View source for Estriol

{{About|estriol as a hormone|its use as a medication|Estriol (medication)}}
{{Chembox
<!-- Images -->
| ImageFile = Estriol.svg
| ImageClass = skin-invert
| ImageSize = 250px
| ImageFile2 = Estriol molecule ball.png
| ImageClass2 = bg-transparent
| ImageSize2 = 235px
<!-- Names -->
| IUPACName = Estra-1,3,5(10)-triene-3,16α,17β-triol
| SystematicName = (1''R'',2''R'',3a''S'',3b''R'',9b''S'',11a''S'')-11a-Methyl-2,3,3a,3b,4,5,9b,10,11,11a-decahydro-1''H''-cyclopenta[''a'']phenanthrene-1,2,7-triol
| OtherNames = Oestriol; E3; Estratriol; Theelol; Trihydroxyestrin; Trihydroxyoestrin; 16α-Hydroxyestradiol
<!-- Sections -->
| Section1 = {{Chembox Identifiers
| CASNo = 50-27-1
| CASNoOther = 1306-04-3
| ChEBI = 27974
| ChEMBL = 193482
| ChemSpiderID = 5553
| InChI = 1S/C18H24O3/c1-18-7-6-13-12-5-3-11(19)8-10(12)2-4-14(13)15(18)9-16(20)17(18)21/h3,5,8,13-17,19-21H,2,4,6-7,9H2,1H3/t13-,14-,15+,16-,17+,18+/m1/s1
| InChIKey = PROQIPRRNZUXQM-ZXXIGWHRSA-N
| KEGG = C05141
| PubChem = 5756
| SMILES = C[C@]12CC[C@H]3[C@H]([C@@H]1C[C@H]([C@@H]2O)O)CCC4=C3C=CC(=C4)O
| UNII = FB33469R8E
  }}
| Section2 = {{Chembox Properties
| C=18 | H=24 | O=3
| MolarMass = 288.387 g/mol
| Appearance = 
| Density = 
| MeltingPt = 
| BoilingPt = 
| Solubility = 
  }}
| Section3 = {{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
  }}
}}

'''Estriol''' ('''E3'''), also spelled '''oestriol''', is a [[steroid]], a weak [[estrogen]], and a minor female [[sex hormone]].<ref name="pmid16112947a">{{cite journal | vauthors = Kuhl H | title = Pharmacology of estrogens and progestogens: influence of different routes of administration | journal = Climacteric | volume = 8 | pages = 3–63 | date = August 2005 | issue = Suppl 1 | pmid = 16112947 | doi = 10.1080/13697130500148875 | s2cid = 24616324 }}</ref><ref name="Puri2005">{{cite book|author=Puri|title=Textbook Of Biochemistry|url=https://books.google.com/books?id=XnPOEEeXXnYC&pg=PA793|date=1 January 2005|publisher=Elsevier India|isbn=978-81-8147-844-3|pages=793–}}</ref> It is one of three major [[endogenous]] estrogens, the others being [[estradiol]] and [[estrone]].<ref name="pmid16112947a"/> Levels of estriol in women who are not [[pregnancy|pregnant]] are almost undetectable.<ref name="IIIBarbieri2013">{{cite book| first1 = Jerome F. | last1 = Strauss | first2 = Robert L. | last2 = Barbieri | name-list-style = vanc |title=Yen and Jaffe's Reproductive Endocrinology|url=https://books.google.com/books?id=KZ95AAAAQBAJ&pg=PA256|date=13 September 2013|publisher=Elsevier Health Sciences|isbn=978-1-4557-2758-2|pages=256–}}</ref> However, during pregnancy, estriol is synthesized in very high quantities by the [[placenta]] and is the most produced estrogen in the body by far,<ref name="IIIBarbieri2013" /><ref name="Goodman2003">{{cite book|author=H. Maurice Goodman|title=Basic Medical Endocrinology|url=https://books.google.com/books?id=ica8EeRFeawC&pg=PA436|date=14 March 2003|publisher=Academic Press|isbn=978-0-08-048836-3|pages=436–}}</ref> although circulating levels of estriol are similar to those of other estrogens due to a relatively high rate of [[metabolism]] and [[excretion]].<ref name="Goodman2003" /><ref name="(Prof.)2001" /> Relative to estradiol, both estriol and estrone have far weaker activity as estrogens.<ref name="pmid16112947a"/>

In addition to its role as a natural hormone, estriol is used as a [[medication]], for instance in [[menopausal hormone therapy]]; for information on estriol as a medication, see the [[estriol (medication)]] article.

