Oestriol and non-protein-bound oestriol concentrations in human peripheral plasma before labour and delivery

Abstract

The concentration of oestriol and the proportion of this hormone not bound to plasma protein were measured using radioimmunoassay and centrifugal ultrafiltration respectively, in 55 samples of plasma obtained from 12 women in the last 2 to 7 weeks of uncomplicated pregnancy. Among individuals, the mean plasma concentration of oestriol varied from 25.8 +/- 94.8 nmol/l; in nine subjects, there was a tendency for oestriol concentrations to increase as delivery approached. The mean proportion of oestriol not bound to plasma protein in the different subjects varied from 13.1 to 18.9%, but values from any individual subject remained essentially constant during the periods of study. These measured values were used to calculate, for each sample, the apparent concentration of oestriol not bound to plasma protein. The results were combined with analogous values for oestradiol and progesterone obtained from the same plasma samples and described in a previous study. It was found that the mean ratio of the concentration of oestriol and oestradiol was 0.75, the mean concentration of non-protein-bound oestriol was 8.7 times that of non-protein-bound oestradiol, and in individual subjects, there was no consistent trend as delivery approached in the ratio of the concentration of progesterone to that of oestriol in either the total or non-protein-bound form.

Saliva oestriol, oestradiol, oestrone and progesterone levels in pregnancy: spontaneous labour at term is preceded by a rise in the saliva oestriol:progesterone ratio

“…Neither they nor Anderson et al (1 985) detected any consistent change in the free E2:progesterone ratio before labour. Moutsatsou & Oakey (1986) reported recently on free E3 levels in the samples used by Anderson et al (1985). They did not find a rise in the E3:progesterone ratio before labour in every subject but the number of samples was small (55 samples from 12 subjects).…”

Myometrium and Preterm Labor: Steroids and Prostaglandins

“…45 In deed, several studies support the view that human parturition is not preceded by significant alterations in maternal plasma estrogen and progesterone con centrations 6 or changes in bound or free concentra tions of these hormones in plasma. [7][8][9] Estrogen con centrations, though, increase progressively prior to delivery in women, implying there is a change in the estrogen to progesterone ratio to favor estrogen. As the antiprogestin RU486 will induce abortion in women and increases uterine contractility but does not cause delivery in rhesus monkeys, 10 a role for progesterone, acting via its receptor, resulting in uterine quiescence is still envisioned in women and a change in estrogen to progesterone action is asso ciated with parturition.…”