Early onset of puberty: tracking genetic and environmental factors

Spatio-temporal trends of the age-at-menarche percentiles among Portuguese women since 1920

BACKGROUND

This work aims to study the spatio-temporal evolution of a woman's age at menarche in the central region of Portugal. One of the concerns of the study is early or late menarches; thus, we consider percentile regression to build the respective curves as opposed to the more traditional mean regression approach.

METHODS

We analysed the data from [Formula: see text] women born in the period 1920-1973 who attended a free breast cancer screening program between 1990 and 2019. Distributional regression models inside the package GAMLSS in R were considered. These methods allowed us not only to model the location (mean) of the specific probability distribution of the age at menarche, but also allowed for the scale (variance) parameter of this distribution to depend on covariates. Additionally, a spatial random-effect was considered in order to capture the correlation at the regional level. The obtained clustered spatial effects were analysed to assess geographical differences among the percentiles of the age at menarche by year of birth.

RESULTS

A decreasing trend in the age at menarche (about 1.5 years in 5 decades) and regional differences for all the considered percentiles were found. Women living in the north-central areas of the central region of Portugal tend to have menarche at older ages.

CONCLUSION

We obtained percentile estimates for the age at menarche by year of birth and region of residence and demonstrated that these two explanatory variables have an impact on the explanation about the decreasing trend in age at a woman's first menstruation.

Leuprolide and triptorelin treatment in children with idiopathic central precocious puberty: an efficacy/tolerability comparison study

Introduction

Central precocious puberty (CPP) results from premature activation of hypothalamic-pituitary-gonadal axis, with the consequent increase of gonadotropin-releasing hormone (GnRH); GnRH agonists (GnRHa) represent the gold-standard therapy in children with CPP although their use might be responsible for pituitary GnRH receptors down-regulation, that in turn suppresses luteinizing hormone (LH) and follicle stimulating hormone (FSH) and blocks of gonadal sex hormones release. The most prescribed GnRHa in the clinical practice are leuprolide and triptorelin, whose use is generally safe and well tolerated; however, mild menopausal-like side effects could appear. The aim of the present study was to investigate and compare the efficacy and tolerability profile of leuprolide and triptorelin in CPP patients.

Methods

110 girls affected by CPP were enrolled in this retrospective study, carried out from 2018 to 2020. The enrolled patients received leuprolide (n = 48) or triptorelin (n = 62). Efficacy was investigated by the means of clinical parameters and radiological changes and side effects were also recorded to evaluate the possible relationship between the two GnRHa treatments and side effects appearance.

Results

At baseline triptorelin patients had significantly higher LH and LH peak levels than leuprolide patients, whereas no significant difference in other patient characteristics was observed between the two groups. The leuprolide treatment lasted 971 days [790-1,171 days] while the duration of triptorelin administration was 792 days [760-1,003 days] (p < 0.001). Overall 46 (41.8%) of the studied patients reported mild menopausal-like symptoms: among these 27 were treated with triptorelin and 19 with leuprolide (p = 0.558). Patients treated with triptorelin, or leuprolide showed headache (27.4% vs. 16.7%), mood swings (12.9% vs. 16.7%), increased appetite (12.9% vs. 18.8%) and nausea (1.6% vs. 10.4%) respectively. Moreover, the onset of side effects appearance related to GnRHa therapy significantly reduces with the increase of the initial bone age (p = 0.038).

Conclusion

Leuprolide and triptorelin treatment appear to be effective and safe without significant difference between the two drugs in term of efficacy and tolerability, making both good options for treating CPP.

Association of prenatal phthalate exposure with pubertal development in Spanish boys and girls

BACKGROUND

Phthalates are widespread, anti-androgenic chemicals known to alter early development, with possible impact on puberty timing.

AIM

To investigate the association of prenatal phthalate exposure with pubertal development in boys and girls.

METHODS

Urinary metabolites of six different phthalate diesters (DEP, DiBP, DnBP, BBzP, DEHP, and DiNP) and non-phthalate plasticizer DINCH® were quantified in two urine samples collected during pregnancy from mothers participating in the INMA Spanish cohort study. Pubertal assessment of their children at age 7-10 years (409 boys, 379 girls) was conducted using the parent-reported Pubertal Development Scale. Modified Poisson and Weighted Quantile Sum (WQS) regression was employed to examine associations between prenatal phthalates and risk of puberty onset, adrenarche, and gonadarche. Effect modification by child weight status was explored by stratified analysis.

RESULTS

Prenatal exposure to DEHP was associated with higher risk of puberty onset (relative risk [RR] = 1.32, 95% CI = 1.09-1.59 per each log-unit increase in concentrations) and gonadarche (RR = 1.23, 95% CI = 1.00-1.50) in boys and higher risk of adrenarche (RR = 1.25, 95% CI = 1.03-1.51) in girls at age 7-10 years. In boys, prenatal exposure to DEP, DnBP, and DEHP was also associated with higher risk of adrenarche or gonadarche (RRs = 1.49-1.80) in those with normal weight, and BBzP and DINCH® exposure with lower risk of adrenarche (RR = 0.49, 95% CI = 0.27-0.89 and RR = 0.47, 95% CI = 0.24-0.90, respectively) in those with overweight/obesity. In girls, DiBP, DnBP, and DINCH® were associated with slightly higher risk of gonadarche (RRs = 1.14-1.19) in those with overweight/obesity. In the WQS model, the phthalate mixture was not associated with puberty in boys or girls.

CONCLUSION

Prenatal exposure to certain phthalates was associated with pubertal development at age 7-10 years, especially earlier puberty in boys with normal weight and girls with overweight/obesity. However, there was no evidence of effect of the phthalate mixture on advancing or delaying puberty in boys or girls.

