Endocrine disrupters and possible contribution to pubertal changes

Acrylamide exposure, sex hormones, and pubertal status in Japanese adolescents

Acrylamide may affect sex hormone levels and the timing of sexual maturation. The present study cross-sectionally examined interrelationship between the urinary metabolite of acrylamide exposure, serum sex hormone levels, and pubertal status in 408 Japanese adolescents aged 13-14 years. Their caregivers completed a questionnaire concerning the health status of their children, including pubertal maturation, and the lifestyles of children and parents. Pubertal status was queried by the Pubertal Development Scale. A major metabolite of acrylamide, N-acetyl-S-(2-carbamoylethyl)-cysteine (AAMA) in first-void urine samples. In male students, urinary AAMA was significantly inversely associated with testosterone, puberty stage, and facial hair growth after controlling for covariates. Serum testosterone and DHEAS were significantly positively associated with puberty stage. In female students, urinary AAMA was not associated with puberty stage, the indices, or any measured hormones. The data suggest that exposure to acrylamide may impact the pubertal development of boys through the effects on testosterone level.

Effects of pharmaceutical and personal care products on pubertal development: Evidence from human and animal studies

Pharmaceutical and personal care products (PPCPs) include a wide range of drugs, personal care products and household chemicals that are produced and used in significant quantities. The safety of PPCPs has become a growing concern in recent decades due to their ubiquitous presence in the environment and potential risks to human health. PPCPs have been detected in various human biological samples, including those from children and adolescents, at concentrations ranging from several ng/L to several thousand μg/L. Epidemiological studies have shown associations between exposure to PPCPs and changes in the timing of puberty in children and adolescents. Animal studies have shown that exposure to PPCPs results in advanced or delayed pubertal onset. Mechanisms by which PPCPs regulate pubertal development include alteration of the hypothalamic kisspeptin and GnRH networks, disruption of steroid hormones, and modulation of metabolic function and epigenetics. Gaps in knowledge and further research needs include the assessment of environmental exposure to pharmaceuticals in children and adolescents, low-dose and long-term effects of exposure to PPCPs, and the modes of action of PPCPs on pubertal development. In summary, this comprehensive review examines the potential effects of exposure to PPCPs on pubertal development based on evidence from human and animal studies.

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.

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.

The increasing burden of testicular seminomas and non-seminomas in adolescents and young adults (AYAs): incidence, treatment, disease-specific survival and mortality trends in the Netherlands between 1989 and 2019

BACKGROUND

Testicular cancer incidence among adolescents and young adults (AYAs, aged 18-39 years at diagnosis) is increasing worldwide and most patients will survive the initial disease. Still, detailed epidemiological information about testicular cancer among AYAs is scarce. This study aimed to provide a detailed overview of testicular cancer trends in incidence, treatment, long-term relative survival and mortality by histological subtype among AYAs diagnosed in the Netherlands between 1989 and 2019.

MATERIALS AND METHODS

Data of all malignant testicular cancers (ICD-code C62) were extracted from the Netherlands Cancer Registry. Mortality data were retrieved from Statistics Netherlands. European age-standardized incidence and mortality rates with average annual percentage change statistics and relative survival estimates up to 20 years of follow-up were calculated.

RESULTS

A total of 12 528 testicular cancers were diagnosed between 1989 and 2019. Comparing 1989-1999 to 2010-2019, the incidence increased from 4.4 to 11.4 for seminomas and from 5.7 to 11.1 per 100 000 person-years for non-seminomas. Rising trends were most prominent for localized disease. Radiotherapy use in localized testicular seminomas declined from 78% in 1989-1993 to 5% in 2015-2019. Meanwhile, there was a slight increase in chemotherapy use. Most AYAs with localized seminomas and non-seminomas received active surveillance only (>80%). Overall, relative survival estimates remained well above 90% even at 20 years of follow-up for both seminomas and non-seminomas. Mortality rates declined from 0.5 to 0.4 per 100 000 person-years between 1989-1999 and 2010-2019.

CONCLUSIONS

The incidence of seminoma and non-seminoma testicular cancers significantly increased in AYAs in the Netherlands between 1989 and 2019. There was a shift towards less-aggressive treatment regimens without negative survival effects. Relative survival estimates remained well above 90% at 20 years of follow-up in most cases. Testicular cancer mortality was already low, but has improved further over time, which makes survivorship care an important issue for these young adults.

