Blood Estrogens in Late Pregnancy: An Evaluation of Methods with Improved Recovery

Abstract

The accuracy of the Roy and Brown procedure for the estimation of estrone, estradiol-17β and estriol in acid-hydrolyzed pregnancy blood has been improved to a considerable extent by substituting oxalated plasma from fasting donors for whole blood and replacing ether extraction of the hydrolysate by continuous extraction for 24 hr with benzene. Recovery of estrone added to nonpregnancy blood “blanks” has been increased from a mean value of 78 to 89 %, of estradiol from 69 to 90%. and of estriol from 54 to 91%. Greater uniformity with different “blanks” has also been accomplished, as reflected in a reduction of SD values: from ±13 to ±3% for estrone, from ±15 to ±2% for estradiol, and from ±20 to ±3% for estriol. A simple method has also been devised and evaluated for the separate estimation of ether-extractable “free” estrogens, in a 12-ml sample of plasma, prior to acid hydrolysis. This method has been applied to 12 late pregnancy specimens with evidence that circulating estrone and estriol are almost entirely either protein-bound or conjugated, whereas the major portion of estradiol in the plasma is “free.” All assays for this investigation were performed in duplicate by H₂SO₄ fluorescence as well as by the micro-Kober procedure. Analysis of the results indicates greater precision and specificity with the less sensitive micro-Kober reaction.