Long-term efficacy and safety of gonadotropin-releasing hormone analog treatment in children with idiopathic central precocious puberty: A systematic review and meta-analysis

OBJECTIVE

To investigate the long-term efficacy and safety of gonadotropin-releasing hormone analog (GnRHa) treatment in children with idiopathic central precocious puberty (CPP).

METHOD

The protocol was registered with International Prospective Register of Systematic Reviews (CRD42018102792). PubMed, EMBASE and the Cochrane Library were searched for eligible comparative and single-arm studies.

RESULTS

We identified a total of 98 studies that included 5475 individuals. The overall risk of bias of the eligible studies ranged from critical to moderate. The overall quality of evidence for each outcome ranged from very low to moderate. Evidence-based comparative studies showed that GnRHa treatment increase final adult height (FAH, cm; studies = 4, n = 242; mean difference [MD] = 4.83; 95% confidence interval [CI], 2.32 to 7.34; I²  = 49%) and decrease body mass index (BMI, kg/m² ; studies = 3, n = 334; MD = -1.01; 95% CI, -1.64 to -0.37; I²  = 0%) in girls with idiopathic CPP compared with no treatment. The incidence of polycystic ovary syndrome (PCOS) did not significantly differ with and without GnRHa treatment (studies = 3, n = 179; risk ratio = 1.21; 95% CI, 0.46 to 3.15; I²  = 48%). The evidence for other long-term outcomes was very weak to deduce the effects of GnRHa treatment. Further, limited evidence is available on its effects in boys.

CONCLUSION

Compared with no treatment, evidence indicates that GnRHa treatment increase FAH and decrease BMI in girls with idiopathic CPP. GnRHa treatment did not evidently increase the risk of PCOS. However, evidence regarding other key long-term outcomes (such as infertility and malignant or metabolic diseases) was considered very weak to suggest the benefits or side effects of GnRHa treatment. Additional high-quality evidence is needed before firm conclusions can be drawn.

Enrichment analyses of diseases and pathways associated with precocious puberty using PrecocityDB

Precocious puberty (PP) is an important endocrine disorder affecting children globally. Several genes, SNPs and comorbidities are reported to be associated with PP; however, this data is scattered across scientific literature and has not been systematically collated and analysed. In this study, we present PrecocityDB as the first manually curated online database on genes and their ontology terms, SNPs, and pathways associated with PP. A tool for visualizing SNP coordinates and allelic variation on each chromosome, for genes associated with PP is also incorporated in PrecocityDB. Pathway enrichment analysis of PP-associated genes revealed that endocrine and cancer-related pathways are highly enriched. Disease enrichment analysis indicated that individuals with PP seem to be highly likely to suffer from reproductive and metabolic disorders such as PCOS, hypogonadism, and insulin resistance. PrecocityDB is a useful resource for identification of comorbid conditions and disease risks due to shared genes in PP. PrecocityDB is freely accessible at http://www.precocity.bicnirrh.res.in . The database source code and content can be downloaded through GitHub ( https://github.com/bic-nirrh/precocity ).

Increased incidence of precocious and accelerated puberty in females during and after the Italian lockdown for the coronavirus 2019 (COVID-19) pandemic

Background

The timing of puberty in girls is occurring at an increasingly early age. While a positive family history is recognised as a predisposing factor for early or precocious puberty, the role of environmental factors is not fully understood.

Aims of the study

To make a retrospective evaluation of the incidence of newly diagnosed central precocious puberty (CPP) and the rate of pubertal progression in previously diagnosed patients during and after the Italian lockdown for COVID-19, comparing data with corresponding data from the previous 5 years. To determine whether body mass index (BMI) and the use of electronic devices increased during lockdown in these patients.

Patients and methods

The study included 49 females with CPP. We divided the patients into two groups: group 1, patients presenting a newly diagnosed CPP and group 2, patients with previously diagnosed slow progression CPP whose pubertal progression accelerated during or after lockdown. We collected auxological, clinical, endocrinological and radiological data which were compared with data from two corresponding control groups (patients followed by our Unit, March to July 2015–2019). Patients’ families completed a questionnaire to assess differences in the use of electronic devices before and during lockdown.

Results

Thirty-seven patients presented newly diagnosed CPP (group 1) and 12, with previously diagnosed but untreated slow progression CPP presented an acceleration in the rate of pubertal progression (group 2). The number of new CPP diagnoses was significantly higher than the mean for the same period of the previous 5 years (p < 0.0005). There were no significant differences between patients in group 1 and control group 1 regarding time between appearance of B2 and CPP diagnosis, although group 1 patients had a significantly earlier chronological age at B2, a more advanced Tanner stage at diagnosis (p < 0.005), higher basal LH and E2 levels, higher LH peak after LHRH test (p < 0.05) and increased uterine length (p < 0.005) and ovarian volume (p < 0.0005). The number of patients with previously diagnosed CPP whose pubertal development accelerated was also statistically higher compared to controls (p < 0.0005). In this group, patients’ basal LH (p < 0.05) and E2 levels (p < 0.0005) became more markedly elevated as did the LH peak after LHRH test (p < 0.05). These patients also showed a significantly accelerated progression rate as measured by the Tanner scale (p < 0.0005), uterine length (p < 0.005), and ovarian volume (p < 0.0005). In both group 1 and group 2, BMI increased significantly (p < 0.05) and patients’ families reported an increased use of electronic devices (p < 0.0005).

Conclusion

Our data show an increased incidence of newly diagnosed CPP and a faster rate of pubertal progression in patients with a previous diagnosis, during and after lockdown compared to previous years. We hypothesize that triggering environmental factors, such as the BMI and the use of electronic devices, were enhanced during lockdown, stressing their possible role in triggering/influencing puberty and its progression. However, more studies are needed to determine which factors were involved and how they interacted.

