Endocrine-disrupting chemicals and their effects on puberty

Developmental life history transitions can be shaped by structural inequities: Insights from the sociology of race

Life history emerges as developmental processes play out over the lifespan of an organism, and the concept of life history intersects with evolutionary biology, ecology, demographics and sociology. Here, we briefly outline the interdisciplinary concept of life history, surveying some of the diversity in life history transitions across animal species, and exploring these transitions as genetically and hormonally-regulated developmental processes. We review some of the data suggesting that social structures are capable of shifting the timing of human life history transitions, with implications for lifetime health outcomes. Social and structural inequity in contemporary society tends to accelerate developmental life history processes, which can create temporal and physiological pressures that intersect with and amplify disadvantage. Focusing specifically on the experiences of Black women in the U.S., we examine the impacts of inequity on the timing of four developmental life history transitions: birth, puberty, first reproduction and menopause. We identify some of the important overlaps between developmental biology, sociology and public health, arguing that these disciplinary intersections can be introduced in many developmental biology classrooms. We propose some pedagogical frameworks designed to help students grow an awareness of how developmental processes can be affected by social inequities, with the ultimate goal of stimulating more cross-disciplinary conversations about life histories and their intersections with social structures.

Associations of area-level and individual-level sociodemographic factors with adolescent phenotypes linked to subsequent cancer risk

BACKGROUND

Indices of Concentration at the Extremes (ICEs) serve as joint proxies for social and environmental hazards for health disparities. We tested the hypothesis that ICEs at birth predict timing of menarche and adolescent overweight and investigated whether ICE associations are mediated by individual-level variables.

METHODS

In this prospective study, a subset of offspring from the Child Health and Development Studies, born 1959-1967 in Oakland, CA were assessed for early age at menarche (<12 vs. >=12) and overweight body mass index, (BMI, >25 kg/m2) at ages 15-17 years. ICEs characterizing neighborhood of birth were calculated using 1960 census tract data for race, income, education, and combined income/race. Associations between ICEs and maternal serum DDT levels were estimated using generalized linear models. Log-linear models estimated associations between ICEs with early menarche and adolescent overweight, adjusted for individual factors including race, socioeconomic status and perinatal serum DDTs and family clustering.

RESULTS

Address at birth was geocoded for 1749 (86.6 %); 42 % had overweight BMI; 15.6 % had early menarche. ICEs at birth predicted timing of menarche and adolescent overweight and were correlated with perinatal DDTs. Most ICE associations with adolescent outcomes were partly mediated by individual level socioeconomic variables, except for the income ICE association with early menarche [adjusted odds ratio: 1.6, 95 %CI:(1.0-2.6)].

CONCLUSIONS

ICEs are accessible metrics of area-level spatial and social segregation that were associated with adolescent overweight, early menarche and DDT exposure. ICEs are useful indicators of high-risk neighborhoods that can be targeted for individual and community-level prevention beginning at birth.

Endocrine-disrupting chemicals and female reproductive health: a growing concern

Female fertility and reproductive health depend on a series of developmental steps from embryogenesis through puberty, in addition to the proper functioning of the reproductive system in adulthood. Two important steps are the establishment of the ovarian reserve and development of the hypothalamic-pituitary-ovarian axis. During reproductive years, maintaining an adequate ovarian reserve of follicles as well as balanced neuroendocrine control of reproductive organs is crucial for fertility. Dysregulation of either of these events, during development or in adulthood, can lead to reproductive disorders. Over the past five decades, human fertility rates have declined, whereas the incidence of female reproductive disorders has risen, trends partially linked to environmental factors such as exposure to endocrine-disrupting chemicals (EDCs). Here we outline epidemiological and mechanistic evidence for how EDCs affect the ovarian reserve during early development, its maintenance during adulthood and the establishment of the hypothalamic-pituitary control of puberty and ovulation. Our Review not only reveals strong support for the role of EDC exposure in the development of female reproductive disorders such as abnormal puberty, impaired fertility, premature menopause or polycystic ovarian syndrome, but also highlights knowledge gaps, including the difficulty to prove causality between exposure and human disease manifestation.

Endocrine-disrupting chemicals and reproductive health: With focus on the developmental window of susceptibility

Sexual differentiation is highly dependent on the fetal hormonal environment, guiding sexual development and establishing the foundation for lifelong reproductive health. This short communication highlights critical windows of sex determination and differentiation, emphasizing the role of steroid sex hormones, alongside other factors, in orchestrating these processes in early life. Growing evidence suggests that endocrine-disrupting chemicals (EDCs) can disrupt these tightly regulated pathways, leading to developmental disturbances that manifest as reproductive disorders at birth or later in life. In males, disrupted androgen signaling during fetal development is linked to hypospadias, cryptorchidism, reduced fertility, and testicular cancer, while in females, EDC exposure may contribute to altered ovarian function, early puberty, polycystic ovary syndrome (PCOS), and infertility. By illustrating how EDCs can interfere with sexual development, this brief review underscores the need for further research and regulatory measures to mitigate their impact on human health.

Research summary, possible mechanisms and perspectives of gut microbiota changes causing precocious puberty

The increasing global incidence of precocious puberty, linked to environmental, metabolic, and genetic factors, necessitates innovative therapies beyond gonadotropin-releasing hormone (GnRH) analogs. Accumulating evidence implicates gut microbiota dysbiosis as a pivotal regulator of pubertal timing via interactions with hormone metabolism (e.g., estrogen reactivation via β-glucuronidase), neuroendocrine pathways (nitric oxide signaling), and immune-inflammatory responses. This review delineates taxonomic alterations in central precocious puberty (CPP) and obesity-related subtypes, including Streptococcus enrichment and Alistipes depletion, alongside functional shifts in microbial metabolite production. Mechanistic insights highlight microbiota-driven modulation of the hypothalamic-pituitary-gonadal (HPG) axis, leptin/insulin dynamics, and epigenetic regulation. Emerging interventions-probiotics, fecal microbiota transplantation (FMT), and dietary modifications-demonstrate efficacy in preclinical models and early clinical studies for delaying puberty onset and restoring hormonal balance. Translational efforts to validate these strategies are critical for addressing the clinical and psychosocial challenges posed by precocious puberty, positioning gut microbiota modulation as a novel therapeutic frontier in pediatric endocrinology.

Insights into pubertal development: a narrative review on the role of epigenetics

PURPOSE

Puberty is a key phase of growth and development, characterized by psychophysical transformations. It is driven by a combination of genetic, hormonal, and environmental variables. Epigenetic mechanisms, including histone post-translational modifications and chromatin remodeling, microRNAs, and DNA methylation, play important roles in orchestrating the developmental processes. We describe environmental factors that may interact with genetics, and factors influencing puberty onset, focusing in particular on epigenetic mechanisms that can help understand the timing and variations that lead to precocious or delayed puberty.

METHODS

We conducted a narrative review of associations between puberty and epigenetic mechanisms through a comprehensive search of PubMed, Scopus, and Web of Science databases.

RESULTS

The chromatin landscape of genes as KISS1 has revealed dynamic changes in histone modifications as puberty approaches, influencing the stimulation or inhibition of gene expression critical for reproductive maturation. MiRNAs regulate gene expression, whereas DNA methylation affects activation or repression of gene transcription of genes involved in pubertal timing. Moreover, studies in animal models have provided insights into the role of DNA methylation and miRNAs in brain sexual differentiation, highlighting the active involvement of epigenetic mechanisms in shaping sexually dimorphic brain structures.

CONCLUSION

This review highlights the importance of understanding the complex interplay between epigenetic regulation and pubertal development, which can lead to new therapeutic options and shed light on the fundamental processes driving reproductive maturation.

Analysis of Tanner stage in children conceived after the diagnosis of infertility: the DESCRT study

PURPOSE

Use of assisted reproductive technology (ART) could lead to abnormal pubertal development in children. We compared pubertal development in children conceived using ART to non-in vitro fertilization fertility treatment (NIFT) and unassisted (UA) conception.

METHODS

Children from the Developmental Epidemiological Study of Children through Reproductive Technology (DESCRT) were assessed for pubertal development according to the standardized protocol. Tanner staging (breast, testes, and pubic hair development) was compared between ART, NIFT, and UA-conceived children. Differences were analyzed using Wilcoxon rank-sum test, Pearson's chi-squared test, and Fisher's exact test. Multivariable logistic regression was used to assess association between method of conception and pubertal development.

RESULTS

The sample included 290 children (164 boys and 126 girls) at median age 6 years (range 4 to 18 years); 229 were conceived using ART compared to a combined reference group of 29 conceived via NIFT and 32 via UA. Statistical analyses adjusted for children's age, height, and weight showed statistically non-significant trends wherein boys conceived via ART tended to be in later Tanner stages for pubarche (OR = 2.33, 95% CI 0.44-12.21) and gonadarche (OR = 4.27, 95% CI 0.44-41.99), and girls tended to be in later stages for pubarche (OR = 4.29, 95% CI 0.40-45.62) and thelarche (OR = 2.23, 95% CI 0.35-14.03) compared to the reference group.

