Characterization of Human Adrenal Steroidogenesis During Fetal Development

MicroRNA regulation of adrenal glucocorticoid and androgen biosynthesis

Steroid hormones are derived from a common precursor molecule, cholesterol, and regulate a wide range of physiologic function including reproduction, salt balance, maintenance of secondary sexual characteristics, response to stress, neuronal function, and various metabolic processes. Among the steroids synthesized by the adrenal and gonadal tissues, adrenal mineralocorticoids, and glucocorticoids are essential for life. The process of steroidogenesis is regulated at multiple levels largely by transcriptional, posttranscriptional, translational, and posttranslational regulation of the steroidogenic enzymes (i.e., cytochrome P450s and hydroxysteroid dehydrogenases), cellular compartmentalization of the steroidogenic enzymes, and cholesterol processing and transport proteins. In recent years, small noncoding RNAs, termed microRNAs (miRNAs) have been recognized as major post-transcriptional regulators of gene expression with essential roles in numerous biological processes and disease pathologies. Although their role in the regulation of steroidogenesis is still emerging, several recent studies have contributed significantly to our understanding of the role miRNAs play in the regulation of the steroidogenic process. This chapter focuses on the recent developments in miRNA regulation of adrenal glucocorticoid and androgen production in humans and rodents.

An integrated single-cell analysis of human adrenal cortex development

The adrenal glands synthesize and release essential steroid hormones such as cortisol and aldosterone, but many aspects of human adrenal gland development are not well understood. Here, we combined single-cell and bulk RNA sequencing, spatial transcriptomics, IHC, and micro-focus computed tomography to investigate key aspects of adrenal development in the first 20 weeks of gestation. We demonstrate rapid adrenal growth and vascularization, with more cell division in the outer definitive zone (DZ). Steroidogenic pathways favored androgen synthesis in the central fetal zone, but DZ capacity to synthesize cortisol and aldosterone developed with time. Core transcriptional regulators were identified, with localized expression of HOPX (also known as Hop homeobox/homeobox-only protein) in the DZ. Potential ligand-receptor interactions between mesenchyme and adrenal cortex were seen (e.g., RSPO3/LGR4). Growth-promoting imprinted genes were enriched in the developing cortex (e.g., IGF2, PEG3). These findings reveal aspects of human adrenal development and have clinical implications for understanding primary adrenal insufficiency and related postnatal adrenal disorders, such as adrenal tumor development, steroid disorders, and neonatal stress.

Dexamethasone affects human fetal adrenal steroidogenesis and subsequent ACTH response in an ex vivo culture model

Introduction

Administration of dexamethasone (DEX) has been used experimentally to suppress androgenization of external genitalia in 46,XX fetuses with congenital adrenal hyperplasia. Despite this, the prenatal biological mechanism-of-action of DEX on fetal development is not known. This study aimed to examine direct effects of DEX on human fetal adrenal (HFA) steroidogenic activity including possible effects on the subsequent response to ACTH-stimulation.

Methods

Human fetal adrenal (HFA) tissue from 30 fetuses (1^st trimester) were cultured ex vivo with A) DEX (10 µm) for 14 days, or B) DEX (10 µm) for 10 days followed by ACTH (1 nM) for 4 days. DEX-mediated effects on HFA morphology, viability, and apoptosis (immunohistochemistry), gene expression (quantitative PCR), and steroid hormone secretion (LC-MS/MS) were investigated.

Results

DEX-treatment caused decreased androstenedione (p<0.05) and increased cortisol (p<0.01) secretion suggesting that direct effects on the adrenal gland may contribute to the negative feedback on the hypothalamic-pituitary-adrenal axis in vivo. An altered response to ACTH stimulation in HFA pre-treated with DEX included increased androgen (p<0.05) and reduced cortisol production (p<0.05), supporting clinical observations of a temporary decreased ACTH-response following prenatal DEX-treatment. Additionally, the secretion of corticosterone was decreased (p<0.0001) following ACTH-stimulation in the initially DEX-treated HFAs.

