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  • Chemistry
1,5-Oestratriene-3-.beta.,16.alpha.,17.beta.-triol
Also known as: 50-27-1, Oestriol, Trihydroxyestrin, Aacifemine, Estratriol, Ovestin
Molecular Formula
C18H24O3
Molecular Weight
288.4  g/mol
InChI Key
PROQIPRRNZUXQM-ZXXIGWHRSA-N
FDA UNII
FB33469R8E

A hydroxylated metabolite of ESTRADIOL or ESTRONE that has a hydroxyl group at C3, 16-alpha, and 17-beta position. Estriol is a major urinary estrogen. During PREGNANCY, a large amount of estriol is produced by the PLACENTA. Isomers with inversion of the hydroxyl group or groups are called epiestriol.
1 2D Structure

1,5-Oestratriene-3-.beta.,16.alpha.,17.beta.-triol

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
(8R,9S,13S,14S,16R,17R)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,16,17-triol
2.1.2 InChI
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
2.1.3 InChI Key
PROQIPRRNZUXQM-ZXXIGWHRSA-N
2.1.4 Canonical SMILES
CC12CCC3C(C1CC(C2O)O)CCC4=C3C=CC(=C4)O
2.1.5 Isomeric SMILES
C[C@]12CC[C@H]3[C@H]([C@@H]1C[C@H]([C@@H]2O)O)CCC4=C3C=CC(=C4)O
2.2 Other Identifiers
2.2.1 UNII
FB33469R8E
2.3 Synonyms
2.3.1 MeSH Synonyms

