Synthesis and metabolism of estriol conjugates

: As an indicator of fetal well being, the urinary estriol value is widely utilized. But the discrepancy between the results of NST and urinary estriol value has recently been pointed out. The estimation of plasma estriol is also recommended as a more reliable means of fetal assessment than that of urinary estriol. The purpose of the study is to clarify the patterns of estriol conjugates in maternal blood, retroplacental blood and cord blood, and further to elucidate the metabolism and secretion of each conjugate in organs and to determine the most useful conjugate as a source of fetal information. In normal pregnancy urine, estriol glucosiduronate is the dominant component of urinary estriol. In preeclampsia, the percentage of G decreased and that of G-S increased. In retroplacental blood, G-S is the main conjugate. On the other hand in cord blood, S is the dominant conjugate. The placental perfusion experiment revealed that the placenta hydrolyzed each conjugate to a free form and did not convert one conjugate to another. Periodical determination of plasma estriol conjugates in pregnant women revealed that the G-S fraction fluctuated most during parturition. The importance of liver as a possible site for estriol conjugation and the role of kidney in selective clearance of estriol conjugates are discussed.