Serum estriol

Serum estriol measurements are commonly used as part of the triple or quad maternal screens for Down syndrome-affected fetuses (see Chapter 54). On average, unconjugated estriol is 0.72 times less than normal (median value at 16 weeks 0.30 to 1.50 pg/L) when fetal Down syndrome is present,... 

Measurement of urinary and serum estriol (E3), once used to assess fetal well-being, is no longer recommended for that... 

The increased risk of trisomy with advanced maternal age motivates more than half of pregnant women in North America to undergo prenatal diagnosis (most commonly, amniocentesis or chorionic villus sampling, discussed in Oiapter 6). Down syndrome can also be screened by assaying maternal serum levels of a-fetoprotein, chorionic gonadotropin, and unconjugated estriol. This so-called triple screen can detect approximately 70% of fetuses with Down syndrome. 

Automated direct HPLC assay for esterol, estriol, cortisone and cortisol in serum and amniotic fluid. (160)... 

Fig. 5.3.7 Disorders that affect the placental/maternal synthesis of estriol and diagnostic analytes for serum and urine. ORD Oxidoreductase deficiency, STS steroid sulfatase deficiency...

GC-MS SIM analysis for prenatal diagnosis requires a different calibration standard from that used for urine from children and adults. Table 5.3.12 shows the steroids present in our external standard and the monitored ions. For serum analysis we employ the highly sensitive ion-trap MS/MS technique described at the beginning of this chapter. Many steroid ratios have been calculated that can be used to distinguish causes of low-estriol, a few that we consider useful are given below, values considered positive for particular disorders are in parenthesis. 

Solid symbols represent positive cases and open symbols, negative. The negative samples had serum unconjugated estriol (uE3) <0.3 multiples of the median, but resulted in normal births without apparent abnormalities. DH 3 dehydroestriol, 3 Estriol, EpialloPD epiallopregnanediol... 

Itoi H, Minakami H, Iwasaki R, Sato I. Comparison of the long-term effects of oral estriol with the effects of conjugated estrogen on serum lipid profile in early menopausal women. Maturitas 2000 36(3) 217-22. 

The antibody A-2 specific for estradiol-17/3 was raised in a rabbit against estradiol-17j8 coupled at C-6 to human serum albumin. The cross reaction with estrone was 6%, and with estriol 0.1%. By means of a Scat-chard plot the affinity constant was calculated to 5.70 x 10 1/M with respect to estradiol-17B. 

The antibody A-3, highly specific for estriol, was obtained from a sheep by immunization with estriol coupled with human serum albumin at C-6. The cross-reaction against estrone was less than 0.01%, and against estradiol-17/8, 0.1%. 

Estrone, estradiol-17/3, and estriol have been estimated in serum by means of RIA including a step of separation with Sephadex G-25 fine minicolumns. 

In order to obtain quicker methods without chromatography, the more specific antibodies A-2 and A-3 have been used to estimate estradiol-17/8 and estriol, respectively. These two antibodies were incubated directly with the residues after extraction of serum with dichloromethane. 

Estriol serum or plasma specimens are stable at room temperature for 24 hours, and can be refrigerated for 2 days and frozen at -20 C for up to 1 year. Patients should not be fasting before specimen collection. 

The cause of preterm labor is unknown, but recent evidence in a mouse model indicates that a maternal serum surfactant protein, SP-A, may trigger labor. Fetal fibronectin and cervical ultrasound have proven value for evaluating patients suspected of having preterm labor. The fetal fibronectin test is described later in the section entitled Laboratory Tests. Use of salivary estriol, corticotropin-releasing hormone, and interleukin-6 for preterm labor prediction is being investigated. 

Figure 54-7 Computation of median values for maternal serum unconjugated estriol (uEj) in the second trimester.The observed average gestational age from Table 54-4 is plotted on the horizontal axis and the median of that week s uEs measurements on the vertical logarithmic axis.The thin vertical lines represent the 95% confidence intervals of the medians.The line represents the results of a linear regression analysis of log uEs versus age weighted by the square root of the number of samples.The equation of that line in completed weeks is median uEj = jQ0.09i6Sx(weeks)-i.6i8 Corresponding equation for day-specific medians is median uE.-...

Figure 54-10 A comparison of the associations between gestational age and the four second trimester maternal serum markers for Down syndrome. For each of the analytes, the median at 15 weeks gestation has been assigned a value of 100%. Each subsequent median is represented as a percentage of that initial median. The marker that has the weakest association with gestational age is dimeric inhibin A (DIA).The strongest associations are found for unconjugated estriol (uEa) and chorionic gonadotropin (CG).The association between gestational age and alpha fetoprotein (AFP) is intermediate.

Figure 54-13 The forms of estriol present in maternal serum, Glucuronidation and sulfation can also occur at the other hydroxyl positions.

Bradley LA, Canick JA, Palomaki GE, Haddow JE. Undetectable maternal serum unconjugated estriol levels in the second trimester risk of perinatal complications associated with placental sulfatase deficiency. Am J Obstet Gynecol 1997 176 531-5. 

Phillips OP, Elias S, Shuhnan LP, Andersen RN, Morgan CD, Simpson JL. Maternal serum screening for fetal Down syndrome in women less than 35 years of age using a-fetoprotein, hCG, and unconjugated estriol a prospective 2-year study. Obstet Gynecol 1992 80 353-8. 

El estrone, E2 estradiol, E3 estriol, EE2 ethynylestradiol, DES diethylstilbestrol, TAM tamoxiphen, BSA bovine serum albumine, AB antibody... 

A Ius, et al. Direct time-resolved fluoroimmunoassay of estriol in serum. J Steroid Biochem 39 189, 1991. 

Ito, K., Oda, M., Tsuji, A., and Maeda, M. (1999) Simultaneous determination of alpha fetoprotein, human chorionic gonadotropin and estriol in serum of pregnant women hy time resolved fluoroimmunoassay. Journal of Pharmaceutical and Biomedi cal Analysis, 20, 169 178. 

Most of the assays now carried out with isoluminol derivatives are solid-phase competitive assays (Fig. 2), in which the analyte to be determined competes with the labeled analyte for the available binding sites on antibodies that are immobilized on the solid phase. Thus, plastic microspheres have been used to immobilize antibodies for estriol (K12) or thyroxine (W9). Estradiol antibodies have been immobilized onto plastic tubes (K7) or beads (K16). In all of the above cases, the amount of immunoconjugated hormone label is inversely proportional to the amount of free hormone in the analytical sample. Unconjugated labels are removed by decantation or aspiration from the solid phase, and the specific, immunoconjugated labels are measured in a luminometer. This approach has been successfully applied to progesterone analyses in either serum (D6) or saliva (D5). A review of several separation-based assays with isoluminol analogs was presented a few years ago by Kohen et al. (K18). 

Effects of Clinical Matrices. The effects of urine and plasma were determined by using high concentration spikes of estriol in these fluids. Binding and displacement of DNE from Ab sites by estriol were readily observable in urine, but not in plasma. This is probably due to a high amount of nonspecific binding by the serum albumins, an observation in common with other assays for this hydrophobic analyte. 

Hayashi, N. Hayata, K. Sekiba, K. Rapid and simultaneous measurement of estrone, estradiol, estriol and estetrol in serum by high performance liquid chromatography with electrochemical detection. Acta Med.Okayama., 1985, 39, 143-153... 

Noma, J. Hayashi, N. Sekiba, K. Automated direct high-performance liquid chromatographic assay for estetrol, estriol, cortisone and cortisol in serum and amniotic fluid. J.Chromatogr., 1991, 568, 35-44... 

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