Adrenarche in nonhuman primates: the evidence for it and the need to redefine it

Update on Adrenarche-Still a Mystery

CONTEXT

Adrenarche marks the timepoint of human adrenal development when the cortex starts secreting androgens in increasing amounts, in healthy children at age 8-9 years, with premature adrenarche (PA) earlier. Because the molecular regulation and significance of adrenarche are unknown, this prepubertal event is characterized descriptively, and PA is a diagnosis by exclusion with unclear long-term consequences.

EVIDENCE ACQUISITION

We searched the literature of the past 5 years, including original articles, reviews, and meta-analyses from PubMed, ScienceDirect, Web of Science, Embase, and Scopus, using search terms adrenarche, pubarche, DHEAS, steroidogenesis, adrenal, and zona reticularis.

EVIDENCE SYNTHESIS

Numerous studies addressed different topics of adrenarche and PA. Although basic studies on human adrenal development, zonation, and zona reticularis function enhanced our knowledge, the exact mechanism leading to adrenarche remains unsolved. Many regulators seem involved. A promising marker of adrenarche (11-ketotestosterone) was found in the 11-oxy androgen pathway. By current definition, the prevalence of PA can be as high as 9% to 23% in girls and 2% to 10% in boys, but only a subset of these children might face related adverse health outcomes.

CONCLUSION

New criteria for defining adrenarche and PA are needed to identify children at risk for later disease and to spare children with a normal variation. Further research is therefore required to understand adrenarche. Prospective, long-term studies should characterize prenatal or early postnatal developmental pathways that modulate trajectories of birth size, early postnatal growth, childhood overweight/obesity, adrenarche and puberty onset, and lead to abnormal sexual maturation, fertility, and other adverse outcomes.

Dehydroepiandrosterone sulfate (DHEAS) in excreta is a good indicator of serum DHEAS in Japanese macaques (Macaca fuscata)

We developed a microplate enzyme immunoassay (EIA) to measure dehydroepiandrosterone sulfate (DHEAS) in the blood, urine, and feces of Japanese macaques and evaluated the relationship between serum DHEAS and excreta DHEAS. Our DHEAS EIA using heterological DHEA derivatives conjugated with enzyme was highly sensitive, and linearities and recoveries for all matrices of Japanese macaques were reliable. For the biological evaluation of the metabolism of DHEAS in Japanese macaques, dissolved DHEAS was injected into the subjects, and consecutively collected serum, urine, and fecal samples were analyzed. The peaks of serum DHEAS were observed 6 h after the administration, while those of urine and feces were observed after 24 h. The fluctuation of those in urine and feces were significantly correlated with serum DHEAS levels. In addition, we measured pregnanediol-glucuronide (PdG), and estrone-conjugate (E₁C) in urine and fecal samples to investigate the effects of administrated DHEAS on these progesterone and estrogen metabolites. The peak of PdG was observed 24 h after administration, then declined sharply. The concentration of E₁C increased 1 week after administration in two out of three subjects. Our results suggest that measuring urinary and fecal DHEAS with our EIA provides a non-invasive alternative to assessing DHEAS levels in the serum of Japanese macaques.

DHEAS and nutritional status among Sidama, Ngandu, and Aka children: Effects of cortisol and implications for adrenarche

OBJECTIVE

Adrenarche, the biological event marked by rising production of dehydroepiandrosterone and its sulfate (DHEAS), may represent a sensitive period in child development, with important implications for adolescence and beyond. Nutritional status, particularly BMI and/or adiposity, has long been hypothesized as a factor in DHEAS production but findings are inconsistent, and few studies have examined this among non-industrialized societies. In addition, cortisol has not been included in these models. We here evaluate effects of height- (HAZ), weight- (WAZ), and BMI- (BMIZ) for-age on DHEAS concentrations among Sidama agropastoralist, Ngandu horticulturalist, and Aka hunter-gatherer children.

METHODS

Heights and weights were collected from 206 children aged 2-18 years old. HAZ, WAZ, and BMIZ were calculated using CDC standards. DHEAS and cortisol assays were used to determine biomarker concentrations in hair. Generalized linear modeling was used to examine effects of nutritional status on DHEAS concentrations, as well as cortisol, controlling for age, sex, and population.

RESULTS

Despite the prevalence of low HAZ and WAZ scores, the majority (77%) of children had BMI z-scores >-2.0 SD. Nutritional status has no significant effect on DHEAS concentrations, controlling for age, sex, and population. Cortisol, however, is a significant predictor of DHEAS concentrations.

CONCLUSIONS

Our findings do not support a relationship between nutritional status and DHEAS. Instead, results suggest an important role for stress and ecology in DHEAS concentrations across childhood. Specifically, effects of environment via cortisol may be influential to patterning of DHEAS. Future work should investigate local ecological stressors and their relationship to adrenarche.

The effects of puberty and sex on adolescent white matter development: A systematic review

Adolescence, the transition between childhood and adulthood, is characterized by rapid brain development in white matter (WM) that is attributed in part to rising levels in adrenal and gonadal hormones. The extent to which pubertal hormones and related neuroendocrine processes explain sex differences in WM during this period is unclear. In this systematic review, we sought to examine whether there are consistent associations between hormonal changes and morphological and microstructural properties of WM across species and whether these effects are sex-specific. We identified 90 (75 human, 15 non-human) studies that met inclusion criteria for our analyses. While studies in human adolescents show notable heterogeneity, results broadly demonstrate that increases in gonadal hormones across pubertal development are associated with macro- and microstructural changes in WM tracts that are consistent with the sex differences found in non-human animals, particularly in the corpus callosum. We discuss limitations of the current state of the science and recommend important future directions for investigators in the field to consider in order to advance our understanding of the neuroscience of puberty and to promote forward and backward translation across model organisms.