Delayed Puberty-Phenotypic Diversity, Molecular Genetic Mechanisms, and Recent Discoveries

This review presents a comprehensive discussion of the clinical condition of delayed puberty, a common presentation to the pediatric endocrinologist, which may present both diagnostic and prognostic challenges. Our understanding of the genetic control of pubertal timing has advanced thanks to active investigation in this field over the last two decades, but it remains in large part a fascinating and mysterious conundrum. The phenotype of delayed puberty is associated with adult health risks and common etiologies, and there is evidence for polygenic control of pubertal timing in the general population, sex-specificity, and epigenetic modulation. Moreover, much has been learned from comprehension of monogenic and digenic etiologies of pubertal delay and associated disorders and, in recent years, knowledge of oligogenic inheritance in conditions of GnRH deficiency. Recently there have been several novel discoveries in the field of self-limited delayed puberty, encompassing exciting developments linking this condition to both GnRH neuronal biology and metabolism and body mass. These data together highlight the fascinating heterogeneity of disorders underlying this phenotype and point to areas of future research where impactful developments can be made.

Long-Term Behavioral Effects of Post-weaning Social Isolation in Males and Females

Adolescence is a developmental period associated with vast neural and behavioral changes which are accompanied by altered sensitivity to stimuli, both stressful and rewarding. Perturbations, especially stressful stimuli, during this period have been shown to alter behavior in adulthood. Social isolation rearing is one such perturbation. This review highlights the long-term behavioral consequences of adolescent social isolation rearing in rodents with a specific focus on anxiety- and addiction-related behaviors. Sex-specific effects are discussed where data are available. We then consider changes in monoaminergic neurotransmission as one possible mechanism for the behavioral effects described. This research on both normative and perturbed adolescent development is crucial to understanding and treating the increased vulnerability to psychiatric disorders seen in humans during this life stage.

Puberty timing associated with obesity and central obesity in Chinese Han girls

Background

There is growing scientific evidence supports a link between increased childhood adiposity and early onset of puberty in girls worldwide in recent decades. However, the data from Chinese girls remain ambiguous. The aims of this study were to estimate the puberty milestones and examine attainment of puberty associated with obesity and central obesity in Chinese Han schoolgirls.

Methods

The cross-sectional school-based study examined 2996 Han schoolgirls aged 9 to 19 years from 6 provinces in China. Trained clinicians assessed  the girls for height, weight, waist circumference, Tanner stages of breast and pubic hair development, and menarcheal status. We classified girls as normal weight, overweight, or obese based on BMI, and as normal weight or central obese based on the waist-height ratio, then estimated and compared median age at a given Tanner stage or greater by weight class using Probit models.

Results

The median age at menarche was 12.36 years. The median ages at breast stages(B) 2 through 5 were 10.03, 11.38, 13.39, and 15.79 years, respectively, and at pubic hair stages(PH) 2 through 5 were 11.62, 12.70, 14.38, and 16.92 years, respectively. Girls from urban areas experienced menarche, B3 and B4 stages, and PH3 through PH5 stages earlier. Girls with central obesity and overweight/obesity reached puberty earlier at almost every Tanner stage of breast and pubic hair than normal girls. Girls with obesity developed PH2 and PH3 earlier than their overweight peers. However, we did not find any significant differences between girls with overweight and obesity at all stages of breast development.

Conclusions

Childhood obesity, including both overweight/obesity and central obesity, is associated with earlier attainment of puberty in Chinese Han schoolgirls.

Serum Osteocalcin Levels in Girls with Central Precocious Puberty: Relation to the Onset of Puberty

Osteocalcin is the non-collagenous protein produced by osteoblasts in bone. When it is released into systemic circulation in its uncarboxylated form, it regulates fat and glucose metabolism. Recent studies have shown that osteocalcin is also involved in male fertility. Because the onset of puberty is determined by ethnic, genetic, environmental, and metabolic factors, we focused on determining the role of osteocalcin in the onset of puberty. Central precocious puberty (CPP) is defined as the activation of the hypothalamic-pituitary-gonadal axis before the age of 8 in girls and 9 in boys. CPP is diagnosed when peak luteinizing hormone (LH) reaches ≥ 5.0 IU/l after stimulation with gonadotropin-releasing hormone (GnRH). This retrospective study included 206 girls who showed breast budding before the age of 8 and whose bone age was more advanced than their chronological age. The CPP group included 100 girls who were diagnosed with CPP, and 106 girls were the non-CPP group whose peak LH did not reach ≥ 5.0 IU/l after GnRH stimulation test. Serum osteocalcin levels were measured to investigate the relationship between osteocalcin and the onset of puberty. Our data showed that serum osteocalcin levels were significantly higher in the CPP group (87.7 ± 24.4 ng/ml vs. 68.3 ± 19.5 ng/ml, P < 0.001). The multivariate analysis revealed that an increase in bone age and peak LH was significantly associated with the serum osteocalcin level. The results of this study suggest that serum osteocalcin is associated with the onset of puberty in girls.

Etiological trends in male central precocious puberty

PURPOSE

In the present study, the etiological trends in male central precocious puberty (CPP) were examined, and annual distribution was evaluated.

METHODS

Seventy-one male CPP subjects who started puberty before 9 years of age were included in this study. All individuals were diagnosed as having CPP at Samsung Medical Center between 2001 and 2016. Chronological age at puberty onset, diagnosis of CPP, bone age, weight (kg), height (cm), puberty stage, brain magnetic resonance imaging findings, testosterone level, basal gonadotropin level, and gonadotropin level after gonadotropin releasing hormone stimulation were analyzed.

