5-3-12(19)10-11(13)2-4-15(14)16(18)6-7-17(18)20/h3-5,10,14,16,19H,2,6-9H2,1H3/t14-,16+,18+/m1/s1
Y Key:WKRLQDKEXYKHJB-HFTRVMKXSA-N
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(verify)
Equilin is a
naturally occurring
estrogen
sex hormone found in
horses as well as a
medication .
[1]
[2]
[3] It is one of the estrogens present in the estrogen
combination drug preparations known as
conjugated estrogens (CEEs; e.g. Premarin ) and
esterified estrogens (EEs; e.g. Estratab , Menest ).
[2]
[3] CEEs is the most commonly used form of estrogen medications in
hormone replacement therapy (HRT) for
menopausal symptoms in the
United States .
[3]
Estrone sulfate is the major estrogen in CEEs (about 50%) while equilin sulfate is the second major estrogen in the formulation, present as about 25% of the total.
[2]
[3]
Pharmacology
Pharmacodynamics
Equilin is an estrogen, or an
agonist of the
estrogen receptors (ERs), the
ERα and
ERβ .
[2] In terms of
relative binding affinity for the ERs, equilin has about 13% and 49% of that of estradiol for the ERα and ERβ, respectively.
[2] Analogously to the reversible transformation of
estrone into
estradiol by
17β-hydroxysteroid dehydrogenase , equilin can be converted into the more potent estrogen
17β-dihydroequilin in the body.
[2]
[3] This estrogen has about 113% and 108% of the relative binding affinities of estradiol for the ERα and ERβ, respectively.
[2]
[3] Equilin is present in CEEs in the form of equilin sulfate, which itself is inactive and acts as a
prodrug of equilin via
steroid sulfatase .
[2]
[3]
Similarly to
synthetic estrogens like
ethinylestradiol , equilin and CEEs have disproportionate effects in certain
tissues such as the
liver and
uterus relative to
bioidentical human estrogens like estradiol and estrone.
[2] Because of their disproportionate potency in the liver, equilin and CEEs have relatively increased effects on
liver protein synthesis compared to estradiol.
[2]
A dosage of 0.25 mg/day equilin sulfate is equivalent to 0.625 mg/day CEEs in terms of relief from
hot flashes .
[2] At a dosage of 0.625 mg/day equilin sulfate, the increases in circulating levels of
sex hormone-binding globulin (SHBG),
corticosteroid-binding globulin , and
angiotensinogen were 1.5 to 8 times those observed with
estrone sulfate .
[2] Equilin has about 42% of the relative potency of CEEs in the
vagina and 80% of the relative potency of CEEs in the
uterus , while its more active form, 17β-dihydroequilin, has about 83% of the relative potency of CEEs in the vagina and 200% of the relative potency of CEEs in the uterus.
[2]
Relative oral potencies of estrogens
Estrogen
HF Tooltip Hot flashes
VE Tooltip Vaginal epithelium
UCa Tooltip Urinary calcium
FSH Tooltip Follicle-stimulating hormone
LH Tooltip Luteinizing hormone
HDL Tooltip High-density lipoprotein -
C Tooltip Cholesterol
SHBG Tooltip Sex hormone-binding globulin
CBG Tooltip Corticosteroid-binding globulin
AGT Tooltip Angiotensinogen
Liver
Estradiol
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Estrone
?
?
?
0.3
0.3
?
?
?
?
?
Estriol
0.3
0.3
0.1
0.3
0.3
0.2
?
?
?
0.67
Estrone sulfate
?
0.9
0.9
0.8–0.9
0.9
0.5
0.9
0.5–0.7
1.4–1.5
0.56–1.7
Conjugated estrogens
1.2
1.5
2.0
1.1–1.3
1.0
1.5
3.0–3.2
1.3–1.5
5.0
1.3–4.5
Equilin sulfate
?
?
1.0
?
?
6.0
7.5
6.0
7.5
?
Ethinylestradiol
120
150
400
60–150
100
400
500–600
500–600
350
2.9–5.0
Diethylstilbestrol
?
?
?
2.9–3.4
?
?
26–28
25–37
20
5.7–7.5
Sources and footnotes
Notes: Values are ratios, with estradiol as standard (i.e., 1.0).
Abbreviations:
HF = Clinical relief of
hot flashes .
VE = Increased
proliferation of
vaginal epithelium .
UCa = Decrease in
UCa Tooltip urinary calcium .
FSH = Suppression of
FSH Tooltip follicle-stimulating hormone levels.
LH = Suppression of
LH Tooltip luteinizing hormone levels.
