Serum 2-hydroxyestradiol 17-sulphate in pregnancy.

2-Hydroxyestradiol 17-sulphate (2-OH E2-17-S) is a catecholized form of sulphated estrogen. In vitro studies showed that its antioxidative effect is almost equal to that of free catecholestrogens, such as 2-OH E2 or 4-OH E2 and alpha-tocoferol, but the existance of 2-OH E2-17-S in human serum has not yet been made clear. 2-OH E2-17-S strongly antagonizes lipid peroxidation, and so it may play an important role in pregnancy, for example as an anti-oxidant in pregnancy-induced hypertension (PIH). The serum level of 2-OH E2-17-S was measured during mid to late pregnancy by a direct radioimmunoassay (RIA) without hydrolysis. The serum levels at 28-31 weeks, 32-35 weeks and 36-40 weeks of gestation were 4.68+/-0.93 (mean+/-SE), 8.38+/-1.21 and 18.31+/-3.41 nmol/l, respectively. The serum level in PIH cases at 36-40 weeks (4.64+/-1.29 nmol/l) was significantly lower than that in normal pregnancy. The 2-OH E2-17-S level in umbilical arteries was significantly higher than that in maternal peripheral vein. These results suggest that the feto-placental unit plays an important role in catecholizing E2-17-S to 2-OH E2-17-S, which may act as an antioxidant in pregnancy.