Molecular epidemiology of hypospadias: Review of genetic and environmental risk factors

Maternal PM2.5 exposure and hypospadias risk in Chinese offspring: Insights from a nationwide surveillance-based study

Research on the association between maternal PM2.5 exposure and hypospadias risk in male offspring, particularly in highly polluted areas, has been limited and inconsistent. This study leveraged data from China's National Population-based Birth Defects Surveillance System spanning the years 2013 to 2019, and employed sophisticated machine learning models to estimate daily PM2.5 levels and other pollutants for mothers at a 1-km resolution and a 6-km buffer surrounding maternal residences. Multivariate logistic regression analyses were performed to evaluate the relationship between PM2.5 exposure and hypospadias risk. For sensitivity analyses, stratification analysis was conducted, and models for one-pollutant and two-pollutants, as well as distributed lag nonlinear models, were constructed. Of the 1194,431 boys studied, 1153 cases of hypospadias were identified. A 10 μg/m3 increase in maternal PM2.5 exposure during preconception and the first trimester was associated with an elevated risk of isolated hypospadias, with Odds Ratios (ORs) of 1.102 (95% CI: 1.023-1.188) and 1.089 (95% CI: 1.007-1.177) at the 1-km grid, and 1.122 (95% CI: 1.034-1.218) and 1.143 (95% CI: 1.048-1.246) within the 6-km buffer. Higher quartiles of PM2.5 exposure were associated with increased odds ratios compared to the lowest quartile. These findings highlight a significant association between PM2.5 exposure during the critical conception period and an elevated risk of isolated hypospadias in children, emphasizing the need for targeted interventions to reduce PM2.5 exposure among expectant mothers.

Incidence of and indications for sperm donor restriction - analysis of patients continuing treatment: a retrospective single-centre study

RESEARCH QUESTION

What are the incidence of and indications for sperm donor restriction due to suspected/confirmed disease risk, and the future treatment choices of patients using these sperm donors?

DESIGN

This single-centre retrospective study involved donors who had restrictions on the use of their imported spermatozoa from January 2010 to December 2019, and current or previous recipients. Indications for sperm restriction and the characteristics of patients undergoing medically assisted reproduction (MAR) treatment with these specimens at the time of restriction were collected. Differential characteristics of women who decided on whether or not to contintue the procedure were assessed. Characteristics potentially leading to treatment continuation were identified.

RESULTS

Of 1124 sperm donors identified, 200 (17.8%) were restricted, most commonly for multifactorial (27.5%) and autosomal recessive (17.5%) disorders. The spermatozoa had been used for 798 recipients, of whom 172, receiving spermatozoa from 100 donors, were informed about the restriction and constituted the 'decision cohort'. The specimens from the restricted donors were accepted by 71 (approximately 40%) patients, with 45 (approximately 63%) eventually using the restricted donor for their future MAR treatment. The odds of accepting the restricted spermatozoa decreased with increasing age (OR 0.857, 95% CI 0.800-0.918, P < 0.001) and the time between MAR treatment and the restriction date (OR 0.806, 95% CI 0.713-0.911, P < 0.001).

CONCLUSION

Donor restriction due to suspected/confirmed disease risk is relatively frequent. This affected a relevant number of women (around 800), of whom 172 (approximately 20%) had to decide whether or not to use these donors further. Although donor screening is being performed thoroughly, there remain health risks for donor children. Realistic counselling of all stakeholders involved is necessary.

Maternal exposure to DDT, DDE, and pyrethroid insecticides for malaria vector control and hypospadias in the VHEMBE birth cohort study, Limpopo, South Africa

Hypospadias is the ectopic opening of the urethra on the penis or scrotum. Exposure to estrogenic and/or anti-androgenic chemicals in utero may play an etiologic role. DDT and the pyrethroids cypermethrin and deltamethrin, are used to control malaria. DDT is estrogenic and its breakdown product DDE is anti-androgenic; cypermethrin and deltamethrin can also disrupt androgen pathways. We examined the relationship between maternal exposure to these insecticides during pregnancy and hypospadias among boys participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) in Limpopo Province, South Africa. We measured peripartum levels of p,p'-DDT and p,p'-DDE in maternal serum and urinary pyrethroid metabolites. We conducted urogenital examination on 359 one-year-old boys. A total of 291 (81.0 %) had phimosis, which prevented full urogenital examination, leaving a final sample of 68 boys for determination of the presence of hypospadias. Diagnosis was based on concordance of two independent physicians. We identified hypospadias in 23 of the 68 boys (34 %). Maternal urinary concentrations of cis-DCCA and trans-DCCA metabolites of cypermethrin and other pyrethroids, were associated with an increased risk for hypospadias, but the other metabolite 3-PBA was not (adjusted relative risk per 10-fold increase = 1.58, 95 % CI 1.07-2.34; 1.61, 95 % CI 1.09-2.36; and 1.48, 95 % CI 0.78-2.78, respectively). No associations were found between p,p'-DDT, p,p'-DDE, 3-PBA or cis-DBCA and hypospadias. We observed a high prevalence of hypospadias among boys without phymosis. Boys with higher prenatal exposure to pyrethroid insecticides were at higher risk of hypospadias. Our findings may have global implications given that pyrethroid insecticides are widely used for malaria control, in agriculture and for home use.

