Modulation of free corticotrophin-releasing hormone, adrenal and placental steroid hormone levels induced by mifepristone during pregnancy.

UNLABELLED Mifepristone is a progesterone receptor antagonist widely used in obstetrics. The aim of the study was to focus on free corticotrophin-releasing hormone (CRH) and also describe modulation of adrenal and placental steroid hormone concentrations induced by mifepristone. METHODS Twenty-six women were enrolled in the study. They received mifepristone for termination of pregnancy. Maternal blood samples were retrieved before administration of mifepristone (600 mg) and 48 h after, just before induction of labor. Bound and free CRH levels were determined in maternal blood concomitantly with cortisol, estriol, progesterone and SDHEA levels. Also paired fetal cord blood samples were collected. RESULTS Maternal plasmatic CRH level did not change after mifepristone absorption but free CRH increased significantly (0.500 ± 0.326 vs. 0.388 ± 0.303 ng/ml, p = 0.040). A significant decrease of progesterone was observed (83.6 ± 49.3 vs. 95.6 ± 54.9 ng/ml, p = 0.001) with a lower progesterone/estriol ratio (26.9 ± 15.7 vs. 40.7 ± 31.1, p = 0.004). There was a strong association between maternal and fetal free CRH (r² = 0.675, p = 0.001), cortisol (r² = 0.570, p = 0.019), and positive but modest correlation for progesterone (r² = 0.341, p = 0.046) and estriol (r² = 0.379, p = 0.025) levels. CONCLUSION Mifepristone has an effect on free CRH level and changes the estriol-progesterone balance.