RESULTS

The 71 patients were divided into 2 groups: idiopathic (group I) and organic (group II) when the lesion was identified as associated with the central nervous system (CNS) or when the patient received chemotherapy for non-CNS tumors before CPP diagnosis, respectively. Forty-four cases (62%) were idiopathic, and 27 (38%) were organic. The proportion of idiopathic CPP was higher than that of organic CPP during the study period. In 51.9% of organic cases, puberty started before 8 years of age, whereas it started after that age in 93.2% of the idiopathic cases.

CONCLUSION

In the present study, among all male CPP cases, 62% were idiopathic. The probability of idiopathic CPP prevalence was higher in males when the puberty onset was after 8 years of age with no history of cranial radiotherapy or chemotherapy.

Preventive Effect and Safety of a Follicle Stimulating Hormone Inhibitory Formulation Containing a Mixture of Coicis Semen and Artemisia capillaris for Precocious Puberty: A Preliminary Experimental Study Using Female Rats

BACKGROUND

Precocious puberty is a common endocrine disease in children. Inappropriate activation of hypothalamic-pituitary-gonadal axis leads to the development of secondary sexual characteristics at an earlier age than normal children and causes short stature in adulthood.

OBJECTIVES

The aim of this study is to evaluate the preventive effects of a herbal formulation containing a mixture of Coicis Semen and Artemisia capillaris (hEIF extract) on precocious puberty.

METHODS

The preventive effect of hEIF extract on precocious puberty in rats was evaluated by measuring blood component after 3 weeks of treatment via oral administration. Network pharmacological analyses were performed to predict the bioactive components of hEIF extract.

RESULTS

In vivo studies showed that hEIF extract significantly reduced follicle stimulating hormone (FSH) levels. After treatment with 200 mg/kg of hEIF extract, the FSH level was 5.33 ± 1.10 ng/mL, whereas the FSH level in the vehicle group was 46.73 ± 0.80 ng/mL. Moreover, the use of hEIF extract did not stimulate body growth and bone accretion in rats. The network pharmacological analysis led to the identification of multiple targets of hEIF extract related to lipolysis and the female sex hormone-related pathways.

CONCLUSION

hEIF extract can be used as an FSH inhibitor for the treatment of precocious puberty.

The Effect of Bisphenol A on Puberty: A Critical Review of the Medical Literature

Many scientific studies have revealed a trend towards an earlier onset of puberty and have disclosed an increasing number of children that display precocious puberty. As an explanation, some authors have considered the global socio-economic improvement across different populations, and other authors have considered the action of endocrine disrupting chemicals (EDCs). Among these, bisphenol A (BPA), an aromatic compound largely used worldwide as a precursor of some plastics and chemical additives, is well known for its molecular oestrogen-like and obesogenic actions. We reviewed the medical literature of the previous 20 years that examined associations between BPA exposure and the age of puberty in humans, considering only those referring to clinical or epidemiological data. Of 19 studies, only 7 showed a correlation between BPA and puberty. In particular, the possible disruptive role of BPA on puberty may be seen in those with central precocious puberty or isolated premature breast development aged 2 months to 4 years old, even if the mechanism is undefined. Some studies also found a close relationship between urinary BPA, body weight, and early puberty, which can be explained by the obesogenic effect of BPA itself. The currently available data do not allow establishment of a clear role for BPA in pubertal development because of the conflicting results among all clinical and epidemiological studies examined. Further research is needed to fully understand the potential role of exposure to EDCs and their adverse endocrine health outcomes.

Association of genetic polymorphisms around the LIN28B gene and idiopathic central precocious puberty risks among Chinese girls

BACKGROUND

Genome-wide association studies have identified rs314276, rs314263, rs7759938, and rs314280 in or near the LIN28B gene as associated with age at menarche. To date, the effect of polymorphisms in this gene on idiopathic central precocious puberty (ICPP) in Chinese girls have not been reported. The aim of this study was to evaluate the association of the four loci with ICPP in Chinese girls.

METHODS

In this study, we conducted a case-control study including 502 girls with ICPP and 489 controls. Four single-nucleotide polymorphisms (SNPs) were genotyped in both groups using an improved multiplex ligation detection reaction (iMLDR) technique.

RESULTS

Of the four SNPs of the LIN28B analyzed, three SNPs, rs314276, rs7759938, and rs314280, were associated with ICPP risk at P < 0.05. The association of rs314276, however, was no longer significant after adjustment for multiple testing. Compared with rs7759938 TT or TC genotype, decreased ICPP risk was associated with CC (OR = 0.527, 95% CI: 0.329-0.843) genotype (P = 0.008). Compared with rs314280 GG or GA genotype, decreased ICPP risk was associated with minor allele carrier (AA) genotype (OR = 0.538, 95% CI: 0.337-0.858, P = 0.009). The two identified variants showed the same association signals for ICPP.

CONCLUSION

In conclusion, common genetic variations (rs7759938 and rs314280) of LIN28B may contribute to ICPP susceptibility in Chinese girls.

Vimentin-Mediated Steroidogenesis Induced by Phthalate Esters: Involvement of DNA Demethylation and Nuclear Factor κB

Di-n-butyl phthalate (DBP) and its active metabolite, monobutyl phthalate (MBP) are the most common endocrine disrupting chemicals. Many studies indicate that high-doses of DBP and/or MBP exhibit toxicity on testicular function, however, little attention have been paid to the effects of low levels of DBP/MBP on steroidogenesis. As we all know, the steroidogenic acute regulatory protein (StAR) is a key regulator involved in the steroidogenesis. Here we found that, in addition to StAR, MBP/DBP increased the steroidogenesis by a cytoskeletal protein, vimentin. Briefly, in murine adrenocortical tumor (Y1) and the mouse Leydig tumor (MLTC-1) cells, vimentin regulated the secretion of progesterone. When these two cells were exposure to MBP, the DNA demethylation in the vimentin promoter was observed. In addition, MBP also induced the activation of nuclear factor kappa B (NF-κB, a transcriptional regulator of vimentin). These two processes improved the transcriptional elevation of vimentin. Knockdown of NF-κB/vimentin signaling blocked the DBP/MBP-induced steroidogenesis. These in vitro results were also confirmed via an in vivo model. By identifying a mechanism whereby DBP/MBP regulates vimentin, our results expand the understanding of the endocrine disrupting potential of phthalate esters.