Characterization With Gene Mutations in Han Chinese Patients With Hypospadias and Function Analysis of a Novel AR Genevariant

It is estimated that around 10-20% of hypospadias are caused by genetic abnormalities worldwide although the spectrum of associated genes does vary across different ethnicities. The prevalence of hypospadias among the Chinese population has been increasing the last couple of decades. However, the pathogenesis underlying the disease and its associated genetic abnormality remains unclear. Here we performed a genetic analysis of 81 children with karyotype 46, XY and the hypospadias phenotype in order to characterize the genetic components that contribute to the development of hypospadias in Chinese patients. 15 candidate genes, including sex determination genes-SOX9, SRY, NR0B1 (DAX1), NR5A1 (SF1), DHH, sex differentiation genes-AR, SRD5A2, MAMLD1, INSL3, and hypospadias-associated genes-FGF8, FGF10, BMP4, BMP7, ATF3, and MID1 were screened by using next generation sequencing. A total of 18 patients were found to have mutations identified by PCR and sequencing, including 11 cases of SRD5A2 genes, 6 cases of AR genes, and 1 case of MID1 gene, respectively. One novel missense mutation p.I817N was discovered in AR gene. Further molecular analysis found that subcellular localization of the AR_{I 81 7N} was the same as that of wild type AR_WT in the absence or presence of hormone. But it led to 50% reduction in AR-induced transcriptional activity in the presence of either the synthetic androgen R1881 or the natural ligand dihydrotestosterone. Our results indicate that SRD5A2 and AR genes are two top candidate genes associated with 46, XY hypospadias in Chinese patients. Further epidemiological and genetic analysis are still needed to further clarify the pathogenesis of hypospadias in Han Chinese patients.

Exploring the risk of hypospadias in children born from mothers living close to a vineyard

Hypospadias (H) is a common birth defect affecting the male urinary tract. It has been suggested that exposure to endocrine disrupting chemicals might increase the risk of H by altering urethral development. However, whether H risk is increased in places heavily exposed to agricultural pesticides, such as vineyards, remains debated and difficult to ascertain. The objective of the work is to test the possible association of H with residential proximity to vineyards. Residential address at birth of 8,766 H cases born 1980–2011 was taken from 17 specialized surgery centers. The geographical distribution of vineyards was obtained from the European Land Parcel Identification System (LPIS) and the distance of address to the nearest vineyard was computed. A first estimate of the variation of H relative risk with distance to vineyards was obtained using as controls 13,105 cryptorchidism (C) cases operated during the same period in the same centers. A separate estimate was obtained from a case-control study using “virtual controls” (VC) defined as points of the map sampled to match the demographic distribution of births within the recruitment territories of the study centers. Non-exposed patients were defined as those with a residence between 5,000 and 10,000 m from the closest vineyard. The residential distance to vineyard was smaller for H than for C cases (p<10⁻⁴). We found 42/8766 H cases (0.48%) and 50/13,105 C cases (0.38%) born to mothers living within 20 m of a vineyard. The odds ratios for H were 2.48 (CI: 1.0 to 5.1) and 2.4 (CI: 1.3 to 4.4), vs C or vs VC, respectively, when pregnant mothers lived 10–20 m from a vineyard. In conclusion, our study supports that children born to mothers living close to a vineyard have a two-fold increased risk of H. For environmental research, the use of VC provides an alternative to classical case control technique.

Etiology of Hypospadias: A Comparative Review of Genetic Factors and Developmental Processes Between Human and Animal Models

Hypospadias is a congenital anomaly of the penis with an occurrence of approximately 1 in 200 boys, but the etiology of the majority of hypospadias has remained unknown. Numerous genes have been reported as having variants in hypospadias patients, and many studies on genetic deletion of key genes in mouse genital development have also been published. Until now, no comparative analysis in the genes related literature has been reported. The basic knowledge of penile development and hypospadias is mainly obtained from animal model studies. Understanding of the differences and similarities between human and animal models is crucial for studies of hypospadias. In this review, mutations and polymorphisms of hypospadias-related genes have been compared between humans and mice, and differential genotype–phenotype relationships of certain genes between humans and mice have been discussed using the data available in PubMed and MGI online databases, and our analysis only revealed mutations in seven out of 43 human hypospadias related genes which have been reported to show similar phenotypes in mutant mice. The differences and similarities in the processes of penile development and hypospadias malformation among human and commonly used animal models suggest that the guinea pig may be a good model to study the mechanism of human penile development and etiology of hypospadias.

