Lexicon
Estriol
Also known as E3
Definition
Estriol (E3) is one of the four principal endogenous estrogens together with estrone (E1), estradiol (E2) and estetrol (E4). [1] Estriol is the main estrogen in pregnancy but has received less attention outside gestation, where emerging evidence points to immunomodulatory roles. [2] Among the three classical estrogens estradiol, estrone and estriol, 17-beta-estradiol (E2) is the predominant and most active, making estriol comparatively weak. [3]
How it works
Depending on the situation, estriol may exert either agonistic or antagonistic effects on estrogen, providing some of the protection of stronger estrogens without their risks. [4] Its emerging immunomodulatory benefits, including reduction of pro-inflammatory cytokines, may underlie potential roles in autoimmune, inflammatory and neurodegenerative conditions such as multiple sclerosis. [2]
Connected concepts
How it's measured
Unconjugated estriol is one of the biochemical markers used in maternal serum screening for Down syndrome, combined with alpha-fetoprotein and human chorionic gonadotropin. [5] [6] Estriol is extensively conjugated after oral administration, so similar serum levels and systemic effectiveness result from oral intake of 10 mg and vaginal application of 0.5 mg of estriol. [7]
What levels mean
Estriol is effective at controlling menopausal symptoms such as hot flashes, insomnia, vaginal dryness and frequent urinary tract infections, and unlike conventional estrogens does not seem to contribute to hypertension. [4] With low-dose local estrogen therapy, circulating estradiol persistently remains in the postmenopausal range, reflecting the minimal systemic exposure that makes ultra-low-dose vaginal estriol suitable even after breast cancer or thromboembolic disease. [8]
Community knowledge
## Estriol & Estetrol Overview
The longevitydocs community's collective insight and shared knowledge on this concept — across text, video, audio and images from members and faculty, reserved for members.
Learn about our Membership planReferences
- 1.Stanczyk FZ. Metabolism of endogenous and exogenous estrogens in women. J Steroid Biochem Mol Biol · 2024
- 2.Ali ES, Mangold C, Peiris AN. Estriol: emerging clinical benefits. Menopause · 2017
- 3.Resanovic I, Rizzo M, Zafirovic S, Bjelogrlic P, Perovic M, Savic K, Patti AM, Isenovic RE. Anti-atherogenic effects of 17β-estradiol. Horm Metab Res · 2013
- 4.Head KA. Estriol: safety and efficacy. Altern Med Rev · 1998
- 5.Spencer K. Screening for Down syndrome. Scand J Clin Lab Invest Suppl · 2014
- 6.Cuckle H. Biochemical screening for Down syndrome. Eur J Obstet Gynecol Reprod Biol · 2000
Community discussion
Clinical pearls and discussion posted by community members on this concept — signed contributions, reserved for members.
Learn about our Membership plan