The human fetal adrenal produces cortisol but no detectable aldosterone throughout the second trimester

Abstract

BackgroundHuman fetal adrenal glands are highly active and, with the placenta, regulate circulating progesterone, estrogen and corticosteroids in the fetus. At birth the adrenals are essential for neonate salt retention through secretion of aldosterone, while adequate glucocorticoids are required to prevent adrenal insufficiency. The objective of this study was to carry out the first comprehensive analysis of adrenal steroid levels and steroidogenic enzyme expression in normal second trimester human fetuses.MethodsThis was an observational study of steroids, messenger RNA transcripts and proteins in adrenals from up to 109 second trimester fetuses (11 weeks to 21 weeks) at the Universities of Aberdeen and Glasgow. The study design was balanced to show effects of maternal smoking.ResultsConcentrations of 19 intra-adrenal steroids were quantified using liquid chromatography and mass spectrometry. Pregnenolone was the most abundant steroid while levels of 17α-hydroxyprogesterone, dehydroepiandrosterone sulphate (DHEAS) and progesterone were also high. Cortisol was present in all adrenals, but aldosterone was undetected and Δ4 androgens were low/undetected. CYP17A1, CYP21A2 and CYP11A1 were all highly expressed and the proteins localized to the adrenal fetal zone. There was low-level expression of HSD3B and CYP11B2, with HSD3B located mainly in the definitive zone. Maternal smoking altered fetal plasma adrenocorticotropic hormone (ACTH) (P = 0.052) and intra-adrenal progesterone, 17α-hydroxyprogesterone and 16α-hydroxyprogesterone, but not plasma or intra-adrenal cortisol, or intra-adrenal DHEAS. Fetal adrenal GATA6 and NR5A1 were increased by maternal smoking.ConclusionsThe human fetal adrenal gland produces cortisol but very low levels of Δ4 androgens and no detectable aldosterone throughout the second trimester. The presence of cortisol in fetal adrenals suggests that adrenal regulation of circulating fetal ACTH remains a factor in development of congenital adrenal hyperplasia during the second trimester, while a relative lack of aldosterone explains the salt-wasting disorders frequently seen in extreme pre-term neonates. Finally, maternal smoking may alter fetal adrenal sensitivity to ACTH, which could have knock-on effects on post-natal health.Electronic supplementary materialThe online version of this article (10.1186/s12916-018-1009-7) contains supplementary material, which is available to authorized users.

Alternative (backdoor) androgen production and masculinization in the human fetus

“…Circulating DHT, however, was not detectable in any of the 42 fetuses (<1ng/ml). The Δ 5 steroids pregnenolone, 17α-hydroxypregnenolone and DHEA were present at the highest levels in the fetal circulation and these steroids probably come from the fetal adrenal gland (16;17). Levels of progesterone were also high and were likely to be derived principally from the placenta (18) (and see below).…”

“…Tissue androsterone levels were highest in the adrenals which is consistent with high CYP17A1 transcript levels and, since the adrenals lack SRD5A1 and appear unable to make 5α-reduced steroids, the substrate for this reaction must come from circulating allopregnanolone. It should be noted that this androsterone was mostly the sulfated form which is a reflection of the high SULT2A1 levels in the human fetal adrenal (17). The presence of androsterone in the fetal adrenals at the end of the first trimester has also been reported previously (22).…”

“…Three sources of human fetal tissues were used in this study: 1) In Aberdeen, human fetuses between 11 and 21 weeks of gestation and classified as normal at scan were collected from women over 16 years of age undergoing elective termination (17) Information about maternal smoking during pregnancy was available for most fetuses. Fetuses were transported to the laboratory within 30 minutes of delivery, weighed, crown-rump length recorded, and sexed.…”

“…Extraction and quantification of tissue steroid levels by LC-HRMS have been described previously (17). Tissue samples (25-65mg) from placenta, liver and adrenals or whole testes (8-20mg, one per fetus) were initially processed to isolate RNA/DNA/protein using Qiagen Allprep kits as above and steroids were then extracted from the column-eluants following addition of internal standards (stable isotope-labeled steroid analogues) (17).…”

“…Extraction and quantification of tissue steroid levels by LC-HRMS have been described previously (17). Tissue samples (25-65mg) from placenta, liver and adrenals or whole testes (8-20mg, one per fetus) were initially processed to isolate RNA/DNA/protein using Qiagen Allprep kits as above and steroids were then extracted from the column-eluants following addition of internal standards (stable isotope-labeled steroid analogues) (17). Following extraction, steroids were separated by reverse-phase liquid chromatography on an Accucore™ PFP column with trimethyl silane (TMS) endcapping (50 mm, 2.1 mm, 2.6 μm, Thermo Fisher Scientific) and using an UltiMate 3000 RSLCnano autosampler/pump (Thermo Fisher Scientific, Waltham, MA, USA).…”