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CAS number 50-27-1 Yes check.svgY
PubChem 5756
MeSH Estriol
Molecular formula C18H24O3
Molar mass 288.38
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Estriol (also oestriol) is one of the three main estrogens produced by the human body.


Synthesis and levels

It is only produced in significant amounts during pregnancy as it is made by the placenta from 16-OHDHEAS, an androgen steroid made in the fetal liver and adrenal glands.

The Human placenta produces Pregnenolone and Progesterone from circulating Cholesterol. Pregnenolone is converted in the fetal adrenal gland into Dehydroepiandrosterone (DHEA), a C19 steroid, then subsequently sulfonated to DHEAS. DHEAS is converted to 16-OH DHEAS in the fetal liver. In the placenta, 16-OH DHEAS is converted to estriol, and is the predominant site of estriol synthesis.

Levels of estriol in non-pregnant women do not change much after menopause, and levels are not significantly different from levels in men.

Therapeutic use

In pregnant women with multiple sclerosis (MS), estriol reduces the disease's symptoms noticeably,[1] according to researchers at UCLA's Geffen Medical School.

Use in screening

Estriol can be measured in maternal blood or urine and can be used as a marker of fetal health and wellbeing. DHEA-S is produced by the adrenal cortex of the fetus. This is converted to estriol by the fetal liver.

If levels of "unconjugated estriol" are abnormally low in a pregnant woman, this may indicate a chromosomal or congenital anomalies like Down syndrome or Edward's syndrome. It is included as part of the triple test & quadruple test 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 non-stress testing. Conditions which can create false positives and false negatives in estriol testing for fetal distress include preeclampsia, anemia and impaired kidney function.[2]


  1. ^ Sicotte NL, Liva SM, Klutch R, et al. (October 2002). "Treatment of multiple sclerosis with the pregnancy hormone estriol". Ann. Neurol. 52 (4): 421–8. doi:10.1002/ana.10301. PMID 12325070.  
  2. ^ Deska Pagana, Kathleen; Pagana, Timothy J. (2002). Mosby's manual of Diagnostic and Laboratory Tests, 2nd Edition.  

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