Hormonal correlates of male dominance rank, age, and genital colouration in vervet monkey (Chlorocebus pygerythrus)

Primates are the most colourful members of the Mammalian clade. In vervet monkeys (Chlorocebus pygerythrus), males are characterized by their red penis and blue scrotum. Such colour signals are often used in conspecific communication, and thus could be used to convey signaller condition. We quantified scrotal and penile colour characteristics using digital photographs between May-June 2016 from males in two neighboring groups along the shores of Lake Nabugabo, Uganda. We examined the relationship between fecal hormones, male dominance rank, age (adult vs. immature), and colour. Adult males were higher ranking than immatures, but there were no rank or age differences in fecal hormone levels. Glucocorticoids and androgens were positively correlated in immature, but not adult males. All scrotal characteristics were predicted by age, with adult males having more teal (i.e., less blue, more green) and more luminant scrota. Within adult males, those with higher androgens levels had more saturated blue scrotal colouration and higher-ranking males were more luminant. Penile colouration was also associated with age and rank. High-ranking males had a more saturated red penis, and adult male penile colour was more luminant and bluer than in immature males. Our findings are consistent with previous reports that scrotal colouration advertises sexual or reproductive maturity (i.e., age), but we also find that within adult males, colour also advertises dominance rank and may be mediated by androgen levels. Penile colouration also appears to signal information about male age and dominance rank but does not appear to be mediated by hormones.

Capturing the dynamic nature of stress exposure in the Pittsburgh Girls Study

Background

The science of stress exposure and health in humans has been hampered by differences in operational definitions of exposures and approaches to defining timing, leading to results that lack consistency and specificity. In the present study we aim to empirically derive variability in type, timing and chronicity of stress exposure for Black and White females using prospectively collected data in the Pittsburgh Girls Study (PGS).

Methods

The PGS is an ongoing 20-year longitudinal, community-based study. In this paper we focused on annual caregiver reports of three domains of stress: subsistence (e.g., resource strain, overcrowding); safety (e.g., community violence, inter-adult aggression), and caregiving (e.g., separation, maternal depression) from early childhood through adolescence. Z-scores were used to conduct a finite mixture model-based latent class trajectory analysis. Model fit was compared using the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). We examined differences in timing and chronicity of stress exposure between Black and White girls.

Results

Distinct trajectory groups characterized by differential timing and chronicity of stress exposure were observed across all stress domains. Six trajectories characterized subsistence and safety stress, and five characterized caregiving stress. Variability in initial level, chronicity, and magnitude and timing of change was observed within and across domains of stressors. Race differences also varied across the domains: race differences in timing and chronicity were most pronounced for the subsistence and safety domains, whereas Black and White girls had similar levels of exposure to caregiving stress.

Conclusions

Substantial variability in timing and chronicity was observed within and across stress domains. Modeling specific domains and dimensions of stress exposure is likely important in testing associations between exposure and health; such specificity may lead to more effective deployment of preventive interventions based on stress exposure.

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Distinct trajectories in exposure were observed for subsistence, safety, and caregiving stress domains.

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Race differences in timing and chronicity of exposure were pronounced for subsistence and safety domains.

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Patterns of exposure (e.g., level, timing) are likely critical for understanding the impact on stress exposure on health.

Normal and Premature Adrenarche

Adrenarche is the maturational increase in adrenal androgen production that normally begins in early childhood. It results from changes in the secretory response to adrenocorticotropin (ACTH) that are best indexed by dehydroepiandrosterone sulfate (DHEAS) rise. These changes are related to the development of the zona reticularis (ZR) and its unique gene/enzyme expression pattern of low 3ß-hydroxysteroid dehydrogenase type 2 with high cytochrome b5A, sulfotransferase 2A1, and 17ß-hydroxysteroid dehydrogenase type 5. Recently 11-ketotestosterone was identified as an important bioactive adrenarchal androgen. Birth weight, body growth, obesity, and prolactin are related to ZR development. Adrenarchal androgens normally contribute to the onset of sexual pubic hair (pubarche) and sebaceous and apocrine gland development. Premature adrenarche causes ≥90% of premature pubarche (PP). Its cause is unknown. Affected children have a significantly increased growth rate with proportionate bone age advancement that typically does not compromise growth potential. Serum DHEAS and testosterone levels increase to levels normal for early female puberty. It is associated with mildly increased risks for obesity, insulin resistance, and possibly mood disorder and polycystic ovary syndrome. Between 5% and 10% of PP is due to virilizing disorders, which are usually characterized by more rapid advancement of pubarche and compromise of adult height potential than premature adrenarche. Most cases are due to nonclassic congenital adrenal hyperplasia. Algorithms are presented for the differential diagnosis of PP. This review highlights recent advances in molecular genetic and developmental biologic understanding of ZR development and insights into adrenarche emanating from mass spectrometric steroid assays.

The effects of puberty and its hormones on subcortical brain development

Puberty triggers a period of structural “re-organization” in the brain, when rising hormone levels act via receptors to influence morphology. However, our understanding of these neuroendocrine processes in humans remains poor. As such, the current longitudinal study characterized development of the human subcortex during puberty, including changes in relation to pubertal (Tanner) stage and hormone (testosterone, dehydroepiandrosterone [DHEA]) levels. Beyond normative group-level patterns of development, we also examined whether individual differences in the rate of pubertal maturation (i.e., “pubertal/hormonal tempo”) were associated with variations in subcortical trajectories. Participants (N = 192; scans = 366) completed up to three waves of MRI assessments between 8.5 and 14.5 years of age. Parents completed questionnaire assessments of pubertal stage at each wave, and adolescents provided hormone samples on a subset of waves. Generalized additive mixture models were used to characterize trajectories of subcortical development. Results showed that development of most subcortical structures was related to pubertal stage, although findings were mostly non-significant when controlling for age. Testosterone and DHEA levels were related to development of the amygdala, hippocampus and pallidum in both sexes, and findings in the amygdala remained significant when controlling for age. Additionally, we found that variability in hormonal (specifically testosterone) tempo was related to right hippocampal development in males, with an accelerated pattern of hippocampal development in those with greater increases in testosterone levels. Overall, our findings suggest prominent hormonal influences on the amygdala and hippocampus, consistent with the prevalence of androgen and estrogen receptors in these regions. We speculate that these findings are most likely reflective of the important role of adrenarcheal processes on adolescent brain development.

There are widespread associations between physical and hormonal indices of puberty and subcortical development.