HDL -
C ,
SHBG ,
CBG , and
AGT = Increase in the serum levels of these
liver proteins . Liver = Ratio of liver estrogenic effects to general/systemic estrogenic effects (hot flashes/
gonadotropins ).
Sources: See template.
Pharmacokinetics
Equilin has about 8% of the
relative binding affinity of
testosterone for SHBG, relative to 12% in the case of
estrone .
[2] In terms of
plasma protein binding , it is bound 26% to SHBG and 13% to
albumin .
[2] The
metabolic clearance rates of equilin and equilin sulfate are 2,640 L/day/m2 and 175 L/day/m2 , respectively.
[2] In accordance, the
biological half-life of equilin sulfate is substantially longer than that of equilin.
[2] Equilin is converted into
17β-dihydroequilin in the
liver and in other
tissues .
[2]
[3] Equilin and 17β-dihydroequilin can also be transformed into
equilenin and
17β-dihydroequilenin .
[2]
[3] Equilin is
excreted in the form of
glucuronide conjugates.
[2]
Chemistry
Equilin, also known as δ7 -estrone or as 7-dehydroestrone, as well as estra-1,3,5(10),7-tetraen-3-ol-17-one, is a
naturally occurring
estrane
steroid and an
analogue of
estrone .
[2]
[3] In terms of
chemical structure and
pharmacology , equilin is to
17β-dihydroequilin (δ7 -17β-estradiol) as estrone is to
estradiol .
[2]
[3]
References
Estrogens
ER Tooltip Estrogen receptor agonists
Steroidal:
Alfatradiol
Certain
androgens /
anabolic steroids (e.g.,
testosterone ,
testosterone esters ,
methyltestosterone ,
metandienone ,
nandrolone esters ) (via estrogenic metabolites)
Certain
progestins (e.g.,
norethisterone ,
noretynodrel ,
etynodiol diacetate ,
tibolone )
Clomestrone
Cloxestradiol acetate
Conjugated estriol
Conjugated estrogens
Epiestriol
Epimestrol
Esterified estrogens
Estetrol †
Estradiol
Estradiol esters (e.g.,
estradiol acetate ,
estradiol benzoate ,
estradiol cypionate ,
estradiol enanthate ,
estradiol undecylate ,
estradiol valerate ,
polyestradiol phosphate ,
estradiol ester mixtures (
Climacteron ))
Estramustine phosphate
Estriol
Estriol esters (e.g.,
estriol succinate ,
polyestriol phosphate )
Estrogenic substances
Estrone
Estrone esters
Ethinylestradiol #
Hydroxyestrone diacetate
Mestranol
Methylestradiol
Moxestrol
Nilestriol
Prasterone (dehydroepiandrosterone; DHEA)
Promestriene
Quinestradol
Quinestrol
Progonadotropins
Antiestrogens
ER Tooltip Estrogen receptor antagonists (incl.
SERMs Tooltip selective estrogen receptor modulators /
SERDs Tooltip selective estrogen receptor downregulators )
Aromatase inhibitors
Antigonadotropins
Androgens /
anabolic steroids (e.g.,
testosterone ,
testosterone esters ,
nandrolone esters ,
oxandrolone ,
fluoxymesterone )
D2 receptor
antagonists (
prolactin releasers) (e.g.,
domperidone ,
metoclopramide ,
risperidone ,
haloperidol ,
chlorpromazine ,
sulpiride )
GnRH agonists (e.g.,
leuprorelin ,
goserelin )
GnRH antagonists (e.g.,
cetrorelix ,
elagolix )
Progestogens (e.g.,
chlormadinone acetate ,
cyproterone acetate ,
gestonorone caproate ,
hydroxyprogesterone caproate ,
medroxyprogesterone acetate ,
megestrol acetate )
Others
ER Tooltip Estrogen receptor
Agonists
Steroidal:
2-Hydroxyestradiol
2-Hydroxyestrone
3-Methyl-19-methyleneandrosta-3,5-dien-17β-ol
3α-Androstanediol
3α,5α-Dihydrolevonorgestrel
3β,5α-Dihydrolevonorgestrel
3α-Hydroxytibolone
3β-Hydroxytibolone
3β-Androstanediol
4-Androstenediol
4-Androstenedione
4-Fluoroestradiol
4-Hydroxyestradiol
4-Hydroxyestrone