{{TOC limit|3}}

==Biological activity==
Estriol is an estrogen, specifically an [[agonist]] of the [[estrogen receptor]]s [[estrogen receptor alpha|ERα]] and [[estrogen receptor beta|ERβ]].<ref name="pmid16112947a"/><ref name="JaouenSalmain2015">{{cite book| first1 = Gérard | last1 = Jaouen | first2 = Michle | last2 = Salmain | name-list-style = vanc |title=Bioorganometallic Chemistry: Applications in Drug Discovery, Biocatalysis, and Imaging|url=https://books.google.com/books?id=n7ynBQAAQBAJ&pg=PA45|date=20 April 2015|publisher=John Wiley & Sons|isbn=978-3-527-33527-5|pages=45–}}</ref><ref name="pmid16554039">{{cite journal | vauthors = Escande A, Pillon A, Servant N, Cravedi JP, Larrea F, Muhn P, Nicolas JC, Cavaillès V, Balaguer P | title = Evaluation of ligand selectivity using reporter cell lines stably expressing estrogen receptor alpha or beta | journal = Biochemical Pharmacology | volume = 71 | issue = 10 | pages = 1459–69 | date = May 2006 | pmid = 16554039 | doi = 10.1016/j.bcp.2006.02.002 }}</ref> It is a far less [[potency (pharmacology)|potent]] estrogen than is estradiol, and as such is a relatively weak estrogen.<ref name="pmid16112947a"/><ref name="pmid16554039" /><ref name="LappanoRosano2010" /><ref name="Becker2001">{{cite book|author=Kenneth L. Becker|title=Principles and Practice of Endocrinology and Metabolism|url=https://books.google.com/books?id=FVfzRvaucq8C&pg=PA1061|year=2001|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-1750-2|pages=932, 1061}}</ref> According to one ''[[in vitro]]'' study, the [[relative binding affinity]] (RBA) of estriol for the human ERα and ERβ was 11.3% and 17.6% of that of estradiol, respectively, and the [[relative transactivational capacity]] of estriol at the ERα and ERβ was 10.6% and 16.6% of that of estradiol, respectively.<ref name="pmid16554039" /> According to another ''in vitro'' study however, the RBA of estriol for the ERα and ERβ were 14% and 21% of those of estradiol, respectively,<ref name="RubanyiKauffman2003">{{cite book| first1 = Gabor M. | last1 = Rubanyi | first2 = R | last2 = Kauffman | name-list-style = vanc |title=Estrogen and the Vessel Wall|url=https://books.google.com/books?id=U6WU25VeOBsC&pg=PA8|date=2 September 2003|publisher=CRC Press|isbn=978-0-203-30393-1|pages=8–}}</ref> suggesting that unlike estradiol and estrone, estriol may have preferential [[affinity (pharmacology)|affinity]] for ERβ.<ref name="JaouenSalmain2015" />

Although estriol is an [[efficacy|efficacious]] agonist of the ERs, it is reported to have mixed [[agonist–antagonist]] ([[partial agonist]]) activity at the ER; on its own, it is weakly estrogenic, but in the presence of estradiol, it is [[antiestrogen]]ic.<ref name="LappanoRosano2010">{{cite journal | vauthors = Lappano R, Rosano C, De Marco P, De Francesco EM, Pezzi V, Maggiolini M | title = Estriol acts as a GPR30 antagonist in estrogen receptor-negative breast cancer cells | journal = Molecular and Cellular Endocrinology | volume = 320 | issue = 1–2 | pages = 162–70 | date = May 2010 | pmid = 20138962 | doi = 10.1016/j.mce.2010.02.006 | s2cid = 24525995 }}</ref><ref name="Becker2001" /> Given by [[subcutaneous injection]] in mice, estradiol is about 10-fold more potent than estrone and about 100-fold more potent than estriol.<ref name="Labhart2012">{{cite book|author=A. Labhart|title=Clinical Endocrinology: Theory and Practice|url=https://books.google.com/books?id=DAgJCAAAQBAJ&pg=PA548|date=6 December 2012|publisher=Springer Science & Business Media|isbn=978-3-642-96158-8|pages=548–}}</ref><ref name="Blackburn2014">{{cite book|author=Susan Blackburn|title=Maternal, Fetal, & Neonatal Physiology|url=https://books.google.com/books?id=RNLsAwAAQBAJ&pg=PA93|date=14 April 2014|publisher=Elsevier Health Sciences|isbn=978-0-323-29296-2|pages=39, 93}}</ref> It is notable that unlike estriol, estrone can be [[metabolism|metabolized]] into estradiol, and most of its potency ''[[in vivo]]'' is in fact actually due to conversion into estradiol.<ref name="pmid16112947a"/>