Effects of testosterone and DHEA are strongest in the amygdala, hippocampus and pallidum.

Individual differences in the tempo of rising testosterone are related to variability in hippocampal development in males.

Pubarche and Gonadarche Onset and Progression Are Differently Associated With Birth Weight and Infancy Growth Patterns

Context

Controversy exists regarding associations between early-life growth patterns and timing of puberty.

Objective

This work aims to investigate associations between birth anthropometry, early growth patterns, and onset/progression of pubertal milestones in boys and girls.

Methods

Among children examined at birth (1997-2003) and at age 36 months in a mother-child cohort, pubertal Tanner stages (B1-5, PH1-5, G1-5) and testicular volume were examined by trained physicians at 1 to 5 follow-up examinations during childhood and adolescence (672 girls and 846 boys, 2006-2013).With parametric survival models we analyzed associations between birth weight, changes in SD scores (SDS) from birth to 36 months (ΔSDS 0-36 > 0.67 SD defining catch-up growth), and age at pubertal onset/attainment of late pubertal stages/menarche.

Results

A 1-kg higher birth weight was associated with earlier onset of B2+ (thelarche): -3.9 months (CI, -6.7 to -1.1 months), G2+ (gonadarche): -2.7 months (-5.3 to -0.1 months), Tvol3+ (testis size > 3 mL): -2.8 months (CI, -4.9 to -0.7 months), but with later G4+ and PH4+ in boys, and a slower progression from B2 to menarche (5.3 months [CI, 1.2 to 9.4 months]) in girls. Catch-up growth was associated with earlier PH2+ (pubarche) in girls (-4.1 months [CI, -7.6 to -0.6 months]), earlier PH2+ in boys (-3.4 months [CI, -6.6 to -0.2 months]), faster progression from B2 to menarche in girls (-9.1 months [CI, 14.6 to 3.5 months]), and earlier G4+ and PH4+ in boys.

Conclusion

Associations between birthweight and infancy catch-up growth differed for gonadarche and pubarche, and for early and late pubertal markers, with similar patterns in both sexes.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

Adrenal cortex development and related disorders leading to adrenal insufficiency

The adult human adrenal cortex produces steroid hormones that are crucial for life, supporting immune response, glucose homeostasis, salt balance and sexual maturation. It consists of three histologically distinct and functionally specialized zones. The fetal adrenal forms from mesodermal material and produces predominantly adrenal C₁₉ steroids from its fetal zone, which involutes after birth. Transition to the adult cortex occurs immediately after birth for the formation of the zona glomerulosa and fasciculata for aldosterone and cortisol production and continues through infancy until the zona reticularis for adrenal androgen production is formed with adrenarche. The development of this indispensable organ is complex and not fully understood. This article gives an overview of recent knowledge gained of adrenal biology from two perspectives: one, from basic science studying adrenal development, zonation and homeostasis; and two, from adrenal disorders identified in persons manifesting with various isolated or syndromic forms of primary adrenal insufficiency.

The Enigma of the Adrenarche: Identifying the Early Life Mechanisms and Possible Role in Postnatal Brain Development

Dehydroepiandrosterone (DHEA) and its sulfated metabolite (DHEAS) are dynamically regulated before birth and the onset of puberty. Yet, the origins and purpose of increasing DHEA[S] in postnatal development remain elusive. Here, we draw attention to this pre-pubertal surge from the adrenal gland—the adrenarche—and discuss whether this is the result of intra-adrenal gene expression specifically affecting the zona reticularis (ZR), if the ZR is influenced by the hypothalamic-pituitary axis, and the possible role of spino-sympathetic innervation in prompting increased ZR activity. We also discuss whether neural DHEA[S] synthesis is coordinately regulated with the developing adrenal gland. We propose that DHEA[S] is crucial in the brain maturation of humans prior to and during puberty, and suggest that the function of the adrenarche is to modulate, adapt and rewire the pre-adolescent brain for new and ever-changing social challenges. The etiology of DHEA[S] synthesis, neurodevelopment and recently described 11-keto and 11-oxygenated androgens are difficult to investigate in humans owing to: (i) ethical restrictions on mechanistic studies, (ii) the inability to predict which individuals will develop specific mental characteristics, and (iii) the difficulty of conducting retrospective studies based on perinatal complications. We discuss new opportunities for animal studies to overcome these important issues.

A Narrative Review of Sex Differences in Eating Disorders: Is There a Biological Basis?

PURPOSE

Eating disorders and their core symptoms (eg, binge eating, body weight/shape concerns) disproportionately affect females, and these sex-differentiated effects become prominent during and after puberty. Although psychosocial influences such as heightened sociocultural pressures for thinness in girls and women contribute to this sex imbalance, biological factors could also play an important role.

METHODS

This narrative review summarizes evidence of biological factors underlying the sex-differentiated prevalence of eating pathology as well as within-sex variability in risk.

FINDINGS

There are sex differences in the pubertal emergence of genetic effects on eating pathology (adrenarche in males; gonadarche in females), and at least some genetic contributions to eating pathology seem to vary between the sexes. Furthermore, sex steroid hormones (eg, testosterone, estradiol, progesterone) are leading contributors to differential risk for eating pathology in males and females across the life span. Emerging data suggest that between-sex and within-sex variability in risk might occur via hormone-driven modulation (activation/deactivation) of genetic influences and neural responsiveness to food-related cues.

IMPLICATIONS

There is a biological basis to heightened risk for eating pathology in females, relative to males, as well as unique biological influences within each sex. Findings from this review highlight the importance of studying both sexes and considering sex-specific biological mechanisms that may underlie differential risk for eating pathology.

Do Dehydroepiandrosterone (DHEA) and Its Sulfate (DHEAS) Play a Role in the Stress Response in Domestic Animals?