The role of NPY2R/NFATc1/DYRK1A regulatory axis in sebaceous glands for sebum synthesis

BACKGROUND

Sebaceous glands (SGs) synthesize and secret sebum to protect and moisturize the dermal system via the complicated endocrine modulation. Dysfunction of SG are usually implicated in a number of dermal and inflammatory diseases. However, the molecular mechanism behind the differentiation, development and proliferation of SGs is far away to fully understand.

METHODS

Herein, the rat volar and mammary tissues with abundant SGs from female SD rats with (post-natal day (PND)-35) and without puberty onset (PND-25) were arrested, and conducted RNA sequencing. The protein complex of Neuropeptide Y receptor Y2 (NPY2R)/NPY5R/Nuclear factor of activated T cells 1 (NFATc1) was performed by immunoprecipitation, mass spectrum and gel filtration. Genome-wide occupancy of NFATc1 was measured by chromatin immunoprecipitation sequencing. Target proteins' expression and localization was detected by western blot and immunofluorescence.

RESULTS

NPY2R gene was significantly up-regulated in volar and mammary SGs of PND-25. A special protein complex of NPY2R/NPY5R/NFATc1 in PND-25. NFATc1 was dephosphorylated and activated, then localized into nucleus to exert as a transcription factor in volar SGs of PND-35. NFATc1 was especially binding at enhancer regions to facilitate the distal SG and sebum related genes' transcription. Dual specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) contributed to NFATc1 phosphorylation in PND-25, and inactivated of DYRK1A resulted in NFATc1 dephosphorylation and nuclear localization in PND-35.

CONCLUSIONS

Our findings unmask the new role of NPY2R/NFATc1/DYRK1A in pubertal SG, and are of benefit to advanced understanding the molecular mechanism of SGs' function after puberty, and provide some theoretical basis for the treatment of acne vulgaris from the perspective of hormone regulation.

Mixed exposure to phthalates and organic UV filters affects Children's pubertal development in a gender-specific manner

BACKGROUND

Previous studies showed phthalates and UV filters are endocrine-disruptive and associated with puberty. However, few studies have examined effects of mixed exposure.

METHODS

Six phthalate metabolites and 12 organic UV filters were detected among 223 school-age children. Puberty development was evaluated at baseline and after 18 months of follow-up. Ordered logistic regression models, least absolute shrinkage and selection operator (LASSO) regression and quantile-based g-computation (qgcomp) were used to evaluate relationships between phthalate metabolites or UV filters exposure and pubertal development.

RESULTS

Six phthalate metabolites and 5 UV filters were detectable in urine samples. In boys, BP-3 and 4'-MAP were negatively associated with genital (ORBP-3 = 0.52, (0.27, 0.93), OR4'-MAP = 0.45, (0.25, 0.74)) and pubic hair development (ORBP-3:0.24, (0.05, 0.76), OR4'-MAP:0.24, (0.05, 0.77)). In girls, MEP levels were associated with advanced breast development (OR: 1.29, (1.04, 1.64)). LASSO regression identified BP-3, 4'-MAP, and OD-PABA for inverse associations with pubertal development in boys. MEP was related to an increase in girls' breast development (OR: 1.64, (1.08, 2.63)). Overall mixture was related to a 70% reduction in boys' genital development stage, with a larger effect size than a single chemical in qgcomp. Mixed exposure was associated with girls' earlier puberty onset (OR: 2.61, (1.06, 6.42)).

CONCLUSIONS

Our results suggested higher levels of phthalate metabolites and UV filters were associated with delayed pubertal development in boys but with earlier puberty in girls. Higher effect size of joint exposure than single chemicals suggested phthalates and UV filters might have synergistic effects on puberty and distort adolescent endocrine function together.

