Estriol (Free E3) RIA
For the quantitative determination of unconjugated estriol in human serum or plasma
Catalog Number: 38-FE3HU-R120
Size: 120 tests
10-05 - ALPCO 2/17/2010
For Research Use Only. Not For Use In Diagnostic Procedures.
1. INTENDED USE
The kit allows for the quantitative determination of unconjugated estriol by RIA in human serum or
plasma samples over the range of 0.5 to 40 ng/ml. This kit is not to be used for the risk evaluation of
trisomy 21. This kit is for research use only. It is not for use in diagnostic procedures.
2. SUMMARY AND EXPLANATION OF THE TEST
Estriol (1,3,5(10)-Estratriene-3,16α,17β-triol) is a C18 steroid hormone with a molecular weight of
288.4 daltons. It is the principal circulatory estrogen hormone in the blood during pregnancy. During
pregnancy, estriol production is predominantly from the fetal/placental unit (1). It is released from the
placenta and conjugated in the maternal liver as glucuronides and sulfates. It exists in the maternal
blood unconjugated (8%) and in conjugated forms (92%). Maternal serum unconjugated estriol levels
increase rapidly following the first trimester from 1.2 ng/ml at 15 weeks to about 12 ng/ml at term.
Estriol circulating in the blood has a short half-life of 20-30 minutes (2, 3), and so variation in the
fetal/placental unit should rapidly be reflected by changes in the maternal serum estriol levels.
Measurement of serum unconjugated estriol can therefore be useful to monitor fetal conditions (4).
Consistently low levels of estriol throughout pregnancy, or a sudden drop of estriol levels in serial
determination may be indicative of fetal distress (5) or placental failure. Chronically low estriol values
may be caused by other factors unrelated to fetal distress or plac