OESTRIOL METABOLISM IN PREGNANT WOMEN

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Abstract
Estriol-16-C14 was administered intravenously to 4 pregnant women prior to sterilisation and surgical interruption of pregnancy and the quantity and nature of radioactive metabolites in the products of conception, systemic venous blood and urine were studied. Thirty minutes following the injection of the isotope, less than 0.5% of the administered dose was found in the amniotic fluid, fetus and placenta. Approximately 40% of the radioactive material recovered from the systemic venous blood withdrawn 10 to 30 minutes following injection was unconjugated (free) estriol. Some 15% of the circulating radioactive material was identified as estriol- 3- sulfate and al-most 10% behaved as estriol-3-sulfate, 16(17 ?)-glucosiduronate. Estriol 16(17?)-glucosiduronate was also detected, but only in minute quantities (0.5% of total). The rest of the circulating radioactive material was present as unidentified "polar conjugates". Urine specimens collected over various intervals revealed a changing pattern of conjugation. Estriol and estriol-3-sulfate were present only in very small amounts in all specimens studied. The bulk of radioactive material was excreted as estriol-16(17 ?)-glucosiduronate and as so-called "polar glucosiduronates" (consisting of di- and perhaps triglucosiduronates of estriol), accompanied by small, but significant, amounts of estriol-3-sulfate, 16(17?)-glucosiduronate-like radioactive material. As time passed following injection of the isotope, the amount of "polar glucosiduronates" present in the urine increased markedly. This was associated with a corresponding decrease in the amount of estriol-16(17?)-glucosiduronate. At least 99% of the estrogen moiety of the urinary radioactive material consisted of estriol. The recovery of radioactivity from the urine, collected during 72 hours, was low, ranging from 41 to 47%.