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 Circadian Clock, Nutritional Signals and Reproduction: A Close Relationship

The circadian rhythm, which is necessary for reproduction, is controlled by clock genes. In the mouse uterus, the oscillation of the circadian clock gene has been observed. The transcription of the core clock gene period (Per) and cryptochrome (Cry) is activated by the heterodimer of the transcription factor circadian locomotor output cycles kaput (Clock) and brain and muscle Arnt-like protein-1 (Bmal1). By binding to E-box sequences in the promoters of Per1/2 and Cry1/2 genes, the CLOCK-BMAL1 heterodimer promotes the transcription of these genes. Per1/2 and Cry1/2 form a complex with the Clock/Bmal1 heterodimer and inactivate its transcriptional activities. Endometrial BMAL1 expression levels are lower in human recurrent-miscarriage sufferers. Additionally, it was shown that the presence of BMAL1-depleted decidual cells prevents trophoblast invasion, highlighting the importance of the endometrial clock throughout pregnancy. It is widely known that hormone synthesis is disturbed and sterility develops in Bmal1-deficient mice. Recently, we discovered that animals with uterus-specific Bmal1 loss also had poor placental development, and these mice also had intrauterine fetal death. Furthermore, it was shown that time-restricted feeding controlled the uterine clock's circadian rhythm. The uterine clock system may be a possibility for pregnancy complications, according to these results. We summarize the most recent research on the close connection between the circadian clock and reproduction in this review.

Environmental disruptors and testicular cancer

PURPOSE

Testicular cancer (TC) is the most common malignancy among young adult males. The etiology is multifactorial, and both environmental and genetic factors play an essential role in the origin and development of this tumor. In particular, exposure to environmental endocrine disruptors (EEDs), resulting from industrialization and urbanization, seems crucial both in pre-and postnatal life. However, the lack of long-term studies on a wide caseload and the difficulty in evaluating their toxic effects in vivo make it challenging to establish a causal link. This review aims to discuss the main human epidemiological studies currently available in the literature to define a possible association between these chemicals and TC.

METHODS

A comprehensive Medline/PubMed and Embase search was performed, selecting all relevant, peer-reviewed papers in English published from 2002 to January 2022. Other relevant papers were selected from the reference lists.

RESULTS

To date, literature evidence is limited due to the scarcity and heterogeneity of human studies and shows controversial data, highlighting the complexity of the topic. However, most human epidemiological studies seem to point toward a correlation between EEDs exposure and TC.

CONCLUSION

Although the molecular mechanisms are not yet fully understood, the role of EEDs in TC onset is plausible, but several factors, such as the individual genetic background, the exposure time, and the complex mechanism of action of these chemicals, do not allow defining the causal link with certainty and make further studies necessary to investigate this complex topic.

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.

Arsenic exposure during juvenile and puberty significantly affected reproductive system development of female SD rats

Infertility affects about 10-15% couples over the world, among which a large number of cases the underlying causes are still unclear. Recent studies suggest that environmental factors may play an important role in these idiopathic infertilities. Arsenic is a heavy metal found in drinking water over the world. Its effect on the development of female reproductive system at the environmental-relevant levels is still largely unknown. To test the hypothesis that arsenic exposure during juvenile and puberty may affect sex maturation and female reproductive system development, SD rats of 3 weeks of age were exposed to arsenic with environmental-relevant levels (0, 0.02, 0.2, or 2 mg/L, n = 16/group) through drinking water for about 44 days until the rats reached adulthood (65 days of age). Arsenic exposure significantly reduced the weights of both ovary and uterus without affecting the body weight. Also, arsenic exposure disturbed estrus cycles and reduced the numbers of primordial follicles and corpora lutea while increased atretic follicles. In addition, arsenic reduced serum levels of estradiol, progesterone and testosterone but increased LH and FSH levels in dose-dependent manners. QPCR and Western blot experiments indicated arsenic selectively down-regulated ovarian steroidogenic-related proteins FSHR, STAR, CYP17A1, HSD3B1 and CYP19A1 and signaling molecules PKA-ERK-JNK-cJUN, without affecting AKT and CREB. As about reproductive capacity, arsenic-exposed dams had smaller pups, reduced litter size and lower number of male pups without a change in female pups. In conclusion, juvenile and pubertal arsenic exposures at environmental-relevant levels significantly reduced reproductive functions and capacity by adult. Since the lowest effective dose is very close to the government safety standards, the relevancy of arsenic over exposure to reproductive defects in human deserves further study.

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 Launch of A Girl's First Period Study: Demystifying Reproductive Hormone Profiles in Adolescent Girls

Limited data exist on the reproductive hormone dynamics that govern the transition from menarche to the establishment of the mature ovulatory cycles of a fertile young woman. It is also unclear how environmental and lifestyle factors could modulate this transition in contemporary girls. Here, we introduce A Girl's First Period Study, an ambitious longitudinal study aimed at charting the early post-menarchal course of a cohort of healthy girls in the Triangle region of North Carolina.