1. (16alpha,17beta)-estra-1,3,5(10)-triene-3,16,17-triol

2. (16beta,17beta)-estra-1,3,5(10)-triene-3,16,17-triol

3. 16 Alpha Hydroxy Estradiol

4. 16-alpha-hydroxy-estradiol

5. 16alpha,17beta Estriol

6. 16alpha,17beta-estriol

7. 16beta Hydroxy Estradiol

8. 16beta-hydroxy-estradiol

9. Epiestriol

10. Estra-1,3,5(10)-triene-3,16beta,17beta-triol

11. Ovestin

2.3.2 Depositor-Supplied Synonyms

1. 50-27-1

2. Oestriol

3. Trihydroxyestrin

4. Aacifemine

5. Estratriol

6. Ovestin

7. Ovestrion

8. Destriol

9. Tridestrin

10. Theelol

11. Oestratriol

12. Orestin

13. Holin

14. 16alpha-hydroxyestradiol

15. Ortho-gynest

16. Deuslon-a

17. Hemostyptanon

18. Hormomed

19. Klimoral

20. Oestriolum

21. Orgastyptin

22. Overstin

23. Thulol

24. Triovex

25. 16alpha,17beta-estriol

26. Gynaesan

27. Hormonin

28. Stiptanon

29. Synapause

30. Triodurin

31. Estriel

32. Trihydroxyoestrin

33. Follicular Hormone Hydrate

34. 16-alpha-hydroxyestradiol

35. Estriolo [italian]

36. 16alpha-hydroxyoestradiol

37. 16alpha,17beta-oestriol

38. 16-alpha,17-beta-estriol

39. 16-alpha,17-beta-oestriol

40. Colpogyn

41. Estriolo

42. Incurin

43. 16alpha-hydroxy-17beta-estradiol

44. Estriol, Unconjugated

45. (16alpha,17beta)-estra-1,3,5(10)-triene-3,16,17-triol

46. 16-alpha-hydroxyoestradiol

47. Deuslon A

48. Nsc-12169

49. 3,16alpha,17beta-estriol

50. 3,16-alpha,17-beta-estriol

51. 3,16-alpha,17-beta-oestriol

52. 16.alpha.-hydroxyestradiol

53. 16.alpha.,17.beta.-estriol

54. 3,16alpha,17beta-trihydroxy-1,3,5(10)-estratriene

55. 16.alpha.-estriol

56. Chlorapatite

57. Gynasan

58. Ovesterin

59. 1,3,5-estratriene-3beta,16alpha,17beta-triol

60. Ovo-vinces

61. 1,3,5-oestratriene-3beta,16alpha,17beta-triol

62. A 13610

63. Klimax E

64. Estra-1,3,5(10)-trien-3,16alpha,17beta-triol

65. Oestra-1,3,5(10)-triene-3,16alpha,17beta-triol

66. 16.alpha.-hydroxyoestradiol

67. 3,16alpha,17beta-trihydroxy-delta-1,3,5-oestratriene

68. 3,16-alpha,17-beta-trihydroxy-delta-1,3,5-estratriene

69. 3,16-alpha,17-beta-trihydroxy-delta-1,3,5-oestratriene

70. 3,16-alpha,17-beta-trihydroxyestra-1,3,5(10)-triene

71. 3,16-alpha,17-beta-trihydroxyoestra-1,3,5(10)-triene

72. (16alpha,17beta)-oestra-1,3,5(10)-triene-3,16,17-triol

73. 1,3,5(10)-estratriene-3,16alpha,17beta-triol

74. 16.alpha.,17.beta.-oestriol

75. 1,3,5(10)-estratriene-3,16-alpha,17beta-triol

76. Chebi:27974

77. Estra-1,3,5(10)-triene-3,16alpha,17beta-triol

78. Oestra-1,3,5(10)-triene-3,16-alpha,17-beta-triol

79. 3,16alpha,17beta-trihydroxy-delta(1,3,5)-estratriene

80. (8r,9s,13s,14s,16r,17r)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,16,17-triol

81. Oe3

82. 16.alpha.-hydroxy-17.beta.-estradiol

83. 16-epiestriol

84. Fb33469r8e

85. Nsc12169

86. Estra-1,3,5(10)-triene-3,16,17-triol, (16a,17b)-

87. Estra-1,3,5(10)-triene-3,16,17-triol

88. Dsstox_cid_2366

89. Dsstox_rid_76559

90. Dsstox_gsid_22366

91. 1306-04-3

92. 3,16.alpha.,17.beta.-estriol

93. Mfcd00003691

94. 16a-hydroxyestradiol

95. Folicular Hormone

96. (1s,10r,11s,13r,14r,15s)-15-methyltetracyclo[8.7.0.0^{2,7}.0^{11,15}]heptadeca-2(7),3,5-triene-5,13,14-triol

97. 3,17.beta.-estriol

98. Ccris 284

99. Estriel (tn)

100. 16-hydroxyestradiol

101. Oestriol [steroidal Oestrogens]

102. Estra-1,3,5(10)-triene-3,16,17-triol, (16.alpha.,17.beta.)-

103. Hsdb 3590

104. Sr-01000721851

105. Einecs 200-022-2

106. Nsc 12169

107. 1,3,5(10)-estratriene-3,16.alpha.,17.beta.-triol

108. Estra-1,3,5(10)-trien-3,16.alpha.,17.beta.-triol

109. Estra-1,3,5(10)-triene-3,16.alpha.,17.beta.-triol

110. 1,3,5(10)-estratriene-3,16,17-triol

111. 1,3,5-estratriene-3.beta.,16-.alpha.,17-.beta.-triol

112. 1,3,5-oestratriene-3-.beta.,16.alpha.,17.beta.-triol

113. 3,16.alpha.,17.beta.-trihydroxy-1,3,5(10)-estratriene

114. 3,16.alpha.,17.beta.-trihydroxyestra-1,3,5(10)-triene

115. Brn 2508172

116. Oestra-1,3,5(10)-triene-3,16.alpha., 17.beta.-triol

117. 3,16.alpha.,17.beta.-trihydroxy-.delta.-1,3,5-estratriene

118. Ovestinon

119. Trimesta

120. 3,16.alpha.,17.beta.-trihydroxy-.delta.-1,3,5-oestratriene

121. Oestriol.

122. Unii-fb33469r8e

123. (16.alpha.,17.beta.)-estra-1,3,5(10)-triene-3,16,17-triol

124. (16.alpha.,17.beta.)-oestra-1,3,5(10)-triene-3,16,17-triol

125. Estriol [usp:inn:ban:jan]

126. 3,16-.alpha.,17-.beta.-oestriol

127. Estra-1,3,5(10)-triene-3,16,17-triol, (16alpha,17beta)-

128. Holin V

129. Cas-50-27-1

130. 16a-estriol

131. Ncgc00166111-01

132. (8r,9s,13s,14s,16r,17r)-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6h-cyclopenta[a]phenanthrene-3,16,17-triol