Discussion

The observed effects suggest that prenatal DEX-treatment can cause direct effects on HFA steroidogenesis and in the subsequent response to ACTH-stimulation. This may indicate a requirement for careful monitoring of adrenal function in prenatally DEX-treated neonates, with particular focus on their mineralocorticoid levels.

Effects of amoxicillin exposure at different stages, doses and courses of pregnancy on adrenal development in fetal mice

Pregnant women are usually treated with amoxicillin before cesarean section to prevent infection. This study aimed to investigate the effects of amoxicillin exposure on fetal adrenal development at different stages, doses and courses of pregnancy. We found prenatal amoxicillin exposure (PAmE) could cause adrenal developmental toxicity in both male and female fetal mice in a stage, dose and course-dependent manner, among which the third trimester, high dose and multiple courses of PAmE could significantly reduce the maximum cross-sectional area and diameter. Besides, the proliferation was inhibited, the apoptosis was enhanced, and the serum corticosterone level and expression of steroidogenic enzymes were decreased in the PAmE group. Further, the insulin-like growth factor 1 (IGF1) signaling pathway were inhibited in the male and female fetal mice at the third trimester, high dose and multiple courses of treatment, and adrenal IGF1 expression was positively correlated with the indicators of adrenal development. In conclusion, PAmE could induce adrenal dysplasia in fetal mice in the stage, dose and course-dependent manner, which was related to the inhibition of IGF1 signaling pathway. This study provides guidance for evaluating the toxicity and risk of fetal adrenal development and the rational use of amoxicillin during pregnancy.

The Androgen Metabolome of Preterm Infants Reflects Fetal Adrenal Gland Involution

CONTEXT

The human adrenal cortex changes with fetal-neonatal transition from the fetal to the adult organ, accompanied by changes in the steroid metabolome.

OBJECTIVE

As it is unclear how the observed developmental changes differ between preterm and full-term neonates, we investigated whether the involution of the fetal adrenals is following a fixed time course related to postmenstrual age or whether it is triggered by birth. Furthermore, the fetal and postnatal androgen metabolome of preterm infants was characterized in comparison to term babies.

METHODS

This was a prospective, longitudinal, 2-center study collecting spot urines of preterm and term infants during the first 12 to 18 months of life. Steroid metabolites were measured from spot urines by gas chromatography-mass spectrometry. Data relating were modeled according to established pre- and postnatal pathways.

RESULTS

Fetal adrenal involution occurs around term-equivalent age in preterm infants and is not triggered by premature birth. Testosterone levels are higher in preterm infants at birth and decline slower until term compared to full-term babies. Dihydrotestosterone levels and the activity of the classic androgen biosynthesis pathway are lower in premature infants as is 5α-reductase activity. No difference was found in the activity of the alternate backdoor pathway for androgen synthesis.

CONCLUSION

Human adrenal involution follows a strict timing that is not affected by premature birth. By contrast, prematurity is associated with an altered androgen metabolome after birth. Whether this reflects altered androgen biosynthesis in utero remains to be investigated.

Steroid profiling in the amniotic fluid: reference range for 12 steroids and interest in 21-hydroxylase deficiency

INTRODUCTION

Determination of steroid levels in the amniotic fluid gives some insight on foetal adrenal and gonadal functions. Our objectives were to establish reference ranges of 12 steroid levels throughout pregnancy and to compare them with steroid levels from pregnancies with foetuses presenting 21-hydroxylase deficiency (21OHD).