In addition to acting as an agonist of the [[nuclear receptor|nuclear]] ERs, estriol at high concentrations (~1,000–10,000&nbsp;nM) also acts as an [[receptor antagonist|antagonist]] of the [[GPER]], a [[membrane estrogen receptor]] where, conversely, estradiol acts as an agonist.<ref name="pmid26023144">{{cite journal | vauthors = Prossnitz ER, Arterburn JB | title = International Union of Basic and Clinical Pharmacology. XCVII. G Protein-Coupled Estrogen Receptor and Its Pharmacologic Modulators | journal = Pharmacol. Rev. | volume = 67 | issue = 3 | pages = 505–40 | date = July 2015 | pmid = 26023144 | pmc = 4485017 | doi = 10.1124/pr.114.009712 }}</ref><ref name="LappanoRosano2010" /><ref name="JaouenSalmain2015" /><ref name="GirgertEmons2014">{{cite journal | vauthors = Girgert R, Emons G, Gründker C | title = Inhibition of GPR30 by estriol prevents growth stimulation of triple-negative breast cancer cells by 17β-estradiol | journal = BMC Cancer | volume = 14 | issue = 1 | pages = 935 | date = December 2014 | pmid = 25496649 | doi = 10.1186/1471-2407-14-935 | pmc = 4364648 | doi-access = free }}</ref> Estradiol increases [[breast cancer]] cell growth via activation of the GPER (in addition to the ER), and estriol has been found to inhibit estradiol-induced proliferation of [[triple-negative breast cancer]] cells through blockade of the GPER.<ref name="GirgertEmons2014" />

{{Selected biological properties of endogenous estrogens in rats}}

==Biochemistry==
[[File:Steroidogenesis.svg|thumb|450px|right|class=skin-invert-image|Human [[steroidogenesis]], showing estriol at bottom right.<ref name="HäggströmRichfield2014">{{citation |last1=Häggström |first1=Mikaeljournal |last2=Richfield |first2=David | name-list-style = vanc |year=2014|title=Diagram of the pathways of human steroidogenesis|journal=WikiJournal of Medicine|volume=1|issue=1|doi=10.15347/wjm/2014.005|issn=2002-4436|doi-access=free}}</ref> In essence, it follows the pathway from dehydroepiandrosterone or DHEA (at left), but with a modified DHEA with an additional OH-group.]]

===Biosynthesis===
====In non-pregnant women====
In women who are not pregnant estriol is produced in only very small quantities, and circulating levels are barely detectable.<ref name="IIIBarbieri2013" /> Unlike estradiol and estrone, estriol is not synthesized in or secreted from the ovaries,<ref name="JaypeeBrothers2006">{{cite book|title=Medical Disorders in Pregnancy – An Update|url=https://books.google.com/books?id=s3j3mp09CAkC&pg=PA4|year=2006|publisher=Jaypee Brothers Publishers|isbn=978-81-8061-711-9|pages=4–}}{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and is instead derived mainly if not exclusively from 16α-[[hydroxylation]] of estradiol and estrone by [[cytochrome P450]] [[enzyme]]s (e.g., [[CYP3A4]]) mainly in the [[liver]].<ref name="HendersonPonder2003" /><ref name="Assali2013">{{cite book|author=N. S. Assali|title=The Maternal Organism|url=https://books.google.com/books?id=mSzLBAAAQBAJ&pg=PA341|date=3 September 2013|publisher=Elsevier|isbn=978-1-4832-6380-9|pages=341–}}</ref> Estriol is cleared from the [[circulatory system|circulation]] rapidly in non-pregnant women, and so circulating levels are very low, but concentrations of estriol in the [[urine]] are relatively high.<ref name="HendersonPonder2003" />

Although circulating levels of estriol are very low outside of pregnancy, [[gravidity and parity|parous]] women have been found to have levels of estriol that are to some degree higher than those of [[nulliparity|nulliparous]] women.<ref name="LappanoRosano2010" />