Prevalence of endocrine disorders among children exposed to Lavender Essential Oil and Tea Tree Essential Oils

Background

Lavender essential oil and tea tree essential oil have become popular ingredients in personal care and household products in recent decades. Questions regarding the safety of these oils in pediatric populations have been raised, proposing a link between these essential oils and endocrine disruption in children, specifically prepubertal gynecomastia. To date, no epidemiological studies have been conducted to evaluate this proposed link.

Methods

This is a cross sectional study conducted among parents of children in the United States to identify the prevalence of endocrine disruption in children aged 2-15 years old. This study also evaluates the potential for a relationship between the exposure of lavender essential oil and tea tree essential oil products and endocrine disrupting outcomes.

Results

In 556 children with a mean age of 6.33 (SD = 3.92), prevalence of endocrine disruption was .016 (SD = 0.13). No cases of prepubertal gynecomastia were identified in either group, and prevalence of precocious puberty, delayed puberty, growth hormone deficiency, and hypothyroidism were all consistent with population norms. Total risk of endocrine disorders among those exposed (0.0194) did not differ from the risk of those unexposed (0.0069). The risk ratio was 2.796 (95% CI: 0.352, 22.163, P = .458).

Conclusion

Children who were regularly exposed to lavender or tea tree essential oils experienced the same risk of endocrine disorders as those who were not exposed.

Differences in Puberty of Girls before and during the COVID-19 Pandemic

In the COVID-19 pandemic, there was an increase in consultations for precocious puberty. We aim to analyze differences in female puberty before and during the COVID-19 pandemic. A cross-sectional analytical study was designed at the Pediatric Endocrinology Clinic of the University Hospital of the Federal University of Maranhão in São Luis, Brazil. We included 55 girls with precocious puberty, 22 who started puberty during the pandemic and 33 who started puberty before the pandemic. Clinical, anthropometric, laboratory and imaging variables were compared between groups. Statistics were performed to determine if there was a statistical difference between the groups. Girls with puberty during the pandemic had higher Z-scores for weight (1.08 ± 1.29 versus 0.69 ± 0.83; p = 0.04), lower ovarian volume (1.88 ± 0.95 versus 3.15 ± 2.31; p = 0.01), and smaller differences between thelarche noticed by the parents and the diagnosis (6.63 ± 5.21 versus 12.15 ± 9.96; p = 0.02). The association between precocious puberty during the pandemic with higher Z-scores for weight, lower ovarian volume, and a reduction in the time between the perception of pubertal findings by parents and the diagnosis suggests the influence of the pandemic on the normal time of puberty.

Sedentary lifestyle and precocious puberty in girls during the COVID-19 pandemic: an Italian experience

OBJECTIVE

This retrospective study aimed to evaluate children observed for suspected precocious puberty in five Italian centers of Pediatric Endocrinology during the first wave of coronavirus disease 2019 pandemic (March-September 2020), compared to subjects observed in the same period of the previous year.

DESIGN

The study population (490 children) was divided according to the year of observation and final diagnosis: transient thelarche, non-progressive precocious puberty, central precocious puberty (CPP), or early puberty.

RESULTS

Between March and September 2020, 338 subjects were referred for suspected precocious puberty, compared to 152 subjects in the same period of 2019 (+122%). The increase was observed in girls (328 subjects in 2020 vs 140 in 2019, P < 0.05), especially during the second half of the period considered (92 girls from March to May vs 236 girls from June to September); while no difference was observed in boys (10 subjects in 2020 vs 12 in 2019). The percentage of girls with confirmed CPP was higher in 2020, compared to 2019 (135/328 girls (41%) vs 37/140 (26%), P < 0.01). Anthropometric and hormonal parameters in 2019 and 2020 CPP girls were not different; 2020 CPP girls showed more prolonged use of electronic devices and a more sedentary lifestyle both before and during the pandemic, compared to the rest of the 2020 population.

CONCLUSIONS

The present findings corroborate the recently reported association between the complex lifestyle changes related to the lockdown and a higher incidence of CPP in Italian girls.

