What is Estriol？

Description

Estrogen is one of the main female sex hormones. This hormone plays a key role in the sex characteristics of adolescent women and is also important for menstruation and pregnancy. Most estrogen is secreted by the ovaries. It includes Estrone (E1), Estradiol (E2), and Estriol (E3). People make E1 after menopause; E2 is the most common type of estrogen that people make; E3 is the main type of estrogen in a pregnant persons bloodstream.Estriol (3,16,17 trihydroxy 1,3,5-oestriene), also known as oestriol, is a dominant estrogen during pregnancy and is secreted mainly by the placenta. It is an 18-carbon steroid (C18H24O3), but it is distinguished by being 16-hydroxylated. Estriol levels rise throughout pregnancy, helping to keep your uterus and unborn baby healthy. It was discovered in 1972 by Edward Adelbert Doisy St. at Louis University[1].

Metabolism

The mother provides cholesterol to the placenta, which converts it to progesterone for release into the maternal and fetal circulations[2]. In the fetus, progesterone is converted to dehydrepandrosterone (DHEA) or dehydroepiandrosterone sulfate (DHEAS) by the fetal zone of the adrenal glands. DHEA/DHEAS is converted to 16-OH DHEA/16-OH DHEAS in the fetal liver. This steroid then enters the placenta and is aromatized into estriol, the primary estrogen secreted by the placenta called non-conjugated estriol (U3). In the maternal cycle, it is transported to and processed by the liver, making it easily soluble in water and excreted in urine[3]. E3 assays have been used to assess fetoplacental function since the early 1960's, and are a component of the current serum marker screens for fetal anomalies.

Benefits

Estriol could offer considerable benefits for postmenopausal women with reduced risks that are normally associated with traditional hormone therapies. These benefits include improved control of menopausal symptoms and better urogenital health. In particular, the immunomodulatory role of estriol in reducing proinflammatory cytokines may be an important new therapeutic option for chronic autoimmune and neurodegenerative illnesses[4]. Since it is a relatively weak estrogen, there is potential for use in men for conditions such as multiple sclerosis.

References

[1] Tsugawa Y, et al. HEstrogen induces estrogen receptor α expression and hepatocyte proliferation in late pregnancy. Biochemical and Biophysical Research Communications, 2019.

[2] Goebelsmann U, et al. Estriol in pregnancy. I. A radioimmunoassay for urinary estriol. American Journal of Obstetrics and Gynecology, 1972; 112: 802-806.

[3] Mueck A, et al. Treatment of vaginal atrophy with estriol and lactobacilli combination: a clinical review. Climacteric, 2018; 21: 140-147.

[4] Falah N, et al. Estriol review: Clinical applications and potential biomedical importance.