MATERIALS AND METHODS

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was applied to 145 "control" amniotic fluid samples from gynaecology activity (12 + 6 to 32 + 4 Gestational Weeks, GW). The following steroids were analysed according to gestational age and compared to 23 amniotic fluid samples from foetuses with classic 21-hydroxylase deficiency confirmed by molecular studies: delta-4-androstenedione (D4), dehydroepiandrosterone (DHEA), 17-hydroxyprogesterone (17OHP), 11-deoxycortisol (11OH), 21-deoxycortisol (21OH), corticosterone, deoxycorticosterone (DOC), testosterone, pregnenolone, 17-hydroxypregnenolone (17Pregn), cortisol and cortisone. Chromosomal sex was determined by karyotype and gestational age by biometric measurements.

RESULTS

Analysis of "control" samples showed a statistically significant difference for D4 and testosterone levels according to foetal sex. Cortisol, corticosterone, and DOC had lower concentrations before 20 GW than after 20 GW, whereas 17Pregn and pregnenolone had higher concentrations before 20 GW. This allowed us to establish age- and sex-dependant reference values. We observed higher 21OH, 17Pregn, D4 and testosterone levels in females 21OHD than female controls. The ratios 17OHP/17Pregn, D4/DHEA and 11OH/17OHP appeared discriminant for the diagnosis of 21OHD.

CONCLUSION

Our study provides information on foetal steroidogenesis and suggests reference values for 12 steroids during pregnancy. This allows a prenatal diagnosis of 21-hydroxylase deficiency within 24 hours and might be useful in the diagnosis of other variations of sex development (VSD).

Evaluation of fetal middle adrenal artery Doppler and fetal adrenal gland size in pregnancies with fetal growth restriction: a case-control study

OBJECTIVES

This study aims to evaluate sonographic measurements of fetal adrenal gland size and middle adrenal artery Doppler in pregnancies with fetal growth restriction (FGR) and in a healthy control group.

METHODS

This prospective study included 107 singleton pregnancies with FGR between 24 and 42 weeks of gestation and 107 pregnancies with fetuses whose growth was appropriate for gestational age (AGA). Adrenal gland size and Doppler parameters of the adrenal artery were measured and the values and obstetric outcomes were compared between the study and control groups.

RESULTS

In the study group, the Z-scores of total adrenal width-length and height, fetal zone width-length and middle adrenal artery-peak systolic velocity (MAA-PSV) were significantly higher than those in the control group (p<0.05). The Z-scores of middle adrenal artery-pulsatility index (MAA-PI) were significantly lower in the study group than in the control group (p<0.05). The rate of neonatal intensive care unit admission in fetuses with high adrenal artery PI scores was higher in the FGR group (p<0.05).

CONCLUSIONS

In the present study, we observed decreased adrenal artery PI, increased adrenal blood flow, and increased fetal adrenal volume in fetuses diagnosed with fetal growth restriction, most likely in response to placental insufficiency and chronic hypoxia.

Prepubertal and pubertal gonadal morphology, expression of cell lineage markers and hormonal evaluation in two 46,XY siblings with 17β-hydroxysteroid dehydrogenase 3 deficiency

OBJECTIVES

17β-hydroxysteroid dehydrogenase 3 (17β-HSD3) deficiency results in insufficient biosynthesis of testosterone and consequently dihydrotestosterone. This is important for the fetal development of male genitalia. Thus, most 46,XY patients with 17β-HSD3 deficiency have a female appearance at birth and present with virilization at puberty. This study presents the differences in the clinical and hormonal data and analyses of gonadal characteristics in two siblings with 17β-HSD3 deficiency.

CASE PRESENTATION

Patient 1 presented with deepening of the voice and signs of virilization at puberty and increased serum levels of testosterone (T) of 10.9 nmol/L (2.9 SDS) and androstenedione (Δ4) of 27 nmol/L (3.3 SDS) were observed. The T/Δ4-ratio was 0.39. Patient 2 was clinically prepubertal at the time of diagnosis, but she also had increased levels of T at 1.97 nmol/L (2.9 SDS), Δ4 at 5 nmol/L (3.3 SDS), and the T/Δ4-ratio was 0.40, but without signs of virilization. Both siblings were diagnosed as homozygous for the splice-site mutation c.277+4A>T in intron 3 of HSD17B3. They were subsequently gonadectomized and treated with hormone replacement therapy. The gonadal histology was overall in accordance with pubertal status, although with a dysgenetic pattern in both patients, including Sertoli-cell-only tubules, few tubules containing germ cells, and presence of microliths.