133. 16a,17b-estriol

134. Estriol, 98%

135. Estriol [hsdb]

136. Estriol, >=97%

137. Estriol [jan]

138. Estriol [mi]

139. 3,16a,17b-estriol

140. Estriol [mart.]

141. Prestwick0_001096

142. Prestwick1_001096

143. Prestwick2_001096

144. Prestwick3_001096

145. Estriol (jp17/usp)

146. E0218

147. Estriol [usp-rs]

148. Estriol [who-dd]

149. Epitope Id:140131

150. 1,3,5(10)-estratrien-3,16.alpha.,17.beta.-triol

151. Estra-1,3,5(10)-triene-3,16-.alpha., L7-.beta.-triol

152. Schembl78033

153. Bspbio_001172

154. Estriol [green Book]

155. 3,16-.alpha.,17-.beta.-trihydroxyoestra-1,3,5(10)-triene

156. 4-06-00-07550 (beilstein Handbook Reference)

157. Mls000069812

158. Bidd:er0124

159. Spbio_003056

160. Estriol [ep Monograph]

161. Bpbio1_001290

162. Chembl193482

163. Gtpl2821

164. Estriol [usp Monograph]

165. Dtxsid9022366

166. Estriol 1.0 Mg/ml In Methanol

167. Hms1571k14

168. Hms2090e20

169. Hms2098k14

170. Hms2234a18

171. Hms3715k14

172. Hms3884p19

173. Bcp23357

174. Hy-b0412

175. Zinc3815418

176. Estriol 100 Microg/ml In Methanol

177. Tox21_112320

178. Tox21_301604

179. Bdbm50410506

180. Lmst02010003

181. S2466

182. Estriol [ema Epar Veterinary]

183. Estriol 1000 Microg/ml In Methanol

184. Akos015894926

185. Tox21_112320_1

186. Bcp9000661

187. Ccg-221096

188. Db04573

189. Estriol 100 Microg/ml In Acetonitrile

190. Estriol, Purum, >=97.0% (hplc)

191. Fd12050

192. Smp1_000122

193. Ncgc00166111-02

194. Ncgc00179277-01

195. Ncgc00255193-01

196. Ncgc00274080-01

197. As-13735

198. Estriol, Meets Usp Testing Specifications

199. Smr000059210

200. Bcp0726000219

201. Ab00514045

202. B1507

203. Estriol, Vetranal(tm), Analytical Standard

204. Wln: L E5 B666ttt&j E1 Fq Gq Oq

205. C05141

206. D00185

207. Estra-1,3,5(10)-triene-3,16a,17b-triol

208. 1,3,5-estratriene-3b,16a,17b-triol

209. 3,16a,17b-trihydroxyestra-1,3,5(10)-triene

210. 3,17.beta.-trihydroxy-1,3,5(10)-estratriene

211. 3,17.beta.-trihydroxyestra-1,3,5(10)-triene

212. Ab00514045-08

213. Ab00514045-09

214. Ab00514045_10

215. (16.alpha.,3,5(10)-triene-3,16,17-triol

216. 003e691

217. Q409721

218. 3,17.beta.-trihydroxy-.delta.-1,3,5-estratriene

219. 3,17.beta.-trihydroxy-.delta.-1,3,5-oestratriene

220. Q-201072

221. Sr-01000721851-3

222. Sr-01000721851-4

223. 1,5(10)-estratriene-3,16.alpha., 17.beta.-triol

224. 1,5(10)-estratriene-3,16.alpha.,17.beta.-triol

225. 3,16alpha,17beta-trihydroxyestra-1,3,5(10)-triene

226. Brd-k17016787-001-03-5

227. Brd-k17016787-001-16-7

228. Estra-1,5(10)-trien-3,16.alpha.,17.beta.-triol

229. Estra-1,5(10)-triene-3,16.alpha.,17.beta.-triol

230. 1,5-estratriene-3.beta.,16-.alpha.,17-.beta.-triol

231. 1,5-oestratriene-3-.beta.,16.alpha.,17.beta.-triol

232. 13b-methyl-1,3,5(10)-gonatriene-3,16a,17b-triol

233. Estra-1,5(10)-trien-3,16.alpha., 17.beta.-triol

234. Estra-1,5(10)-triene-3,16.alpha., 17.beta.-triol

235. Estriol, European Pharmacopoeia (ep) Reference Standard

236. Oestra-1,5(10)-triene-3,16.alpha., 17.beta.-triol

237. Oestra-1,5(10)-triene-3,16.alpha.,17.beta.-triol

238. 6ec6f23b-a991-4606-8bc7-146d915dab31

239. Estriol, United States Pharmacopeia (usp) Reference Standard

240. (16a,17b)-estra-1,3,5(10)-triene-3,16,17-triol

241. (s)-1,2,3,4-tetrahydro-3-isoquinolinecarboxylic Acidt-butyl Ester