Integrated Genomic and Bioinformatics Approaches to Identify Molecular Links between Endocrine Disruptors and Adverse Outcomes

Exposure to Endocrine Disrupting Chemicals (EDC) has been linked with several adverse outcomes. In this review, we examine EDCs that are pervasive in the environment and are of concern in the context of human, animal, and environmental health. We explore the consequences of EDC exposure on aquatic life, terrestrial animals, and humans. We focus on the exploitation of genomics technologies and in particular whole transcriptome sequencing. Genome-wide analyses using RNAseq provides snap shots of cellular, tissue and whole organism transcriptomes under normal physiological and EDC perturbed conditions. A global view of gene expression provides highly valuable information as it uncovers gene families or more specifically, pathways that are affected by EDC exposures, but also reveals those that are unaffected. Hypotheses about genes with unknown functions can also be formed by comparison of their expression levels with genes of known function. Risk assessment strategies leveraging genomic technologies and the development of toxicology databases are explored. Finally, we review how the Adverse Outcome Pathway (AOP) has exploited this high throughput data to provide a framework for toxicology studies.

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.

Impact of intra-uterine life on future health

Since the emergence of the concept of developmental origins of health and disease (DOHaD), suggested by Barker in the 1980s, numerous epidemiological studies in humans have confirmed the relationship between maternal obesity during pregnancy and the risk of offspring developing various chronic adult illnesses. These effects of intrauterine life are independent of inheritance of disease susceptibility genes and/or socio-economic factors. Regarding potential mechanisms, recent data from animal models suggests a role of insulin resistance early in development. Another potential mechanism, in the case of maternal obesity, is increased placental nutrient transfer. The DOHaD concept also includes fetal exposure to environmental endocrine disruptors (EEDs). A Danish group for the first time recently analyzed EED passage across the placenta in humans throughout pregnancy. This study showed different levels of bioaccumulation depending on the fetal organ, with greater vulnerability in male than female fetuses. Recent clinical studies suggested an association between fetal exposure to particular EEDs and precocious puberty, increased incidence of cryptorchidism and impaired sperm quality in adulthood. These modifications of the in-utero environment also appear to be responsible for epigenetic changes that are transmittable over several generations. A recent example of this is the demonstration of the transmission of polycystic ovary syndrome (PCOS) in mice. In summary, an increasing number of examples of the impact of intrauterine life on the health of offspring have appeared in recent years, illustrating the important role that endocrinologists can play in preventing particular pathologies in future generations.

Dietary Habits and Relationship with the Presence of Main and Trace Elements, Bisphenol A, Tetrabromobisphenol A, and the Lipid, Microbiological and Immunological Profiles of Breast Milk

Breastfeeding is the best way to feed an infant, although it can also be a source of abiotic contaminants such as heavy metals or bisphenol A (BPA). The early life exposure to these compounds can lead to serious toxic effects in both the short and long-term. These substances can reach breast milk through the mother’s habits, diet being one of the main routes of exposure. The aim of the present work was to analyse possible associations between the dietary habits of women and the content of major trace elements, BPA, fatty acids and lipids, and the microbiological and immunological profiles of human milk. Possible associations between major trace elements and BPA and the lipid, microbiological and immunological profiles were also analysed. The results of this study support that the microbiological composition of human milk is associated with the dietary habits of the women, and that the consumption of canned drinks is related to the presence of BPA in human milk. Furthermore, some relationships were found between the amount of major trace elements and the microbiological and immunological profile of the milk samples. Finally, the presence of BPA was associated with changes in the immunological profile of human milk.

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.

Biological clock and heredity in pubertal timing: what is new?

Puberty represents a milestone during a person's life and is characterized by several physical and psychological changes which end with the achievement of sexual maturation and of fertility. Puberty onset depends on a series of sophisticated, not completely understood, mechanisms certainly involving Gonadotropin-Releasing Hormone (GnRH) and its effects on pituitary gonadotropins. As recent evidence has demonstrated that pubertal timing deeply affects future adult health life, much efforts have been performed in order to clarify the exact actors involved in the onset and progression of puberty. Genetic factors are undoubtedly essential players in the regulation of pubertal development, accounting for approximately 50-80% of its variability. Mutations in genes such as KISS1, MKRN3 and DLK1 have been associated with central precocious puberty. Interestingly, a possible involvement of epigenetic mechanisms has been proposed as additional element able to affect pubertal phase. Environmental factors have recently attracted much attention. Indeed, an overall decrease in the age of puberty has been observed in the last decades. As genetic factors require long time to exert their effect, other players, such as environmental ones, may be involved. Special focus has been posed on nutritional status, endocrine-disrupting chemicals with non-conclusive results. Pubertal timing deeply affects future life, suggesting the need to clarify mechanisms driving pubertal onset and progression, in order to identify tailored therapeutic strategies and targets.

Endocrine disrupting chemicals: strategies to protect present and future generations

Introduction: Endocrine-disrupting chemicals (EDCs) are chemicals that alter the actions of hormones. In the 21^st Century, numerous expert groups of clinicians, scientists, and environmental activists have called for action to protect present and future generations from the harm induced by EDC exposures. These demands for regulatory responses come because of the strong weight of the evidence from epidemiology, wildlife, and controlled laboratory studies.Areas covered: In this review, we examine the conclusions drawn by experts from different scientific and medical disciplines. We also address several areas where recent findings or work has changed the landscape of EDC work including new approaches to identify and evaluate the evidence for EDCs using a key characteristics approach, the need to expand our understanding of vulnerable periods of development, and the increasing concern that traditional methods used to evaluate toxicity of environmental chemicals are insufficient for EDCs and how collaborative science could help to address these gaps.Expert opinion: The science is clear: there is more than enough evidence to demonstrate that EDCs affect the health of humans and wildlife. Waiting to act is a decision that puts the health of current and future generations at risk.

Epigenome-wide association study for atrazine induced transgenerational DNA methylation and histone retention sperm epigenetic biomarkers for disease

Atrazine is a common agricultural herbicide previously shown to promote epigenetic transgenerational inheritance of disease to subsequent generations. The current study was designed as an epigenome-wide association study (EWAS) to identify transgenerational sperm disease associated differential DNA methylation regions (DMRs) and differential histone retention regions (DHRs). Gestating female F0 generation rats were transiently exposed to atrazine during the period of embryonic gonadal sex determination, and then subsequent F1, F2, and F3 generations obtained in the absence of any continued exposure. The transgenerational F3 generation males were assessed for disease and sperm collected for epigenetic analysis. Pathology was observed in pubertal onset and for testis disease, prostate disease, kidney disease, lean pathology, and multiple disease. For these pathologies, sufficient numbers of individual males with only a single specific disease were identified. The sperm DNA and chromatin were isolated from adult one-year animals with the specific diseases and analyzed for DMRs with methylated DNA immunoprecipitation (MeDIP) sequencing and DHRs with histone chromatin immunoprecipitation (ChIP) sequencing. Transgenerational F3 generation males with or without disease were compared to identify the disease specific epimutation biomarkers. All pathologies were found to have disease specific DMRs and DHRs which were found to predominantly be distinct for each disease. No common DMRs or DHRs were found among all the pathologies. Epimutation gene associations were identified and found to correlate to previously known disease linked genes. This is one of the first observations of potential sperm disease biomarkers for histone retention sites. Although further studies with expanded animal numbers are required, the current study provides evidence the EWAS analysis is effective for the identification of potential pathology epimutation biomarkers for disease susceptibility.

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.

Exogenous Oestrogen Impacts Cell Fate Decision in the Developing Gonads: A Potential Cause of Declining Human Reproductive Health

The increasing incidence of testicular dysgenesis syndrome-related conditions and overall decline in human fertility has been linked to the prevalence of oestrogenic endocrine disrupting chemicals (EDCs) in the environment. Ectopic activation of oestrogen signalling by EDCs in the gonad can impact testis and ovary function and development. Oestrogen is the critical driver of ovarian differentiation in non-mammalian vertebrates, and in its absence a testis will form. In contrast, oestrogen is not required for mammalian ovarian differentiation, but it is essential for its maintenance, illustrating it is necessary for reinforcing ovarian fate. Interestingly, exposure of the bi-potential gonad to exogenous oestrogen can cause XY sex reversal in marsupials and this is mediated by the cytoplasmic retention of the testis-determining factor SOX9 (sex-determining region Y box transcription factor 9). Oestrogen can similarly suppress SOX9 and activate ovarian genes in both humans and mice, demonstrating it plays an essential role in all mammals in mediating gonad somatic cell fate. Here, we review the molecular control of gonad differentiation and explore the mechanisms through which exogenous oestrogen can influence somatic cell fate to disrupt gonad development and function. Understanding these mechanisms is essential for defining the effects of oestrogenic EDCs on the developing gonads and ultimately their impacts on human reproductive health.