In animal husbandry, stress is often associated with poor health and welfare. Stress occurs when a physiological control system detects a state of real or presumptive threat to the animal's homeostasis or a failure to control a fitness-critical variable. The definition of stress has mostly relied on glucocorticoids measurement, even though glucocorticoids represent one stress-response system, the hypothalamus-pituitary-adrenocortical axis, which is not precise enough as it is also related to metabolic regulation and activated in non-stressful situations (pleasure, excitement, and arousal). The mammal adrenal can synthesize the androgenic steroid dehydroepiandrosterone (DHEA) and its sulfate metabolite (DHEAS), which have been associated to the stress response in several studies performed mostly in humans and laboratory animals. Although the functions of these steroids are not fully understood, available data suggest their antagonistic effects on glucocorticoids and, in humans, their secretion is affected by stress. This review explores the scientific literature on DHEA and DHEAS release in domestic animals in response to stressors of different nature (inflammatory, physical, or social) and duration, and the extra-adrenal contribution to circulating DHEA. Then, the potential use of DHEA in conjunction with cortisol to improve the definition of the stress phenotype in farmed animals is discussed. Although the focus of this review is on farmed animals, examples from other species are reported when available.

Timing of the Infancy-Childhood Growth Transition in Rural Gambia

The Karlberg model of human growth describes the infancy, childhood, and puberty (ICP) stages as continuous and overlapping, and defined by transitions driven by sequential additional effects of several endocrine factors that shape the growth trajectory and resultant adult size. Previous research has suggested that a delayed transition from the infancy to the childhood growth stage contributes to sub-optimal growth outcomes. A new method developed to analyze the structure of centile crossing in early life has emerged as a potential tool for identifying the infancy-childhood transition (ICT), through quantifying patterns of adjacent monthly weight-for-age z-score (WAZ) deviation correlations. Using this method, the infancy-childhood transition was identified as taking place at around 12 months of age in two cohorts of UK infants. Here, we apply this method to data collected as part of a longitudinal growth study in rural Gambia [the Hormonal and Epigenetic Regulators of Growth, or HERO-G study, N = 212 (F = 99, M = 113)], in order to identify the ICT and assess whether timing of this transition differs across groups based on sex or birth seasonality. We calculated Pearson correlation coefficients for adjacent monthly WAZ score deviations. Based on the patterns of change in the correlation structure over time, our results suggest that the infancy-childhood transition occurs at around 9 months of age in rural Gambian infants. This points to an accelerated ICT compared to UK infants, rather than a delayed ICT. A comparatively later transition, seen in UK infants, allows maximal extension of the high rates of growth during the infancy stage; an earlier transition as seen in Gambian infants cuts short this period of rapid growth, potentially impacting on growth outcomes in childhood while diverting energy into other processes critical to responses to acute infectious challenges. Growth in later developmental stages in this population offers an extended window for catch-up.

Human-like adrenal development in wild chimpanzees: A longitudinal study of urinary dehydroepiandrosterone-sulfate and cortisol

The development of the adrenal cortex varies considerably across primates, being most conspicuous in humans, where a functional zona reticularis-the site of dehydroepiandrosterone-sulfate (DHEA/S) production-does not develop until middle childhood (5-8 years). Prior reports suggest that a human-like adrenarche, associated with a sharp prepubertal increase in DHEA/S, may only occur in the genus Pan. However, the timing and variability in adrenarche in chimpanzees remain poorly described, owing to the lack of longitudinal data, or data from wild populations. Here, we use urine samples from East African chimpanzees (Pan troglodytes schweinfurthii) collected over 20 years at Kanyawara in Kibale National Park, Uganda, to trace the developmental trajectories of DHEAS (n = 1,385 samples, 53 individuals) and cortisol (n = 12,726 samples, 68 individuals). We used generalized additive models (GAM) to investigate the relationship between age, sex, and hormone levels. Adrenarche began earlier in chimpanzees (~2-3 years) compared with what has been reported in humans (6-8 years) and, unlike humans, male and female chimpanzees did not differ significantly in the timing of adrenarche nor in DHEAS concentrations overall. Similar to what has been reported in humans, cortisol production decreased through early life, reaching a nadir around puberty (8-11 years), and a sex difference emerged with males exhibiting higher urinary cortisol levels compared with females by early adulthood (15-16 years). Our study establishes that wild chimpanzees exhibit a human-like pattern of cortisol production during development and corroborates prior reports from captive chimpanzees of a human-like adrenarche, accompanied by significant developmental increases in DHEAS. While the role of these developmental hormone shifts are as yet unclear, they have been implicated in stages of rapid behavioral development once thought unique to humans, especially in regard to explaining the divergence of female and male social behavior before pubertal increases in gonadal hormones.

Tissue steroid levels in response to reduced testicular estrogen synthesis in the male pig, Sus scrofa

Production of steroid hormones is complex and dependent upon steroidogenic enzymes, cofactors, receptors, and transporters expressed within a tissue. Collectively, these factors create an environment for tissue-specific steroid hormone profiles and potentially tissue-specific responses to drug administration. Our objective was to assess steroid production, including sulfated steroid metabolites in the boar testis, prostate, and liver following inhibition of aromatase, the enzyme that converts androgen precursors to estrogens. Boars were treated with the aromatase inhibitor, letrozole from 11 to 16 weeks of age and littermate boars received the canola oil vehicle. Steroid profiles were evaluated in testes, prostate, and livers of 16, 20, and 40 week old boars using liquid chromatography/mass spectrometry. Testis, prostate, and liver had unique steroid profiles in vehicle-treated animals. Only C18 steroid hormones were altered by treatment with the aromatase inhibitor, letrozole; no significant differences were detected in any of the C19 or C21 steroids evaluated. Testis was the only tissue with significantly decreased free estrogens following treatment with the aromatase inhibitor; estrone and estradiol concentrations were lower (p < 0.05) in testes from 16, 20, and 40 week letrozole-treated boars. However, concentrations of the sulfated conjugates, estrone-sulfate and estradiol-sulfate, were significantly decreased (p<0.05) in 16 and 20 week boar testes, prostates, and livers from letrozole-treated boars. Hence, the distribution of estrogens between the free and conjugated forms was altered in a tissue-specific manner following inhibition of aromatase. The results suggest sulfated testicular estrogens are important estrogen precursors for the prostate, potentially enabling peripheral target tissues to synthesize free estrogens in the male pig.