CONCLUSION

As ART becomes more widespread, developmental concerns become increasingly prominent. While results were statistically non-significant, we observed a trend toward differences in pubertal development between ART-conceived children and those conceived without assistance or NIFT.

[Research progress on glycolipid metabolism of Sertoli cell in the development of spermatogenic cell]

Sertoli cells play an important role in the process of spermatogenesis, and the abnormalities in spermatogenesis are closely related to disruptions in glycolipid metabolism. The metabolic environment of Sertoli cells is hypoxic, with glycolysis and fatty acid β-oxidation being the primary metabolic pathways. In Sertoli cells, glycolysis produces lactate to provide energy for spermatogenic cells, while fatty acid β-oxidation generates ATP. Currently, the relationship between glycolipid metabolism in Sertoli cells and spermatogenic cell development, as well as the interplay between glucose and lipid metabolism remain unclear. Various hormones, including sex hormones, can affect glucose metabolism in Sertoli cells by endocrine regulation. The activation or inhibition of signaling pathways such as AMPK, mTOR, and Akt can alter the expression levels of glycolysis-related transporter genes and the synthesis of fatty acids, thereby affecting glycolipid metabolism in Sertoli cells. Some transcription factors such as PPARγ can regulate downstream fatty acid metabolism-related genes by directly binding to their response elements and promoting the oxidation of fatty acids in Sertoli cells. In this article we elaborate on the key factors influencing glycolipid metabolism in Sertoli cells and their interconnections, as well as their potential clinical implications, offering new insights for precisely targeted treatments of male infertility.

A Leptin Receptor Mutation Which Impairs Fertility in Ewes Causes Delayed Puberty in Male and Female Mice

Reproductive function is tightly linked to nutritional status due to its high energetic demands. Leptin, a key adipose tissue-derived hormone signalling energy reserves to the brain, integrates metabolic status with the hypothalamic-pituitary-gonadal axis to ensure reproductive function is maintained or suppressed appropriately. Mutations in leptin or its receptor (LepR) are known to cause infertility and obesity in mice. In Davisdale ewes, 2 naturally occurring LepR mutations (R62C and P1019S) were associated with delayed puberty and subfertility, but their effects in males or in other species remain to be determined. This study examined the impact of analogous LepR mutations (A63C and P1018S) in mice using CRISPR-Cas9 gene editing. Puberty onset, adult fertility, and metabolic phenotypes were assessed in wild-type, heterozygous, and homozygous mutant mice. The A63C mutation, located in the extracellular domain of the receptor, resulted in increased body weight and adiposity in females, along with delays in puberty onset in both sexes. Despite these delays, adult reproductive function was maintained. Immunohistochemical analysis revealed no detectable reductions in leptin-induced pSTAT3, pERK1/2, or pmTOR signalling in the hypothalamic arcuate nucleus in either mutant line, indicating these pathways remain largely intact. These findings demonstrate the conserved importance of this region of the leptin receptor for puberty onset and adiposity across species, but also the resilience of leptin signalling in preserving reproductive function despite genetic variation.

Monosome Stalls the Translation Process Mediated by IGF2BP in Arcuate Nucleus for Puberty Onset Delay

Puberty onset through hypothalamic-pituitary-gonad (HPG) axis as an important reproductive event in postnatal development is initiated from hypothalamic arcuate nucleus (ARC). The growing evidence indicates that translational control also plays an essential role in the final expression of gonadotropin genes. To investigate the role of protein translation and behavior of ribosomes in pubertal onset, the global profiles of transcriptome, single ribosome (monosome), polysome, and tandem mass tag proteome were comprehensively investigated in rat hypothalamic ARCs of different pubertal stages using RNA sequencing, polyribo sequencing, and mass spectrum. Transcriptome-wide enrichments of N6-methyladenosine and IGF2BP2 were investigated using meRIP and RIP sequencing. Monosome was robustly enriched on a large proportion of mRNA in early puberty rats (postnatal day (PND)-25) compared to late puberty (PND-35 and PND-45). Monosome-enriched mRNAs, including HPG axis-related genes, had a large number of upstream ORFs (uORF, < 100 nt) and displayed translational repression in early puberty. Furthermore, insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) could particularly interact with and facilitate monosome to bind with mRNA in early puberty. Finally, ectopic over-expression of IGF2BP2 in hypothalamic ARC via lateral ventricle injection in vivo could recruit monosome to aggregate on mRNA and delay puberty onset. We uncovered a novel regulatory mechanism of IGF2BP2 and monosome for translational control in puberty onset, which shed light on the neuroendocrine regulatory network involved in HPG axis activation.

Long-Term Exposure to Fine Particulate Matter (PM2.5) Components and Precocious Puberty Among School-Aged Children: Cross-Sectional Study

Background

The increasing incidence of precocious puberty is a major health challenge for Chinese children, while related risk factors remain less well explored. Exposure to ambient fine particulate matter (PM2.5) is a leading environmental hazard in China. Although certain components of PM2.5 have been reported to be endocrine disruptors for sex hormones, population-based evidence is still lacking on the association between PM2.5 exposure and precocious puberty in China.

Objective

Based on a cross-sectional survey covering 30 cities in 2017 to 2019, this study was designed to explore the association between long-term exposure to PM2.5 and its 5 major components with precocious puberty in China and to check the potential modifying effects of family-related and personal factors.

Methods

We included 34,105 children aged 6 to 9 years. We collected the 5-year average concentrations of PM2.5 and its 5 major components (sulfate, nitrate, ammonium, organic matter, and black carbon) in the area (at a spatial resolution of 0.1° × 0.1°) where each school was located. We used mixed effect logistic regression to estimate the effect sizes of the total mass of PM2.5 and each of its components on precocious puberty, and we examined the modifying effects of family-related and personal factors using an additional interactive term. A weighted quantile sum (WQS) regression model was applied to identify the weights of each component in explaining the effect size of the total mass of PM2.5.

Results

We found that the odds ratio (OR) for precocious puberty per IQR increase in the concentration of total PM2.5 mass was 1.27 (95% CI 0.92-1.75) for the whole population, 2.12 (95% CI 1.27-3.55) for girls, and 0.90 (95% CI 0.62-1.30) for boys. Similarly, the effect sizes of the 5 major components were all substantial for girls but minimal for boys. Results of the WQS analysis showed that organic matter could explain the highest proportion of the effect of PM2.5, with the weight of its contribution being 0.71. Modification effects of family income and dietary habits were only observed in certain population subgroups.

Conclusions

Long-term exposure to total PM2.5 mass was significantly associated with precocious puberty in girls, with organic matter identified as the major effect contributor. The results add evidence on the detrimental effects of PM2.5 on children's development and growth.

Potential Role of Sleep Disturbance in the Development of Early Puberty: Past Clinical Evidence for Future Management

The incidence of early puberty in children has been increasing. It has been suspected that both genetic and various environmental factors such as nutrition and hormonal exposure could influence the mechanisms underlying the earlier onset of puberty. Interestingly, several previous studies have reported a strong connection between sleep and puberty. Specifically, it was discovered that luteinizing hormone (LH), a potential marker for the onset of puberty, was increased during the deep sleep period. Furthermore, a high prevalence of early puberty was observed in patients with sleep disorders, especially in those experiencing narcolepsy. In this review article, findings related to the association between sleep disturbance and early puberty have been comprehensively summarized. Any contrary findings are also included and discussed. Advances in the knowledge surrounding sleep disturbance have led to a greater understanding of a correlation between early puberty and sleep disorder and provide alternative therapeutic options for the treatment of central precocious puberty in the future.

Emerging Trend of Central Precocious Puberty: A Retrospective Study of Cases Diagnosed Before and During the COVID-19 Pandemic in a Portuguese Tertiary-Level Hospital

INTRODUCTION

In light of the recent evidence suggesting an increase in idiopathic central precocious puberty (ICPP) during the COVID-19 pandemic, this study aimed to assess the incidence of newly diagnosed ICPP cases and compare differences in demographic, anthropometric, and clinical characteristics pre-pandemic and during the pandemic.

METHODS

We conducted a retrospective study at a national reference pediatric endocrinology unit in Portugal to evaluate the proportion of referrals for precocious puberty (PP) and, within this group, the number of ICPP cases diagnosed before (group 1: January 2018 to March 2020) and during the pandemic (group 2: April 2020 to June 2022). Additionally, we compared the demographic, anthropometric, and clinical characteristics of ICPP patients between the two groups.

RESULTS

Out of 258 patients referred for PP, 20 were diagnosed with ICPP (19 girls and one boy). Sixteen cases were diagnosed during the pandemic, marking a significant increase (16 vs. 4, p = 0.023), especially among girls. Additionally, thelarche onset occurred earlier during the pandemic (6.9 vs. 7.3, decimal age (DA) in years, p = 0.035). Despite pandemic challenges, a prompt medical response was observed, with a shorter time from first visit to treatment (DA at the onset of treatment - DA at first visit: 0.19 vs. 0.79 years; p = 0.015). No other parameters showed significant differences. Referrals for PP during the pandemic were not significantly higher than pre-pandemic (144 of 904 vs. 114 of 758, p > 0.05).