CONCLUSIONS

Two siblings with 17β-HSD3 deficiency differed in pubertal development at the time of diagnosis and showed marked differences in their clinical presentation, hormonal profile, gonadal morphology and expression of cell lineage markers. Early diagnosis of 17β-HSD3 deficiency appears beneficial to ameliorate long-term consequences.

The intracellular cholesterol pool in steroidogenic cells plays a role in basal steroidogenesis

The framework of steroidogenesis across steroidogenic cells is constructed around cholesterol - the precursor substrate molecule for all steroid hormones - including its cellular uptake, storage in intracellular lipid droplets, mobilization upon steroidogenic stimulation, and finally, its transport to the mitochondria, where steroidogenesis begins. Thus, cholesterol and the mitochondria are highly interconnected in steroidogenic cells. Moreover, accruing evidence suggests that autophagy and mitochondrial dynamics are important cellular events in the regulation of trophic hormone-induced cholesterol homeostasis and steroidogenesis. However, a potential role of cholesterol in itself in the regulation of steroidogenic factors and events remain largely unexplored. We tested the hypothesis that cholesterol plays a role in the regulation of cell-intrinsic factors and events involving steroidogenesis. Here, we show that depleting the intracellular cholesterol pool in steroidogenic cells induces autophagy, affects mitochondrial dynamics, and upregulates steroidogenic factors and basal steroidogenesis in three different steroidogenic cell types producing different steroid hormones. Notably, the cholesterol insufficiency-induced changes in different steroidogenic cell types occur independent of pertinent hormone stimulation and work in a dynamic and temporal manner with or without hormonal stimulation. Such effects of cholesterol deprivation on autophagy and mitochondrial dynamics were not observed in the non-steroidogenic cells, indicating that cholesterol insufficiency-induced changes in steroidogenic cells are specific to steroidogenesis. Thus, our data suggests a role of cholesterol in steroidogenesis beyond being a mere substrate for steroid hormones. The implications of our findings are broad and offer new insights into trophic hormone-dependent and hormone-independent steroidogenesis during development, as well as in health and disease.

A spatiotemporal steroidogenic regulatory network in human fetal adrenal glands and gonads

Human fetal adrenal glands produce substantial amounts of dehydroepiandrosterone (DHEA), which is one of the most important precursors of sex hormones. However, the underlying biological mechanism remains largely unknown. Herein, we sequenced human fetal adrenal glands and gonads from 7 to 14 gestational weeks (GW) via 10× Genomics single-cell transcriptome techniques, reconstructed their location information by spatial transcriptomics. Relative to gonads, adrenal glands begin to synthesize steroids early. The coordination among steroidogenic cells and multiple non-steroidogenic cells promotes adrenal cortex construction and steroid synthesis. Notably, during the window of sexual differentiation (8-12 GW), key enzyme gene expression shifts to accelerate DHEA synthesis in males and cortisol synthesis in females. Our research highlights the robustness of the action of fetal adrenal glands on gonads to modify the process of sexual differentiation.