New frontiers on the molecular underpinnings of hypospadias according to severity

Hypospadias, which is characterised by the displacement of the urethral meatus from its typical anatomical location in males, shows various degrees of severity. In this systematic review, we surveyed our current understanding of the genetics of isolated hypospadias in humans according to the severity of the condition. We found that sequencing and genotyping approaches were the preferred methods of study and that single nucleotide polymorphisms were the most common finding associated with hypospadias. Most genes fell into four gene-pathway categories related to androgens, oestrogens, growth factors, or transcription factors. Few hypospadias studies classify their findings by severity. Taken together, we argue that it is advantageous to take into consideration the severity of the condition in search of novel candidates in the aetiology of hypospadias. Abbreviations: AR: androgen receptor; ATF3: activating transcription factor 3; BMP4: bone morphogenetic protein 4; BMP7: bone morphogenetic protein 7; CYP17: steroid 17-alpha-hydroxylase/17,20 lyase; CYP1A1: cytochrome P450 1A1; CYP3A4: cytochrome P450 3A4; CNVs: copy number variants; DGKK: diacylglycerol kinase kappa; ESR1: oestrogen receptor 1; ESR2: oestrogen receptor 2; FGF8: fibroblast growth factor 8; FGF10: fibroblast growth factor 10; FGFR2: fibroblast growth factor receptor 2; HOXA4: homeobox protein Hox-A4; HOXB6: homeobox protein Hox-B6; HSD17B3: hydroxysteroid 17-beta dehydrogenase 3; MAMLD1: mastermind-like domain-containing protein 1; SF-1: splicing factor 1; SHH: sonic hedgehog; SNPs: single nucleotide polymorphisms; SOX9: SRY-box 9; SRD5A2: steroid 5 alpha-reductase 2; SRY: sex-determining region Y protein; STAR: steroidogenic acute regulatory protein; STARD3: StAR-related lipid transfer protein 3; STS: steryl-sulfatase; WT1: Wilms tumour protein; ZEB1: zinc finger oestrogen-box binding homeobox 1.

Anogenital distance in newborn infants conceived by assisted reproduction and natural conception

RESEARCH QUESTION

Does anogenital distance (AGD) differ in newborn infants conceived through assisted reproduction technology (ART) compared with those conceived naturally?

DESIGN

This case-control study looked at anthropometric and anogenital measurements in 247 male and 200 female newborns born after ART (n = 121) or natural conception (n = 326), within 24 h of birth. Anogenital measurements included distance from the centre of the anus to the anterior clitoris (AGDAC) and to the posterior fourchette (AGDAF) in female infants, and from the centre of the anus to the posterior base of the scrotum (AGDAS) and to the anterior base of the penis (AGDAP) in male infants.

RESULTS

ART mothers were older, more likely to be nulliparous and delivered by Caesarean section at an earlier gestational week. AGDAS of male infants was approximately twice the AGDAF of female infants (17.6 ± 5.0 versus 9.1 ± 3.6 mm). AGDAF in female infants conceived by ART compared with those conceived naturally was not significantly different (8.8 ± 3.6 versus 9.3 ± 3.6 mm; P = 0.404). AGDAC were also comparable for both groups (27.4 ± 6.3 versus 27.7 ± 7.1 mm; P = 0.770). In male infants, no significant difference was seen between ART and natural conception groups in terms of AGDAS (17.4 ± 4.6 versus 17.7 ± 5.2 mm, P = 0.742) and AGDAP (37.5 ± 6.6 versus 38.0 ± 6.7 mm, P = 0.589). When adjusted for gestational age, weight, length and head circumference, mode of conception was not associated with differences in any of the anogenital measurements.

CONCLUSIONS

AGD measurements in infants conceived by ART are no different from those of infants conceived naturally.

The genetic factors contributing to hypospadias and their clinical utility in its diagnosis

Hypospadias is among the most common congenital malformations in male neonates. It results from abnormal penile and urethral development, but is a multifactorial disorder that is highly heterogeneous, with several genetic and environmental determinants. Monogenic and chromosomal abnormalities are present in approximately 30% of cases, although the genetic factors contributing to hypospadias remain unknown in 70% of cases. While defects in androgen synthesis can lead to this malformation, mutational analyses have shown several genes, such as sonic hedgehog, fibroblast growth factors, bone morphogenetic proteins, homeobox genes, and the Wnt family, are involved in the normal development of male external genitalia. Mutations in the genes of penile development (e.g., HOX, FGF, Shh) and testicular determination (e.g., WT1, SRY), luteinizing hormone receptor, and androgen receptor have also been proposed to be implicated in hypospadias. Here we review the recent advances in this field and discuss the potential genes that could determine the risk of hypospadias.