A tale of two steroids: The importance of the androgens DHEA and DHEAS for early neurodevelopment

DHEA and DHEAS are neuroactive neurosteroids that interact with several major receptor systems in the brain, including sigma (σ), glutamate, and GABA-A receptors. It has been recognized as early as 1952, that the loss of DHEA/DHEAS in adult life is associated with neuropsychiatric disorders (eg schizophrenia, depression). However, the mechanistic role for DHEA/DHEAS in any of these domains remains speculative, not the least because the presence of these androgens in the adrenal gland and brain is largely confined to humans and only some non-human primates. DHEA and DHEAS are dynamically regulated from before birth and before the onset of puberty, and therefore an understanding of the synthesis, regulation, and functions of this important androgen pathway warrants attention. Here, we draw attention to the possible modulating influence of DHEA/DHEAS in early brain development from fetal life to the remarkable increase of these steroids in early childhood - the adrenarche. We propose that the pre-pubertal DHEA/DHEAS surge plays a key role in modulating early brain development, perhaps by prolonging brain plasticity during childhood to allow the pre-adolescent brain to adapt and re-wire in response to new, and ever-changing social challenges. Nonetheless, the aetiology of neurodevelopmental phenomena in relation to DHEA/DHEAS synthesis and action cannot be easily studied in humans due to the obvious ethical restrictions on mechanistic studies, the uncertainty of predicting the future mental characteristics of individuals, and the difficulty of conducting retrospective investigations based on pre-birth and/or neonatal complications. We discuss new opportunities for animal studies to resolve these important questions.

Tourette Syndrome as a Disorder of the Social Decision Making Network

Tourette syndrome is a common neurodevelopmental disorder defined by the presence of tics, stereotyped involuntary movements and phonations. Considerable evidence points to developmental abnormalities of the basal ganglia as tic substrates. Basal ganglia dysfunction does not account for important features of Tourette syndrome, including its natural history, male predominance, and the characteristic quality and distribution of tics. The latter mainly involve eye, face, and head movements, in addition to a variety of simple to complex phonations. A major normal function of these movements, and of phonations as well, is social signaling. Many important species- and sex-specific stereotyped social behaviors are mediated by a phylogenetically conserved network of subcortical nuclei, the social behavior network (SBN). Some SBN nuclei are sexually dimorphic, and SBN function is modulated strongly by gonadal steroids. Recent studies indicate that the SBN meshes with the basal ganglia to form a larger network, the Social Decision Making Network (SDM; O'Connell and Hofmann [2011]). The SDM concept overlaps significantly with Holstege's (1993) model of an emotional motor system mediating socially relevant facial movements and phonations. Dopaminergic signaling within the basal ganglia component of the SDM may regulate social act motivation with the SBN component responsible for act expression. Developmental SDM abnormalities can explain all major Tourette syndrome features, including natural history, male predominance, the characteristic distribution of tics, and their stereotyped quality. Some data directly support this hypothesis. Tourette syndrome may be a disorder of social communication manifesting primarily as abnormal involuntary movements.

Hormones and Human and Nonhuman Primate Growth

The aim of this paper was to review information pertaining to the hormonal regulation of nonhuman primate growth, with specific focus on the growth hormone (GH)-insulin-like growth factor (IGF) axis and adrenal androgens. Hormones of the GH-IGF axis are consistently associated with measures of growth - linear, weight, or both - during the growth period; in adulthood, concentrations of IGF-I, IGF-binding protein-3, and GH-binding protein are not associated with any measures of size. Comparing patterns of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) may be especially relevant for understanding whether the childhood stage of growth and development is unique to humans and perhaps other apes. Genetic, hormonal, and morphological data on adrenarche in other nonhuman primate species suggest that this endocrine transition is delayed in humans, chimpanzees, and possibly gorillas, while present very early in postnatal life in macaques. This suggests that although perhaps permitted by an extension of the pre-adolescent growth period, childhood builds upon existing developmental substrates rather than having been inserted de novo into an ancestral growth trajectory. Hormones can provide insight regarding the evolution of the human growth trajectory.

Occurrence of sulfonated steroids and ovarian expression of steroid sulfatase and SULT1E1 in cyclic cows

Historically sulfonated steroids were primarily considered as inactive metabolites destined for elimination. However, more recently they have been increasingly recognized as precursors for the production of bioactive steroids in target tissues and as functional molecules without preceding hydrolysis. In order to comprehensively characterize their occurrence in cyclic cows and their formation and hydrolysis in bovine ovarian steroidogenesis, ovaries from cyclic cows were screened for the expression of oestrogen sulfotransferase (SULTE1) and steroid sulfatase (STS) by Western blot and immunohistochemistry. Moreover, a broad spectrum of 13 sulfonated steroids was measured applying liquid chromatography-tandem mass spectrometry (LC-MS/MS) in blood samples collected from three cycling heifers during defined stages of the ovarian cycle and in fluid obtained from ovarian follicles of different size. SULT1E1 was undetectable in ovarian tissues. For STS only a weak immunostaining was found predominantly in granulosa cells of larger follicles. However, no specific band occurred in Western blot. In blood, concentrations of all sulfonated steroids investigated were below the limit of quantification (LOQ). In follicular fluid, only cholesterol sulfate was measured in considerable concentrations (328.3 ± 63.8 ng/ml). However, the role of cholesterol sulfate in bovine follicular steroidogenesis remains unclear as concentrations were obviously unrelated to follicular size. The remaining sulfonated steroids investigated were undetectable or only slightly exceeded LOQ in a minor proportion of samples. The results are clearly contrary to a role of sulfonated steroids as important precursors, intermediates or products of bovine ovarian steroidogenesis.

The tempo of human childhood: a maternal foot on the accelerator, a paternal foot on the brake

Relative to the life history of other great apes, that of humans is characterized by early weaning and short interbirth intervals (IBIs). We propose that in modern humans, birth until adrenarche, or the rise in adrenal androgens, developmentally corresponds to the period from birth until weaning in great apes and ancestral hominins. According to this hypothesis, humans achieved short IBIs by subdividing ancestral infancy into a nurseling phase, during which offspring fed at the breast, and a weanling phase, during which offspring fed specially prepared foods. Imprinted genes influence the timing of human weaning and adrenarche, with paternally expressed genes promoting delays in childhood maturation and maternally expressed genes promoting accelerated maturation. These observations suggest that the tempo of human development has been shaped by consequences for the fitness of kin, with faster development increasing maternal fitness at a cost to child fitness. The effects of imprinted genes suggest that the duration of the juvenile period (adrenarche until puberty) has also been shaped by evolutionary conflicts within the family.