Mixed corticomedullary tumor of the adrenal gland

Mixed corticomedullary tumor (MCMT) of the adrenal gland is an extremely rare tumor characterized by an admixture of steroidogenic cells and chromaffin cells in a single tumor mass simultaneously producing adrenocortical hormones and catecholamines; it is associated with ectopic adrenocorticotropic hormone (ACTH) in some cases. We reviewed and summarized clinicopathological data of 28 MCMTs, including four metastatic tumors in 26 previous reports. These reports included 21 females and 7 males, and the average tumor sizes were 4.8 ± 2.5 cm and 12.6 ± 6.4 cm in the non-metastatic and metastatic groups, respectively (P<0.001). The clinical manifestations and laboratory data were as follows: Cushing or subclinical Cushing syndrome, 58% (14/24); hypertension, 71% (17/24); elevated adrenocortical hormones, 75% (18/24); elevated catecholamines, 75% (18/24); and ectopic ACTH, 71% (10/14). All four patients with metastatic MCMTs had poor prognoses and elevated adrenocortical hormone levels; however, only two patients had elevated catecholamine levels. Immunohistochemistry was essential for the pathologic diagnosis of MCMTs. In this study, using an improved technique, we detected ectopic ACTH-producing cells in the same paraffin-embedded sections reported to be negative in our previous reports. As MCMT is composed of cells with embryologically different origins, its pathogenesis has been explained by various hypotheses. We compared MCMT to the adrenal gland of birds and the early stage of human fetuses, in which nests of chromaffin cells and steroidogenic cells admix without the formation of cortex and medulla. MCMT is characterized by the immaturity of organogenesis and might be classified as an adrenal embryonal tumor.

The effects of selected inhibitors on human fetal adrenal steroidogenesis differs under basal and ACTH-stimulated conditions

BACKGROUND

Disordered fetal adrenal steroidogenesis can cause marked clinical effects including virilization of female fetuses. In postnatal life, adrenal disorders can be life-threatening due to the risk of adrenal crisis and must be carefully managed. However, testing explicit adrenal steroidogenic inhibitory effects of therapeutic drugs is challenging due to species-specific characteristics, and particularly the impact of adrenocorticotropic hormone (ACTH) stimulation on drugs targeting steroidogenesis has not previously been examined in human adrenal tissue. Therefore, this study aimed to examine the effects of selected steroidogenic inhibitors on human fetal adrenal (HFA) steroid hormone production under basal and ACTH-stimulated conditions.

METHODS

This study used an established HFA ex vivo culture model to examine treatment effects in 78 adrenals from 50 human fetuses (gestational weeks 8-12). Inhibitors were selected to affect enzymes critical for different steps in classic adrenal steroidogenic pathways, including CYP17A1 (Abiraterone acetate), CYP11B1/2 (Osilodrostat), and a suggested CYP21A2 inhibitor (Efavirenz). Treatment effects were examined under basal and ACTH-stimulated conditions in tissue from the same fetus and determined by quantifying the secretion of adrenal steroids in the culture media using liquid chromatography-tandem mass spectrometry. Statistical analysis was performed on ln-transformed data using one-way ANOVA for repeated measures followed by Tukey's multiple comparisons test.

RESULTS

Treatment with Abiraterone acetate and Osilodrostat resulted in potent inhibition of CYP17A1 and CYP11B1/2, respectively, while treatment with Efavirenz reduced testosterone secretion under basal conditions. ACTH-stimulation affected the inhibitory effects of all investigated drugs. Thus, treatment effects of Abiraterone acetate were more pronounced under stimulated conditions, while Efavirenz treatment caused a non-specific inhibition on steroidogenesis. ACTH-stimulation prevented the Osilodrostat-mediated CYP11B1 inhibition observed under basal conditions.

CONCLUSIONS

Our results show that the effects of steroidogenic inhibitors differ under basal and ACTH-stimulated conditions in the HFA ex vivo culture model. This could suggest that in vivo effects of therapeutic drugs targeting steroidogenesis may vary in conditions where patients have suppressed or high ACTH levels, respectively. This study further demonstrates that ex vivo cultured HFAs can be used to evaluate steroidogenic inhibitors and thereby provide novel information about the local effects of existing and emerging drugs that targets steroidogenesis.