CONCLUSION

This study revealed a significant four-fold increase in the diagnosis of ICPP during the pandemic, particularly among girls. Furthermore, in the pandemic group, thelarche onset was earlier, raising the question of whether increased parental presence at home contributed to heightened awareness of pubertal changes. Despite the challenges posed by the pandemic in terms of referrals and follow-up, these results point to efficient work that led to prompt treatment initiation without delays, unlike in other pathologies, as mainly observed in adults. Surprisingly, no significant increase in body mass index was observed, suggesting that other factors may be involved. To substantiate these findings and uncover additional potential contributing factors for the development of ICPP, a more extensive research effort is warranted.

PFAS Levels, Early Life Factors, and Mammographic Breast Density in Premenopausal Women

BACKGROUND

Mammographic breast density (MBD) is a strong risk factor and an intermediate phenotype for breast cancer, yet there are limited studies on how environmental pollutants are associated with MBD.

OBJECTIVE

We investigated associations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonate (PFHxS) levels with measures of MBD and evaluated if early life factors modified any associations.

METHODS

Metabolon performed metabolomics analysis using ultrahigh-performance liquid chromatography/tandem accurate mass spectrometry in fasting blood from 705 premenopausal women completing their annual screening mammogram in St. Louis, Missouri. We calculated least square means (LSM) of mammographic volumetric percent density (VPD), dense volume (DV), and nondense volume (NDV) by quartiles (Q) of PFOS, PFOA, and PFHxS from multivariable linear regression modeling overall and stratified by recruitment period, race, age at menarche, and body shape at age 10. Models were adjusted for age, age at menarche, body fat percentage, race, family history of breast cancer, oral contraceptive use, alcohol consumption, parity/age at first birth, and body shape at age 10.

RESULTS

PFOS, PFOA, and PFHxS were not significantly associated with VPD or NDV. PFHxS was significantly positively associated with DV (Q 1 = 67.64   cm 3 , Q 2 = 69.91   cm 3 , Q 3 = 69.06   cm 3 , Q 4 = 75.79   cm 3 ; p -trend = 0.03 ). PFOS was positively associated with DV (Q 1 = 65.45   cm 3 , Q 2 = 70.74   cm 3 , Q 3 = 73.31   cm 3 , Q 4 = 73.52   cm 3 ; p -trend = 0.06 ) with DV being 8.1%, 12%, and 12.3% higher in Q2, Q3, and Q4 compared to Q1. Among women who were underweight/normal weight at age 10, PFOS was positively associated with VPD (Q 1 = 9.02 % , Q 2 = 9.11 % , Q 3 = 9.48 % , Q 4 = 9.92 % ; p -trend = 0.04 ) while there was an inverse association among women who were overweight/obese at age 10 (Q 1 = 7.46 % , Q 2 = 6.94 % , Q 3 = 6.78 % , Q 4 = 5.47 % ; p -trend = 0.005 ) (p -interaction = 0.04 ).

DISCUSSION

We report novel associations of PFHxS and PFOS with DV in premenopausal women. PFOS, PFOA, and PFHxS were not associated with VPD and NDV. In addition, body shape at age 10 may modify the associations of PFOS with MBD. Further studies are needed to validate our findings and to evaluate the associations of other per- and polyfluoroalkyl substances (PFAS), as well as mixtures of PFAS, with MBD. https://doi.org/10.1289/EHP14065.

Bisphenol A Disrupts Ribosome Function during Ovarian Development of Mice

This study examines the impact of Bisphenol A (BPA), a prevalent environmental estrogenic toxicant, on the ovarian development of mice. Mice were exposed to varying BPA doses from in utero to postnatal stages, up to weaning (day 21, PND 21) and puberty (day 45, PND 45). The BPA content in the serum of the offspring mice on PND 45 was higher than that of the mice sacrificed at PND 21. However, the ovary organ index of the mice of PND 21 was significantly increased, and the ovarian structure was damaged when exposed to BPA. In contrast, the mice with PND 45 did not show apparent ovarian lesions. On the other hand, granulosa cell apoptosis was detected in both PND 21 and PND 45 mice ovaries, and ERβ was increased under the influence of BPA. Transcriptomic analysis revealed BPA's significant impact on ribosomal gene expression, marked downregulation of Rpl21 and Rpsa, and upregulation of Rps2 in both age groups. These transcriptomic alterations were further corroborated by real-time PCR, highlighting a dose-dependent effect of BPA on Rps2. Our findings confirm BPA's detrimental effects on ovarian health, with more pronounced damage in younger mice, suggesting heightened vulnerability in this group. The study underscores ribosomes as critical targets in BPA-induced ovarian developmental disruptions.

Association of prenatal exposure to phthalates and synthetic phenols with pubertal development in three European cohorts

BACKGROUND

There is limited epidemiological evidence on the association of prenatal exposure to phthalates and synthetic phenols with altered pubertal timing.

OBJECTIVE

To examine the association of prenatal exposure to phthalates, bisphenol A (BPA), parabens, benzophenone 3 (BP-3), and triclosan (TCS) with pubertal development in girls and boys from three European cohorts.

METHODS

Urinary metabolites of six different phthalate diesters (DEP, DiBP, DnBP, BBzP, DEHP, and DiNP), BPA, methyl- (MePB), ethyl- (EtPB), propyl- (PrPB), and butyl-paraben (BuPB), BP-3, and TCS were quantified in one or two (1st and 3rd trimester) urine samples collected during pregnancy (1999-2008) from mothers in three birth cohorts: INMA (Spain), EDEN (France), and MoBa (Norway). Pubertal development of their children was assessed at a single visit at age 7-12 years (579 girls, 644 boys) using the parent-reported Pubertal Development Scale (PDS). Mixed-effect Poisson and g-computation and Bayesian Kernel Machine Regression (BKMR) were employed to examine associations of individual and combined prenatal chemical exposure, respectively, with the probability of overall pubertal onset, adrenarche, and gonadarche (stage 2+) in girls and boys. Effect modification by child body mass index (BMI) was also assessed.

RESULTS

Maternal concentrations of the molar sum of DEHP and of DiNP metabolites were associated with a slightly higher probability of having started puberty in boys (relative risk, RR [95% CI] = 1.13 [0.98-1.30] and 1.20 [1.06-1.34], respectively, for a two-fold increase in concentrations), with a stronger association for DiNP in boys with overweight or obesity. In contrast, BPA, BuPB, EtPB, and PrPB were associated with a lower probability of pubertal onset, adrenarche, and/or gonadarche in all boys (e.g. overall puberty, BPA: RR [95% CI] = 0.93 [0.85-1.01] and BuPB: 0.95 [0.90-1.00], respectively), and the association with BPA was stronger in boys with underweight/normal weight. In girls, MEHP and BPA were associated with delayed gonadarche in those with underweight/normal weight (RR [95% CI] = 0.86 [0.77-0.95] and 0.90 [0.84-0.97], respectively). Most of these associations were trimester specific. However, the chemical mixture was not associated with any pubertal outcome in boys or girls.

CONCLUSIONS

Prenatal exposure to certain phthalates and synthetic phenols such as BPA may impact the pubertal development of boys, and weight status may modify this effect. BPA may also alter the pubertal development of girls.

The impact of environmental factors and contaminants on thyroid function and disease from fetal to adult life: current evidence and future directions

The thyroid gland regulates most of the physiological processes. Environmental factors, including climate change, pollution, nutritional changes, and exposure to chemicals, have been recognized to impact thyroid function and health. Thyroid disorders and cancer have increased in the last decade, the latter increasing by 1.1% annually, suggesting that environmental contaminants must play a role. This narrative review explores current knowledge on the relationships among environmental factors and thyroid gland anatomy and function, reporting recent data, mechanisms, and gaps through which environmental factors act. Global warming changes thyroid function, and living in both iodine-poor areas and volcanic regions can represent a threat to thyroid function and can favor cancers because of low iodine intake and exposure to heavy metals and radon. Areas with high nitrate and nitrite concentrations in water and soil also negatively affect thyroid function. Air pollution, particularly particulate matter in outdoor air, can worsen thyroid function and can be carcinogenic. Environmental exposure to endocrine-disrupting chemicals can alter thyroid function in many ways, as some chemicals can mimic and/or disrupt thyroid hormone synthesis, release, and action on target tissues, such as bisphenols, phthalates, perchlorate, and per- and poly-fluoroalkyl substances. When discussing diet and nutrition, there is recent evidence of microbiome-associated changes, and an elevated consumption of animal fat would be associated with an increased production of thyroid autoantibodies. There is some evidence of negative effects of microplastics. Finally, infectious diseases can significantly affect thyroid function; recently, lessons have been learned from the SARS-CoV-2 pandemic. Understanding how environmental factors and contaminants influence thyroid function is crucial for developing preventive strategies and policies to guarantee appropriate development and healthy metabolism in the new generations and for preventing thyroid disease and cancer in adults and the elderly. However, there are many gaps in understanding that warrant further research.

Frequency of perfume in 398 children's cosmetics

OBJECTIVE

Perfume (Parfum) or fragrance is a natural or synthetic cosmetic ingredient added to emit a pleasant aroma or to improve the odor of a cosmetic formula. It is a mixture of substances, not revealed by the manufacturer, which may contain ingredients with allergenic potential, endocrine disruptors, and other possible harmful effects on human health. This study aims to analyze children's cosmetics labels to assess the presence of Perfume.

METHODS

The researchers randomly visited points of sale in Curitiba, the capital of a southern Brazilian state; in order to catalog the largest possible number of children's cosmetics items.

RESULTS

398 children's cosmetics were analyzed and found Parfum on 295 (74.1 %) of the labels, including 90.4 and 79,1 % of the shampoos and wet wipes, respectively.

CONCLUSION

Exposure of children's skin to fragrances can lead to local side effects such as allergies, but also to systemic effects, and the lack of knowledge of the general population and health professionals about its possible deleterious effects emphasizes the importance of changes in the regulation of cosmetics aiming to reduce the use of this ingredient.

Enhanced identification of endocrine disruptors through integration of science-based regulatory practices and innovative methodologies: The MERLON Project

The prevalence of hormone-related health issues caused by exposure to endocrine disrupting chemicals (EDCs) is a significant, and increasing, societal challenge. Declining fertility rates together with rising incidence rates of reproductive disorders and other endocrine-related diseases underscores the urgency in taking more action. Addressing the growing threat of EDCs in our environment demands robust and reliable test methods to assess a broad variety of endpoints relevant for endocrine disruption. EDCs also require effective regulatory frameworks, especially as the current move towards greater reliance on non-animal methods in chemical testing puts to test the current paradigm for EDC identification, which requires that an adverse effect is observed in an intact organism. Although great advances have been made in the field of predictive toxicology, disruption to the endocrine system and subsequent adverse health effects may prove particularly difficult to predict without traditional animal models. The MERLON project seeks to expedite progress by integrating multispecies molecular research, new approach methodologies (NAMs), human clinical epidemiology, and systems biology to furnish mechanistic insights and explore ways forward for NAM-based identification of EDCs. The focus is on sexual development and function, from foetal sex differentiation of the reproductive system through mini-puberty and puberty to sexual maturity. The project aims are geared towards closing existing knowledge gaps in understanding the effects of EDCs on human health to ultimately support effective regulation of EDCs in the European Union and beyond.

Time-varying associations of gestational and childhood triclosan with pubertal and adrenarchal outcomes in early adolescence

Background

Triclosan is an endocrine-disrupting chemical, but associations with pubertal outcomes remain unclear. We examined associations of gestational and childhood triclosan with adolescent hormone concentrations and pubertal stage.

Methods

We quantified urinary triclosan concentrations twice during pregnancy and seven times between birth and 12 years in participants recruited from Cincinnati, OH (2003-2006). We averaged concentrations across pregnancy and childhood and separately considered individual exposure periods in multiple informant models. At 12 years, we measured serum hormone concentrations (males [n = 72] and females [n = 84]-dehydroepiandrosterone-sulfate, luteinizing hormone, follicle-stimulating hormone; males-testosterone; females-estradiol). Also at age 12 years, participants self-reported physical development and menarchal timing. We estimated associations (95% confidence interval) of triclosan with hormone concentrations, more advanced physical development, and age at menarche.

Results

For females, each doubling of childhood triclosan was associated with 16% lower estradiol concentrations (-29%, 0%), with stronger associations for measures closer to adolescence. We found suggestive evidence that higher triclosan at any age was associated with ~10% (for gestational triclosan: -18%, -2%) lower follicle-stimulating hormone concentrations among males and early postnatal (1-3 years) triclosan was associated with 63% (5%, 96%) lower odds of advanced pubic hair development in females. In multiple informant models, each doubling of gestational triclosan concentrations was associated with 5% (0%, 9%) earlier age at menarche, equivalent to 5.5 months.

Conclusion

Gestational and childhood triclosan concentrations were related to some pubertal outcomes including hormone concentrations and age at menarche. Our findings highlight the relevance of elucidating potential sex-specific and time-dependent actions of triclosan.

Experience-dependent neurodevelopment of self-regulation in adolescence

Adolescence is a period of rapid biobehavioral change, characterized in part by increased neural maturation and sensitivity to one's environment. In this review, we aim to demonstrate that self-regulation skills are tuned by adolescents' social, cultural, and socioeconomic contexts. We discuss adjacent literatures that demonstrate the importance of experience-dependent learning for adolescent development: environmental contextual influences and training paradigms that aim to improve regulation skills. We first highlight changes in prominent limbic and cortical regions-like the amygdala and medial prefrontal cortex-as well as structural and functional connectivity between these areas that are associated with adolescents' regulation skills. Next, we consider how puberty, the hallmark developmental milestone in adolescence, helps instantiate these biobehavioral adaptations. We then survey the existing literature demonstrating the ways in which cultural, socioeconomic, and interpersonal contexts drive behavioral and neural adaptation for self-regulation. Finally, we highlight promising results from regulation training paradigms that suggest training may be especially efficacious for adolescent samples. In our conclusion, we highlight some exciting frontiers in human self-regulation research as well as recommendations for improving the methodological implementation of developmental neuroimaging studies and training paradigms.

Endocrine Disruptors and Metabolic Changes: Impact on Puberty Control

OBJECTIVE

This study aims to explore the significant impact of environmental chemicals on disease development, focusing on their role in developing metabolic and endocrine diseases. The objective is to understand how these chemicals contribute to the increasing prevalence of precocious puberty, considering various factors, including epigenetic changes, lifestyle, and emotional disturbances.

METHODS

The study employs a comprehensive review of descriptive observational studies in both human and animal models to identify a degree of causality between exposure to environmental chemicals and disease development, specifically focusing on endocrine disruption. Due to ethical constraints, direct causation studies in human subjects are not feasible; therefore, the research relies on accumulated observational data.

RESULTS

Puberty is a crucial life period with marked physiological and psychological changes. The age at which sexual characteristics develop is changing in many regions. The findings indicate a correlation between exposure to endocrine-disrupting chemicals and the early onset of puberty. These chemicals have been shown to interfere with normal hormonal processes, particularly during critical developmental stages such as adolescence. The research also highlights the interaction of these chemical exposures with other factors, including nutritional history, social and lifestyle changes, and emotional stress, which together contribute to the prevalence of precocious puberty.

CONCLUSION

Environmental chemicals significantly contribute to the development of certain metabolic and endocrine diseases, particularly in the rising incidence of precocious puberty. Although the evidence is mainly observational, it adequately justifies regulatory actions to reduce exposure risks. Furthermore, these findings highlight the urgent need for more research on the epigenetic effects of these chemicals and their wider impact on human health, especially during vital developmental periods.

Long-term exposure to ambient PM2.5 and its components on menarche timing among Chinese adolescents: evidence from a representative nationwide cohort

BACKGROUND

Ambient air pollutants have been suggested to affect pubertal development. Nevertheless, current studies indicate inconsistent effects of these pollutants, causing precocious or delayed puberty onset. This study aimed to explore the associations between long-term exposure to particulate matter with aerodynamic diameters ≤ 2.5 μm (PM2.5) along with its components and menarche timing among Chinese girls.

METHOD

Self-reported age at menarche was collected among 855 girls from China Health and Nutrition Survey 2004 to 2015. The pre-menarche annual average concentrations of PM2.5 and its components were calculated on the basis of a long-term (2000-2014) high-resolution PM2.5 components dataset. Generalized linear models (GLM) and logistic regression models were used to analyze the associations of exposure to a single pollutant (PM2.5, sulfate, nitrate, ammonium, black carbon and organic matter) with age at menarche and early menarche (< 12 years), respectively. Weighted quantile sum methods were applied to examine the impacts of joint exposure on menarche timing.

RESULTS

In the adjusted GLM, per 1 µg/m3 increase of annual average concentrations of nitrate and ammonium decreased age at menarche by 0.098 years and 0.127 years, respectively (all P < 0.05). Every 1 µg/m3 increase of annual average concentrations of PM2.5 (OR: 1.04, 95% CI: 1.00-1.08), sulfate (OR: 1.23, 95% CI: 1.01-1.50), nitrate (OR: 1.23, 95% CI: 1.06-1.43) and ammonium (OR: 1.32, 95% CI: 1.06-1.66) were significantly positively associated with early menarche. Higher level of joint exposure to PM2.5 and its components was associated with 11% higher odds of early menarche (P = 0.04). Additionally, the estimated weight of sulfate was the largest among the mixed pollutants.

CONCLUSIONS

Long-term exposure to PM2.5 and its components could increase the risk of early menarche among Chinese girls. Moreover, sulfate might be the most critical components responsible for this relationship. Our study provides foundation for targeted prevention of PM2.5 components.

Multi-omic analysis of precocious puberty girls: pathway changes and metabolite validation

Objective

Precocious puberty (PP) is a prevalent endocrine disorder affecting the physical and mental wellbeing of children. Identifying the triggering factors of PP has become a central issue. This study seeks to investigate the metabolomic and transcriptomic alterations in PP.

Material and methods

First, 37 school-aged girls diagnosed with PP and 25 age-matched prepubertal control girls were recruited, and the fecal samples were collected for non-targeted metabolomic analysis to screen for differentially expressed metabolites (DEMs). Subsequently, an animal model of PP was constructed by danazol administration to neonatal female rats, and both fecal non-targeted metabolomics and serum next-generation transcriptomic sequencing were performed to screen DEMs and differentially expressed genes (DEGs) in PP. Moreover, the DEM co-existing in clinical and animal models was administrated to PP rats to explore the role of the target metabolite in PP.

Results

A total of 24 DEMs in PP clinical samples and 180 DEMs and 425 DEGs in PP animal samples were identified. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these DEMs and DEGs were enriched in disease-associated pathways, including fatty acid synthesis, glycerolipid metabolism, pyrimidine metabolism, steroid hormone biosynthesis, progesterone-mediated oocyte maturation, and gonadotropin-releasing hormone (GnRH) signaling pathway, forming a tight DEM-DEG pathway regulatory network. Further DEM validation demonstrated that thymine supplementation delayed the opening of the vagina and development of PP in model rats.

Conclusion

This study reveals that the metabolomic and transcriptomic changes, along with enriched pathways, are implicated in PP based on clinical and animal analyses. The findings may provide new strategies and research avenues for PP treatment.

Effects of the COVID-19 pandemic on the incidence of central precocious puberty; a narrative review

Central precocious puberty (CPP) is the premature activation of the hypothalamus-pituitary-gonadal axis, resulting in the early development of secondary sexual characteristics. CPP classically occurs before the age of 8 years in girls and 9 years in boys. The aetiology of this precocious onset of puberty is governed by complex mechanistic interactions between genetic and environmental factors. The rates of CPP have been documented to have been rising before the COVID-19 pandemic; despite this, the incidence of CPP has increased exponentially since the start of the pandemic. There are multiple theories potentially explaining this change in incidence of CPP over COVID-19. These include the direct effect of SARS-coV-2 infection, increasing body mass index of adolescents over sequential lockdowns, changes in sleep patterns, increased use of electronic devices and levels of stress, and additionally potential earlier detection of signs of CPP by parents and carers. Whilst there is evidence from observational cohorts, case studies and animal models for each of these factors, it is difficult to definitively prove which has had the greatest impact due to the mainly retrospective nature of the human research that has been conducted. Moreover, studies set in diverse settings with varying population make comparison complex. Additionally, each country responded differently to the COVID-19 pandemic and the lockdowns varied between locations, hence the effect of lockdown was not equal or universal. Despite this, similar trends have been identified, with various lifestyle changes that occurred over the pandemic being potentially influential factors on the development of CPP.

A novel ERβ high throughput microscopy platform for testing endocrine disrupting chemicals

In this study we present an inducible biosensor model for the Estrogen Receptor Beta (ERβ), GFP-ERβ:PRL-HeLa, a single-cell-based high throughput (HT) in vitro assay that allows direct visualization and measurement of GFP-tagged ERβ binding to ER-specific DNA response elements (EREs), ERβ-induced chromatin remodeling, and monitor transcriptional alterations via mRNA fluorescence in situ hybridization for a prolactin (PRL)-dsRED2 reporter gene. The model was used to accurately (Z' = 0.58-0.8) differentiate ERβ-selective ligands from ERα ligands when treated with a panel of selective agonists and antagonists. Next, we tested an Environmental Protection Agency (EPA)-provided set of 45 estrogenic reference chemicals with known ERα in vivo activity and identified several that activated ERβ as well, with varying sensitivity, including a subset that is completely novel. We then used an orthogonal ERE-containing transgenic zebrafish (ZF) model to cross validate ERβ and ERα selective activities at the organism level. Using this environmentally relevant ZF assay, some compounds were confirmed to have ERβ activity, validating the GFP-ERβ:PRL-HeLa assay as a screening tool for potential ERβ active endocrine disruptors (EDCs). These data demonstrate the value of sensitive multiplex mechanistic data gathered by the GFP-ERβ:PRL-HeLa assay coupled with an orthogonal zebrafish model to rapidly identify environmentally relevant ERβ EDCs and improve upon currently available screening tools for this understudied nuclear receptor.

The Role of Endocrine Disruptors Bisphenols and Phthalates in Obesity: Current Evidence, Perspectives and Controversies

Excess body weight constitutes one of the major health challenges for societies and healthcare systems worldwide. Besides the type of diet, calorie intake and the lack of physical exercise, recent data have highlighted a possible association between endocrine-disrupting chemicals (EDCs), such as bisphenol A, phthalates and their analogs, and obesity. EDCs represent a heterogeneous group of chemicals that may influence the hormonal regulation of body mass and adipose tissue morphology. Based on the available data from mechanistic, animal and epidemiological studies including meta-analyses, the weight of evidence points towards the contribution of EDCs to the development of obesity, associated disorders and obesity-related adipose tissue dysfunction by (1) impacting adipogenesis; (2) modulating epigenetic pathways during development, enhancing susceptibility to obesity; (3) influencing neuroendocrine signals responsible for appetite and satiety; (4) promoting a proinflammatory milieu in adipose tissue and inducing a state of chronic subclinical inflammation; (5) dysregulating gut microbiome and immune homeostasis; and (6) inducing dysfunction in thermogenic adipose tissue. Critical periods of exposure to obesogenic EDCs are the prenatal, neonatal, pubertal and reproductive periods. Interestingly, EDCs even at low doses may promote epigenetic transgenerational inheritance of adult obesity in subsequent generations. The aim of this review is to summarize the available evidence on the role of obesogenic EDCs, specifically BPA and phthalate plasticizers, in the development of obesity, taking into account in vitro, animal and epidemiologic studies; discuss mechanisms linking EDCs to obesity; analyze the effects of EDCs on obesity in critical chronic periods of exposure; and present interesting perspectives, challenges and preventive measures in this research area.

Zinc oxide nanoparticles-induced testis damage at single-cell resolution: Depletion of spermatogonia reservoir and disorder of Sertoli cell homeostasis

The widespread application of zinc oxide nanoparticles (ZnO NPs) in our daily life has initiated an enhanced awareness of their biosafety concern. An incredible boom of evidence of organismal disorder has accumulated for ZnO NPs, yet there has been no relevant study at the single-cell level. Here, we profiled > 28,000 single-cell transcriptomes and assayed > 25,000 genes in testicular tissues from two healthy Sprague Dawley (SD) rats and two SD rats orally exposed to ZnO NPs. We identified 10 cell types in the rat testis. ZnO NPs had more deleterious effects on spermatogonia, Sertoli cells, and macrophages than on the other cell types. Cell-cell communication analysis indicated a sharp decrease of interaction intensity for all cell types except macrophages in the ZnO NPs group than in the control group. Interestingly, two distinct maturation states of spermatogonia were detected during pseudotime analysis, and ZnO NPs induced reservoir exhaustion of undifferentiated spermatogonia. Mechanically, ZnO NPs triggered fatty acid accumulation in GC-1 cells through protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling and peroxisome proliferator-activated receptor alpha (PPARα)/acyl-CoA oxidase 1 (Acox1) axis, contributing to cell apoptosis. In terms of Sertoli cells, downregulated genes were highly enriched for tight junction. In vitro and in vivo experiments verified that ZnO NPs disrupted blood-testis barrier formation and growth factors synthesis, which subsequently inhibited the proliferation and induced the apoptosis of spermatogonia. As for the macrophages, ZnO NPs activated oxidative stress of Raw264.7 cells through nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway and promoted cell apoptosis through extracellular signal-regulated kinase (ERK) 1/2 pathway. Collectively, our work reveals the cell type-specific and cellularly heterogenetic mechanism of ZnO NPs-induced testis damage and paves the path for identifying putative biomarkers and therapeutics against this disorder.

PFAS and Phthalate/DINCH Exposure in Association with Age at Menarche in Teenagers of the HBM4EU Aligned Studies

Early puberty has been found to be associated with adverse health outcomes such as metabolic and cardiovascular diseases and hormone-dependent cancers. The decrease in age at menarche observed during the past decades has been linked to an increased exposure to endocrine-disrupting compounds (EDCs). Evidence for the association between PFAS and phthalate exposure and menarche onset, however, is inconsistent. We studied the association between PFAS and phthalate/DINCH exposure and age at menarche using data of 514 teenagers (12 to 18 years) from four aligned studies of the Human Biomonitoring for Europe initiative (HBM4EU): Riksmaten Adolescents 2016-2017 (Sweden), PCB cohort (follow-up; Slovakia), GerES V-sub (Germany), and FLEHS IV (Belgium). PFAS concentrations were measured in blood, and phthalate/DINCH concentrations in urine. We assessed the role of each individual pollutant within the context of the others, by using different multi-pollutant approaches, adjusting for age, age- and sex-standardized body mass index z-score and household educational level. Exposure to di(2-ethylhexyl) phthalate (DEHP), especially mono(2-ethyl-5-hydroxyhexyl) phthalate (5OH-MEHP), was associated with an earlier age at menarche, with estimates per interquartile fold change in 5OH-MEHP ranging from -0.34 to -0.12 years in the different models. Findings from this study indicated associations between age at menarche and some specific EDCs at concentrations detected in the general European population, but due to the study design (menarche onset preceded the chemical measurements), caution is needed in the interpretation of causality.

Approach to the Patient: Central Precocious Puberty

Central precocious puberty (CPP) classically refers to premature activation of the hypothalamic-pituitary-gonadal axis with onset of sexual development before the age of 8 years in girls and 9 years in boys. A decrease in the age of thelarche has been reported over the past several decades; however, the tempo of pubertal progression can be slower and adult height may not be adversely affected in many of the girls who experience thelarche at 6-8 years. Outside of this secular trend in the development itself, the past several decades have also brought about advances in diagnosis and management. This includes the widespread use of an ultrasensitive luteinizing hormone assay, decreasing the need for stimulation testing and a better understanding of the genetics that govern the onset of puberty. Additionally, management of CPP using gonadotropin-releasing hormone analogs (GnRHas) has changed with the advent of new longer-acting formulations. Emerging long-term outcomes of GnRHa administration with regards to obesity, cardiovascular risk factors and fertility are reassuring. Despite these advancements, clinical care in CPP is hampered by the lack of well-designed controlled studies, and management decisions are frequently not supported by clear practice guidelines. Data in boys with CPP are limited and this article focuses on the diagnosis and management of CPP in girls, particularly, in those who present with thelarche at the age of 6-8 years.

Is blue light exposure a cause of precocious puberty in male rats?

Purpose

Our study aimed to examine the effects of blue light exposure on prepubertal male rats' puberty and testis tissue.

Methods

Eighteen 21-day-old male Sprague Dawley rats were divided into three groups consisting of six rats in each group: Control Group (CG), Blue Light-6 hours (BL-6), and Blue Light-12 hours (BL-12). CG rats were maintained with 12/12-hour light-dark cycles. The rats of BL-6 and BL-12 were exposed to blue light (450-470nm/irradiance level 0.03uW/cm2) for 6 hours and 12 hours, respectively. Rats were exposed to blue light until the first signs of puberty. The ELISA method was used to analyze the serum levels of FSH, LH, testosterone, DHEA-S, leptin, ghrelin, melatonin, glutathione, glutathione peroxidase, and malondialdehyde. Testes were dissected for histomorphological examination.

Results

The medians of the pubertal entry days of the CG, BL-6, and BL-12 were 38^th, 30^th, and 28^th days, respectively. (p:0.001) The FSH, LH, and testosterone concentrations of all groups were similar. The FSH concentration increased as the LH concentration increased (r: 0.82 p: 0.001). The serum LH concentration increased as serum testosterone, and DHEAS decreased, respectively (r: -0.561, p: 0.01) (r:-0.55 p:0.01). Testicular lengths and weights of the BL groups were smaller compared to CG (p: 0.03),(p: 0.04). GPx was higher for BL-6 and BL-12 than the CG (p:0.021, p:0.024). Testis tissue was compatible with the pubertal period in all groups. As the blue light exposure time increased, spermatogenesis was suppressed, and capillary dilatation and edema in the testis tissue increased.

Conclusion

Our study is the first to show the effects of blue light exposure on male rats' puberty process. And we showed that exposure to blue light and the duration of exposure lead to precocious puberty in male rats. The blue light exposure suppressed spermatogenesis, marked vasodilatation in the interstitial area of the testis, and disrupted the integrity of the basement membrane. These findings intensified with increasing exposure time.

The Congenital and Acquired Mechanisms Implicated in the Etiology of Central Precocious Puberty

The etiology of central precocious puberty (CPP) is multiple and heterogeneous, including congenital and acquired causes that can be associated with structural or functional brain alterations. All causes of CPP culminate in the premature pulsatile secretion of hypothalamic GnRH and, consequently, in the premature reactivation of hypothalamic-pituitary-gonadal axis. The activation of excitatory factors or suppression of inhibitory factors during childhood represent the 2 major mechanisms of CPP, revealing a delicate balance of these opposing neuronal pathways. Hypothalamic hamartoma (HH) is the most well-known congenital cause of CPP with central nervous system abnormalities. Several mechanisms by which hamartoma causes CPP have been proposed, including an anatomical connection to the anterior hypothalamus, autonomous neuroendocrine activity in GnRH neurons, trophic factors secreted by HH, and mechanical pressure applied to the hypothalamus. The importance of genetic and/or epigenetic factors in the underlying mechanisms of CPP has grown significantly in the last decade, as demonstrated by the evidence of genetic abnormalities in hypothalamic structural lesions (eg, hamartomas, gliomas), syndromic disorders associated with CPP (Temple, Prader-Willi, Silver-Russell, and Rett syndromes), and isolated CPP from monogenic defects (MKRN3 and DLK1 loss-of-function mutations). Genetic and epigenetic discoveries involving the etiology of CPP have had influence on the diagnosis and familial counseling providing bases for potential prevention of premature sexual development and new treatment targets in the future. Global preventive actions inducing healthy lifestyle habits and less exposure to endocrine-disrupting chemicals during the lifespan are desirable because they are potentially associated with CPP.

Early Life Environmental Exposure to Cadmium, Lead, and Arsenic and Age at Menarche: A Longitudinal Mother-Child Cohort Study in Bangladesh

BACKGROUND

Several metals act as endocrine disruptors, but there are few large longitudinal studies about associations with puberty onset.

OBJECTIVES

We evaluated whether early life cadmium, lead, and arsenic exposure was associated with timing of menarche.

METHODS

In a mother-child cohort in rural Bangladesh (n=935), the exposure was assessed by concentrations in maternal erythrocytes in early pregnancy and in girls' urine at 5 and 10 years of age using inductively coupled plasma mass spectrometry. The girls were interviewed twice, at average ages 13.3 [standard deviation (SD)=0.43] and 13.8 (SD=0.43) y, and the date of menarche, if present, was recorded. Associations were assessed using Kaplan-Meier analysis and multivariable-adjusted Cox regression.

RESULTS

In total, 77% of the girls (n=717) had reached menarche by the second follow-up. The median age of menarche among all girls was 13.0 y (25th-75th percentiles: 12.4-13.7 y). At 10 years of age, median urinary cadmium was 0.25μg/L (5th-95th percentiles: 0.087-0.72μg/L), lead 1.6μg/L (0.70-4.2μg/L), and arsenic 54μg/L (19-395μg/L). Given the same age, girls in the highest quartile of urinary cadmium at 5 and 10 years of age had a lower rate of menarche than girls in the lowest quartile, with an adjusted hazard ratio of (HR) 0.80 (95% CI: 0.62, 1.01) at 5 years of age, and 0.77 (95% CI: 0.60, 0.98) at 10 years of age. This implies that girls in the highest cadmium exposure quartile during childhood had a higher age at menarche. Comparing girls in the highest to the lowest quartile of urinary lead at 10 years of age, the former had a higher rate of menarche [adjusted HR = 1.23 (95% CI: 0.97, 1.56)], implying lower age at menarche, whereas there was no association with urinary lead at 5 years of age. Girls born to mothers in the highest quartile of erythrocyte arsenic during pregnancy were less likely to have attained menarche than girls born to mothers in the lowest quartile [adjusted HR= 0.79 (95% CI: 0.62, 0.99)]. No association was found with girls' urinary arsenic exposure.

DISCUSSION

Long-term childhood cadmium exposure was associated with later menarche, whereas the associations with child lead exposure were inconclusive. Maternal exposure to arsenic, but not cadmium or lead, was associated with later menarche. https://doi.org/10.1289/EHP11121.

A mouse model mimicking gender-affirming treatment with pubertal suppression followed by testosterone in transmasculine youth

STUDY QUESTION

Can mice serve as a translational model to examine the reproductive consequences of pubertal suppression with GnRH agonist (GnRHa) followed by testosterone (T) administration, a typical therapy in peripubertal transmasculine youth?

SUMMARY ANSWER

An implanted depot with 3.6 mg of GnRHa followed by T enanthate at 0.45 mg weekly can be used in peripubertal female mice for investigating the impact of gender-affirming hormone therapy in transmasculine youth.

WHAT IS KNOWN ALREADY

There is limited knowledge available in transgender medicine to provide evidence-based fertility care, with the current guidelines being based on the assumption of fertility loss. We recently successfully developed a mouse model to investigate the reproductive consequences of T therapy given to transgender men. On the other hand, to our knowledge, there is no mouse model to assess the reproductive outcomes in peripubertal transmasculine youth.

STUDY DESIGN, SIZE, DURATION

A total of 80 C57BL/6N female mice were used in this study, with n = 7 mice in each experimental group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We first assessed the effectiveness of GnRHa in arresting pubertal development in the female mice. In this experiment, 26-day-old female mice were subcutaneously implanted with a GnRHa (3.6 mg) depot. Controls underwent a sham surgery. Animals were euthanized at 3, 9, 21 and 28 days after the day of surgery. In the second experiment, we induced a transmasculine youth mouse model. C57BL/6N female mice were subcutaneously implanted with a 3.6 mg GnRHa depot on postnatal day 26 for 21 days and this was followed by weekly injections of 0.45 mg T enanthate for 6 weeks. The control for the GnRH treatment was sham surgery and the control for T treatment was sesame oil vehicle injections. Animals were sacrificed 0.5 weeks after the last injection. The data collected included the day of the vaginal opening and first estrus, daily vaginal cytology, weekly and terminal reproductive hormones levels, body/organ weights, ovarian follicular distribution and corpora lutea (CL) counts.

MAIN RESULTS AND THE ROLE OF CHANCE

GnRHa implanted animals remained in persistent diestrus and had reduced levels of FSH (P = 0.0013), LH (P = 0.0082) and estradiol (P = 0.0155), decreased uterine (P < 0.0001) and ovarian weights (P = 0.0002), and a lack of CL at 21 days after GnRHa implantation. T-only and GnRHa+T-treated animals were acyclic throughout the treatment period, had sustained elevated levels of T, suppressed LH levels (P < 0.0001), and an absence of CL compared to controls (P < 0.0001). Paired ovarian weights were reduced in the T-only and GnRHa+T groups compared with the control and GnRHa-only groups.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although it is an appropriate tool to provide relevant findings, precaution is needed to extrapolate mouse model results to mirror human reproductive physiology.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this study describes the first mouse model mimicking gender-affirming hormone therapy in peripubertal transmasculine youth. This model provides a tool for researchers studying the effects of GnRHa-T therapy on other aspects of reproduction, other organ systems and transgenerational effects. The model is supported by GnRHa suppressing puberty and maintaining acyclicity during T treatment, lower LH levels and absence of CL. The results also suggest GnRHa+T therapy in peripubertal female mice does not affect ovarian reserve, since the number of primordial follicles was not affected by treatment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Michigan Institute for Clinical and Health Research grants KL2 TR 002241 and UL1 TR 002240 (C.D.C.); National Institutes of Health grants F30-HD100163 and T32-HD079342 (H.M.K.); University of Michigan Office of Research funding U058227 (A.S.); American Society for Reproductive Medicine/Society for Reproductive Endocrinology and Infertility grant (M.B.M.); and National Institutes of Health R01-HD098233 (M.B.M.). The University of Virginia Center for Research in Reproduction Ligand Assay and Analysis Core Facility was supported by the Eunice Kennedy Shriver NICHD/NIH grants P50-HD028934 and R24-HD102061. The authors declare that they have no competing interests.

Perinatal exposure to the fungicide ketoconazole alters hypothalamic control of puberty in female rats

INTRODUCTION

Estrogenic endocrine disrupting chemicals (EDCs) such as diethylstilbestrol (DES) are known to alter the timing of puberty onset and reproductive function in females. Accumulating evidence suggests that steroid synthesis inhibitors such as ketoconazole (KTZ) or phthalates may also affect female reproductive health, however their mode of action is poorly understood. Because hypothalamic activity is very sensitive to sex steroids, we aimed at determining whether and how EDCs with different mode of action can alter the hypothalamic transcriptome and GnRH release in female rats.

DESIGN

Female rats were exposed to KTZ or DES during perinatal (DES 3-6-12μg/kg.d; KTZ 3-6-12mg/kg.d), pubertal or adult periods (DES 3-12-48μg/kg.d; KTZ 3-12-48mg/kg.d).

RESULTS

Ex vivo study of GnRH pulsatility revealed that perinatal exposure to the highest doses of KTZ and DES delayed maturation of GnRH secretion before puberty, whereas pubertal or adult exposure had no effect on GnRH pulsatility. Hypothalamic transcriptome, studied by RNAsequencing in the preoptic area and in the mediobasal hypothalamus, was found to be very sensitive to perinatal exposure to all doses of KTZ before puberty with effects persisting until adulthood. Bioinformatic analysis with Ingenuity Pathway Analysis predicted "Creb signaling in Neurons" and "IGF-1 signaling" among the most downregulated pathways by all doses of KTZ and DES before puberty, and "PPARg" as a common upstream regulator driving gene expression changes. Deeper screening ofRNAseq datasets indicated that a high number of genes regulating the activity of the extrinsic GnRH pulse generator were consistently affected by all the doses of DES and KTZ before puberty. Several, including MKRN3, DNMT3 or Cbx7, showed similar alterations in expression at adulthood.

CONCLUSION

nRH secretion and the hypothalamic transcriptome are highly sensitive to perinatal exposure to both DES and KTZ. The identified pathways should be exploredfurther to identify biomarkers for future testing strategies for EDC identification and when enhancing the current standard information requirements in regulation.

Gestational bisphenol A exposure advances puberty onset in female offspring: Critical time window identification

Increasing evidence shows that the early onset of puberty in female offspring may be caused by maternal prenatal exposure to bisphenol A (BPA) during pregnancy; however, the critical time window of maternal prenatal BPA exposure remains unknown. Here, we identify the critical time window of gestational BPA exposure that induces early onset of puberty in female offspring. Pregnant CD-1 mice were gavaged with BPA (8 mg/kg) daily during the early gestational stage (GD1-GD6), middle gestational stage (GD7-GD12) or late gestational stage (GD13-GD18). We show that maternal BPA exposure during the early and middle gestational stages could advance the vaginal opening time and increase the serum levels of kisspeptin-10 and GnRH in the female offspring at PND 34. Mechanistically, maternal BPA exposure during early and middle gestation could significantly increase CpG island methylation in the Eed gene promoters but reduce the mRNA expression of Eed in the hypothalamus tissues of the female offspring. In conclusion, the critical period of maternal BPA exposure-induced early onset of puberty in female offspring is early and middle gestation; this BPA-induced early onset of puberty might be partly attributed to epigenetic programming of the Eed gene in the hypothalamus. This study provides important insights regarding the relationship and the mechanisms between BPA and offspring pubertal development.

Age at Menarche, Growth Velocity, and Adiposity Indices in Italian Girls Aged 10 to 14

Age at menarche (AAM) is an effective marker of puberty timing but its onset could be influenced by several intrinsic and extrinsic factors. This study aimed to assess the AAM in a sample of Italian adolescents and to investigate its association with anthropometric variables. Considering the rise in overweight/obesity worldwide, special attention was paid to a possible decrease in AAM as adiposity indices increase. A longitudinal study was carried out on 117 middle school girls in Northern Italy. Data concerning menarche and anthropometric traits (standing and sitting height, weight, waist circumference, and skinfold thicknesses) were directly collected. Lower limb length and indices of adiposity and growth were calculated. The median AAM was 11.66 (95% IC: 11.31-11.68). Age-adjusted ANCOVA between mature and non-mature girls showed significant differences in growth-related traits and WHtR. No preponderance of overweight/obesity among mature participants was found. AAM was not significantly associated with weight or the growth velocity of adiposity indices in a subsample of maturers. Moreover, the median AAM of our sample was similar to that found in women born about 60 years ago in the same region. In conclusion, in addition to a stabilization of AAM since the 1960s, our results suggest that there is no significant correlation between increased adiposity and early AAM.

Endocrine disrupting chemicals: effects on pituitary, thyroid and adrenal glands

BACKGROUND

In recent years, scientific research has increasingly focused on Endocrine Disrupting Chemicals (EDCs) and demonstrated their relevant role in the functional impairment of endocrine glands. This induced regulatory authorities to ban some of these compounds and to carefully investigate others in order to prevent EDCs-related conditions. As a result, we witnessed a growing awareness and interest on this topic.

AIMS

This paper aims to summarize current evidence regarding the detrimental effects of EDCs on pivotal endocrine glands like pituitary, thyroid and adrenal ones. Particularly, we directed our attention on the known and the hypothesized mechanisms of endocrine dysfunction brought by EDCs. We also gave a glimpse on recent findings from pioneering studies that could in the future shed a light on the pathophysiology of well-known, but poorly understood, endocrine diseases like hormone-producing adenomas.

CONCLUSIONS

Although intriguing, studies on endocrine dysfunctions brought by EDCs are challenging, in particular when investigating long-term effects of EDCs on humans. However, undoubtedly, it represents a new intriguing field of science research.

Trends Toward Earlier Puberty Timing in Girls and Its Likely Mechanisms

This is the first of two installments examining early puberty in girls. The first paper will discuss secular trends in onset of puberty and the possible mechanisms to explain these developments. The potential etiologies examined will include the role of endocrine-disrupting chemicals and obesogens, the impact of body mass index and obesity, genetic and biologic pathways, and the influence of lifestyle behaviors. The second paper of the two-part series will examine the potential health impacts of early puberty on young and adult women and offer suggestions for clinical management and public health prevention.

Exposure to antibiotics and precocious puberty in children: A school-based cross-sectional study in China

Foods and water can be contaminated with antibiotics in China, which may affect children's health, but evidence on antibiotic exposure with precocious puberty (PP) is limited. This study explored the association of antibiotic exposure with PP in a school-based setting. A cross-sectional study with multistage stratified cluster random sampling was conducted in Zhongshan City, Guangdong Province and Qufu City, Shandong Province in China from October 11 to December 5, 2019. A first-morning urine sample was collected to detect antibiotic exposure. We detected 33 of 45 types of antibiotics from eight categories in 928 primary school children aged 6-12 years using HPLS-MS/MS. Detection rate of antibiotics was stratified by sex, study site, and BMI. The Tanner stages were assessed by professional pediatricians from local hospitals. PP is defined as the onset of secondary characters before 8-year-old or menarche before 10-year-old for girls and before 9-year-old for boys. Multivariable logistic regression was performed to examine the association between antibiotic exposure and PP after adjusting potential confounders. The overall detection rate of antibiotics was 93.0% in 928 children. We found the detection rate of tetracyclines and fluoroquinolones in children with PP was significantly higher than that of children with normal puberty (41.4% vs 29.9%, 56.8% vs 50.6%, respectively, all p < 0.05). Both fluoroquinolones (odds ratio (OR): 1.835, 95% confidence interval (CI): 1.066-3.158) and tetracyclines (OR: 2.120, 95% CI: 1.175-3.825) were associated with increased OR of PP after adjusting sex, age, BMI, study site, and family income. Specifically, compared to the values less than the limits of detection, low concentration of ofloxacin from fluoroquinolones (OR: 2.056, 95% CI: 1.091-3.875) and high concentration of chlortetracycline (OR: 3.027, 95% CI: 1.126-8.140) and tetracycline from tetracyclines (OR: 2.756, 95% CI: 1.167-6.506) were associated with increased OR of PP. Exposure to antibiotics, especially fluoroquinolones and tetracyclines was positively associated with precocious puberty.

The Role of Genetics in Central Precocious Puberty: Confirmed and Potential Neuroendocrine Genetic and Epigenetic Contributors and Their Interactions with Endocrine Disrupting Chemicals (EDCs)

Despite the growing prevalence of central precocious puberty (CPP), most cases are still diagnosed as “idiopathic” due to the lack of identifiable findings of other diagnostic etiology. We are gaining greater insight into some key genes affecting neurotransmitters and receptors and how they stimulate or inhibit gonadotropin-releasing hormone (GnRH) secretion, as well as transcriptional and epigenetic influences. Although the genetic contributions to pubertal regulation are more established in the hypogonadotropic hypogonadism (HH) literature, cases of CPP have provided the opportunity to learn more about its own genetic influences. There have been clinically confirmed cases of CPP associated with gene mutations in kisspeptin and its receptor (KISS1, KISS1R), Delta-like noncanonical Notch ligand 1 (DLK1), and the now most commonly identified genetic cause of CPP, makorin ring finger protein (MKRN3). In addition to these proven genetic causes, a number of other candidates continue to be evaluated. After reviewing the basic clinical aspects of puberty, we summarize what is known about the various genetic and epigenetic causes of CPP as well as discuss some of the potential effects of endocrine disrupting chemicals (EDCs) on some of these processes.

Prenatal Exposure to an EDC Mixture, NeuroMix: Effects on Brain, Behavior, and Stress Responsiveness in Rats

Humans and wildlife are exposed to endocrine-disrupting chemicals (EDCs) throughout their lives. Environmental EDCs are implicated in a range of diseases/disorders with developmental origins, including neurodevelopment and behavior. EDCs are most often studied one by one; here, we assessed outcomes induced by a mixture designed to represent the real-world situation of multiple simultaneous exposures. The choice of EDCs, which we refer to as “NeuroMix,” was informed by evidence for neurobiological effects in single-compound studies and included bisphenols, phthalates, vinclozolin, and perfluorinated, polybrominated, and polychlorinated compounds. Pregnant Sprague Dawley rats were fed the NeuroMix or vehicle, and then offspring of both sexes were assessed for effects on postnatal development and behaviors and gene expression in the brain in adulthood. In order to determine whether early-life EDCs predisposed to subsequent vulnerability to postnatal life challenges, a subset of rats were also given a stress challenge in adolescence. Prenatal NeuroMix exposure decreased body weight and delayed puberty in males but not females. In adulthood, NeuroMix caused changes in anxiety-like, social, and mate preference behaviors only in females. Effects of stress were predominantly observed in males. Several interactions of NeuroMix and stress were found, especially for the mate preference behavior and gene expression in the brain. These findings provide novel insights into how two realistic environmental challenges lead to developmental and neurobehavioral deficits, both alone and in combination, in a sex-specific manner.

Integrated analysis of proteomics and metabolomics in girls with central precocious puberty

BACKGROUND

Central precocious puberty (CPP) is a multifactorial and complex condition. Traditional studies focusing on a single indicator cannot always elucidate this panoramic condition but these may be revealed by using omics techniques.

OBJECTIVE

Proteomics and metabolomics analysis of girls with CPP were compared to normal controls and the potential biomarkers and pathways involved were explored.

METHODS

Serum proteins and metabolites from normal girls and those with CPP were compared by LC-MS/MS. Multivariate and univariate statistical analysis were used to identify the differentially expressed proteins (DEPs) and differentially expressed metabolites (DEMs). Functional annotation and pathway enrichment analysis were performed by using GO and KEGG databases, and candidate markers were screened. Finally, bioinformatic analysis was used to integrate the results of proteomics and metabolomics to find the key differential proteins, metabolites and potential biomarkers of CPP.

RESULTS

134 DEPs were identified in girls with CPP with 71 up- and 63 down-regulated, respectively. Up-regulated proteins were enriched mainly in the extracellular matrix, cell adhesion and cellular protein metabolic processes, platelet degranulation and skeletal system development. The down-regulated proteins were mainly enriched in the immune response. Candidate proteins including MMP9, TIMP1, SPP1, CDC42, POSTN, COL1A1, COL6A1, COL2A1 and BMP1, were found that may be related to pubertal development. 103 DEMs were identified, including 42 up-regulated and 61 down-regulated metabolites which were mainly enriched in lipid and taurine metabolic pathways. KGML network analysis showed that phosphocholine (16:1(9Z)/16:1(9Z)) was involved in arachidonic acid, glycerophospholipid, linoleic acid and α-linolenic acid metabolism and it may be used as a biomarker of CPP.

CONCLUSIONS

Our study is the first to integrate proteomics and metabolomics to analyze the serum of girls with CPP and we found some key differential proteins and metabolites as well as a potential biomarker for this condition. Lipid metabolism pathways are involved and these may provide a key direction to further explore the molecular mechanisms and pathogenesis of CPP.

Early and precocious puberty during the COVID-19 pandemic

During the year 2020, the COVID-19 pandemic rapidly became a severe health emergency worldwide. In order to contrast the spread of the novel SARS-CoV-2, many countries implemented extraordinary restrictive measures, such as a strict lockdown and school closures. The pandemic had a great impact on children and adolescents' daily life, leading to a much more sedentary lifestyle, to larger use of electronic devices and to an increase in stress-related symptoms. These conspicuous changes acted as disruptors of children's normal development. Since the beginning of the pandemic, many studies reported an increase in the number of precocious puberty cases as well as a faster progression rate of puberty itself, if compared to the pre-pandemic years. In this review, our aim was to evaluate the incidence of new cases of early and precocious puberty during the COVID-19 pandemic, analyzing variations in the timing of puberty and in pubertal progression rate, and to investigate the role of environmental and lifestyle factors during the pandemic in modulating the physiopathology of pubertal development. While a direct effect of SARS-CoV-2 infection remains, at the moment, a remote hypothesis, both physical and psychological factors related to the pandemic seem to have a role in triggering GnRH pulsatile secretion leading to earlier pubertal onset. It is indeed important to stress the need to clarify the exact role of COVID-19 in early pubertal onset comparing data from all over the world; long-term comprehensive studies are also pivotal to explain whether this phenomenon will continue while we resume pre-pandemic habits.

Signaling Proteins That Regulate Spermatogenesis Are the Emerging Target of Toxicant-Induced Male Reproductive Dysfunction

There is emerging evidence that environmental toxicants, in particular endocrine disrupting chemicals (EDCs) such as cadmium and perfluorooctanesulfonate (PFOS), induce Sertoli cell and testis injury, thereby perturbing spermatogenesis in humans, rodents and also widelife. Recent studies have shown that cadmium (e.g., cadmium chloride, CdCl₂) and PFOS exert their disruptive effects through putative signaling proteins and signaling cascade similar to other pharmaceuticals, such as the non-hormonal male contraceptive drug adjudin. More important, these signaling proteins were also shown to be involved in modulating testis function based on studies in rodents. Collectively, these findings suggest that toxicants are using similar mechanisms that used to support spermatogenesis under physiological conditions to perturb Sertoli and testis function. These observations are physiologically significant, since a manipulation on the expression of these signaling proteins can possibly be used to manage the toxicant-induced male reproductive dysfunction. In this review, we highlight some of these findings and critically evaluate the possibility of using this approach to manage toxicant-induced defects in spermatrogenesis based on recent studies in animal models.