Tourette syndrome: a disorder of the social decision-making network

Tourette syndrome is a common neurodevelopmental disorder defined by characteristic involuntary movements, tics, with both motor and phonic components. Tourette syndrome is usually conceptualized as a basal ganglia disorder, with an emphasis on striatal dysfunction. While considerable evidence is consistent with these concepts, imaging data suggest diffuse functional and structural abnormalities in Tourette syndrome brain. Tourette syndrome exhibits features that are difficult to explain solely based on basal ganglia circuit dysfunctions. These features include the natural history of tic expression, with typical onset of tics around ages 5 to 7 years and exacerbation during the peri-pubertal years, marked sex disparity with higher male prevalence, and the characteristic distribution of tics. The latter are usually repetitive, somewhat stereotyped involuntary eye, facial and head movements, and phonations. A major functional role of eye, face, and head movements is social signalling. Prior work in social neuroscience identified a phylogenetically conserved network of sexually dimorphic subcortical nuclei, the Social Behaviour Network, mediating many social behaviours. Social behaviour network function is modulated developmentally by gonadal steroids and social behaviour network outputs are stereotyped sex and species specific behaviours. In 2011 O'Connell and Hofmann proposed that the social behaviour network interdigitates with the basal ganglia to form a greater network, the social decision-making network. The social decision-making network may have two functionally complementary limbs: the basal ganglia component responsible for evaluation of socially relevant stimuli and actions with the social behaviour network component responsible for the performance of social acts. Social decision-making network dysfunction can explain major features of the neurobiology of Tourette syndrome. Tourette syndrome may be a disorder of social communication resulting from developmental abnormalities at several levels of the social decision-making network. The social decision-making network dysfunction hypothesis suggests new avenues for research in Tourette syndrome and new potential therapeutic targets.

Species Comparison of Postnatal Development of the Female Reproductive System

The postnatal development of the female reproductive system in laboratory animals and humans is reviewed. To enable a meaningful species comparison of the developing female reproductive system, common definitions of developmental processes were established with a focus made on aspects that are similar across species. A species comparison of the key endocrine, morphologic, and functional (onset of ovarian cycles and ability to reproduce) features of postnatal development of the female reproductive system is provided for human, nonhuman primate, dog, rat, and also mouse, minipig, and rabbit where possible. Species differences in the timing and control of female sexual maturation are highlighted. Additionally, a species comparison of the type and timing of female reproductive ovarian cycles was compiled. Human development provided the frame of reference, and then other common laboratory species were compared. The comparison has inherent challenges because the processes involved and sequence of events can differ greatly across species. Broad strokes were taken to assign a particular average age to an event and are to be used with caution. Methods of evaluation of postnatal female reproductive development in laboratory animals are discussed. Lastly, control rodent data from one of the author's laboratory on vaginal opening, first estrus, estrous cyclicity, and the histopathology involved with the developing female rat and mouse are presented. The information provided in this review is intended to be a resource for the design and interpretation of juvenile animal toxicity testing and ultimately, the relevance of the data to characterize potential risks for women and girls. Birth Defects Research 110:163-189, 2018. © 2017 Wiley Periodicals, Inc.

Non-invasive monitoring of physiological markers in primates

The monitoring of endocrine markers that inform about an animal's physiological state has become an invaluable tool for studying the behavioral ecology of primates. While the collection of blood samples usually requires the animal to be caught and immobilized, non-invasively collected samples of saliva, urine, feces or hair can be obtained without any major disturbance of the subject of interest. Such samples enable repeated collection which is required for matching behavioral information over long time periods with detailed information on endocrine markers. We start our review by giving an overview of endocrine and immune markers that have been successfully monitored in relation to topics of interest in primate behavioral ecology. These topics include reproductive, nutritional and health status, changes during ontogeny, social behavior such as rank relationships, aggression and cooperation as well as welfare and conservation issues. We continue by explaining which hormones can be measured in which matrices, and potential problems with measurements. We then describe different methods of hormone measurements and address their advantages and disadvantages. We finally emphasize the importance of thorough validation procedures when measuring a specific hormone in a new species or matrix.

Determination of 17OHPreg and DHEAS by LC-MS/MS: Impact of Age, Sex, Pubertal Stage, and BMI on the Δ5 Steroid Pathway

BACKGROUND

Dehydroepiandrosterone sulfate (DHEAS) and 17-hydroxypregnenolone (17OHPreg) are important for understanding the Δ5 pathway (e.g., in adrenarche and obesity). Although mass spectrometry has become the state-of-the-art method for quantifying steroids, there are few comprehensive age-, sex-, and pubertal stage-specific reference ranges for children.

AIMS

To develop a sensitive and reliable ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for simultaneous quantification of DHEAS and 17OHPreg and to establish entire age-, sex- and pubertal stage-specific reference ranges in children.

METHODS

A total of 684 children, 453 (243 female, 210 male) with normal body mass index (BMI; <90th) and 231 (132 female, 99 male) obese subjects (>97th), were categorized into 11 age groups, and age- and Tanner stage (PH)-specific reference ranges were determined.

RESULTS

The limit of detection was 0.05 nmol/L for 17OHPreg and 0.5 nmol/L for DHEAS. Levels of both steroids declined after the neonatal period. Comparisons with RIA assays (Siemens, Munich, Germany) (DHEAS) and an in-house kit (17OHPreg) revealed 0.95 and 0.93, respectively, as coefficients of determination. Although DHEAS-generally higher in boys-increased continuously starting at 3 to 6 years, 17OHPreg remained largely constant. In obese patients, both were significantly elevated, also in part after alignment to Tanner stages (PH).