Sexual Dimorphism of Corticosteroid Signaling during Kidney Development

Sexual dimorphism involves differences between biological sexes that go beyond sexual characteristics. In mammals, differences between sexes have been demonstrated regarding various biological processes, including blood pressure and predisposition to develop hypertension early in adulthood, which may rely on early events during development and in the neonatal period. Recent studies suggest that corticosteroid signaling pathways (comprising glucocorticoid and mineralocorticoid signaling pathways) have distinct tissue-specific expression and regulation during this specific temporal window in a sex-dependent manner, most notably in the kidney. This review outlines the evidence for a gender differential expression and activation of renal corticosteroid signaling pathways in the mammalian fetus and neonate, from mouse to human, that may favor mineralocorticoid signaling in females and glucocorticoid signaling in males. Determining the effects of such differences may shed light on short term and long term pathophysiological consequences, markedly for males.

Adrenal medulla development and medullary-cortical interactions

The mammalian adrenal gland is composed of two distinct tissue types in a bidirectional connection, the catecholamine-producing medulla derived from the neural crest and the mesoderm-derived cortex producing steroids. The medulla mainly consists of chromaffin cells derived from multipotent nerve-associated descendants of Schwann cell precursors. Already during adrenal organogenesis, close interactions between cortex and medulla are necessary for proper differentiation and morphogenesis of the gland. Moreover, communication between the cortex and the medulla ensures a regular function of the adult adrenal. In tumor development, interfaces between the two parts are also common. Here, we summarize the development of the mammalian adrenal medulla and the current understanding of the cortical-medullary interactions under development and in health and disease.

Establishment of a Novel Human Fetal Adrenal Culture Model that Supports de Novo and Manipulated Steroidogenesis

CONTEXT

Disorders affecting adrenal steroidogenesis promote an imbalance in the normally tightly controlled secretion of mineralocorticoids, glucocorticoids, and androgens. This may lead to differences/disorders of sex development in the fetus, as seen in virilized girls with congenital adrenal hyperplasia (CAH). Despite the important endocrine function of human fetal adrenals, neither normal nor dysregulated adrenal steroidogenesis is understood in detail.

OBJECTIVE

Due to significant differences in adrenal steroidogenesis between human and model species (except higher primates), we aimed to establish a human fetal adrenal model that enables examination of both de novo and manipulated adrenal steroidogenesis.

DESIGN AND SETTING

Human adrenal tissue from 54 1st trimester fetuses were cultured ex vivo as intact tissue fragments for 7 or 14 days.

MAIN OUTCOME MEASURES

Model validation included examination of postculture tissue morphology, viability, apoptosis, and quantification of steroid hormones secreted to the culture media measured by liquid chromatography-tandem mass spectrometry.

RESULTS

The culture approach maintained cell viability, preserved cell populations of all fetal adrenal zones, and recapitulated de novo adrenal steroidogenesis based on continued secretion of steroidogenic intermediates, glucocorticoids, and androgens. Adrenocorticotropic hormone and ketoconazole treatment of ex vivo cultured human fetal adrenal tissue resulted in the stimulation of steroidogenesis and inhibition of androgen secretion, respectively, demonstrating a treatment-specific response.

CONCLUSIONS

Together, these data indicate that ex vivo culture of human fetal adrenal tissue constitutes a novel approach to investigate local effects of pharmaceutical exposures or emerging therapeutic options targeting imbalanced steroidogenesis in adrenal disorders, including CAH.

Cord blood androgen levels of females from same sex and opposite sex twins - A pilot study

OBJECTIVE

Opposite-sex twins have shown behavioural and reproductive differences between females and males. These differences may be determined by higher intrauterine levels of androgens among females that were exposed to a male co-twin. The aim of this study was to compare cord blood androgen levels in females from same-sex and opposite-sex twins.

DESIGN

A prospective study. In this pilot study, we compared cord blood androgens (DHEA-S, Δ-4 androstenedione, total testosterone-TT) and sex hormone-binding globulin (SHBG) levels in 20 females from same sex and 20 females from opposite-sex dichorionic diamniotic twins. We used generalized estimating equation (GEE) modelling to assess differences in cord blood androgens between females from same-sex twin pregnancies and females from opposite-sex twin pregnancies.

