Estriol (E3)

Estriol is one of the three main naturally occurring forms of estrogen, a group of hormones predominantly associated with female reproductive functions and secondary sexual characteristics. Unlike estradiol and estrone, which are more potent estrogens, estriol is considered a weaker estrogen. It is produced during pregnancy, primarily by the placenta, and its levels increase significantly during this time.

Estriol's primary role during pregnancy is to support the development and maintenance of the uterine lining and the growing fetus. It helps ensure a healthy pregnancy by promoting uterine blood flow, the growth of the placenta, and the development of the mammary glands in preparation for breastfeeding.

Due to its specific association with pregnancy, estriol is sometimes used as a biomarker to assess the well-being of both the fetus and the placenta. Doctors may measure estriol levels in a pregnant woman's blood or urine as part of prenatal screening tests to monitor the health of the pregnancy.

While estriol's role in non-pregnant individuals is limited compared to estradiol and estrone, its unique properties and functions make it an essential component of the hormonal balance during pregnancy, contributing to the overall well-being of both the mother and the developing baby.