CONCLUSIONS

UPLC-MS/MS is sensitive and reliable for quantifying DHEAS and 17OHPreg. Our data support differential maturation of CYP17 during adrenarche with successively increasing 17,20-lyase activity but largely constant 17α-hydroxylation activity. Endocrine interpretation of 17OHPreg and DHEAS must consider differential patterns for age, sex, pubertal stage, and BMI.

Molecular Mechanisms of Stem/Progenitor Cell Maintenance in the Adrenal Cortex

The adrenal cortex is characterized by three histologically and functionally distinct zones: the outermost zona glomerulosa (zG), the intermediate zona fasciculata, and the innermost zona reticularis. Important aspects of the physiology and maintenance of the adrenocortical stem/progenitor cells have emerged in the last few years. Studies have shown that the adrenocortical cells descend from a pool of progenitors that are localized in the subcapsular region of the zG. These cells continually undergo a process of centripetal displacement and differentiation, which is orchestrated by several paracrine and endocrine cues, including the pituitary-derived adrenocorticotrophic hormone, and angiotensin II. However, while several roles of the endocrine axes on adrenocortical function are well established, the mechanisms coordinating the maintenance of an undifferentiated progenitor cell pool with self-renewal capacity are poorly understood. Local factors, such as the composition of the extracellular matrix (ECM) with embedded signaling molecules, and the activity of major paracrine effectors, including ligands of the sonic hedgehog and Wnt signaling pathways, are thought to play a major role. Particularly, the composition of the ECM, which exhibits substantial differences within each of the three histologically distinct concentric zones, has been shown to influence the differentiation status of adrenocortical cells. New data from other organ systems and different experimental paradigms strongly support the conclusion that the interactions of ECM components with cell-surface receptors and secreted factors are key determinants of cell fate. In this review, we summarize established and emerging data on the paracrine and autocrine regulatory loops that regulate the biology of the progenitor cell niche and propose a role for bioengineered ECM models in further elucidating this biology in the adrenal.

A systematic review of adrenarche as a sensitive period in neurobiological development and mental health

Substantial hormonal and neurobiological changes occur during puberty, and are widely argued to render this period of life a sensitive period in terms of risk for mental health problems. However, there is a paucity of research focusing on adrenarche, the earlier phase of pubertal development. Furthermore, there is a limited understanding of the association between adrenarche and neural development during this phase of life. We systematically reviewed research examining human adrenarcheal development as operationalized by hormonal levels of DHEA and DHEA-S, in relation to indices of mental health (Systematic Review 1). We then reviewed the limited amount of literature that has examined the association between adrenarcheal development and brain structure or function (Systematic Review 2). In general, studies showed that earlier timing of adrenarche was associated with greater mental health symptoms, and there is emerging support that brain development plays a role in this relationship. However, several methodological inconsistencies were noted. We propose that future research in this area test a theoretical model of adrenarche as a sensitive period of neurobiological development, whereby timing of exposure to hormones interacts with brain development, biological sex, and psychosocial stress to influence environmental sensitivity and risk for mental health problems through adolescence.

Cytochrome b5 modulates multiple reactions in steroidogenesis by diverse mechanisms

Cytochrome b5 (cyt-b5) is a relatively small haemoprotein which plays an important role in the regulation of mammalian steroidogenesis. This unique protein has the ability to modulate the activity of key steroidogenic enzymes via a number of diverse reaction mechanisms. Cyt-b5 can augment the 17,20-lyase activity of CYP17A1 by promoting the interaction of CYP17A1 and POR; enhance the 16-ene-synthase activity of CYP17A1 by acting as an electron donor; and enhance the activity of 3βHSD by increasing the affinity of 3βHSD for its cofactor NAD(+). We review the modulation of CYP17A1 and 3βHSD activity by cyt-b5 and discuss the reaction mechanisms associated with each activity. The physiological importance of cyt-b5 in regulating mammalian steroidogenesis is presented and the impact of inactivating cyt-b5 mutations are reviewed. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.

Premature adrenarche: etiology, clinical findings, and consequences

Adrenarche means the morphological and functional change of the adrenal cortex leading to increasing production of adrenal androgen precursors (AAPs) in mid childhood, typically at around 5-8 years of age in humans. The AAPs dehydroepiandrosterone (DHEA) and its sulfate conjugate (DHEAS) are the best serum markers of adrenal androgen (AA) secretion and adrenarche. Normal ACTH secretion and action are needed for adrenarche, but additional inherent and exogenous factors regulate AA secretion. Inter-individual variation in the timing of adrenarche and serum concentrations of DHEA(S) in adolescence and adulthood are remarkable. Premature adrenarche (PA) is defined as the appearance of clinical signs of androgen action (pubic/axillary hair, adult type body odor, oily skin or hair, comedones, acne, accelerated statural growth) before the age of 8 years in girls or 9 years in boys associated with AAP concentrations high for the prepubertal chronological age. To accept the diagnosis of PA, central puberty, adrenocortical and gonadal sex hormone secreting tumors, congenital adrenal hyperplasia, and exogenous source of androgens need to be excluded. The individually variable peripheral conversion of circulating AAPs to biologically more active androgens (testosterone, dihydrotestosterone) and the androgen receptor activity in the target tissues are as important as the circulating AAP concentrations as determinants of androgen action. PA has gained much attention during the last decades, as it has been associated with small birth size, the metabolic and polycystic ovarian syndrome (PCOS), and thus with an increased risk for type 2 diabetes and cardiovascular diseases in later life. The aim of this review is to describe the known hormonal changes and their possible regulators in on-time and premature adrenarche, and the clinical features and possible later health problems associating with PA.

Regulation of the adrenocortical stem cell niche: implications for disease

Stem cells are endowed with the potential for self-renewal and multipotency. Pluripotent embryonic stem cells have an early role in the formation of the three germ layers (ectoderm, mesoderm and endoderm), whereas adult tissue stem cells and progenitor cells are critical mediators of organ homeostasis. The adrenal cortex is an exceptionally dynamic endocrine organ that is homeostatically maintained by paracrine and endocrine signals throughout postnatal life. In the past decade, much has been learned about the stem and progenitor cells of the adrenal cortex and the multiple roles that these cell populations have in normal development and homeostasis of the adrenal gland and in adrenal diseases. In this Review, we discuss the evidence for the presence of adrenocortical stem cells, as well as the various signalling molecules and transcriptional networks that are critical for the embryological establishment and postnatal maintenance of this vital population of cells. The implications of these pathways and cells in the pathophysiology of disease are also addressed.

