Estriol

CAS No:	50-27-1
EINECS No:	200-014-8
Synonyms:	oestriol, E3, estra-1,3,5(10)-triene-3,16α,17β-triol, (16α,17β)-estra-1,3,5(10)-triene-3,16,17-triol, 16α-hydroxyestradiol, oestriol, theelol, trihydroxyestrin; trihydroxyoestrin

Product Summary

Estriol is a naturally occurring estrogen with lower potency and a safer profile compared to estradiol. It plays a significant role during pregnancy, Estriol is widely studied in the context of hormone therapy, menopause, autoimmune regulation, and urogenital health. Due to its unique receptor dynamics, it offers selective tissue effects, making it an attractive candidate for targeted estrogen therapy in both clinical and experimental settings.

Formula: C₁₈H₂₄O₃
Molecular Weight: 288.39

Function

The hormone estriol is primarily produced in significant quantities during pregnancy. It is the weakest of the three major endogenous estrogens (estradiol, estrone, estriol) and plays a role in:

Maintaining pregnancy.
Modulating immune function during gestation.
Supporting urogenital and skin health in postmenopausal women.
Providing estrogenic effects with reduced risk of breast or endometrial stimulation compared to stronger estrogens.

Mechanism of Action

Estriol binds to estrogen receptors (ERα and ERβ) in target tissues. It:

Has lower binding affinity than estradiol but selectively activates certain pathways.
Acts as a partial agonist or antagonist depending on tissue context.
Stimulates DNA transcription in estrogen-sensitive tissues (vaginal epithelium, bone, brain, etc.).
Has anti-inflammatory and antioxidant effects in some models.

Applications in Scientific Research

Hormone replacement therapy (HRT) models for menopause
Vaginal atrophy and urogenital aging research
Autoimmune disease modulation, especially multiple sclerosis (pregnancy protection studies)
Breast cancer biology (anti-proliferative vs. estradiol)
Endocrine studies (estrogen receptor activity, selective estrogen receptor modulators – SERMs)

Packaging & Storage

Store at 2–8 °C.

References

Raz R, Stamm WE. 1993: A controlled trial of intravaginal estriol in postmenopausal women with recurrent urinary tract infections, N Engl J Med. 329(11): 753–6.
Takahashi K, et al. 2000: Safety and efficacy of oestriol for symptoms of natural or surgically induced menopause, Hum Reprod. 15(5): 1028–36.
Weber MA, et al. 2017: The effect of vaginal oestriol cream on subjective and objective symptoms of stress urinary incontinence and vaginal atrophy: An international multi-centre pilot study, Gynecol Obstet Invest. 82(1): 15–21.
Hirschberg AL, et al. 2020: Efficacy and safety of ultra-low dose 0.005% estriol vaginal gel for the treatment of vulvovaginal atrophy in postmenopausal women with early breast cancer treated with nonsteroidal aromatase inhibitors: a phase II, randomized, double-blind, placebo-controlled trial, Menopause. 27(5): 526–34.
Vermillion MS, et al. 2018: Estriol reduces pulmonary immune cell recruitment and inflammation to protect female mice from severe influenza, Endocrinol. 159(9): 3306–20.
Katzenellenbogen BS. 1984: Biology and receptor interactions of estriol and estriol derivatives in vitro and in vivo, J Steroid Biochem. 20(4B): 1033–7.
Girgert R, et al. 2014: Inhibition of GPR30 by estriol prevents growth stimulation of triple-negative breast cancer cells by 17β-estradiol, BMC Cancer. 14:935.
Hemer GM, Englund DE. 1992: Effects of vaginally-administered oestriol on post-menopausal urogenital disorders: a cytohormonal study, Maturitas. 14(3): 171–9.
Clark JH, Markaverich BM. 2015: The agonistic and antagonistic actions of estriol, J Steroid Biochem. 20(4B): 1005–13.
Ugarte R. 2022: FMO study of the interaction energy between human estrogen receptor alpha and selected ligands, arXiv:2212.05089.
Baker ME. 2019: Steroid receptors and vertebrate evolution, Mol Cell Endocrinol. 496: 110526.
Lappano R, et al. 2010: Estriol acts as a GPR30 antagonist in estrogen receptor-negative breast cancer cells, Mol Cell Endocrinol. 320(1–2): 162–70.