Hormones & Steroids

Estriol (E3)

Estriol (E3) is one of three major estrogens, the others being estradiol (E2) and estrone. Its levels are only detectable during pregnancy where it is synthesized in very high quantities by the placenta (levels increase 100-fold during pregnancy). Its role is to ensure a quiescent uterus during prelabor and as such it can be used as a marker of fetal health and well-being. During pregnancy, 90 to 95% of estriol in the maternal circulation is conjugated in the form of estriol glucuronide and estriol sulfate, and levels of unconjugated estriol are slightly less than those of unconjugated estradiol and similar to those of unconjugated estrone. If levels of unconjugated estriol (free estriol) are abnormally low in a pregnant woman, this may indicate chromosomal or a congenital anomaly like Down syndrome or Edward’s syndrome. Estriol is included as part of the triple test and quadruple test for antenatal screening for fetal anomalies. However, because many pathological conditions in a pregnant woman can cause deviations in estriol levels, screening tests are often seen as less definitive of fetal-placental health than a nonstress test. Conditions which can create false positives and false negatives in estriol testing for fetal distress include pre-eclampsia, anemia, and impaired kidney function. Estriol tests are usually a solid-phase competitive immunoassay that quantitatively measures unconjugated estriol in serum.

Reagents for Immunoassay Development

Suitable for use in Competitive ELISA, CLIA & RIA


MAb to Estriol (E3) • Produced in Cell Culture


Estriol (E3) Antigen, HRP conjugated • Estriol linked at the 6 position • Buffer: Tris containing protein stabilizers

Suitable for use in ELISA


Endocrine Disorders - Reagents for Assay Development

Powered by