Estriol (also oestriol) is one of the three main estrogens produced by the human body. It is only produced in significant amounts during pregnancy as it is made by the fetus. During pregnancy the production of estriol depends on an intact maternal-placental-fetal unit. Fetal-placental production of estriol leads to a progressive rise in maternal circulating levels reaching a late-gestational peak several orders of magnitude greater than nonpregnant levels. In the maternal circulation, estriol undergoes rapid conjugation in the liver followed by urinary excretion with a halflife of ~20 minutes. Since normal estriol production depends on an intact maternal-placental-fetal circulation and functional fetal metabolism, maternal estriol levels have been used to monitor fetal status during pregnancy, particularly during the third trimester. DHEA is produced by the adrenal cortex of the fetus, this is converted to estriol by the placenta. If levels are abnormally low in a pregnant woman, this may indicate a problem with the development in the child. Levels of estriol in non-pregnant women do not change much after menopause, and levels are not significantly different from levels in men.

May be diagnosed by:   

• Determination of specific antibodies based on the ELISA technique
• Determination of specific antibodies based on the RIA-technique

Free Estriol ELISA:

Competitive immunoenzymatic colorimetric method for quantitative determination of free Estriol in serum or plasma.

Principle of the Assay:   

Microtiter strip wells are precoated with anti-Estriol antibodies (solid-phase). Free Estriol in the sample competes with added horseradish peroxidase labelled Estriol (enzyme-labelled antigen) for antibody binding. After incubation a bound/free separation is performed by solid-phase washing. The immune complex formed by enzyme-labelled antigen is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is inversely proportional to the amount of free Estriol in the sample. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorption at 450 nm is read using an ELISA microwell plate reader.

Specific performance characteristics:  

Correlation with RIA performed on 63 samples is r = 0.995

Order information: