Developmental variations in environmental influences including endocrine disruptors on pubertal timing and neuroendocrine control: Revision of human observations and mechanistic insight from rodents

Temporal trend of age at menarche in Korean females born between 1927 and 2004: a population-based study

Backgrounds

The age at menarche has decreased worldwide. Previous studies on Korean adolescents have reported a downward trend in age at menarche. This study aimed to investigate the current trends in age at menarche among Korean adolescents using nationally representative data.

Materials and methods

The study used data from the Korea National Health and Nutrition Examination Survey 2007-2021. A total of 50,730 females born between 1927 and 2004 with information on age at menarche were included. The trend in age at menarche was analyzed according to 15 birth-year groups (with 5-year intervals) using quantile regression analysis.

Results

The mean age at menarche decreased from 16.92 ± 0.06 years for females born before 1935 to 12.45 ± 0.04 years for females born between 2000 and 2004 (p <.001). According to the percentile group of age at menarche, mean menarche age decreased by -0.071 years per year (95% confidence interval [CI], -0.072 to -0.070) in total, -0.050 years per year (95% CI, -0.052 to -0.048) in the 3rd percentile group, -0.088 years per year (95% CI, -0.091 to -0.085) in the 97th percentile group (p <.001 for all). A decreasing trend of age at menarche was more prominent in the obesity group (-0.080 years per year, 95% CI, -0.082 to -0.078) compared to the non-obesity group (-0.069 years per year, 95% CI, -0.071 to -0.068) (p <.001 for both).

Conclusion

Ongoing downward trend in age at menarche was observed in Korean females born until 2004, decreasing by 0.71 years per decade. The downward trend was faster in individuals with a higher percentile of age at menarche and in those with obesity.

Indications of younger age at menarche in Greek adolescents but with no relation to body mass index

PURPOSE

This study aimed to present recent trends in the pubertal timing of a Greek female sample.

METHODS

Data were collected retrospectively from medical records of healthy females aged 6-18 years who attended a tertiary Adolescent Friendly Health Center over a 5-year period (2016-2020) and included gestational age, birth anthropometrics, and age of thelarche and/or pubarche and/or menarche, along with corresponding anthropometric, hormonal, and biochemical measurements.

RESULTS

Data from 298 girls' medical records were included in the analysis. Median age at menarche, thelarche, and pubarche was 12, 9, and 9 years, respectively. The mean interval between pubertal onset and menarche was 1.99 years. The mean body mass index (BMI) at menarche and thelarche was 20.99 kg/m2 and 18.90 kg/m2, respectively. The mean weight at menarche was 49.6 kg, whereas the mean height difference between thelarche and menarche was 19.17 cm. Among participants, 6.3% had premature menarche, while 24.0% had premature thelarche. Birth weight was moderately correlated with BMI at thelarche/pubarche (rs=0.334, p = 0.005). Birth weight and BMI at thelarche/pubarche were not predictive of premature menarche or premature thelarche. Median (interquartile range, IQR) levels at menarche vs. thelarche were significantly higher for insulin-like growth factor-1 [358.00 (140.50) vs. 176.00 (55.00) ng/ml], follicle stimulation hormone [5.65 (3.14) vs. 3.10 (4.23) mIU/ml], testosterone [25.50 (31.00) vs. 13.00 (21.00) ng/dl], dehydroepiandrosterone sulfate [117.00 (112.50) vs. 46.40 (51.90) µg/dl], and insulin [17.40 (15.05) vs. 8.47 (4.97) µIU/ml].

CONCLUSION

The timing of pubertal stages in the Greek female sample studied followed the recent international downward trends. Younger age at menarche was not related to BMI.

Associations of glyphosate exposure and serum sex steroid hormones among 6-19-year-old children and adolescents

Glyphosate, ranked as one of the most widely used herbicides in the world, has raised concerns about its potential disruptive effects on sex hormones. However, limited human evidence was available, especially for children and adolescents. The present study aimed to examine the associations between exposure to glyphosate and sex hormones among participants aged 6-19 years, utilizing data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2013 and 2016. Children and adolescents who had available data on urinary glyphosate, serum sex steroid hormones, including testosterone (TT), estradiol (E2) and sex hormone binding globulin (SHBG), and covariates were selected. Additionally, the ratio of TT to E2 (TT/E2) and the free androgen index (FAI), which was calculated using TT/SHBG, were also included as sex hormone indicators. Survey regression statistical modeling was used to examine the associations between urinary glyphosate concentration and sex hormone indicators by age and sex group. Among the 964 participants, 83.71% had been exposed to glyphosate (>lower limit of detection). The survey regression revealed a marginally negative association between urinary glyphosate and E2 in the overall population, while this association was more pronounced in adolescents with a significant trend. In further sex-stratified analyses among adolescents, a significant decrease in E2, FAI, and TT (p trend <0.05) was observed in female adolescents for the highest quartile of urinary glyphosate compared to the lowest quartile. However, no similar association was observed among male adolescents. Our findings suggest that exposure to glyphosate at the current level may decrease the levels of sex steroids in adolescents, particularly female adolescents. Considering the cross-sectional study design, further research is needed to confirm our findings.

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.

Quantification of overnight urinary gonadotropin excretion predicts imminent puberty in girls: a semi-longitudinal study

PURPOSE

We explored the alternative of using overnight fold change in gonadotropin levels by comparing the last-night-voided (LNV) and first-morning-voided (FMV) urine concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as a conceptual analogy to the invasive gonadotropin-releasing hormone (GnRH) stimulation test setting.

METHODS

We investigated the nocturnal changes in the immunoreactivity levels of urinary gonadotropins between early and late prepubertal stages as well as between early and late pubertal stages in FMV and LNV urine samples from 30 girls, of whom those who were prepubertal were further investigated through follow-up visits within the 1-year period from the start of the study.

RESULTS

ROC analysis revealed that the FMV total U-LH and FMV U-FSH concentrations at or above 0.3 IU/L and 2.5 IU/L, respectively, were excellent predictors of forthcoming onset of puberty within 1 year (100% sensitivity, 100% specificity, AUC: 1.00, and n = 10, for both). FMV total U-LH concentration at or above 0.8 IU/L represented the cut-off for clinical signs of puberty. FMV/LNV total U-LH and FMV/LNV U-FSH ratios at or below 4.11 and 1.38, respectively, were also good predictors of the onset of clinical puberty within 1 year. An overnight increase (FMV/LNV ratio) in total U-LH concentrations and in the U-LH/U-FSH ratio at or below 1.2-fold in pubertal girls was associated with the postmenarcheal pubertal stage.

CONCLUSION

FMV total U-LH and U-FSH above 0.3 IU/L and 2.5 IU/L, respectively, can be used as cut-off values to predict the manifestation of the clinical signs of puberty within 1 year. FMV total U-LH concentrations 0.3-0.8 IU/L and 0.6 IU/L may represent the range and the threshold, respectively, that reflect the loosening of the central brake on the GnRH pulse generator. An overnight increase of 20% or less in total U-LH concentrations and in the U-LH/U-FSH ratio in an early pubertal girl may serve as an indicator of imminent menarche, a presumed timing of which can be unraveled by future longitudinal studies.

Sleep deprivation alters pubertal timing in humans and rats: the role of the gut microbiome

STUDY OBJECTIVES

Evidence implied that sleeping duration is associated with the timing of puberty and that sleep deprivation triggers early pubertal onset in adolescents. Sleep deprivation can affect metabolic changes and gut microbiota composition. This study investigated the effects of sleep deprivation on pubertal onset and gut microbiota composition in animal models and a human cohort.

METHODS

This study comprised 459 boys and 959 girls from the Taiwan Pubertal Longitudinal Study. Sleep duration was evaluated using the self-report Pittsburgh Sleep Quality Index questionnaire. Early sexual maturation was defined by pediatric endocrinologist assessments. Mediation analyses were done to examine the association between sleep parameters, obesity, and early sexual maturation. Besides, Sprague Dawley juvenile rats were exposed to 4 weeks of chronic sleep deprivation. Vaginal opening (VO) and preputial separation (PS) were observed every morning to determine pubertal onset in female and male rats.

RESULTS

The sleep-deprived juvenile rats in the sleep-deprived-female (SDF) and sleep-deprived-male (SDM) groups experienced delayed VO (mean VO days: 33 days in control; 35 days in SDF; p-value < 0.05) and PS (mean PS days: 42 days in control; 45 days in SDM; p-value < 0.05), respectively. Relative to their non-sleep-deprived counterparts, the sleep-deprived juvenile rats exhibited lower body weight and body fat percentage. Significant differences in relative bacterial abundance at genus levels and decreased fecal short-chain-fatty-acid levels were identified in both the SDF and SDM groups. In the human cohort, insufficient sleep increased the risk of early sexual maturation, particularly in girls (OR, 1.44; 95% CI: 1.09 to 1.89; p-value < 0.01). Insufficient sleep also indirectly affected early sexual maturation in girls, with obesity serving as the mediator.

CONCLUSIONS

Overall, sleep deprivation altered the timing of puberty in both animal and human models but in different directions. In the rat model, sleep deprivation delayed the pubertal onset in juvenile rats through gut dysbiosis and metabolic changes, leading to a low body weight and body fat percentage. In the human model, sleep deprivation led to fat accumulation, causing obesity in girls, which increased the risk of early puberty.

Association between exposure to persistent organic pollutants and pubertal timing in boys and girls: A systematic review and meta-analysis

In recent years, the phenomenon of abnormal pubertal timing in children has become increasingly common worldwide. Persistent organic pollutants (POPs) may be one of the risk factors contributing to this phenomenon, but the relationship between them is unclear based on current evidence. The purpose of this study was to determine the association of POPs exposure with pubertal timing in girls and boys by conducting a systematic review and meta-analysis. We searched PubMed and Embase databases for studies before June 1, 2023. Meta-analysis was performed by pooling relative risk (RR) or odds ratio (OR) or prevalence ratio (PR) or hazard ratio (HR) estimates with 95 % confidence intervals (CIs). Subgroup analysis, publication bias assessment and sensitivity analysis were also carried out. A total of 21 studies were included, involving 2479 boys and 8718 girls. The results of meta-analysis showed that exposure to POPs was significantly associated with delayed pubertal timing in girls (RR: 0.85; 95 % CI: 0.79-0.91; p < 0.001). There was no statistically significant association between exposure to POPs and pubertal timing in boys (RR: 1.18; 95 % CI: 0.99-1.40; p = 0.070). Subgroup analysis showed that there may be gender differences in the effects of exposure to POPs on pubertal timing. Our results suggested that exposure to POPs could delay pubertal timing in girls. However, based on current evidence, no significant association was found between POPs exposure and pubertal timing in boys.

Identification of urine biomarkers associated with early puberty in children: An untargeted metabolomics analysis

A trend toward earlier pubertal maturation in both sexes has been shown in many countries. Early puberty affects an increasing proportion of children for reasons that remain obscure. Novel candidate biomarkers are strongly needed. We sought to apply untargeted metabolomic profiling to identify triggering mechanisms and candidate biomarkers in children with early puberty. Participants aged 7 - 12 years old were recruited directly from two elementary schools of Bengbu, Anhui Province, China, from Feb 2021 to May 2021. Early puberty was determined by breast and testicular development at baseline (May 2021) and 6-month later. Ultra-high-performance liquid chromatography-based untargeted metabolomic profiling was performed on urine samples of children with early puberty and control subjects. Metabolomic profiling for early puberty in a sex dependent manner. For boys, we identified several perturbed pathways, including histidine metabolism, glycine, serine and threonine metabolism, and selenoamino acid metabolism, associated with early puberty. In contrast, there were differences in pyruvate metabolism, one carbon pool by folate, and D-glutamine and D-glutamate metabolism pathways in girls with early puberty compared with controls. In addition, 4-hydroxyhippuric acid and 5-methoxytryptophol were shown as potential independent diagnostic biomarker for early puberty in boys, 3-hydroxybenzoic acid and glutaminylproline were shown as early biomarker for early puberty in girls, achieving area under the ROC curve of 0.71 and 0.72 in discriminating early puberty boys, and 0.70 and 0.74 in discriminating early puberty girls from controls. Through metabolomic analysis, we have identified metabolic perturbations and potential biomarkers of early puberty.

The effect of cognitive behavioral therapy on stress and anxiety of mothers of girls with precocious puberty symptoms: a randomized controlled trial

INTRODUCTION

Precocious puberty in girls has been associated with an increased risk of stress and anxiety in their mothers. This study aimed to investigate the effect of cognitive behavioral therapy (CBT) on perceived stress and anxiety of mothers of girls with precocious puberty symptoms.

METHODS

This randomized controlled trial was conducted on 70 mothers of girls with precocious puberty symptoms in Tabriz-Iran, 2021. The participants were randomly assigned to CBT and control groups through blocked randomization. Group counseling was provided to the intervention group in eight sessions of 45-60 min weekly with 5 to 7 women. A booklet containing explanations about puberty was provided for the both groups. Data were collected using the questionnaires of socio-demographic characteristics, Spielberger State-Trait Anxiety Inventory (STAI), Perceived Stress Scale (PSS) and quality of life (SF-36). Independent t-test, ANCOVA, chi-square, and fisher's exact tests were used to compare the outcomes between the groups.

FINDINGS

After the intervention, based on ANCOVA test with adjusting the baseline values, mean scores of stress (mean difference (MD): -10.75; 95% confidence interval (95% CI): -11.77 to -9.72; P < 0.001), state anxiety (MD: -14.36; 95% CI: -15.7 to -12.7; P < 0.001) and trait anxiety (MD: -12.8; 95% CI: -14.4 to -11.1; P < 0.001) were significantly lower in CBT group compared to the control group. Also mean score of quality of life (MD: 9.82; 95% CI: -6.74 to -12.90; P < 0.001) was significantly higher in CBT group compared to the control group.

CONCLUSION

Based on the results, group CBT is effective in reducing stress and anxiety and improving the quality of life of mothers of girls with precocious puberty symptoms. However, more studies are required to make a definite conclusion in this field.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials (IRCT): IRCT20110826007418N6. Date of registration: 11/10/2021. URL: https://en.irct.ir/trial/57346 ; Date of first registration: 11/10/2021.

Associations of prenatal and postnatal exposure to perfluoroalkyl substances with pubertal development and reproductive hormones in females and males: The HOME study

BACKGROUND

Prenatal and childhood exposure to per- and polyfluoroalkyl substances (PFAS) may be associated with lower reproductive hormones and later puberty, but epidemiological studies evaluating these associations are scarce.

OBJECTIVES

We examined associations of PFAS concentrations assessed from pregnancy to adolescence with pubertal development and reproductive hormones at age 12 years.

METHODS

We studied 200 mother-child pairs from the HOME Study in Cincinnati, OH (enrolled: 2003-2006). We quantified serum concentrations of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoate (PFNA), and perfluorohexane sulfonate (PFHxS) in pregnant women and their children at age 3, 8 and 12 years. At age 12 years, children self-assessed pubertal development using Tanner staging of pubic hair growth (males and females) and breast growth (females), and age at menarche. We quantified serum concentrations of dehydroepiandrosterone sulfate, luteinizing hormone, and follicle-stimulating hormone in both sexes; estradiol in females; testosterone in males. We estimated associations of PFAS with pubertal outcomes and reproductive hormones using a combination of ordinal regression, Cox proportional-hazard regression, and linear regression. Quantile-based g-computation was used for PFAS mixture.

RESULTS

In females, adolescent PFAS concentrations and their mixture were associated with later pubic hair growth, breast maturation, and age at menarche, but there was no pattern for prenatal or other postnatal concentrations. For instance, in females, each doubling in adolescent PFAS concentrations was associated with 79 % (PFOA), 63 % (PFOS), 56 % (PFNA), and 47 % (PFHxS) lower odds of attaining a higher stage for breast growth. In addition, adolescent PFAS concentrations were consistently associated with lower estradiol concentrations in females. No pattern was observed for associations of PFAS concentrations with pubic hair growth or reproductive hormones in males.

CONCLUSIONS

We observed associations between PFAS concentrations in adolescence and later pubertal development in females, but this could be due to reverse causation induced by excretion of PFAS through menstrual fluid.

Sexually dimorphic impact of preconceptional and gestational exposure to a real-life environmental chemical mixture (biosolids) on offspring growth dynamics and puberty in sheep

Humans are ubiquitously exposed to complex mixtures of environmental chemicals (ECs). This study characterised changes in post-natal and peripubertal growth, and the activation of the reproductive axis, in male and female offspring of sheep exposed to a translationally relevant EC mixture (in biosolids), during pregnancy. Birthweight in both sexes was unaffected by gestational biosolids exposure. In contrast to females (unaffected), bodyweight in biosolids males was significantly lower than controls across the peripubertal period, however, they exhibited catch-up growth eventually surpassing controls. Despite weighing less, testosterone concentrations were elevated earlier, indicative of early puberty in the biosolids males. This contrasted with females in which the mean date of puberty (first progesterone cycle) was delayed. These results demonstrate that developmental EC-mixture exposure has sexually dimorphic effects on growth, puberty and the relationship between body size and puberty. Such programmed metabolic/reproductive effects could have significant impacts on human health and wellbeing.

Maternal intake of folate and folic acid during pregnancy and pubertal timing in girls and boys: A population-based cohort study

BACKGROUND

Folate is essential for normal foetal development as it plays an important role for gene expression during different periods of foetal development. Thus, prenatal exposure to folate may have a programming effect on pubertal timing.

OBJECTIVES

To study the association between maternal intake of folate during pregnancy and pubertal timing in girls and boys.

METHODS

We studied 6585 girls and 6326 boys from a Danish population-based Puberty Cohort, 2000-2021. Information on maternal intake of folate from diet and folic acid from supplements was obtained from a food-frequency questionnaire in mid-pregnancy, and total folate was calculated as dietary folate equivalents. Information on age at menarche in girls, age at first ejaculation and voice break in boys, and Tanner stages, acne and axillary hair in both girls and boys was obtained every 6 months throughout puberty. We estimated mean monthly differences according to exposure groups for each pubertal milestone in addition to a combined estimate for the average age at attaining all pubertal milestones using multivariable interval-censored regression models. Total folate was analysed in quintiles, continuous and as restricted cubic splines.