Epigenetic regulation of female puberty

Substantial progress has been made in recent years toward deciphering the molecular and genetic underpinnings of the pubertal process. The availability of powerful new methods to interrogate the human genome has led to the identification of genes that are essential for puberty to occur. Evidence has also emerged suggesting that the initiation of puberty requires the coordinated activity of gene sets organized into functional networks. At a cellular level, it is currently thought that loss of transsynaptic inhibition, accompanied by an increase in excitatory inputs, results in the pubertal activation of GnRH release. This concept notwithstanding, a mechanism of epigenetic repression targeting genes required for the pubertal activation of GnRH neurons was recently identified as a core component of the molecular machinery underlying the central restraint of puberty. In this chapter we will discuss the potential contribution of various mechanisms of epigenetic regulation to the hypothalamic control of female puberty.

Urinary bisphenol A and age at menarche among adolescent girls: evidence from NHANES 2003-2010

BACKGROUND

Bisphenol A (BPA) is an environmental estrogen used in the manufacture of polycarbonate plastics and epoxy resins used to make food and beverage packaging. Increasing evidence suggests that BPA mimics estrogens in the body and may be associated with putative markers of breast cancer risk.

OBJECTIVES

We analyzed the National Health and Nutrition Examination Survey (NHANES) 2003-2010 data to investigate the association of BPA with age at menarche in adolescent girls. We hypothesized that urinary BPA, as a surrogate biomarker for BPA exposure, is associated with earlier age at menarche, and that body mass index (BMI) may modulate this association.

METHODS

We conducted cross-sectional analyses of urinary BPA, BMI and age of menarche in a subsample of 987 adolescent girls aged 12-19, using pooled data from the 2003-2010 NHANES. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) for the association between urinary BPA and early onset of menarche, with adjustment for sampling design. We additionally assessed interaction of BPA with BMI.

RESULTS

Adolescent girls with moderate BPA levels appeared to be less likely to have early onset of menarche than those with the lowest levels (OR=0.57; 95% CI=0.30, 1.08) after adjusting for age, race/ethnicity, parental education, country of birth, NHANES cycle, BMI and creatinine. BMI appeared to modify the BPA-menarche association.

CONCLUSIONS

Although a non-significant trend suggests increasing urinary BPA may be associated with delayed menarche in adolescent girls, these results are based on cross-sectional data. Results should be clarified in carefully designed longitudinal cohort studies.

Are CYP1A1, CYP17 and CYP1B1 mutation genes involved on girls with precocious puberty? A pilot study

OBJECTIVES

To investigate three genes associated with puberty timing in girls with central precocious puberty by evaluating the association between polymorphism in the gene sequence codifying the enzymes participating in steroidogenesis, CYP1A1, CYP17, and CYP1B1 and central precocious puberty.

STUDY DESIGN

A total of 177 patients was included and divided into two groups: Case group with 73 girls diagnosed with central precocious puberty; Control group with 104 girls with puberty onset after 8 years of age who were followed at the Sector of Gynecology of Childhood and Adolescence, Division of Gynecology Clinic, HC-FMUSP. Polymorphism presence was assessed in the genes involved in estrogen metabolism (CYP1A1, CYP17, and CYP1B1) by the restriction fragment length polymorphism (RFLP) technique using DNA from peripheral blood.

RESULTS

No significant difference in the distribution of the CYP1A1 Mspl (p=0.86) and CYP17 (p=0.12) genotypes was detected between the two study groups. As for CYP1B1 Eco571, the mutated C/C genotype was found to be more frequent in the control group than in the case group (p=0.03).

CONCLUSION

Our data suggest the CYP1B1 Eco571 gene variant is associated with puberty timing.

Nongenetic determinants of age at menarche: a systematic review

BACKGROUND

The acceleration of pubertal development is an important medical and social problem, as it may result in increased morbidity and mortality in later life. This systematic review summarizes relevant data about nongenetic factors, which contribute to age at menarche (AAM), and suggests those which may be the most important.

METHODS

The available literature from 1980 till July 2013 was searched using PubMed and Google Scholar databases. Finally, 154 papers were selected for the analysis.

RESULTS

Environmental factors, which may affect AAM, vary in populations of different ethnicity. The prenatal, infancy, and early childhood periods are the most susceptible to these factors. Body weight, high animal protein intake, family stressors (e.g., single parenting), and physical activity seem to influence AAM in most populations.

CONCLUSIONS

The data about influence of nongenetic factors on AAM are still inconsistent. The factors affecting prenatal and early childhood growth seem to have a larger effect on further sexual maturation. Further studies are needed in order to validate the association between other environmental determinants and AAM in different ethnical groups.