Why primate models matter

Research involving nonhuman primates (NHPs) has played a vital role in many of the medical and scientific advances of the past century. NHPs are used because of their similarity to humans in physiology, neuroanatomy, reproduction, development, cognition, and social complexity-yet it is these very similarities that make the use of NHPs in biomedical research a considered decision. As primate researchers, we feel an obligation and responsibility to present the facts concerning why primates are used in various areas of biomedical research. Recent decisions in the United States, including the phasing out of chimpanzees in research by the National Institutes of Health and the pending closure of the New England Primate Research Center, illustrate to us the critical importance of conveying why continued research with primates is needed. Here, we review key areas in biomedicine where primate models have been, and continue to be, essential for advancing fundamental knowledge in biomedical and biological research.

The influence of age and season on fecal dehydroepiandrosterone-sulfate (DHEAS) concentrations in Japanese macaques (Macaca fuscata)

Dehydroepiandrosterone (DHEA) and its sulfate, DHEAS, are the most abundant steroid hormones in primates, providing a large reservoir of precursors for the production of androgens. DHEAS levels decline with age in adult humans and nonhuman primates, prompting its consideration as a biomarker of senescence. However, the mechanisms responsible for this age-related decrease and its relationship to reproduction remain elusive. This research investigated DHEAS concentrations in fecal samples in order to determine age-related changes in captive Japanese macaques, as well as to assess the possible influence of seasonality. The subjects were 25 female Japanese macaques (2weeks to 14years-old) housed outdoors in social groups at the Primate Research Institute. We collected three fecal samples from each animal during the breeding season (October to December) and three additional samples from adult females during the non-breeding season (May to June). The hormonal concentrations were determined using enzyme immunoassay. DHEAS concentration was negatively correlated with age, but we did not find a significant difference between breeding and non-breeding seasons. Neonatal macaques had the highest DHEAS concentrations of all age groups. We suggest that elevated neonatal DHEAS is possibly a residue from fetal adrenal secretion and that, as in humans, it might assist in neurobiological development.

Nonhuman primate models of polycystic ovary syndrome

With close genomic and phenotypic similarity to humans, nonhuman primate models provide comprehensive epigenetic mimics of polycystic ovary syndrome (PCOS), suggesting early life targeting for prevention. Fetal exposure to testosterone (T), of all nonhuman primate emulations, provides the closest PCOS-like phenotypes, with early-to-mid gestation T-exposed female rhesus monkeys exhibiting adult reproductive, endocrinological and metabolic dysfunctional traits that are co-pathologies of PCOS. Late gestational T exposure, while inducing adult ovarian hyperandrogenism and menstrual abnormalities, has less dysfunctional metabolic accompaniment. Fetal exposures to dihydrotestosterone (DHT) or diethylstilbestrol (DES) suggest androgenic and estrogenic aspects of fetal programming. Neonatal exposure to T produces no PCOS-like outcome, while continuous T treatment of juvenile females causes precocious weight gain and early menarche (high T), or high LH and weight gain (moderate T). Acute T exposure of adult females generates polyfollicular ovaries, while chronic T exposure induces subtle menstrual irregularities without metabolic dysfunction.

Neonatal amygdala lesions alter basal cortisol levels in infant rhesus monkeys

The amygdala is mostly thought to exert an excitatory influence on the hypothalamic-pituitary-adrenal (HPA) axis, although its role regulating HPA basal tone is less clear, particularly during primate development. The current study examined the effects of neonatal amygdala lesions on basal HPA function and the postnatal testosterone (T) surge of rhesus monkeys reared with their mothers in large outdoor social groups. An early morning basal blood sample was collected at 2.5 months of age, whereas at 5 months samples were collected not only at sunrise, but also at mid-day and sunset to examine the diurnal rhythm of cortisol. At 2.5 months of age sham-operated males exhibited higher cortisol than females, but this sex difference was abolished by neonatal amygdalectomy, with lesioned males also showing lower basal cortisol than controls. Although neonatal amygdalectomy did not alter the postnatal T surge, there was a positive relationship between T and basal cortisol levels. At 5 months of age, neither the sex difference in cortisol, nor its correlation with T levels were apparent any longer. Instead, the diurnal cortisol rhythm of both males and females with amygdalectomy showed a blunted decline from mid-day to sunset compared to controls. These results indicate that neonatal amygdala damage alters basal HPA function in infant rhesus monkeys, affecting males only at early ages (at 2.5 months), while leaving the postnatal T surge intact, and resulting in a flattened diurnal rhythm in both genders at the later ages. Thus, the primate amygdala has a critical influence on the HPA axis in the first few months of life.

In the zone: understanding zona reticularis function and its transformation by adrenarche

The human adrenal cortex comprises three distinct zones with unique steroid products, namely the zona glomerulosa, which secretes the mineralocorticoids, the zona fasciculate, which secretes the glucocorticoids and the zona reticularis (ZR), which at adrenarche, begins to produce the so-called adrenal androgens. Of all the adrenal zones, we still understand control of ZR emergence the least, and yet the consequences of such dysregulation can be devastating. Premature adrenarche is a growing problem and the correspondingly inappropriate emergence of ZR function can negatively influence puberty and lead to adult infertility. Our understanding is limited and more needs to be done. The purpose of these three reviews is to provide a survey of where we are in our current understanding of what adrenarche is, and indeed if it is unique to humans at all. Furthermore, these reviews describe what is also known of how the functional ZR emerges during adrenarche and what steroids of physiologic relevance result beyond the widely known DHEA and DHEAS elevated at this time. Such advances in human, primate and indeed stem-cell biology are clearly laying the foundation for new directions in the hunt for the factors involved in the regulation and functional emergence of a ZR at the appropriate time, as well as insight into how they may fail. Given support for these new directions, considerable progress can clearly be made.