RESULTS

Maternal intake of total folate in mid-pregnancy was not associated with pubertal timing in girls (combined estimate for overall pubertal timing per standard deviation (SD 325 μg/day) decrease in maternal intake of total folate: -0.14 months (95% confidence interval [CI] -0.51, 0.22)). Boys had slightly later overall pubertal timing per standard deviation (SD 325 μg/day) decrease in maternal intake of total folate (combined estimate: 0.40 months, 95% CI 0.01, 0.72). Spline plots supported these findings.

CONCLUSIONS

Prenatal exposure to low maternal intake of total folate in mid-pregnancy was not associated with pubertal timing in girls but associated with slightly later pubertal timing in boys. This minor delay is likely not of clinical importance.

Effects of exposure to the explosive and environmental pollutant 2,4,6-trinitrotoluene on ovarian follicle development in rats

Although 2,4,6-trinitrotoluene (TNT) is a dangerous carcinogen in environmental pollution, information on the reproductive effects of TNT explosive contamination is limited. To explore the possible ovarian effects, TNT explosive-exposed rat models were established, and Wistar female rats were exposed to low and high TNT (40 g and 80 g, air and internal) explosives. After a month of exposure, the estrous cycle, ovarian histopathology, and follicle counting were conducted. Serum hormones follicle-stimulating hormone (FSH), luteinizing hormone (LH), anti-Müllerian hormone (AMH), progesterone, testosterone, and estradiol were detected, and the mRNA and protein expression of steroidogenic enzymes were measured. The results showed that the diestrus phase duration was significantly (P < 0.05) increased in the high TNT-exposed groups. In addition, the proportions of preantral follicles were significantly (P < 0.05) decreased in the high TNT-exposed groups, as well as the proportions of atretic follicles. The serum estradiol levels were significantly (P < 0.05) increased, and the follicle-stimulating hormone and luteinizing hormone levels were significantly (P < 0.05) decreased in the high TNT-exposed groups. The mRNA levels of steroidogenic acute regulatory protein (Star), cytochrome P450 cholesterol side chain cleavage (Cyp11a1, Cyp17a1 and Cyp19a1), hydroxysteroid dehydrogenase 3b (Hsd3b) and steroidogenic factor-1 (SF-1) were significantly (P < 0.05) increased in the TNT-exposed groups. The protein levels of Star, Cyp11a1 and Hsd3b were increased (P < 0.05) in the TNT-exposed groups. These results indicate that the exposure of rats to TNT explosive can subsequently affect ovarian follicle development, suggesting that the mechanism may involve disrupting steroidogenesis.

The Effects of Pubertal Timing on Academic Performance in Adolescence and Career Success in Adulthood: Evidence from a 16-year Longitudinal Study

Previous research showed inconsistent effects of pubertal timing on adolescent academic performance and adult career success. Moreover, the relative importance of biological vs. perceived pubertal timing has not been examined. This study examined effects of biological and perceived pubertal timing on academic performance throughout adolescence and career success in adulthood together with sex differences in an understudied population of pre-dominantly Black youth from lower income families. The sample included 704 youth (52% male, 76% Black, 22% White) interviewed at four time points (Mean ages: 11.8, 13.2, 17.6, and 27.7 years). The results from a mediation path model showed that among males, perceived off-time pubertal timing uniquely predicted lower concurrent academic performance as well as lower objective career success in adulthood; this effect was mediated by lower academic performance throughout adolescence. Additionally, results from bivariate correlation analyses showed associations between early biological pubertal timing and lower concurrent academic performance in males and early perceived pubertal timing and lower concurrent academic performance among females. These findings contribute to the understanding of more nuanced links between pubertal timing, academic performance and subsequent career success in an understudied population of pre-dominantly Black youth from lower income families.

Estrogenic and non-estrogenic effects of bisphenol A and its action mechanism in the zebrafish model: An overview of the past two decades of work

Bisphenol A (BPA) is the most simple and predominant component of the Bisphenol family. BPA is widely present in the environment and the human body as a result of its extensive usage in the plastic and epoxy resins of consumer goods like water bottles, food containers, and tableware. Since the 1930s, when BPA's estrogenic activity was first observed, and it was labeled as a "mimic hormone of E2", studies on the endocrine-disrupting effects of BPA then have been widely conducted. As a top vertebrate model for genetic and developmental studies, the zebrafish has caught tremendous attention in the past two decades. By using the zebrafish, the negative effects of BPA either through estrogenic signaling pathways or non-estrogenic signaling pathways were largely found. In this review, we tried to draw a full picture of the current state of knowledge on the estrogenic and non-estrogenic effects of BPA with their mechanisms of action through the zebrafish model of the past two decades, which may help to fully understand the endocrine-disrupting effects of BPA and its action mechanism, and give a direction for the future studies.

Continuous body temperature as a window into adolescent development

Continuous body temperature is a rich source of information on hormonal status, biological rhythms, and metabolism, all of which undergo stereotyped change across adolescence. Due to the direct actions of these dynamic systems on body temperature regulation, continuous temperature may be uniquely suited to monitoring adolescent development and the impacts of exogenous reproductive hormones or peptides (e.g., hormonal contraception, puberty blockers, gender affirming hormone treatment). This mini-review outlines how traditional methods for monitoring the timing and tempo of puberty may be augmented by markers derived from continuous body temperature. These features may provide greater temporal precision, scalability, and reduce reliance on self-report, particularly in females. Continuous body temperature data can now be gathered with ease across a variety of wearable form factors, providing the opportunity to develop tools that aid in individual, parental, clinical, and researcher awareness and education.

The future of evolutionary medicine: sparking innovation in biomedicine and public health

Evolutionary medicine - i.e. the application of insights from evolution and ecology to biomedicine - has tremendous untapped potential to spark transformational innovation in biomedical research, clinical care and public health. Fundamentally, a systematic mapping across the full diversity of life is required to identify animal model systems for disease vulnerability, resistance, and counter-resistance that could lead to novel clinical treatments. Evolutionary dynamics should guide novel therapeutic approaches that target the development of treatment resistance in cancers (e.g., via adaptive or extinction therapy) and antimicrobial resistance (e.g., via innovations in chemistry, antimicrobial usage, and phage therapy). With respect to public health, the insight that many modern human pathologies (e.g., obesity) result from mismatches between the ecologies in which we evolved and our modern environments has important implications for disease prevention. Life-history evolution can also shed important light on patterns of disease burden, for example in reproductive health. Experience during the COVID-19 (SARS-CoV-2) pandemic has underlined the critical role of evolutionary dynamics (e.g., with respect to virulence and transmissibility) in predicting and managing this and future pandemics, and in using evolutionary principles to understand and address aspects of human behavior that impede biomedical innovation and public health (e.g., unhealthy behaviors and vaccine hesitancy). In conclusion, greater interdisciplinary collaboration is vital to systematically leverage the insight-generating power of evolutionary medicine to better understand, prevent, and treat existing and emerging threats to human, animal, and planetary health.

Effects of benzo[a]pyrene on the reproductive axis: Impairment of kisspeptin signaling in human gonadotropin-releasing hormone primary neurons

The neuroendocrine control of reproduction is strictly coordinated at the central level by the pulsatile release of gonadotropin-releasing hormone (GnRH) by the hypothalamic GnRH neurons. Alterations of the GnRH-network, especially during development, lead to long-term reproductive and systemic consequences, also causing infertility. Recent evidence shows that benzo[a]pyrene (BaP), a diffuse pollutant that can play a role as an endocrine disruptor, affects gonadal function and gamete maturation, whereas data demonstrating its impact at hypothalamic level are very scarce. This study investigated the effects of BaP (10 μM) in a primary cell culture isolated from the human fetal hypothalamus (hfHypo) and exhibiting a clear GnRH neuron phenotype. BaP significantly decreased gene and protein expression of both GnRH and kisspeptin receptor (KISS1R), the master regulator of GnRH neuron function. Moreover, BaP exposure increased phospho-ERK1/2 signaling, a well-known mechanism associated with KISS1R activation. Interestingly, BaP altered the electrophysiological membrane properties leading to a significant depolarizing effect and it also significantly increased GnRH release, with both effects being not affected by kisspeptin addition. In conclusion, our findings demonstrate that BaP may alter GnRH neuron phenotype and function, mainly interfering with KISS1R signaling and GnRH secretion and therefore with crucial mechanisms implicated in the central neuroendocrine control of reproduction.

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.

The effect of endocrine-disrupting chemicals on placental development

Endocrine-disrupting chemicals (EDCs) or endocrine disruptors are substances that are either naturally occurring or artificial and are released into the natural environment. Humans are exposed to EDCs through ingestion, inhalation, and skin contact. Many everyday household items, such as plastic bottles and containers, the liners of metal food cans, detergents, flame retardants, food, gadgets, cosmetics, and pesticides, contain endocrine disruptors. Each hormone has a unique chemical makeup and structural attributes. The way that endocrine hormones connect to receptors is described as a "lock and key" mechanism, with each hormone serving as the key (lock). This mechanism is enabled by the complementary shape of receptors to their hormone, which allows the hormone to activate the receptors. EDCs are described as exogenous chemicals or compounds that have a negative impact on organisms' health by interacting with the functioning of the endocrine system. EDCs are associated with cancer, cardiovascular risk, behavioural disorders, autoimmune abnormalities, and reproductive disorders. EDCs exposure in humans is highly harmful during critical life stages. Nonetheless, the effect of EDCs on the placenta is often underestimated. The placenta is especially sensitive to EDCs due to its abundance of hormone receptors. In this review, we evaluated the most recent data on the effects of EDCs on placental development and function, including heavy metals, plasticizers, pesticides, flame retardants, UV filters and preservatives. The EDCs under evaluation have evidence from human biomonitoring and are found in nature. Additionally, this study indicates important knowledge gaps that will direct future research on the topic.

Perinatal exposure to low doses of cypermethrin induce the puberty-related hormones and decrease the time to puberty in the female offspring

Pyrethroid insecticides are ubiquitously detected in environmental media, food, and urine samples. Our previous epidemiological study reported a correlation between increased pyrethroid exposure and delayed pubertal development in Chinese girls. In this study, we further investigated the effects of perinatal exposure to low doses of cypermethrin (CP) on pubertal onset and hypothalamic-pituitary-ovarian axis in the female mice offspring. The treatment of CP with 60 μg/kg/day from gestation day 6 (GD6) to postnatal day 21 (PND21) significantly decreased the time to puberty in the female offspring. Exposure of CP increased the serum levels of gonadotropin-releasing hormone (GnRH) and the expression of GnRH genes in a dose-dependent manner in the female offspring. CP also induced the serum levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as the expression of gonadotropin subunit genes [LHβ, FSHβ, and chorionic gonadotropin α (Cgα)]. Furthermore, CP induced serum estradiol (E₂) levels and the expression of steroidogenesis-related genes [steroidogenic acute regulatory (StAR) and Cytochrome p 450, family 11, subfamily A, polypeptide 1 (CYP11A1)] in the ovary. In accordance with the in vivo tests, administration of CP (6.7, 20, and 60 μg/L) stimulated a dose-dependent increase in the synthesis and secretion of the puberty-related hormones in the explants of hypothalamus, pituitary, and ovary. The interference with calcium channels in the ovary may be responsible for CP-induced pubertal onset. Our study provided evidence that perinatal exposure to low doses of CP induced puberty-related hormones and decreased the time to puberty in the female offspring.

Impact of Physiologically Relevant Genistein Exposure at Different Time Windows on Puberty Onset and Neuroendocrine Function in Female Rats

SCOPE

Puberty timing, critical for adulthood wellbeing, is influenced by the environment, life-style, and diets. However, differential puberty-interfering effects of soy and soy isoflavone are observed in both epidemiological and toxicological studies. Additionally, their impact on neuroendocrine function at various pre-pubertal developmental windows is unclear.

METHODS AND RESULTS

This study investigates the effect of genistein, a typical soy isoflavone, at neonatal, lactational, and post-weaning stages on the time of vaginal opening and determines the levels of neuroendocrine factors in female rats using immunofluorescence, immunochemistry, and enzyme-linked immunosorbent assays. A physiologically relevant dosage (10 mg kg^-1 ) is used to resemble human exposure. The results show that genistein exposure at lactational stage significantly accelerates vaginal opening time, marginally increases hypothalamic gonadotropin-releasing hormone (GnRH) secretion, significantly enhances kisspeptin receptor expression, and markedly elevates blood levels of GnRH, luteinizing hormone, and follicle-stimulating hormone, while neonatal and post-weaning exposures do not induce significant alternations.

CONCLUSION

Lactational stage may be an important window for genistein to impact reproductive development and neuroendocrine regulations.

Polycyclic aromatic hydrocarbons are associated with later puberty in girls: A longitudinal study

The objective of this study is to explore associations between PAH exposures and puberty timing in girls. Beginning in May 2014, 734 girls age 7.2-11.8 years in Chongqing, China, were enrolled in a prospective cohort study. They were followed up every 6 months from enrollment through June 2021, at which point participants were ages 13.6-18.3 years. Metabolite concentrations of four PAHs (1-hydroxypyrene [1-OHPyr], 2-hydroxynaphthalene [2-OHNap], 2-hydroxyfluorine [2-OHFlu], and 9-hydroxyphenanthrene [9-OHPhe]) were measured in urine samples at baseline. At each follow up visit, the Tanner's Sexual Maturity Rating scale was administered. Cox proportional hazards models were used to estimate associations between four urinary PAH metabolite concentrations and four markers of puberty: menarche, breast development, pubic hair development, and axillary hair development. Geometric mean concentrations of 1-OHPyr, 2-OHNap, 2-OHFlu and 9-OHPhe in urine were 0.47 μg/L, 3.31 μg/L, 1.49 μg/L, 3.75 μg/L, respectively. There were statistically significant associations between several urinary PAH metabolite concentrations and puberty outcomes. PAH metabolite concentrations were grouped as Low (<25th percentile, referent group), Moderate (25th-75th percentile) or High (>75th). Girls with moderate levels of 1-OHPyr were at higher risk of delayed pubic hair development (hazard ratio [HR]: 0.82, 95 % confidence interval [CI]: 0.68-0.99). Delayed breast development (HR: 0.77, 95 % CI: 0.60-0.99) and pubic hair development (HR: 0.76, 95 % CI: 0.60-0.95) were associated with high 2-OHNap. High c 2-OHFlu was associated with delayed pubic hair development (HR: 0.77, 95 % CI: 0.61-0.96). Delayed breast (HR: 0.79, 95 % CI: 0.64-0.97), pubic hair (HR: 0.79, 95 % CI: 0.65-0.96) and axillary hair development (HR: 0.80, 95 % CI: 0.65-0.99) was associated with moderate 9-OHPhe. In conclusion, PAH exposure may delay puberty onset in girls.

Influence on the adult male Leydig cell biomarker insulin‐like peptide 3 of maternal exposure to estrogenic and anti‐androgenic endocrine disrupting compound mixtures: A retrospective study

Insulin-like peptide 3 (INSL3) is a peptide biomarker secreted specifically by the mature Leydig cells of the testes. It is constitutive, has low within-individual variance, and effectively measures the functional capacity of Leydig cells to make testosterone. In young adult men there is a large 10-fold range of serum INSL3 concentration, persisting into old age, and implying that later hypogonadal status might be programmed in early life. To determine whether maternal exposure to environmental endocrine disrupting compounds (EDCs) influences adult serum INSL3 concentration, using a retrospective paradigm, INSL3 was measured in young adult male rats (80-90 days) from the F1 generation of females maternally exposed to varied doses of bisphenol A (BPA), butylparaben, epoxiconazole, and fludioxonil as single compounds, as well as estrogenic and anti-androgenic mixtures of BPA and butylparaben, and di(2-ethylhexyl) phthalate and procymidone respectively. A mixture of BPA and butylparaben significantly reduced circulating INSL3 concentration in adult male progeny. The remaining compounds or mixtures tested, though sufficient to induce other effects in the F1 generation were without significant effect. Maternal exposure to low concentrations of some EDCs may be a contributing factor to the variation in the Leydig cell biomarker INSL3 in young adulthood, though caution is warranted translating results from rats to humans.

Constitutional delay of growth and puberty in female mice is induced by circadian rhythm disruption in utero

Constitutional delay of growth and puberty (CDGP) refers to the late onset of puberty. CDGP is associated with poor psychosocial outcomes and elevated risk of cardiovascular and osteoporotic diseases, especially in women. The environmental factors that contribute to CDGP are poorly understood. Here, we investigated the effects of chronic circadian disturbance (CCD) during the fetal stage on the pubertal development of female mice. Compared to non-stressed female (NS-F) mice that were not exposed to CCD in utero, adolescent CCD female (CCD-F) mice exhibited phenotypes that were consistent with CDGP, including lower body weight, reduced levels of circulating gonadal hormones, decreased expression of gonadal hormones and steroid synthesis-related enzymes in the ovary and hypothalamus, irregular estrus cycles, and tardive vaginal introitus initial opening (VO) days (equivalent to the menarche). Phenotypic differences in the above-noted parameters were not observed in CCD-F mice once they had reached adulthood. The expression of genes involved in fatty acid metabolism was perturbed in the ovary and hypothalamus of CCD-F mice. In addition, the ovaries of these animals exhibited altered diurnal expression profiles of circadian clock genes. Together, our findings not only suggest that CCD during fetal development may result in delayed puberty in female mice, they also offer insights on potential mechanisms that underlie CDGP.

Association of urinary metabolites of non-persistent pesticides with serum sex hormones among the US females: NHANES 2013-2014

BACKGROUND

Evidence indicated the possibility of non-persistent pesticides disrupting the homeostasis of sex hormones. However, few studies have focused on this relationship in females. We aimed to explore the relationship between non-persistent pesticide exposure and sex hormones among the US females from the National Health and Nutrition Examination Survey 2013-2014.

METHODS

A total of 790 females, including girls (6-11 years), female adolescents (12-19 years), and adult females (>19 years), were enrolled in this study. Age stratified associations of individual non-persistent pesticide metabolites and their mixtures with sex hormones were analyzed by weighted multiple linear regression and Bayesian kernel machine regression (BKMR) using spot urinary non-persistent pesticide measurement, including 2,4-dichlorophenoxyacetic acid (2,4-D), 3,5,6-trichloropyridinol (TCPY), para-nitrophenol (PNP) and 3-phenoxybenzoic acid (3-PBA), and three serum sex hormones [total testosterone (TT), estradiol (E2) and sex hormone binding globulin (SHBG)].

RESULTS

In girls, weighted multivariate linear regression indicated that both 2,4-D and PNP were negatively associated with TT, and TCPY was inversely associated with SHBG. In female adolescents, TCPY was negatively associated with TT and E2, and 3-PBA was negatively associated with SHBG; positive associations were detected both in 2,4-D with SHBG, and in PNP with TT. In adult females, a higher concentration of 3-PBA was associated with higher levels of TT. The BKMR model showed that in female adolescents, the concentrations of pesticide metabolite mixtures at or above the 55th percentile were negatively related to the levels of E2 compared with their mixtures at 50th percentile, and an inverse U-shaped exposure-response function between PNP and E2 was found.

CONCLUSIONS

Associations between the four non-persistent pesticide metabolites and serum sex hormones were identified in the US females from NHANES 2013-2014 and these associations were age dependent, especially in adolescents. Large-scale cohort studies are needed to confirm these findings and elucidate the potential biological mechanisms.

The Association Between Heavy Metals Exposure and Sex Hormones: a Systematic Review on Current Evidence

The general population is voluntarily or unintentionally exposed to heavy metals through ingestion of food, polluted water, or contact with soil, dust, or polluted air. A number of metals are considered as endocrine disruptors and can alter the level of reproductive hormones. This study aims to systematically review the epidemiological studies on the association between heavy metals exposure and sex hormones level. We conducted a systematic search from available databases, including PubMed, Clarivate Web of Science, Scopus, Google Scholar, and Cochrane Collaboration, until April 2021. The relevant studies were selected, and two reviewers conducted the quality assessment. Then, data were extracted based on the inclusion criteria. We identified nine articles related to the association between heavy metals exposure and sex hormones level. We summarized the relevant information. Due to the diversity of metals and the variety of sex hormones, the effect of exposure on hormones level was not clear; however in most studies, at least for one metal, a significant association (inverse or positive) was observed between metals exposure and hormones level. Heavy metals exposure may potentially alter sex hormone levels; however, further research is needed to evaluate the impact of this association.

Prenatal Environmental Exposure to Persistent Organic Pollutants and Reproductive Hormone Profile and Pubertal Development in Dutch Adolescents

Persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), may interfere with hormonal processes. Knowledge about the effects of prenatal exposure to PCBs and their hydroxylated metabolites (OH-PCBs) on pubertal development is limited. Therefore, the aim of the current study was to determine whether prenatal environmental PCB and OH-PCB exposure are associated with reproductive hormone levels and pubertal characteristics in 13- to 15-year-old children. In this Dutch observational cohort study, 194 mother–infant pairs were included (1998–2002). Maternal pregnancy serum levels of PCBs, OH-PCBs, and other POPs were measured. At follow-up (2014–2016), we measured serum or plasma levels of reproductive hormones in their children. We assessed Tanner stages and testicular volume (by clinician or standardized self-assessment), and participants completed questionnaires on pubertal onset. In total, 101 adolescents (14.4 ± 0.8 years; 53.7% of invited) participated, and 55 were boys. In boys, higher prenatal PCB levels were associated with higher testosterone levels, higher pubic hair stage, larger testicular volume, and younger age at onset of growth spurt and voice break. In girls, higher prenatal PCB levels were associated with higher stages for breast development. In conclusion, higher prenatal PCB exposure could be associated with more advanced pubertal development in 13- to 15-year-old children.

Associations between exposure to a mixture of phenols, parabens, and phthalates and sex steroid hormones in children 6-19 years from NHANES, 2013-2016

BACKGROUND

Humans are typically exposed to mixtures of environmental endocrine-disrupting chemicals simultaneously, but most studies have considered only a single chemical or a class of similar chemicals.

OBJECTIVES

We examined the association of exposure to mixtures of 7 chemicals, including 2 phenols [bisphenol A (BPA) and bisphenol S (BPS)], 2 parabens [methylparaben (MeP) and propyl paraben (PrP)], and 3 phthalate metabolites [Mono-benzyl phthalate (MBzP), mono-isobutyl phthalate (MiBP), mono (carboxyoctyl) phthalate (MCOP)] with sex steroid hormones.

METHODS

A total of 1179 children aged 6-19 years who had complete data on both 7 chemicals and sex steroid hormones of estradiol (E₂), total testosterone (TT), and sex hormone-binding globulin (SHBG) were analyzed from the U.S. National Health and Nutrition Examination Survey 2013-2016. Free androgen index (FAI) calculated by TT/SHBG, and the ratio of TT to E₂ (TT/E₂) were also estimated. Puberty was defined if TT ≥ 50 ng/dL in boys, E₂ ≥ 20 pg/mL in girls; otherwise prepuberty was defined. Linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were performed to estimate the associations of individual chemical or chemical mixtures with sex hormones.

RESULTS

The linear regression showed that 2 phenols, 2 parabens, and 3 phthalate metabolites were generally negatively associated with E₂, TT, FAI, and TT/E₂, while positively with SHBG. Moreover, these associations were more pronounced among pubertal than prepubertal children. The aforementioned associations were confirmed when further applying WQS and BKMR, and the 3 phthalates metabolites were identified to be the most heavily weighing chemicals.

CONCLUSIONS

Exposure to phenols, parabens, and phthalates, either individuals or as a mixture, was negatively associated with E₂, TT, FAI and TT/E₂, while positively with SHBG. Those associations were stronger among pubertal children.

Maternal thyroid disease in pregnancy and timing of pubertal development in sons and daughters

OBJECTIVE

To study whether maternal thyroid disease in pregnancy is associated with pubertal timing in sons and daughters.

DESIGN

Cohort study.

SETTING

National birth cohort and health registers.

PATIENT(S)

A total of 15,763 mothers and children from the Danish National Birth Cohort and its Puberty Cohort.

INTERVENTION(S)

Register-based and self-reported information on maternal thyroid diseases during pregnancy (hyperthyroidism, hypothyroidism, benign goiter, or no thyroid disease [reference group]).

MAIN OUTCOME MEASURE(S)

The adjusted mean age difference (months) at attaining several self-reported pubertal milestones collected every 6 months using an interval-censored regression and the average difference in age at attaining all pubertal milestones using the Huber-White robust variance estimation (primary outcome).

RESULT(S)

Sons of mothers with hyperthyroidism had earlier pubertal development (average difference, -2.9 [95% confidence interval (CI), -5.0 to -0.7] months) than unexposed sons. Maternal hypothyroidism was not associated with pubertal development in sons (average difference, -1.2 [95% CI, -5.1 to 2.7] months). We observed nonstatistically significant indications of earlier pubertal development in sons of mothers with benign goiter (average difference, -1.9 [95% CI, -4.6 to 0.9] months). Maternal thyroid disease was not associated with pubertal development in daughters (average difference (months), hyperthyroidism, -0.8 [95% CI, -2.8 to 1.2]; hypothyroidism, 0.3 [95% CI, -3.1 to 3.8]; and benign goiter, 0.7 [95% CI, -2.0 to 3.4]).

CONCLUSION(S)

We found indications of earlier pubertal development in sons of mothers with hyperthyroidism. More research is needed to further investigate the observed sex-specific association.

Early programming of reproductive health and fertility: novel neuroendocrine mechanisms and implications in reproductive medicine

BACKGROUND

According to the Developmental Origins of Health and Disease (DOHaD) hypothesis, environmental changes taking place during early maturational periods may alter normal development and predispose to the occurrence of diverse pathologies later in life. Indeed, adverse conditions during these critical developmental windows of high plasticity have been reported to alter the offspring developmental trajectory, causing permanent functional and structural perturbations that in the long term may enhance disease susceptibility. However, while solid evidence has documented that fluctuations in environmental factors, ranging from nutrient availability to chemicals, in early developmental stages (including the peri-conceptional period) have discernible programming effects that increase vulnerability to develop metabolic perturbations, the impact and eventual mechanisms involved, of such developmental alterations on the reproductive phenotype of offspring have received less attention.

OBJECTIVE AND RATIONALE

This review will summarize recent advances in basic and clinical research that support the concept of DOHaD in the context of the impact of nutritional and hormonal perturbations, occurring during the periconceptional, fetal and early postnatal stages, on different aspects of reproductive function in both sexes. Special emphasis will be given to the effects of early nutritional stress on the timing of puberty and adult gonadotropic function, and to address the underlying neuroendocrine pathways, with particular attention to involvement of the Kiss1 system in these reproductive perturbations. The implications of such phenomena in terms of reproductive medicine will also be considered.

SEARCH METHODS

A comprehensive MEDLINE search, using PubMed as main interface, of research articles and reviews, published mainly between 2006 and 2021, has been carried out. Search was implemented using multiple terms, focusing on clinical and preclinical data from DOHaD studies, addressing periconceptional, gestational and perinatal programming of reproduction. Selected studies addressing early programming of metabolic function have also been considered, when relevant.

OUTCOMES

A solid body of evidence, from clinical and preclinical studies, has documented the impact of nutritional and hormonal fluctuations during the periconceptional, prenatal and early postnatal periods on pubertal maturation, as well as adult gonadotropic function and fertility. Furthermore, exposure to environmental chemicals, such as bisphenol A, and maternal stress has been shown to negatively influence pubertal development and gonadotropic function in adulthood. The underlying neuroendocrine pathways and mechanisms involved have been also addressed, mainly by preclinical studies, which have identified an, as yet incomplete, array of molecular and neurohormonal effectors. These include, prominently, epigenetic regulatory mechanisms and the hypothalamic Kiss1 system, which likely contribute to the generation of reproductive alterations in conditions of early nutritional and/or metabolic stress. In addition to the Kiss1 system, other major hypothalamic regulators of GnRH neurosecretion, such as γ-aminobutyric acid and glutamate, may be targets of developmental programming.

WIDER IMPLICATIONS

This review addresses an underdeveloped area of reproductive biology and medicine that may help to improve our understanding of human reproductive disorders and stresses the importance, and eventual pathogenic impact, of early determinants of puberty, adult reproductive function and fertility.

Intergenerational protein deficiency and adolescent reproductive function of subsequent female generations (F1 and F2) in rat model

Background

Efficient reproductive function is an important characteristic that has evolved through natural selection. Nutrition can modulate reproductive activities at different levels, and its effect on reproduction is deemed complex and less predictable.

Objective

This study aims at investigating the underlying effect of persistent dietary protein deficiency during early life on reproductive parameters of subsequent (F₁ and F₂) generations.

Method

Rats in group of four (4) were fed daily, different ration of protein diet (PD) formulated as: 21% protein diet, 10%protein diet, 5%protein diet and control diet (rat chow, containing 16–18% protein). They were fed ad libitum before mating, throughout gestation and lactation, and next generations were weaned to the maternal diet. Reproductive function analysis (which include; gestation and pubertal hormonal profiling, onset of puberty, oestrus cyclicity, sexual response) and morphometric analysis of the ovarian structure were carried out to assess associated consequences.

Results

There was significant reduction in the fertility index (Control; 85.8%., 21%PD; 88.43%., as compared to 10%PD; 65.9%., 5%PD; 35.78%.,) at F_1, also recurring in F₂ respectively as a consequence of altered reproductive function in the protein deficient models at P ≤ 0.05. Low protein diet posed suboptimal intrauterine condition, which was linked to increased prenatal morbidity and mortality (control; 11.3%., 21%PD; 3.3%., 10%PD; 27.4%., 5%PD; 32.9%), low birthweight (control; 5.29, 4.9 g., 21%PD; 5.5, 5.06 g., 10%PD; 4.05, 3.86 g., 5%PD; 2.7, 2.5 g) at F₁ and F₂ respectively, delayed onset of puberty (with average pubertal age set at: control; PND 36, 21%PD; PND 38 while 10%PD; PND 62., and 5%PD; PND 67), followed by induced cycle irregularity, altered follicular maturation and endocrine dysfunction, more severe in 5%PD.

Conclusion

Reproductive status of a female organism depends on the maintenance of ovarian structure and function that has been associated with the hypothalamic pituitary-gonadal axis, hormonal events and sexual maturity. There is therefore an association between persistent early life protein deficiency and reproductive response which mechanistically involves life-long changes in key ovarian cytoarchitecture and function.

•

Intergenerational protein malnutrition exerts female hormonal dysregulation and irregular cyclicity at adolescence.

•

It delayed pubertal attainment and reproductive performance that persists to the next–generation of rats.

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Perinatal protein deficiency also altered the ovarian morphology with an implication on fertility index across generations.

A Putative Adverse Outcome Pathway Network for Disrupted Female Pubertal Onset to Improve Testing and Regulation of Endocrine Disrupting Chemicals

The average age for pubertal onset in girls has declined over recent decades. Epidemiological studies in humans and experimental studies in animals suggest a causal role for endocrine disrupting chemicals (EDCs) that are present in our environment. Of concern, current testing and screening regimens are inadequate in identifying EDCs that may affect pubertal maturation, not least because they do not consider early-life exposure. Also, the causal relationship between EDC exposure and pubertal timing is still a matter of debate. To address this issue, we have used current knowledge to elaborate a network of putative adverse outcome pathways (pAOPs) to identify how chemicals can affect pubertal onset. By using the AOP framework, we highlight current gaps in mechanistic understanding that need to be addressed and simultaneously point towards events causative of pubertal disturbance that could be exploited for alternative test methods. We propose 6 pAOPs that could explain the disruption of pubertal timing by interfering with the central hypothalamic trigger of puberty, GnRH neurons, and by so doing highlight specific modes of action that could be targeted for alternative test method development.

Genetic, epigenetic and enviromental influencing factors on the regulation of precocious and delayed puberty

The pubertal development onset is controlled by a network of genes that regulate the gonadotropin releasing hormone (GnRH) pulsatile release and the subsequent increase of the circulating levels of pituitary gonadotropins that activate the gonadal function. Although the transition from pre-pubertal condition to puberty occurs physiologically in a delimited age-range, the inception of pubertal development can be anticipated or delayed due to genetic and epigenetic changes or environmental conditions. Most of the genetic and epigenetic alterations concern genes which encode for kisspeptin, GnRH, LH, FSH and their receptor, which represent crucial factors of the hypothalamic-pituitary-gonadal (HPG) axis. Recent data indicate a central role of the epigenome in the regulation of genes in the hypothalamus and pituitary that could mediate the flexibility of pubertal timing. Identification of epigenetically regulated genes, such as Makorin ring finger 3 (MKRN3) and Delta-like 1 homologue (DLK1), respectively responsible for the repression and the activation of pubertal development, provides additional evidence of how epigenetic variations affect pubertal timing. This review aims to investigate genetic, epigenetic, and environmental factors responsible for the regulation of precocious and delayed puberty.

Emerging Roles of Epigenetics in the Control of Reproductive Function: Focus on Central Neuroendocrine Mechanisms

Reproduction is an essential function for perpetuation of the species. As such, it is controlled by sophisticated regulatory mechanisms that allow a perfect match between environmental conditions and internal cues to ensure adequate pubertal maturation and achievement of reproductive capacity. Besides classical genetic regulatory events, mounting evidence has documented that different epigenetic mechanisms operate at different levels of the reproductive axis to finely tune the development and function of this complex neuroendocrine system along the lifespan. In this mini-review, we summarize recent evidence on the role of epigenetics in the control of reproduction, with special focus on the modulation of the central components of this axis. Particular attention will be paid to the epigenetic control of puberty and Kiss1 neurons because major developments have taken place in this domain recently. In addition, the putative role of central epigenetic mechanisms in mediating the influence of nutritional and environmental cues on reproductive function will be discussed.

Transient central precocious puberty: a new entity among the spectrum of precocious puberty?

Objective

Recently, we observed some cases of Precocious Puberty (PP) with a partial central activation of hypothalamic-pituitary-gonadal (HPG) axis that tended to normalized in 6–12 months. To evaluate the frequency of this form within the spectrum of forms of PP, we retrospectively assessed the clinical, hormonal and ultrasound characteristics of patients attending to our Center for signs of PP, between 2007 and 2017. To hypothesize some causes of this “pubertal poussée” a questionnaire about environmental data was provided to patients.

Methods

96 girls were recruited for the study and divided into three Groups. Group 1: 56 subjects with Central PP (CPP) requiring treatment with GnRH analogue; Group 2: 22 subjects with transient activation of pubertal axis, that tended to normalize, “Transient CPP”(T-CPP); Group 3: 18 subjects with Isolated Thelarche (IT).

Results

Mean age at diagnosis was 6.8 ± 1.0 years in Group 1, 5.9 ± 1.3 years in Group 2 and 5.6 ± 1.5 years in Group 3. A significant increase of diagnosis of T-CPP was observed over the study period. Significantly higher use of some homeopathic medicines and potential exposure to pesticides was reported in Group 2 vs Group 1.

Conclusions

To our knowledge, we first reported a form defined as T-CPP, characterized by partial activation in the HPG axis normalizing over time. An increased use of homeopathic medicines and exposure to environmental pollutants in these patients was evidenced.

Update about the disrupting-effects of phthalates on the human reproductive system

Phthalate esters are synthetic chemicals used in the plastic industry as plasticizers and consumable products. According to United Nations, about 400 million tons of plastic are produced every year. In parallel with increased production, the concerns about its effects on human health have increased because phthalates are endocrine-disrupting compounds. Humans are continuously exposed to phthalates through different routes of exposure. Experimental data have associated the phthalates exposure to adverse effects on development and reproduction in women (e.g., earlier puberty, primary ovarian insufficiency, endometriosis, preterm birth, or in vitro fertilization) and men (e.g., anogenital distance, cryptorchidism, hypospadias, and changes in adult reproductive function) although there is no consensus. Therefore, one question arises: could the increase in infertility be related to phthalates exposure? To answer this question, we aimed to assess the disrupting-effects of phthalates on the human reproductive system. For this, we reviewed the current literature based on epidemiological and experimental data and experimental studies in humans. The phthalate effects were discussed in a separate mode for female and male reproductive systems. In summary, phthalates induce toxicity in the reproductive system and human development. The increased plastic production may be related to the increase in human infertility.

Peripubertal Bisphenol A Exposure Imparts Detrimental Age-Related Changes in Body Composition, Cognition, and Hydrogen Sulfide Production Capacities

Aims: Peripubertal endocrine disruption has immediate and lifelong consequences on health, cognition, and lifespan. Disruption comes from dietary, environmental, and pharmaceutical sources. The plasticizer Bisphenol A (BPA) is one such endocrine disrupting chemical. However, it is unclear whether peripubertal BPA exposure incites long-lasting physiological, neuro-cognitive, and/or longevity-related metabolic impairments. Catabolism of cysteine via transsulfuration enzymes produces hydrogen sulfide (H2S), a redox-modulating gasotransmitter causative to endocrine and metabolic homeostasis and improved cognitive function with age. As thyroid hormone (TH) regulates hepatic H2S production and BPA is a TH receptor antagonist, we hypothesized that BPA exposure during peripubertal development impairs metabolic and neuro-cognitive/behavioral endpoints in aged mice, in part, due to altered peripheral and/or localized H2S production and redox status. Results: To test this, male C57BL/6J mice at 5 weeks of age were orally exposed daily for 5 weeks to 250 μg BPA/kg, defined as low dose group (LD BPA), or 250 mg BPA/kg, defined as high dose group (HD BPA). Both LD and HD BPA exposure decreased lean mass and increased fat mass accompanied by decreased serum total TH at advanced ages. In addition, LD BPA had an anxiogenic effect whereas HD BPA caused cognitive deficits. Notably, HD BPA disrupted tissue-specific H2S production capacities and/or protein persulfidation, with the former negatively correlated with memory deficits and oxidative stress. Innovation and Conclusion: These findings provide a potential mechanism of action for acute and long-term health impacts of BPA-induced peripubertal endocrine disruption and bolster the need for improved monitoring and limitation of adolescent BPA exposure.

Endocrine-disrupting chemicals and their effects on puberty

Sexual maturation in humans is characterized by a unique individual variability. Pubertal onset is a highly heritable polygenic trait but it is also affected by environmental factors such as obesity or endocrine disrupting chemicals. The last 30 years have been marked by a constant secular trend toward earlier age at onset of puberty in girls and boys around the world. More recent data, although more disputed, suggest an increased incidence in idiopathic central precocious puberty. Such trends point to a role for environmental factors in pubertal changes. Animal data suggest that the GnRH-neuronal network is highly sensitive to endocrine disruption during development. This review focuses on the most recent data regarding secular trend in pubertal timing as well as potential new epigenetic mechanisms explaining the developmental and transgenerational effects of endocrine disrupting chemicals on pubertal timing.

Ambient air pollution and endocrinologic disorders in childhood

Ambient air pollution has been proposed as an important environmental risk factor that increases global mortality and morbidity. Over the past decade, several human and animal studies have reported an association between exposure to air pollution and altered metabolic and endocrine systems in children. However, the results for these studies were mixed and inconclusive and did not demonstrate causality because different outcomes were observed due to different study designs, exposure periods, and methodologies for exposure measurements. Current proposed mechanisms include altered immune response, oxidative stress, neuroinflammation, inadequate placental development, and epigenetic modulation. In this review, we summarized the results of previous pediatric studies that reported effects of prenatal and postnatal air pollution exposure on childhood type 1 diabetes mellitus, obesity, insulin resistance, thyroid dysfunction, and timing of pubertal onset, along with underlying related mechanisms.

Multi- and Transgenerational Outcomes of an Exposure to a Mixture of Endocrine-Disrupting Chemicals (EDCs) on Puberty and Maternal Behavior in the Female Rat

BACKGROUND

The effects of endocrine-disrupting chemicals (EDCs) on fertility and reproductive development represent a rising concern in modern societies. Although the neuroendocrine control of sexual maturation is a major target of EDCs, little is known about the potential role of the hypothalamus in puberty and ovulation disruption transmitted across generations.

OBJECTIVES

We hypothesized that developmental exposure to an environmentally relevant dose of EDC mixture could induce multi- and/or transgenerational alterations of sexual maturation and maternal care in female rats through epigenetic reprograming of the hypothalamus. We investigated the transmission of a disrupted reproductive phenotype via the maternal germline or via nongenomic mechanisms involving maternal care.

METHODS

Adult female Wistar rats were exposed prior to and during gestation and until the end of lactation to a mixture of the following 13 EDCs: di-n-butyl phthalate (DnBP), di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), vinclozolin, prochloraz, procymidone, linuron, epoxynaxole, dichlorodiphenyldichloroethylene, octyl methoxynimmate, 4-methylbenzylidene camphor (4-MBC), butylparaben, and acetaminophen. Perinatally exposed offspring (F1) were mated with unexposed males to generate germ cell (F2) and transgenerationally exposed (F3 and F4) females. Sexual maturation, maternal behavior, and hypothalamic targets of exposure were studied across generations.

RESULTS

Germ cell (F2) and transgenerationally (F3) EDC-exposed females, but not F1, displayed delayed pubertal onset and altered folliculogenesis. We reported a transgenerational alteration of key hypothalamic genes controlling puberty and ovulation (Kiss1, Esr1, and Oxt), and we identified the hypothalamic polycomb group of epigenetic repressors as actors of this mechanism. Furthermore, we found a multigenerational reduction of maternal behavior (F1-F3) induced by a loss in hypothalamic dopaminergic signaling. Using a cross-fostering paradigm, we identified that the reduction in maternal phenotype was normalized in EDC-exposed pups raised by unexposed dams, but no reversal of the pubertal phenotype was achieved.

DISCUSSION

Rats developmentally exposed to an EDC mixture exhibited multi- and transgenerational disruption of sexual maturation and maternal care via hypothalamic epigenetic reprogramming. These results raise concerns about the impact of EDC mixtures on future generations. https://doi.org/10.1289/EHP8795.

Environmentally relevant perinatal exposure to DBP disturbs testicular development and puberty onset in male mice

Di-n-butyl phthalate (DBP) is considered as a potential modifier of puberty. However, different results indicate that DBP plays an accelerated, delayed, or neutral role in the initiation of puberty. Furthermore, whether the effect of DBP on puberty will disrupt the function of reproductive system in the adults is still ambiguous. Therefore, we aimed to investigate the effect of maternal exposure to DBP on the onset of puberty in male offspring mice and the subsequent changes in the development of reproductive system. Here, pregnant mice were treated with 0 (control), 50, 250, or 500 mg/kg/day DBP in 1 mL/kg corn oil administered daily by oral gavage from gestation day (GD) 12.5 to parturition. Compared with the control group, the 50 mg/kg/day DBP group accelerated puberty onset and testicular development were quite remarkable in male offspring mice during early puberty. Furthermore, in 22-day male offspring mice, 50 mg/kg/day DBP induced increased levels of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone in serum, and promoted the expression of steroidogenesis-related genes in the testes. Testicular Leydig cells (LCs) were isolated from the testes of 3-week-old mice and treated with 0 (control), 0.1, 1 mM monobutyl phthalate (MBP, the active metabolite of DBP) for 24 h. Consistent with the in vivo results, the expression of steroidogenesis-related genes and testosterone production were increased in LCs following exposure to 0.1 mM MBP. In adulthood, testes of the male offspring mice exposed to all doses of DBP exhibited adverse morphology compared with the control group. These results demonstrated that maternal exposure to 50 mg/kg/day DBP induced earlier puberty and precocious development of the testis, and eventually damaged the reproductive system in the later life.

Outdoor air pollution and hormone-assessed pubertal development in children: Results from the GINIplus and LISA birth cohorts

BACKGROUND

Air pollution is hypothesized to affect pubertal development. However, the few studies on this topic yielded overall mixed results. These studies did not consider important pollutants like ozone, and none of them involved pubertal development assessed by estradiol and testosterone measurements. We aimed to analyze associations between long-term exposure to four pollutants and pubertal development based on sex hormone concentrations among 10-year-old children.

METHODS

These cross-sectional analyses were based on the 10-year follow-up medical examinations of 1945 children from the Munich and Wesel centers of the GINIplus and LISA German birth cohorts. Female and male pubertal development was assessed by dichotomizing the concentration of hormones in serum at 18.4 pmol/L and 0.087 nmol/L using the lower limits of quantification for estradiol and testosterone, respectively. Land-use regression models derived annual average concentrations of particulate matter with an aerodynamic diameter < 2.5 and 10 µm (PM_2.5 and PM₁₀), as well as spatial models assessed yearly average concentrations of nitrogen dioxide (NO₂) and ozone, were calculated at the 10-year residential addresses. To evaluate associations, we utilized logistic regressions adjusted for potential covariates. The analyses were stratified by area and sex.

RESULTS

Around 73% of the 943 females and 25% of the 1002 males had a high level of hormones and had already started puberty at the age of 10. Overall, we found no statistically significant associations between exposure to particles (PM_2.5 or PM₁₀) and pubertal development. Results on NO₂ and ozone were not significant as well; for instance, per 10 µg/m³ increase in ozone concentration, odds ratios and 95% confidence intervals were 0.900 (0.605, 1.339) and 0.830 (0.573, 1.203) for females and males, respectively. Stratified by area, the aforementioned results did not reveal any associations either.

CONCLUSIONS

Our study did not observe the associations between ambient air pollutants and pubertal development determined by estradiol and testosterone levels in children. However, due to the current limited number of studies on this topic, our results should be cautiously interpreted. Future longitudinal studies are needed to assess the association.

Hypertensive disorders in pregnancy and timing of pubertal development in daughters and sons

STUDY QUESTION

Do maternal hypertensive disorders affect pubertal development in daughters and sons?

SUMMARY ANSWER

Pubertal development tended to occur earlier in daughters of mothers with 'preeclampsia, eclampsia or HELLP syndrome' (hemolysis, elevated liver enzymes and low blood platelets) or hypertension in pregnancy compared to daughters born of normotensive mothers.