Concentrations of urinary parabens and reproductive hormones in girls 6-17 years living in Canada

BACKGROUND

Parabens are chemical substances used as preservatives for their antibacterial and antifungal properties in many personal care products, and sometimes in pharmaceutical and food products. Concerns for adverse human health effects arise from animal studies showing endocrine disrupting effects, such as changes in the timing of puberty and alterations in reproductive hormone activity. Our objective was to examine the association between urinary concentrations of parabens and serum concentrations of estradiol, progesterone, follicle stimulating hormone [FSH], and luteinizing hormone [LH]) in girls from the general population.

METHODS

We conducted a cross-sectional study in girls ages 6-17 years, using data from the Canadian Health Measures Survey (2014-2015). The association between concentrations of creatinine-standardized urinary parabens and serum hormone concentrations was analyzed with multivariable linear regressions, adjusting for potential confounders (i.e., age, body mass index, ethnicity, household income, sampling season; prenatal exposure to cigarette smoke for girls 6-11 years).

RESULTS

The 382 girls and teens included in the study had a mean age of 11.0 years; 76% were white and 73% had a body mass index in the range normal/underweight. Most participants (92%) had least one paraben detected in their urine. Girls with higher urinary paraben concentrations had significantly lower serum concentrations of estradiol, LH, and FSH, but not of progesterone. A doubling in the sum of urinary parabens was associated with 5.8% lower estradiol (95% CI -9.3, -2.1), 4.2% lower FSH (95% CI -7.9, -0.3), and 10.8% lower LH (95% CI -17.4, -3.7). The analysis of individual compounds showed that all four parabens were similarly associated with lower concentrations of estradiol, FSH, and LH. We further analyzed younger girls (6-11 years) and found that urinary parabens were similarly associated with lower estradiol and LH (doubling in the sum of parabens associated with 5.9% lower estradiol [95% CI -10.5, -1.0] and 10.9% lower LH [95% CI -20.2, -0.6]). In this younger subgroup, the association estimate for FSH, however, was attenuated and no longer statistically significant.

DISCUSSION

We observed that exposure to parabens was associated with reduced concentrations of circulating reproductive hormones, suggesting that these chemicals could alter the development and function of the endocrine system in girls. Further prospective research using long-term assessment of parabens exposure and of reproductive development may better determine endocrine disrupting effects of parabens.

Connections Between Obesity and Puberty: Invited by Manuel Tena-Sempere, Cordoba

The relationship between obesity and puberty remains controversial. Whereas cross-sectional and longitudinal studies show a clear shift toward earlier puberty in obese girls, the trend in obese boys remains less obvious. Overweight boys mature earlier whereas obese boys mature later compared to healthy weight boys. Newer epidemiologic studies attempt to address these knowledge gaps. This review provides a detailed overview of the recent literature regarding secular trends in pubertal onset and tempo, and the connection with obesity. Additionally, this review summarizes potential mediators that permit obesity to promote early puberty. Other factors such as socioeconomic status, in utero exposures, nutritional, and even endocrine disrupting chemicals can cause perturbation of both metabolism and the endocrine axis that can ultimately have effects on pubertal development.

Clinical expression of endocrine disruptors in children

PURPOSE OF REVIEW

Health status is the result of complex interaction between individual factors, general environmental factors and specific factors as nutrition or the presence of chemicals. Aim of this review is to point out the more recent knowledge covering the role of the endocrine disrupting chemical (EDC) on pediatric population wellbeing.

RECENT FINDINGS

Prenatal, postnatal life and puberty are the three main temporal windows of susceptibility when EDCs may act. The mechanism is independent from dose or duration of exposition, sex, age or combination of chemicals and may also be transgenerational, affecting both growth and pubertal timing. A window of susceptibility for breast cancer has been detected. Thyroid gland is influenced by environmental chemicals, both in utero and during childhood. Alteration in Thyrotropin stimulating hormone (TSH) levels and neurodevelopmental impairment have been demonstrate. It has been detected a pro-obesogenic action of specific chemicals, impairing also glucose homeostasis during childhood.

SUMMARY

With a multidisciplinary approach and the use of big data platforms, an attempt has to be made to verify biological variations related to a disease, and how much the risk is influenced by the presence of the endocrine disruptors. This may help the future generation to better interpret uncommunicable diseases.