====In pregnant women====
Estriol is produced in quantities that are notable only during [[pregnancy]].<ref name="IIIBarbieri2013" /> Levels of estriol increase 1,000-fold during pregnancy,<ref name="LappanoRosano2010" /> whereas levels of estradiol and estrone increase 100-fold,<ref name="Blackburn2014" /> and estriol accounts for 90% of the estrogens in the urine of pregnant women.<ref name="(Prof.)2001">{{cite book|author=Roger Smith (Prof.)|title=The Endocrinology of Parturition: Basic Science and Clinical Application|url=https://books.google.com/books?id=0N6Ua0O8gWwC&pg=PA89|date=1 January 2001|publisher=Karger Medical and Scientific Publishers|isbn=978-3-8055-7195-1|pages=89–}}</ref> At term, the daily production of estriol by the placenta is 35 to 45&nbsp;mg,<ref name="Blackburn2014" /> and levels in the maternal circulation are 8 to 13&nbsp;ng/dL.<ref name="IIIBarbieri2013" />

The [[placenta]] produces [[pregnenolone]] and [[progesterone]] from circulating [[cholesterol]].<ref name="Goodman2003"/> Pregnenolone is taken up by the fetal [[adrenal gland]]s and converted into [[dehydroepiandrosterone]] (DHEA), which is then [[sulfation|sulfated]] by [[steroid sulfotransferase]] into [[dehydroepiandrosterone sulfate]] (DHEA-S).{{Citation needed|date=October 2016}} DHEA-S is [[hydroxylation|hydroxylated]] by high [[CYP3A7]] expression and activity into [[16α-hydroxy-DHEA-S]] (16α-OH-DHEA-S) in the fetal [[liver]] and to a limited extent in the fetal adrenal glands.<ref name="IIIBarbieri2013" /><ref name="Yamazaki2014">{{cite book|author=Hiroshi Yamazaki|title=Fifty Years of Cytochrome P450 Research|url=https://books.google.com/books?id=9mslBAAAQBAJ&pg=PA385|date=23 June 2014|publisher=Springer|isbn=978-4-431-54992-5|pages=385–}}</ref> 16α-OH-DHEA-S is then taken up by the placenta.<ref name="IIIBarbieri2013" /> Due to high expression of [[steroid sulfatase]] in the placenta, 16α-OH-DHEA-S is rapidly cleaved into [[16α-OH-DHEA]].<ref name="IIIBarbieri2013" /> Then, 16α-OH-DHEA is converted by [[3β-hydroxysteroid dehydrogenase]] [[HSD3B1|type I]] (3β-HSD1) into [[16α-hydroxyandrostenedione]] (16α-OH-A4) and 16α-OH-A4 is converted by [[aromatase]] into [[16α-hydroxyestrone]] (16α-OH-E1),<ref name="AcademicPress2005">{{cite book|title=Vitamins and Hormones|url=https://books.google.com/books?id=DUst5mwBfN0C&pg=PA282|date=7 September 2005|publisher=Academic Press|isbn=978-0-08-045978-3|pages=282–}}</ref> which is subsequently converted into estriol by [[17β-hydroxysteroid dehydrogenase]] and then secreted predominantly into the maternal circulation.<ref name="IIIBarbieri2013" /><ref name="HendersonPonder2003">{{cite book | first1 = Brian E. | last1 = Henderson | first2 = Bruce | last2 = Ponder | first3 = Ronald K. | last3 = Ross | name-list-style = vanc |title=Hormones, Genes, and Cancer|url=https://books.google.com/books?id=VzIWd4faVVQC&pg=PA25|date=13 March 2003|publisher=Oxford University Press|isbn=978-0-19-977158-5|pages=25–}}</ref> Approximately 90% of precursors in estriol formation originate from the fetus.<ref name="HendersonPonder2003" />

During pregnancy, 90 to 95% of estriol in the maternal circulation is [[conjugation (biochemistry)|conjugated]] in the form of [[estriol glucuronide]] and [[estriol sulfate]], and levels of unconjugated estriol are slightly less than those of unconjugated estradiol and similar to those of unconjugated estrone.<ref name="(Prof.)2001" /> As such, target tissues are likely to be exposed to similar amounts of free estriol, estradiol, and estrone during pregnancy.<ref name="(Prof.)2001" />

