Serum free estriol and estriol glucuronide fractions in hydatidiform mole measured by radioimmunoassay.

Serum or plasma total unconjugated estriol and total estriol glucuronide fractions were measured in 14 patients with unaborted hydatidiform mole between 11 and 25 weeks of gestation and in 20 normal pregnant patients between 8 and 17 weeks of gestation. The estriol fractions were separated by solvent partition, and the estriol was measured by radioimmunoassay using antiserum against estriol-16-17-dihemisuccinate conjugated to bovine serum albumin. The values (means and ranges) found in normal pregnant patients were as follows: estriol 1.3 ng/ml (0.3-2.9); estriol glucuronide, 11.1 ng/ml (4.7-24.8). Wide ranges of values were found in patients with molar pregnancies compared to those with normal pregnancies of equivalent gestation, some values being within the upper range of normal and others being well below the normal range. Of the 14 molar pregnancies studied, 9 (64%) were associated with serum estriol values which were below the ranges for normal pregnancy, and 8 (57%) were associated with similarly low estriol glucuronide values. The incidences of low estriol and estriol glucuronide values were less than those reported for low urinary estriol excretion in hydatidiform moles. No correlation was found between any of the serum estriol fractions and the serum hCG values or with the presence of theca lutein cysts in the ovaries. It was suggested that the trophoblast was the principal source of estriol in these molar pregnancies.