PATIENTS

Twenty opposite-sex twin pairs (female-male twins) and 20 same-sex twin pairs (female-female).

MEASUREMENTS

Cord blood total testosterone, Δ-4 androstenedione, DHEA-S and sex hormone-binding globulin (SHBG) levels.

RESULTS

No difference in the levels of androgens as Δ-4 androstenedione, total testosterone and SHBG was identified between females that were exposed to a female co-twin compared with females that were exposed to a male co-twin. DHEA-S levels were significantly lower among females from opposite-sex twins compared with females from same-sex twins.

CONCLUSIONS

Our preliminary data do not support the hypothesis that females exposed to male co-twins are exposed to higher levels of androgens in utero compared with females exposed to female co-twins. Further studies are needed to explain the reported behavioural and reproductive differences among opposite-sex twins.

The Prenatal Hormone Milieu in Autism Spectrum Disorder

Though the etiology of autism spectrum disorder (ASD) remains largely unknown, recent findings suggest that hormone dysregulation within the prenatal environment, in conjunction with genetic factors, may alter fetal neurodevelopment. Early emphasis has been placed on the potential role of in utero exposure to androgens, particularly testosterone, to theorize ASD as the manifestation of an "extreme male brain." The relationship between autism risk and obstetric conditions associated with inflammation and steroid dysregulation merits a much broader understanding of the in utero steroid environment and its potential influence on fetal neuroendocrine development. The exploration of hormone dysregulation in the prenatal environment and ASD development builds upon prior research publishing associations with obstetric conditions and ASD risk. The insight gained may be applied to the development of chronic adult metabolic diseases that share prenatal risk factors with ASD. Future research directions will also be discussed.

Zone-specific reference ranges of fetal adrenal artery Doppler indices: a longitudinal study

Background

The fetal adrenal gland is a highly vascularized organs and develops two recognizable distinct zones in uetro, inner fetal zone (FZ) and outer definitive zone (DZ). Based on the region supplied, middle adrenal artery (MAA) mainly contribute to FZ while inferior adrenal artery (IAA) mainly to the inferior part of DZ. The purpose of this study was to establish reference ranges of adrenal artery Doppler indices of IAA and MAA, and assess zonal difference of blood supply to fetal adrenal gland.

Methods

The pulsatility index (PI), resistance index (RI), and systolic:diastolic ratio (S/D) of the IAA and MAA were obtained serially at 4-week intervals in normal fetuses. The MAA and IAA were referred based on the course and location in the gland: IAA referring the artery that mainly branches from the renal artery and walks along the renal upper pole, distributing the inferoposterior part of DZ in the adrenal gland while MAA as arterial blood flowing along the single central adrenal vein in the medial part of the gland. Multilevel modeling was performed to establish the gestational age-associated reference ranges for IAA and MAA. Differences in Doppler indices between the IAA and MAA were assessed.

Results

One hundred sixty-eight fetuses with 843 observations were included. The IAA had a higher detection rate than the MAA (100% vs 89.2%, p < 0.05). The resistance of IAA had a reduction around 35 weeks of gestation and that of MAA remained unchanged throughout the second half of pregnancy. Lower PI, RI and S/D were observed in the MAA than in the IAA (p < 0.05) from 752 paired measurements.

Conclusion

There is a zonal difference in blood supply in favor of the fetal zone, which may correspond to its unique function. Reference ranges of Doppler parameters in adrenal artery maybe beneficial for further evaluation of fetal hemodynamics.