242. Estra-1(10),2,4-triene-3,16,17-triol, (16alpha,17beta)-

243. Estra-1,5(10)-triene-3,16,17-triol, (16.alpha.,17.beta.)-

244. (9beta,13alpha,16beta,17beta)-estra-1(10),2,4-triene-3,16,17-triol

245. 13.beta.-methyl-1,3,5(10)-gonatriene-3,16.alpha.,17.beta.-triol

246. Estriol For System Suitability, European Pharmacopoeia (ep) Reference Standard

247. Estriol Solution, 1.0 Mg/ml In Methanol, Ampule Of 1 Ml, Certified Reference Material

248. (13s,16r,17r)-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6h-cyclopenta[a]phenanthrene-3,16,17-triol

249. (8r,13s,16r,17r)-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6h-cyclopenta[a]phenanthrene-3,16,17-triol

250. (8r,9s,13s,14s,16r,17r)-13-methyl-6,7,8,9,11,12,14,15,16, 17-decahydrocyclopenta[a]phenanthrene-3,16,17-triol

2.4 Create Date
2005-03-26
3 Chemical and Physical Properties
Molecular Weight 288.4 g/mol
Molecular Formula C18H24O3
XLogP32.5
Hydrogen Bond Donor Count3
Hydrogen Bond Acceptor Count3
Rotatable Bond Count0
Exact Mass288.17254462 g/mol
Monoisotopic Mass288.17254462 g/mol
Topological Polar Surface Area60.7 Ų
Heavy Atom Count21
Formal Charge0
Complexity411
Isotope Atom Count0
Defined Atom Stereocenter Count6
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Therapeutic Uses

/Estriol is indicated as/ hormone replacement therapy for treatment of atrophic vaginitis and kraurosis in post-menopausal women.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


/Estriol is indicated for the/ treatment of pruritus vulvae and dyspareunia associated with atrophic vaginal epithelium.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


4.2 Drug Warning

Gynest Cream is not indicated during pregnancy. If pregnancy occurs during use of Gynest Cream, treatment should be withdrawn immediately.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Gynest Cream contains arachis oil (peanut oil) and should not be applied by patients known to be allergic to peanuts. As there is a possible relationship between allergy to peanuts and allergy to soya, patients with soya allergy should also avoid Gynest Cream.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Before initiating or re-instituting HRT, a complete personal and family medical history should be taken. Physical (including pelvic and breast) examination should be guided by this and by the contra-indications and warnings for use. During treatment, periodic check-ups are recommended of a frequency and nature adapted to the individual woman. Women should be advised what changes in their breasts should be reported to their doctor or nurse. Investigations, including mammography, should be carried out in accordance with currently accepted screening practices, modified to the clinical needs of the individual.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


The risk of endometrial hyperplasia and carcinoma is increased when systemic estrogens are administered alone for prolonged periods of time. The endometrial safety of long-term or repeated use of topical vaginal estrogens is uncertain. Therefore, if repeated, treatment should be reviewed at least annually, with a special consideration given to any symptoms of endometrial hyperplasia or carcinoma.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


For more Drug Warnings (Complete) data for ESTRIOL (40 total), please visit the HSDB record page.