4-Methoxyestradiol
4-Methoxyestrone
5-Androstenediol
7-Oxo-DHEA
7α-Hydroxy-DHEA
7α-Methylestradiol
7β-Hydroxyepiandrosterone
8,9-Dehydroestradiol
8,9-Dehydroestrone
8β-VE2
10β,17β-Dihydroxyestra-1,4-dien-3-one (DHED)
11β-Chloromethylestradiol
11β-Methoxyestradiol
15α-Hydroxyestradiol
16-Ketoestradiol
16-Ketoestrone
16α-Fluoroestradiol
16α-Hydroxy-DHEA
16α-Hydroxyestrone
16α-Iodoestradiol
16α-LE2
16β-Hydroxyestrone
16β,17α-Epiestriol (16β-hydroxy-17α-estradiol)
17α-Estradiol (
alfatradiol )
17α-Dihydroequilenin
17α-Dihydroequilin
17α-Epiestriol (16α-hydroxy-17α-estradiol)
17α-Ethynyl-3α-androstanediol
17α-Ethynyl-3β-androstanediol
17β-Dihydroequilenin
17β-Dihydroequilin
17β-Methyl-17α-dihydroequilenin
Abiraterone
Abiraterone acetate
Alestramustine
Almestrone
Anabolic steroids (e.g.,
testosterone and
esters ,
methyltestosterone ,
metandienone (methandrostenolone) ,
nandrolone and
esters , many others; via estrogenic metabolites)
Atrimustine
Bolandiol
Bolandiol dipropionate
Butolame
Clomestrone
Cloxestradiol
Conjugated estriol
Conjugated estrogens
Cyclodiol
Cyclotriol
DHEA
DHEA-S
ent -Estradiol
Epiestriol (16β-epiestriol, 16β-hydroxy-17β-estradiol)
Epimestrol
Equilenin
Equilin
ERA-63 (ORG-37663)
Esterified estrogens
Estetrol
Estradiol
Estramustine
Estramustine phosphate
Estrapronicate
Estrazinol
Estriol
Estrofurate
Estrogenic substances
Estromustine
Estrone
Etamestrol (eptamestrol)
Ethinylandrostenediol
Ethinylestradiol
Ethinylestriol
Ethylestradiol
Etynodiol
Etynodiol diacetate
Hexolame
Hippulin
Hydroxyestrone diacetate
Lynestrenol
Lynestrenol phenylpropionate
Mestranol
Methylestradiol
Moxestrol
Mytatrienediol
Nilestriol
Norethisterone
Noretynodrel
Orestrate
Pentolame
Prodiame
Prolame
Promestriene
RU-16117
Quinestradol
Quinestrol
Tibolone
Xenoestrogens:
Anise -related (e.g.,
anethole ,
anol ,
dianethole ,
dianol ,
photoanethole )
Chalconoids (e.g.,
isoliquiritigenin ,
phloretin ,
phlorizin (phloridzin) ,
wedelolactone )
Coumestans (e.g.,
coumestrol ,
psoralidin )
Flavonoids (incl.
7,8-DHF ,
8-prenylnaringenin ,
apigenin ,
baicalein ,
baicalin ,
biochanin A ,
calycosin ,
catechin ,
daidzein ,
daidzin ,
ECG ,
EGCG ,
epicatechin ,
equol ,
formononetin ,
glabrene ,
glabridin ,
genistein ,
genistin ,
glycitein ,
kaempferol ,
liquiritigenin ,
mirificin ,
myricetin ,
naringenin ,
penduletin ,
pinocembrin ,
prunetin ,
puerarin ,
quercetin ,
tectoridin ,
tectorigenin )
Lavender oil
Lignans (e.g.,
enterodiol ,
enterolactone ,
nyasol (cis -hinokiresinol) )
Metalloestrogens (e.g.,
cadmium )
Pesticides (e.g.,
alternariol ,
dieldrin ,
endosulfan ,
fenarimol ,
HPTE ,
methiocarb ,
methoxychlor ,
triclocarban ,
triclosan )
Phytosteroids (e.g.,
digitoxin (
digitalis ),
diosgenin ,
guggulsterone )
Phytosterols (e.g.,
β-sitosterol ,
campesterol ,
stigmasterol )
Resorcylic acid lactones (e.g.,
zearalanone ,
α-zearalenol ,
β-zearalenol ,
zearalenone ,
zeranol (α-zearalanol) ,
taleranol (teranol, β-zearalanol) )
Steroid -like (e.g.,
deoxymiroestrol ,
miroestrol )
Stilbenoids (e.g.,
resveratrol ,
rhaponticin )
Synthetic xenoestrogens (e.g.,
alkylphenols ,
bisphenols (e.g.,
BPA ,
BPF ,
BPS ),
DDT ,
parabens ,
PBBs ,
PHBA ,
phthalates ,
PCBs )
Others (e.g.,
agnuside ,
rotundifuran )
Mixed (
SERMs Tooltip Selective estrogen receptor modulators ) Antagonists
Coregulator-binding modulators:
ERX-11
GPER Tooltip G protein-coupled estrogen receptor
Agonists Antagonists Unknown