Estrogens in Human Male Gonadotropin Secretion and Testicular Physiology From Infancy to Late Puberty

Several reports in humans as well as transgenic mouse models have shown that estrogens play an important role in male reproduction and fertility. Estrogen receptor alpha (ERα) and beta (ERβ) are expressed in different male tissues including the brain. The estradiol-binding protein GPER1 also mediates estrogen action in target tissues. In human testes a minimal ERα expression during prepuberty along with a marked pubertal up-regulation in germ cells has been reported. ERβ expression was detected mostly in spermatogonia, primary spermatocytes, and immature spermatids. In Sertoli cells ERβ expression increases with age. The aromatase enzyme (cP450arom), which converts androgens to estrogens, is widely expressed in human tissues (including gonads and hypothalamus), even during fetal life, suggesting that estrogens are also involved in human fetal physiology. Moreover, cP450arom is expressed in the early postnatal testicular Leydig cells and spermatogonia. Even though the aromatase complex is required for estrogen synthesis, its biological relevance is also related to the regulation of the balance between androgens and estrogens in different tissues. Knockout mouse models of aromatase (ArKO) and estrogen receptors (ERKOα, ERKOβ, and ERKOαβ) provide an important tool to study the effects of estrogens on the male reproductive physiology including the gonadal axis. High basal serum FSH levels were reported in adult aromatase-deficient men, suggesting that estrogens are involved in the negative regulatory gonadotropin feedback. However, normal serum gonadotropin levels were observed in an aromatase-deficient boy, suggesting a maturational pattern role of estrogen in the regulation of gonadotropin secretion. Nevertheless, the role of estrogens in primate testis development and function is controversial and poorly understood. This review addresses the role of estrogens in gonadotropin secretion and testicular physiology in male humans especially during childhood and puberty.

Alternative pathway androgen biosynthesis and human fetal female virilization

In the classic androgen biosynthesis pathway, testosterone is converted to 5α-dihydrotestosterone, a step crucially required for normal male genital virilization. Congenital adrenal hyperplasia (CAH) due to P450 oxidoreductase deficiency (PORD) is an inborn disorder that disrupts classic androgen biosynthesis. However, some affected girls present with severe genital virilization at birth. We hypothesized that this is explained by a prenatally active, alternative biosynthesis pathway to 5α-dihydrotestosterone. We show that adrenals and genital skin cooperate to produce androgens via the alternative pathway during the major period of human sexual differentiation and that neonates with PORD still produce alternative pathway androgens during the first weeks of life. This indicates that alternative pathway androgen biosynthesis drives prenatal virilization in CAH due to PORD.

Androgen biosynthesis in the human fetus proceeds through the adrenal sex steroid precursor dehydroepiandrosterone, which is converted to testosterone in the gonads, followed by further activation to 5α-dihydrotestosterone in genital skin, thereby facilitating male external genital differentiation. Congenital adrenal hyperplasia due to P450 oxidoreductase deficiency results in disrupted dehydroepiandrosterone biosynthesis, explaining undervirilization in affected boys. However, many affected girls are born virilized, despite low circulating androgens. We hypothesized that this is due to a prenatally active, alternative androgen biosynthesis pathway from 17α-hydroxyprogesterone to 5α-dihydrotestosterone, which bypasses dehydroepiandrosterone and testosterone, with increased activity in congenital adrenal hyperplasia variants associated with 17α-hydroxyprogesterone accumulation. Here we employ explant cultures of human fetal organs (adrenals, gonads, genital skin) from the major period of sexual differentiation and show that alternative pathway androgen biosynthesis is active in the fetus, as assessed by liquid chromatography–tandem mass spectrometry. We found androgen receptor expression in male and female genital skin using immunohistochemistry and demonstrated that both 5α-dihydrotestosterone and adrenal explant culture supernatant induce nuclear translocation of the androgen receptor in female genital skin primary cultures. Analyzing urinary steroid excretion by gas chromatography–mass spectrometry, we show that neonates with P450 oxidoreductase deficiency produce androgens through the alternative androgen pathway during the first weeks of life. We provide quantitative in vitro evidence that the corresponding P450 oxidoreductase mutations predominantly support alternative pathway androgen biosynthesis. These results indicate a key role of alternative pathway androgen biosynthesis in the prenatal virilization of girls affected by congenital adrenal hyperplasia due to P450 oxidoreductase deficiency.