[[Estrone]] and [[estradiol]] are also produced in the placenta during pregnancy.<ref name="IIIBarbieri2013" /> However, in the case of estrone and estradiol, DHEA-S is taken up by the placenta and cleaved by steroid sulfatase into [[dehydroepiandrosterone]] (DHEA), DHEA is converted by [[3β-hydroxysteroid dehydrogenase]] [[HSD3B1|type I]] into [[androstenedione]], and androstenedione is aromatized into estrone.<ref name="IIIBarbieri2013" /> Then, placental [[17β-hydroxysteroid dehydrogenase]] interconverts estrone and estradiol and the two hormones are secreted into the maternal circulation.<ref name="IIIBarbieri2013" /> DHEA-S that is taken up by the placenta is mainly produced by the fetal adrenal glands.<ref name="IIIBarbieri2013" />

===Distribution===
Estriol is poorly bound to [[sex hormone-binding globulin]] (SHBG),<ref name="Buchsbaum2012">{{cite book |author= H.J. Buchsbaum |title= The Menopause |url= https://books.google.com/books?id=z0LuBwAAQBAJ&pg=PA62 |date=6 December 2012 |publisher= Springer Science & Business Media |isbn= 978-1-4612-5525-3 |pages= 62–}}</ref> with much lower [[binding affinity]] for this protein, relative to estradiol, and hence a greater fraction available for [[biological activity]].<ref name="LorenzoHorowitz2015">{{cite book | first1 = Joseph | last1 = Lorenzo | first2 = Mark | last2 = Horowitz | first3 = Yongwon | last3 = Choi | first4 = Hiroshi | last4 = Takayanagi | first5 = Georg | last5 = Schett | name-list-style = vanc |title= Osteoimmunology: Interactions of the Immune and Skeletal Systems |url= https://books.google.com/books?id=eOGcBAAAQBAJ&pg=PA216 |date= 23 September 2015 |publisher= Elsevier Science |isbn= 978-0-12-800627-6|pages=216–}}</ref>

===Metabolism===
Estriol is [[metabolism|metabolized]] via [[glucuronidation]] and [[sulfation]].<ref name="OettelSchillinger2012" /><ref name="MuseyKirdani1973" />

===Excretion===
The main [[urine|urinary]] [[metabolite]]s of [[exogenous]] estriol administered via [[intravenous injection]] in [[baboon]]s have been found to be [[estriol 16α-glucuronide]] (65.8%), [[estriol 3-glucuronide]] (14.2%), [[estriol 3-sulfate]] (13.4%), and [[estriol 3-sulfate 16α-glucuronide]] (5.1%).<ref name="OettelSchillinger2012">{{cite book | first1 = Michael | last1 = Oettel | first2 = Ekkehard | last2 = Schillinger | name-list-style = vanc |title= Estrogens and Antiestrogens II: Pharmacology and Clinical Application of Estrogens and Antiestrogen |url= https://books.google.com/books?id=wBvyCAAAQBAJ&pg=PA265 |date= 6 December 2012 |publisher= Springer Science & Business Media |isbn= 978-3-642-60107-1 |pages=265–}}</ref><ref name="MuseyKirdani1973">{{cite journal | vauthors = Musey PI, Kirdani RY, Bhanalaph T, Sandberg AA | title = Estriol metabolism in the baboon: analysis of urinary and biliary metabolites | journal = Steroids | volume = 22 | issue = 6 | pages = 795–817 | date = December 1973 | pmid = 4203562 | doi = 10.1016/0039-128X(73)90054-8}}</ref> The [[metabolism]] and [[excretion]] of estriol in these animals closely resembled that which has been observed in humans.<ref name="MuseyKirdani1973" /> In non-pregnant women, estriol urinary excretion ranges between 0.02–0.1 mg every 24 hours. In comparison, in near-term pregnant women, estriol urinary excretion ranges from 50–150 mg every 24 hours.<ref>{{cite web |title=Estriol |url=https://fertilitypedia.org/edu/biological-control/estriol |website=Fertilitypedia |access-date=1 February 2023 |language=en}}</ref>

==Medical use==
{{Main|Estriol (medication)}}

Estriol is used as a [[medication]], primarily in [[hormone replacement therapy|hormone therapy]] for [[menopause|menopausal]] [[symptom]]s.<ref name="pmid16112947a"/>

==Chemistry==
{{See also|List of estrogens}}
{{Chemical structures of major endogenous estrogens|align=right|caption=Note the [[hydroxyl group|hydroxyl]] (–OH) [[functional group|group]]s: estrone (E1) has one, estradiol (E2) has two, estriol (E3) has three, and estetrol (E4) has four.}}

