ESPE Abstracts

Intact steroid hormone biosynthesis is essential for growth and development of the human fetus and embryo. In the present study, gas chromatography-mass spectrometry was employed to characterize the steroidal milieu in amniotic fluid (n=65; male: female = 35: 30) of mid-gestation (median: 18.8^th week, range: 16.0^th – 24.6^th week) by a comprehensive targeted steroid hormone metabolomics approach. The levels of 52 steroids including pregnenolone and 17-OH-pregnenolone metabolites, dehydroepiandrosterone (DHEA) and its metabolites, progesterone and 17-OH-progesterone metabolites, sex hormones as well as corticosterone and cortisol metabolites were measured. The dominating steroids were the group of pregnenolone and 17-OH-pregnenolone metabolites (mean ± SD: 138.0 ± 59.3 ng/mL), followed by the group of progesterone and 17-OH-progesterone metabolites (107.3 ± 44.3 ng/mL), and thereafter DHEA and its metabolites (97.1 ± 56.5 ng/mL). With respect to sex steroids, only testosterone showed a significantly higher value in male fetuses (P<0.0001) reflecting testicular endocrine activity. Furthermore, the hormonal constellation in amniotic fluid was not indicative of an active androgenic "backdoor" pathway. Of all estrogen metabolites, estriol showed by far the highest concentrations (33.2 ± 26.1 ng/mL). Interestingly, cortisol metabolites were clearly present (59.6 ± 13.6 ng/mL) though fetal de novo synthesis of cortisol is assumed to start from gestational 28^th week onwards. Tetrahydrocortisone (THE) levels are 4 times higher than tetrahydrocortisol (THF) levels. Our comprehensive characterization of the steroidal milieu in amniotic fluid of mid-gestation shows presence of all relevant classes of steroid hormones. The steroidal milieu in amniotic fluid mirrors the steroidome of the feto-placental unit. Our set of basic data lays the foundation for further studies characterizing various diseases affecting steroid metabolism.