4.3 Drug Indication

Used as a test to determine the general health of an unborn fetus.


The treatment of hormone-dependent urinary incontinence due to sphincter mechanism incompetence in ovariohysterectomised bitches.


5 Pharmacology and Biochemistry
5.1 Pharmacology

Estriol (also oestriol) is one of the three main estrogens produced by the human body. It is only produced in significant amounts during pregnancy as it is made by the placenta. In pregnant women with multiple sclerosis (MS), estriol reduces the disease's symptoms noticeably, according to researchers at UCLA's Geffen Medical School.


5.2 ATC Code

QG03CA04


G03CA04

S76 | LUXPHARMA | Pharmaceuticals Marketed in Luxembourg | Pharmaceuticals marketed in Luxembourg, as published by d'Gesondheetskeess (CNS, la caisse nationale de sante, www.cns.lu), mapped by name to structures using CompTox by R. Singh et al. (in prep.). List downloaded from https://cns.public.lu/en/legislations/textes-coordonnes/liste-med-comm.html. Dataset DOI:10.5281/zenodo.4587355


G - Genito urinary system and sex hormones

G03 - Sex hormones and modulators of the genital system

G03C - Estrogens

G03CA - Natural and semisynthetic estrogens, plain

G03CA04 - Estriol


G - Genito urinary system and sex hormones

G03 - Sex hormones and modulators of the genital system

G03C - Estrogens

G03CC - Estrogens, combinations with other drugs

G03CC06 - Estriol


5.3 Absorption, Distribution and Excretion

Estriol is readily absorbed following intravaginal application. Peak serum estriol concentrations are generally observed within 2 hours following intravaginal application and remain elevated for 6 hours.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Systemic bioavailability on vaginal administration is better than after oral administration. Intravaginal application of 1 mg estriol in women with senile atrophy of the vaginal epithelium results in serum levels similar to those seen after oral administration of 10 mg estriol.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Plasma estriol levels increased from <90pmol/L (26 pg/mL) about fifty fold over a few hours after intravaginal administration of Gynest Cream. Eight to ten hours after administration, 50% of women still had estriol levels above 90pmol/L (26 pg/mL).

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Estriol circulates with the blood, about 14% free, 8% bound to SHBG and the rest bound to albumin.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


More than 95% of estriol is excreted in the urine, predominantly in the form of glucuronides.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


5.4 Metabolism/Metabolites

Primary metabolites of estriol include the 16-alpha-glucuronide, 3-glucuronide, 3-sulfate and 3-sulfate 16-alpha-glucuronide.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


The metabolic disposition of estrogens includes oxidative metabolism (largely hydroxylation) and conjugative metabolism by glucuronidation, sulfonation and/or O-methylation. Estradiol is converted to estrone by a 17beta-hydroxysteroid dehydrogenase; the estrone produced is further metabolized to 16alpha-hydroxyoestrone and then to estriol.

IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: https://monographs.iarc.fr/ENG/Classification/index.php, p. V91 145 (2007)


Estriol is a common metabolite of estrone and estradiol-17-beta in animals and in humans. Estriol is excreted in humans as conjugated and unconjugated 2-hydroxy estriol after 2-hydroxylation.

IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: https://monographs.iarc.fr/ENG/Classification/index.php, p. V21 336 (1979)


5.5 Mechanism of Action

Estriol levels can be measured to give an indication of the general health of the fetus. DHEA-S is produced by the adrenal cortex of the fetus. This is converted to estriol by the placenta. If levels of "unconjugated estriol" are abnormally low in a pregnant woman, this may indicate a problem with the development of the child. The drug interacts with a target cell receptor. When the estrogen receptor has bound its ligand it can enter the nucleus of the target cell, and regulate gene transcription which leads to formation of messenger RNA. The mRNA interacts with ribosomes to produce specific proteins that express the effect of estriol upon the target cell. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary.


... Synthetic estriol, is chemically and biologically identical to endogenous human estriol. Estriol, a weak estrogen, is a natural metabolite of estradiol, the predominant estrogen. Estriol exerts estrogenicity by binding to estrogen receptors, present in the female genital tract. Estriol, oral or vaginal, similar to estradiol, corrects lowered proliferation and abnormal physiology in the atrophic vaginal epithelium seen in estrogen deficient states, such as after natural or surgical menopause. In contrast, the histology of the endometrium after using Gynest Cream rarely shows minor signs of proliferation in previously atrophic endometria.

Datapharm Communications Ltd; Electronic Medicines Compendium (eMC), Summary of Product Characteristics (SPC) for Gynest 0.01% w/w Cream (Last updated June 2009). Available from, as of March 16, 2011: https://www.medicines.org.uk/EMC/medicine/24108/SPC/Gynest+0.01++w+w+Cream/


Estrogens have an important role in the reproductive, skeletal, cardiovascular, and central nervous systems in women, and act principally by regulating gene expression. Biologic response is initiated when estrogen binds to a ligand-binding domain of the estrogen receptor resulting in a conformational change that leads to gene transcription through specific estrogen response elements (ERE) of target gene promoters; subsequent activation or repression of the target gene is mediated through 2 distinct transactivation domains (ie, AF-1 and AF-2) of the receptor. The estrogen receptor also mediates gene transcription using different response elements (ie, AP-1) and other signal pathways. Recent advances in the molecular pharmacology of estrogen and estrogen receptors have resulted in the development of selective estrogen receptor modulators (eg, clomiphene, raloxifene, tamoxifen, toremifene), agents that bind and activate the estrogen receptor but that exhibit tissue-specific effects distinct from estrogen. Tissue-specific estrogen-agonist or -antagonist activity of these drugs appears to be related to structural differences in their estrogen receptor complex (eg, specifically the surface topography of AF-2 for raloxifene) compared with the estrogen (estradiol)-estrogen receptor complex. A second estrogen receptor also has been identified, and existence of at least 2 estrogen receptors (ER-alpha, ER-beta) may contribute to the tissue-specific activity of selective modulators. While the role of the estrogen receptor in bone, cardiovascular tissue, and the CNS continues to be studied, emerging evidence indicates that the mechanism of action of estrogen receptors in these tissues differs from the manner in which estrogen receptors function in reproductive tissue. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130


Intracellular cytosol-binding proteins for estrogens have been identified in estrogen-responsive tissues including the female genital organs, breasts, pituitary, and hypothalamus. The estrogen-binding protein complex (ie, cytosol-binding protein and estrogen) distributes into the cell nucleus where it stimulates DNA, RNA, and protein synthesis. The presence of these receptor proteins is responsible for the palliative response to estrogen therapy in women with metastatic carcinoma of the breast. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130


Estrogens have generally favorable effects on blood cholesterol and phospholipid concentrations. Estrogens reduce LDL-cholesterol and increase HDL-cholesterol concentrations in a dose-related manner. The decrease in LDL-cholesterol concentrations associated with estrogen therapy appears to result from increased LDL catabolism, while the increase in triglyceride concentrations is caused by increased production of large, triglyceride-rich, very-low-density lipoproteins (VLDLs); changes in serum HDL-cholesterol concentrations appear to result principally from an increase in the cholesterol and apolipoprotein A-1 content of HDL2- and a slight increase in HDL3-cholesterol. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130


For more Mechanism of Action (Complete) data for ESTRIOL (12 total), please visit the HSDB record page.


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