Estriol, also known as 16α-hydroxyestradiol or as estra-1,3,5(10)-triene-3,16α,17β-triol, is a [[natural compound|naturally occurring]] [[estrane]] [[steroid]] with [[double bond]]s between the C1 and C2, C3 and C4, and C5 and C10 positions and [[hydroxyl group]]s at the C3, C16α, and C17β positions.<ref name="Elks2014">{{cite book|author=J. Elks|title=The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies|url=https://books.google.com/books?id=0vXTBwAAQBAJ&pg=PA899|date=14 November 2014|publisher=Springer|isbn=978-1-4757-2085-3|pages=899–}}</ref><ref name="IndexNominum2000">{{cite book|title=Index Nominum 2000: International Drug Directory|url=https://books.google.com/books?id=5GpcTQD_L2oC&pg=PA407|date=January 2000|publisher=Taylor & Francis|isbn=978-3-88763-075-1|pages=407–}}</ref> The name ''estriol'' and the abbreviation ''E3'' were derived from the chemical terms ''[[estrin (compound)|'''estr'''in]]'' (estra-1,3,5(10)-triene) and '''''[[triol]]''''' (three hydroxyl groups).

==History==
Estriol was discovered in 1930.<ref name="Josimovich2013">{{cite book|author=J.B. Josimovich|title=Gynecologic Endocrinology|url=https://books.google.com/books?id=9vv2BwAAQBAJ&pg=PA31|date=11 November 2013|publisher=Springer Science & Business Media|isbn=978-1-4613-2157-6|pages=31–}}</ref><ref name="SartorelliJohns2013">{{cite book|first1 = Alan C. | last1 = Sartorelli | first2 = David G. | last2 = Johns | name-list-style = vanc |title=Antineoplastic and Immunosuppressive Agents|url=https://books.google.com/books?id=aU_oCAAAQBAJ&pg=PA104|date=27 November 2013|publisher=Springer Science & Business Media|isbn=978-3-642-65806-8|pages=104–}}</ref> It was isolated and purified from the [[urine]] of pregnant women by Marrian and colleagues.<ref name="Josimovich2013" /><ref name="SartorelliJohns2013" />

==Use in screening==
Estriol can be measured in maternal blood or urine and can be used as a marker of fetal health and well-being. If levels of unconjugated estriol (uE3 or free estriol) are abnormally low in a pregnant woman, this may indicate chromosomal or congenital anomalies like [[Down syndrome]] or [[Edward's syndrome]]. It is included as part of the [[triple test]] and [[quadruple test]]<ref>{{Cite web|url=https://medlineplus.gov/ency/article/007311.htm|title=Quadruple screen test: MedlinePlus Medical Encyclopedia|website=medlineplus.gov|language=en|access-date=2018-11-07}}</ref> for antenatal screening for fetal anomalies.

Because many pathological conditions in a pregnant woman can cause deviations in estriol levels, these screenings are often seen as less definitive of fetal-placental health than a [[nonstress test]]. Conditions which can create [[false positives]] and [[false negatives]] in estriol testing for fetal distress include [[preeclampsia]], [[anemia]], and impaired [[kidney function]].<ref name="isbn0-323-05747-0">{{cite book | vauthors = Pagana TJ, Pagana KD | title = Mosby's Manual of Diagnostic and Laboratory Tests | publisher = Mosby | location = St. Louis | year = 2009 | pages = [https://archive.org/details/isbn_9780323057479/page/240 240] | isbn = 978-0-323-05747-9 | url = https://archive.org/details/isbn_9780323057479/page/240 | url-access = registration }}</ref>

==References==
{{Reflist}}

==Further reading==
* {{cite journal | vauthors = Merrill RC | title = Estriol: a review | journal = Physiological Reviews | volume = 38 | issue = 3 | pages = 463–80 | date = July 1958 | pmid = 13567043 | doi = 10.1152/physrev.1958.38.3.463 }}

{{Endogenous steroids}}
{{Estrogen receptor modulators}}

[[Category:Estranes]]
[[Category:Estrogens]]
[[Category:GPER antagonists]]
[[Category:Hormones of the hypothalamus-pituitary-gonad axis]]
[[Category:Hormones of the pregnant female]]
[[Category:Hydroxyarenes]]
[[Category:Sex hormones]]
[[Category:Triols]]