WHAT IS KNOWN ALREADY

The existing literature suggests some or no association between preeclampsia and pubertal development in daughters, but not in sons. None of the previous studies has investigated the possible association between other types of hypertensive disorders (hypertension, eclampsia or HELLP syndrome) and pubertal timing in children.

STUDY DESIGN, SIZE, DURATION

Longitudinal cohort study consisting of 15 819 mother-child pairs with information on maternal hypertensive disorders collected during pregnancy and information on pubertal development collected half-yearly from the age of 11 years and until fully developed or 18 years of age.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants are children from the Puberty Cohort nested within the Danish National Birth Cohort. The exposure was register-based and self-reported information on maternal hypertensive disorders during pregnancy. The outcomes were children's self-reported information on pubertal development, including Tanner stage 1-5 (pubic hair (both daughters and sons) and breast development (daughters) or genital development (sons)), first menstrual bleeding (daughters) or first ejaculation (sons), voice break episode (sons), axillary hair development and acne occurrence (both daughters and sons). The main outcome was mean difference in age at attaining each pubertal milestone and a combined pubertal marker in children of mothers with hypertensive disorders in pregnancy (either hypertension (n = 490), 'preeclampsia, eclampsia or HELLP syndrome' (n = 419) or 'unspecific hypertensive disorders' (n = 334) with unexposed children as reference (n = 14 576)).

MAIN RESULTS AND THE ROLE OF CHANCE

In daughters of mothers with 'preeclampsia, eclampsia or HELLP syndrome', we observed tendencies of earlier pubertal timing (combined marker: -2.0 (95% CI: -3.9; 0.0) months). In daughters of mothers with hypertension, several pubertal milestones tended to occur earlier than in daughters of normotensive mothers; however, all 95% CIs overlapped the null resulting in a combined pubertal marker of -1.0 (95% CI: -3.2; 1.1) months. In sons of mothers with any of the hypertensive disorders, we observed no difference in pubertal timing (combined markers: 'preeclampsia, eclampsia or HELLP syndrome': 0.1 (95% CI: -2.0; 2.1) months; hypertension: -0.6 (95% CI: -2.3; 1.1) months; 'unspecific hypertensive disorders': 0.2 (95% CI: -1.9; 2.2) months).

LIMITATIONS, REASONS FOR CAUTION

The study is subject to non-differential misclassification of self-reported information on maternal hypertensive disorders in pregnancy and current pubertal status; possibly causing bias toward the null.

WIDER IMPLICATIONS OF THE FINDINGS

Hypertensive disorders in pregnancy might accelerate pubertal timing in daughters; however, more studies are needed for causal conclusions.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Faculty of Health at Aarhus University. The authors have no financial relationships or competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Characterization of pubertal development of girls in rural Bangladesh

This study aimed to describe the timing and patterns of pubertal maturation of girls living in rural Bangladesh. Starting in September 2015, a total of 15,320 girls from a birth cohort, aged 9 to 15 years at initial encounter, were visited twice at about a one year interval, typically in their birth month. Participants were asked to self-report extent of pubertal maturation, including breast development, pubic hair growth and age at menarche, if applicable. Pubertal stage (abbreviated as B2 and B3-4 for breast development and PH2 and PH3-4 for pubic hair growth) was assigned. Data from both visits were pooled, yielding a total of 29,377 age-related observations per pubertal characteristic. Probit regression models were used to estimate distributions of age at which each stage of pubertal development was attained. Before age 8, <3% of the study population initiated pubertal maturation as indicated by onset of breast development (B2). The median (95% confidence interval) age of B2 and B3-4 was 11.02 (11.00–11.04) and 12.82 (12.80–12.83) years, respectively; and 12.93 (12.91–12.94) and 14.29 (14.27–14.31) years for the onset (PH2) and advanced stage (PH3-4) of pubic hair growth, respectively. Median age at menarche was 13.17 (13.15–13.19) years, with 2.15 years of timespan from B2 to menarche. Girls in rural Bangladesh progressed through puberty following a well-documented sequence of sexual maturation stages. The age at which each pubertal milestone took place was somewhat later, but the tempo from breast development to menarche was comparable to that observed elsewhere. Our findings present a current norm of pubertal maturation in a typical, rural adolescent population in South Asia, which could help inform future studies and interventions to preserve or improve early adolescent health and development.

AMP-activated protein kinase (AMPK) signaling in GnRH neurons links energy status and reproduction

BACKGROUND

Reproduction is tightly coupled to body energy and metabolic status. GnRH neurons, master elements and final output pathway for the brain control of reproduction, directly or indirectly receive and integrate multiple metabolic cues to regulate reproductive function. Yet, the molecular underpinnings of such phenomenon remain largely unfolded. AMP-activated protein kinase (AMPK), the fundamental cellular sensor that becomes activated in conditions of energy deficit, has been recently shown to participate in the control of Kiss1 neurons, essential gatekeepers of the reproductive axis, by driving an inhibitory valence in situations of energy scarcity at puberty. However, the contribution of AMPK signaling specifically in GnRH neurons to the metabolic control of reproduction remains unknown.

METHODS

Double immunohistochemistry (IHC) was applied to evaluate expression of active (phosphorylated) AMPK in GnRH neurons and a novel mouse line, named GAMKO, with conditional ablation of the AMPK α1 subunit in GnRH neurons, was generated. GAMKO mice of both sexes were subjected to reproductive characterization, with attention to puberty and gonadotropic responses to kisspeptin and metabolic stress.

RESULTS

A vast majority (>95%) of GnRH neurons co-expressed pAMPK. Female (but not male) GAMKO mice displayed earlier puberty onset and exaggerated LH (as surrogate marker of GnRH) responses to kisspeptin-10 at the prepubertal age. In adulthood, GAMKO females retained increased LH responsiveness to kisspeptin and showed partial resilience to the inhibitory effects of conditions of negative energy balance on the gonadotropic axis. The modulatory role of AMPK in GnRH neurons required preserved ovarian function, since the differences in LH pulsatility detected between GAMKO and control mice subjected to fasting were abolished in ovariectomized animals.

CONCLUSIONS

Altogether, our data document a sex-biased, physiological role of AMPK signaling in GnRH neurons, as molecular conduit of the inhibitory actions of conditions of energy deficit on the female reproductive axis.

Cellular and molecular features of EDC exposure: consequences for the GnRH network

The onset of puberty and the female ovulatory cycle are important developmental milestones of the reproductive system. These processes are controlled by a tightly organized network of neurotransmitters and neuropeptides, as well as genetic, epigenetic and hormonal factors, which ultimately drive the pulsatile secretion of gonadotropin-releasing hormone. They also strongly depend on organizational processes that take place during fetal and early postnatal life. Therefore, exposure to environmental pollutants such as endocrine-disrupting chemicals (EDCs) during critical periods of development can result in altered brain development, delayed or advanced puberty and long-term reproductive consequences, such as impaired fertility. The gonads and peripheral organs are targets of EDCs, and research from the past few years suggests that the organization of the neuroendocrine control of reproduction is also sensitive to environmental cues and disruption. Among other mechanisms, EDCs interfere with the action of steroidal and non-steroidal receptors, and alter enzymatic, metabolic and epigenetic pathways during development. In this Review, we discuss the cellular and molecular consequences of perinatal exposure (mostly in rodents) to representative EDCs with a focus on the neuroendocrine control of reproduction, pubertal timing and the female ovulatory cycle.

In utero and peripubertal metals exposure in relation to reproductive hormones and sexual maturation and progression among boys in Mexico City

BACKGROUND

Endocrine disrupting chemicals (EDCs) such as metals have been reported to alter circulating reproductive hormone concentrations and pubertal development in animals. However, the relationship has rarely been investigated among humans, with the exception of heavy metals, such as Pb and Cd. Our aim was to investigate measures of in utero and peripubertal metal exposure in relation to reproductive hormone concentrations and sexual maturation and progression among boys from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohorts.

METHODS

Our analysis included 118 pregnant women and their male children from the ELEMENT study. Essential and non-essential metals were measured in urine collected from the mothers during the third trimester of pregnancy and their male children at 8-14 years. Reproductive hormone concentrations [serum testosterone, estradiol, dehydroepiandrosterone sulfate (DHEA-S), inhibin B, and sex hormone-binding globulin (SHBG)] were measured in blood samples from the children at 8-14 years. We also assessed Tanner stages for sexual maturation (genital, pubic hair development, and testicular volume), at two time points (8-14, 10-18 years). We used linear regression to independently examine urinary metal concentrations in relation to each peripubertal reproductive hormones adjusting for child age and BMI. Generalized estimation equations (GEEs) were used to evaluate the association of in utero and peripubertal metal exposures with sexual maturation and progression during follow-up based on Tanner staging and testicular volume.

RESULTS

In utero and prepubertal concentrations of some urinary metals were associated with increased concentrations of peripubertal reproductive hormones, especially non-essential metal(loid)s As and Cd (in utero), and Ba (peripubertal) as well as essential metal Mo (in utero) in association with testosterone. More advanced pubic hair developmental stage and higher testicular volume at the early teen visit was observed for boys with higher non-essential metal concentrations, including in utero Al and peripubertal Ba, and essential metal Zn concentration (peripubertal). These metals were also associated with slower pubertal progression between the two visits.

CONCLUSION

These findings suggest that male reproductive development may be associated with both essential and non-essential metal exposure during in utero and peripubertal windows.