Precocious puberty--perspectives on diagnosis and management

The term 'precocious puberty' signifies the onset of secondary sexual characters before the age of 9 y in boys and 8 y in girls. Menarche before 9.5 y is also considered precocious. These definitions are constantly evolving due to the secular trends observed all over the world. It is crucial to decide whether the child has central (gonadotropin-dependent, GDPP) or peripheral (gonadotropin-independent, GIPP) form of precocious puberty. Some benign conditions such as premature thelarche and premature pubarche may mimic precocious puberty. A systematic approach with detailed history and clinical examination helps to arrive at a diagnosis in most cases. An underlying neurologic disorder is more likely in a very young boy. Basal LH level is the best screening test to diagnose GDPP. LH level less than 0.1 IU/L by a very sensitive assay indicates prepubertal stage. Stimulation tests using gonadotropin releasing hormone (GnRH) or its analog (GnRHa), leuprolide help to confirm the diagnosis of GDPP. High resolution MRI of brain helps to detect abnormalities in hypothalamus and pituitary region. GnRH analogs (GnRHa) are the only effective treatment for GDPP at present. In girls, breast size may regress; menses ceases and vaginal mucosa becomes non-estrogenized. In boys testicular volumes remain static or decrease and genital growth regresses. The effects of GnRH analogs are reversible on discontinuation of therapy, with restoration of normal function within 3 mo after stopping treatment. Treatment of GIPP however is far from satisfactory.

Endocrine disrupting chemicals affect the gonadotropin releasing hormone neuronal network

Endocrine disrupting chemicals have been shown to alter the pubertal process. The controlling levels of the Gonadotropin releasing hormone (GnRH) network involve GnRH itself, KiSS1, and the transcriptional regulators enhanced at puberty 1 (EAP1), Thyroid Transcription Factor 1 (TTF1), and Yin Yang 1 (YY1). While Genistein and Bisphenol A (BPA) have been shown to advance the advent of puberty, exposure to Dioxin delayed pubertal onset. Utilizing in vitro approaches, we observed that Genistein and BPA suppress inhibitory and activate stimulatory components of the GnRH network, while Dioxin exhibit an inhibitory effect at all regulatory hierarchical levels of the GnRH network. It repressed KiSS1, Gnrh, Ttf1 and Yy1 transcription via the xenobiotic response element (XRE), while EAP1 was not affected. Therefore, EDCs alter the neuroendocrine GnRH regulatory network at all hierarchical levels.

Control of puberty: genetics, endocrinology, and environment

PURPOSE OF REVIEW

The aim of this review is to summarize recent advances regarding the genetic components of the complex and coordinated process of puberty, an update of the genes implicated in disorders of puberty, the endocrinologic changes of puberty, and influences of environment in the light of our current understanding of the mechanism of the onset of puberty.

RECENT FINDINGS

The timing of puberty varies greatly in the general population among ethnic groups throughout the world, suggesting the genetic control of puberty. Several studies on the pathological conditions of pubertal onset provide unique information about the interactions of either the genetic susceptibility of or environmental influences on hypothalamic control of pubertal onset. However, these findings suggested that no isolated pathway or external factor is solely responsible for the neuroendocrine control of puberty.

SUMMARY

Puberty is initiated by gonadotropin-releasing hormone from the hypothalamus followed by a complex sequence of endocrine changes and is regulated by both genetic and environmental factors. New attempts to use genetics and genomics might enhance our understanding of the spectrum of pubertal development.

Mechanisms affecting neuroendocrine and epigenetic regulation of body weight and onset of puberty: potential implications in the child born small for gestational age (SGA)

Signaling peptides produced in peripheral tissues such as gut, adipose tissue, and pancreas communicate with brain centers, such as hypothalamus and hindbrain to manage energy homeostasis. These regulatory mechanisms of energy intake and storage have evolved during long periods of hunger in the evolution of man to protect the species from extinction. It is now clear that these circuitries are influenced by prenatal and postnatal environmental factors including endocrine disruptive chemicals. Hypothalamic appetite regulatory systems develop and mature in utero and early infancy, and involve signaling pathways that are important also for the regulation of puberty onset. Recent studies in humans and animals have shown that metabolic pathways involved in regulation of growth, body weight gain and sexual maturation are largely affected by epigenetic programming that can impact both current and future generations. In particular, intrauterine and early infantile developmental phases of high plasticity are susceptible to factors that affect metabolic programming that therefore, affect metabolic function throughout life. In children born small for gestational age, poor nutritional conditions during gestation can modify metabolic systems to adapt to expectations of chronic undernutrition. These children are potentially poorly equipped to cope with energy-dense diets and are possibly programmed to store as much energy as possible, leading to later obesity, metabolic syndrome, disturbed regulation of normal puberty and early onset of cardiovascular disease. Most cases of disturbed energy balance are likely a result of a combination of genetics, epigenetics and environment. This review will discuss potential mechanisms linking intrauterine growth retardation with changes in growth, energy homeostasis and sexual maturation.

Perinatal environmental exposures affect mammary development, function, and cancer risk in adulthood

Puberty is an important transition that enables reproduction of mammalian species. Precocious puberty, specifically early thelarche (the appearance of breast "buds"), in girls of multiple ethnic backgrounds is a major health problem in the United States and other countries. The cause for a continued decrease in the age of breast development in girls is unknown, but environmental factors likely play a major role. Laboratory and epidemiological studies have identified several individual environmental factors that affect breast development, but further progress is needed. Current research needs include increased attention to and recording of prenatal and neonatal environmental exposures, testing of marketed chemicals for effects on the mammary gland, and understanding of the mammary gland-specific mechanisms that are altered by chemicals. Such research is required to halt the increasing trend toward puberty at earlier ages.

Contemporary issues in precocious puberty

Precocious puberty poses significant diagnostic and therapeutic challenge to the physician. Recent advances in the understanding of pathophysiology of precocious puberty have resulted in improved management. Timely intervention is mandatory to achieve successful outcome. The identification of critical role of KISS-1-kisspeptin-GPR54 system has gone a long way to provide an insight into pubertal physiology. It is likely that the system would become an important diagnostic and therapeutic target in children with precocious puberty. Epidemiological studies point toward earlier thelarche. This is, however, associated with slower progression as the age of menarche is static. These changes have led to suggestions of lowering the age cutoffs for precocious puberty in girls. New developments in assessment of precocious puberty including gonadotropin releasing hormone (GnRH) agonist test have made characterization of precocious puberty easier. Longstanding GnRH analogs have become the mainstay of treatment of gonadotropin-dependent precocious puberty, while aromatase inhibitors and inhibitors of sex hormone action are increasingly being used in gonadotropin-independent precocious puberty.

A study on the menstruation of Korean adolescent girls in Seoul

PURPOSE

Westernized eating habits have been associated with early-age menstruation, which increases the incidence of dysmenorrhea and premenstrual syndrome among adolescent girls. We therefore surveyed changes in menarche timing and the general menstrual characteristics of adolescent girls in Seoul, Korea.

METHODS

We surveyed 538 teenage girls who visited our hospital between July and November 2007. Items explored included age at menarche, general menstrual characteristics, occurrence of premenstrual syndrome and treatment thereof, and an association between present dysmenorrhea and a family history of the condition.

RESULTS

Average age at menarche was 12.6 years, with 29% (n=156) subjects beginning menstruation at age 12 years. The prevalence of dysmenorrhea was 82% (n=435). The main symptoms were abdominal (53.2%) and lower back pain (34.2%), and 15.2% of girls who experienced such symptoms required medication. Present dysmenorrhea, and a family history thereof, were statistically correlated (P<0.05). In addition, 58.8% (n=316) of teenage girls had symptoms of premenstrual syndrome. The most frequent psychological symptoms were fatigue (36.4%) and nervousness (38.7%), whereas the most common physical symptom was menstrual cramps (46.5%). Most subjects (87.6%) tolerated the symptoms of premenstrual syndrome without medication; 11.4% took medicines including painkillers; but only 0.1% of subjects visited a doctor.

CONCLUSION

The average age at menarche in Korean girls was 12.6 years, thus younger than in the past. Most teenage girls experienced dysmenorrhea and premenstrual syndrome, but few consulted a doctor. Organized treatment plans are required to manage menstrual problems in teenage girls.

Genetic determinants of pubertal timing in the general population

Puberty is an important developmental stage during which reproductive capacity is attained. The timing of puberty varies greatly among healthy individuals in the general population and is influenced by both genetic and environmental factors. Although genetic variation is known to influence the normal spectrum of pubertal timing, the specific genes involved remain largely unknown. Genetic analyses have identified a number of genes responsible for rare disorders of pubertal timing such as hypogonadotropic hypogonadism and Kallmann syndrome. Recently, the first loci with common variation reproducibly associated with population variation in the timing of puberty were identified at 6q21 in or near LIN28B and at 9q31.2. However, these two loci explain only a small fraction of the genetic contribution to population variation in pubertal timing, suggesting the need to continue to consider other loci and other types of variants. Here we provide an update of the genes implicated in disorders of puberty, discuss genes and pathways that may be involved in the timing of normal puberty, and suggest additional avenues of investigation to identify genetic regulators of puberty in the general population.

Premature pubarche in Mediterranean girls: high prevalence of heterozygous CYP21 mutation carriers

AIM

This study investigated the prevalence and consequences of heterozygous CYP21A2 mutations in premature pubarche (PP) girls.

MAIN FINDING

We investigated 36 French Mediterranean girls with isolated PP. We performed synacthen testing with 17OHP and 21-deoxycortisol evaluation, along with molecular analysis of the CYP21A2 gene in girls with abnormal elevation of one of these two adrenal steroids. Three girls (8.3%) had nonclassical adrenal hyperplasia, secondary to compound heterozygosity that associated at least one severe mutation for the three girls. A heterozygous mutation of the CYP21A2 gene was confirmed by molecular biology in eight girls (22%); a deletion of the CYP21A2 gene was found in one of them. Biological hyperandrogenism was found in the prepubertal CYP21A2 mutation carriers, whereas the four heterozygous girls who were followed long enough to have reached pubertal age presented biological and clinical hyperandrogenism.

CONCLUSIONS

We underline the high prevalence of heterozygous CYP21A2 mutations in girls with PP and demonstrate the usefulness of systematic screening by synacthen testing, both to improve their future clinical management and to prevent the transmission of classical adrenal hyperplasia to future offspring. Because of the severe metabolic and cardiovascular consequences of hyperandrogenism, long-term follow-up of these heterozygous patients is mandatory.

Decline in age at menarche among Spanish women born from 1925 to 1962

BACKGROUND

While the timing of reproductive events varies across populations, a downward trend in age at menarche has nevertheless been reported in most of the developed world over the past century. Given the impact of change in age at menarche on health conditions, this study sought to examine secular trends in age at menarche among women living in Navarre (Northern Spain) who participated in a population-based breast cancer screening programme.

METHODS

The study was based on 110545 women born from 1925 to 1962. Trends were tested using a linear regression model, in which year of birth was entered continuously as the predictor and age at menarche (years) as the response variable, using size of town and region of birth as covariates.

RESULTS

Among women born in Navarre between 1925 and 1962, age at menarche declined steadily from an average of 13.72 years in the 1925-1929 birth-cohorts to 12.83 years in the 1958-1962 birth-cohorts. Controlling for size of town or city of birth, age at menarche declined by an average of 0.132 years every 5 years over the period 1925-1962. This decline was greater in women born in rural versus urban settings. Trends were also different among regions of birth.

CONCLUSION

We report a population-based study showing a downward trend in age of onset of menarche among Spanish women born in the period 1925-1962, something that is more pronounced among women born in rural settings and varies geographically.

Pre- and postnatal nutritional histories influence reproductive maturation and ovarian function in the rat

BACKGROUND

While prepubertal nutritional influences appear to play a role in sexual maturation, there is a need to clarify the potential contributions of maternal and childhood influences in setting the tempo of reproductive maturation. In the present study we employed an established model of nutritional programming to evaluate the relative influences of prenatal and postnatal nutrition on growth and ovarian function in female offspring.

METHODS

Pregnant Wistar rats were fed either a calorie-restricted diet, a high fat diet, or a control diet during pregnancy and/or lactation. Offspring then were fed either a control or a high fat diet from the time of weaning to adulthood. Pubertal age was monitored and blood samples collected in adulthood for endocrine analyses.

RESULTS

We report that in the female rat, pubertal timing and subsequent ovarian function is influenced by the animal's nutritional status in utero, with both maternal caloric restriction and maternal high fat nutrition resulting in early pubertal onset. Depending on the offspring's nutritional history during the prenatal and lactational periods, subsequent nutrition and body weight gain did not further influence offspring reproductive tempo, which was dominated by the effect of prenatal nutrition. Whereas maternal calorie restriction leads to early pubertal onset, it also leads to a reduction in adult progesterone levels later in life. In contrast, we found that maternal high fat feeding which also induces early maturation in offspring was associated with elevated progesterone concentrations.

CONCLUSIONS

These observations are suggestive of two distinct developmental pathways leading to the acceleration of pubertal timing but with different consequences for ovarian function. We suggest different adaptive explanations for these pathways and for their relationship to altered metabolic homeostasis.

Precocious puberty and normal variant puberty: definition, etiology, diagnosis and current management

This review describes several aspects of the management of precocious puberty (PP) and variants in girls and boys. PP is characterized by early pubertal changes, acceleration of growth velocity and rapid bone maturation that often result in reduced adult height. Onset of pubertal signs before the age of 8 years in girls and 9 years in boys should always be evaluated carefully. The main principles of therapy are to stop the progression of secondary sex characteristics and menses (in girls), to increase final adult height, to promote psychosocial well-being, and to treat the underlying cause if known.

What controls the timing of puberty? An update on progress from genetic investigation

PURPOSE OF REVIEW

Puberty is an important developmental stage during which reproductive capacity is attained. Genetic and environmental factors both influence the timing of puberty, which varies greatly among individuals. However, although genetic variation is known to influence the normal spectrum of pubertal timing, the specific genes involved remain unknown.

RECENT FINDINGS

Recent genetic analyses have identified a number of genes responsible for rare disorders of pubertal timing such as hypogonadotropic hypogonadism and Kallmann syndrome. However, although the genetic basis of population variation in the timing of puberty is an active area of investigation, no genetic loci have been reproducibly associated with pubertal timing thus far.

SUMMARY

This review provides an update of the genes implicated in disorders of puberty, discusses genes and pathways that may be involved in the timing of normal puberty, and suggests additional avenues of investigation to identify genetic regulators of puberty in the general population.

Rationale for diagnosing deficiency of ChEs and for applying exogenous HuChEs to the treatment of diseases

Recent evidence strongly demonstrates that acetylcholine (ACh) is not only involved in the function of the central and peripheral nervous systems, including the parasympathetic and somatic systems, but also acts as a ubiquitous cell signaling molecule or cytotransmitter, and as a hormone with paracrine, juxtacrine and autocrine properties. This active molecule exerts versatile and potent functions primarily through its specific nicotinic and muscarinic receptors (nAChRs and mAChRs, respectively). These functions modulate numerous biomechanisms, including cell growth, survival, proliferation and differentiation, cell-cell contact, cell cycle, locomotion, electrical activity, immune function, apoptosis, organization of the cytoskeleton, trophic functions, secretion, adhesion, resorption, and stress-response-regulation. By nature, the precise ACh levels and responses from receptors must be controlled and regulated by its degrading enzymes, the cholinesterases (ChEs), namely, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Once ChEs become critically deficient in quality and quantity, ACh signaling will be uncontrollably aberrant and persistent. An in-depth account of the fundamental roles of ChEs, comprising their diverse soluble and membrane-bound forms, in maintaining the functional equilibrium of ACh in the macro and microenvironment has been undertaken. This work also covers ACh receptors, signaling pathways, other interdependent and interrelated substances, functional processes, role of ChEs as first-line gatekeepers and defenses for the architecture of cells, tissues and organisms, physically, chemically, and structurally. The mechanisms of many diseases ranging from the acute cholinergic crisis to the chronic degenerative and hypergenerative disorders such as Alzheimer's disease, cancers, atopic dermatitis, may involve a deficiency of ChEs or imbalance between ACh and ChEs, initially or consequentially. It is therefore essential to ascertain a ChE deficiency, or an imbalance between ACh and ChEs, in tissues and body fluids in order for conducting clinical diagnosis, prevention and treatment. An argument is put forward on the rationale of applying exogenous human ChEs to reverse enzymatic deficiency and correct the imbalance between ACh and ChEs, to repair the affected receptors and protect against their further loss in the body, and consequently to alleviate the signs and symptoms of diseases. Evidence is adduced for the safety and efficacy of ChEs treatment.

Environmental evaluation of a child with developmental disability

Children's health can be affected adversely by the environment in which they live. It is well recognized that some environmental chemicals are harmful to the brain, but the role these chemicals play in the development of specific disabilities such as attention deficit hyperactivity disorder and autism is not certain. Parents of children who have developmental disabilities often ask the primary care physician whether certain environmental toxicants might be the cause of the illness. A detailed environmental history and physical examination may help clarify whether there is a plausible relationship between an environmental toxicant and a child's disability.