Association of In Utero Exposure to Polybrominated Diphenyl Ethers With the Risk of Hypospadias

IMPORTANCE

Polybrominated diphenyl ethers (PBDEs) are added to many consumer products as flame retardants, and their endocrine-disrupting properties are a growing health concern in pregnancy.

OBJECTIVE

To investigate whether in utero PBDE exposure as measured in maternal hair is associated with increased risk for hypospadias.

DESIGN, SETTING, AND PARTICIPANTS

In this case-control study, the setting was the urology clinic of a tertiary pediatric hospital between January 3, 2011, and April 1, 2013. Participants were children diagnosed as having hypospadias and their mothers and a control group of children without hypospadias and their mothers. Dates of data analysis were September 3, 2017, to December 28, 2017.

EXPOSURES

Gestational exposure to 8 PBDEs as measured in the 3-cm segment closest to the skull of maternal hair by gas chromatography-mass spectroscopy as a proxy for in utero exposure. The mothers resided in the same household for the duration of their pregnancy.

MAIN OUTCOMES AND MEASURES

Difference in total maternal hair PBDE levels between the hypospadias and control groups.

RESULTS

Total PBDE levels were significantly higher among mothers of infants with hypospadias (n = 152) (total PBDE level, 51.4 pg/mg; interquartile range, 35.8-78.5 pg/mg) than among controls (n = 64) (total PBDE level, 35.8 pg/mg; interquartile range, 18.1-69.9 pg/mg) (P = .02). Of the 152 women with sufficient hair samples for analysis in the case group, 89 completed a questionnaire and were included in a multivariable analysis, and of the 64 women with sufficient hair samples for analysis in the control group, 54 completed a questionnaire and were included in a multivariable analysis. Adjusting for potential confounders, hypospadias was associated with a relative 48.2% (95% CI, 23.2%-65.4%) higher maternal level of total PBDE levels in the multivariable analysis.

CONCLUSIONS AND RELEVANCE

In this analysis, mothers of children with hypospadias were exposed during pregnancy to significantly higher levels of PBDEs. The results of this study suggest that level of exposure to PBDEs during gestation may have a role in the etiology of hypospadias.

Description of mutation spectrum and polymorphism of Wilms' tumor 1 (WT1) gene in hypospadias patients in the Indonesian population

INTRODUCTION

Hypospadias is one of the most common congenital anomalies of the penis. Previous studies reported mutation of the Wilms' tumor 1 (WT1) gene as a cause of hypospadias. The aim of this study is to describe the WT1 mutation spectrum and polymorphism in hypospadias patients in Indonesia.

MATERIAL AND METHODS

DNA was isolated from 74 hypospadias patients at the Division of Pediatric Surgery, Department of Surgery Hasan Sadikin Hospital. All exons in the WT1 gene were amplified by a PCR method, followed by Sanger sequencing. Mutation analysis was performed using BioEdit software and in silico analysis using Mutation Taster, Polymorphism Phenotyping-2 (PolyPhen-2), and Sorting Intolerant from Tolerant (SIFT).

RESULT

DNA analysis results showed two types of heterozygous mutations in five subjects (Table), hence the frequency of WT1 mutations was 6.7% (10/148 allele). The first mutation was a missense mutation identified in twin boys. The second was a novel heterozygous alteration in the non-coding region nine bp upstream of exon 6 (c.366-9T>C), which was identified in three patients. One heterozygous polymorphism in the coding region of exon 7 (c.471A>G/rs16754) was identified in 10 subjects. This variant did not cause any change in amino acid products (silence polymorphism). Allele frequency for the G allele (mutant allele) and A allele (wild type) was 13.5% and 86.5%, respectively.

DISCUSSION

WT1 is one of the best known hypospadias genes. The WT1 gene is involved in male genital development in the early and late periods of sex determination, and hence is known as a long-term expression gene in genitalia development. Mutation analysis of WT1 in a Chinese population identified that the WT1 mutation frequency was 4.4%. The WT1 mutation frequency identified in the present study was higher, at 6.7%. Coincidentally, research subjects with p.R158H variants were monozygotic twin siblings with midshaft hypospadias accompanied by undescended testis in one and penoscrotal hypospadia with micropenis in the other. The incidence of familial hypospadias in male siblings suffering from hypospadias was reported to be 9.6% in a study conducted by Sorensen et al. Moreover, in the present study polymorphism c.471A>G(rs16754) at exon 7 was identified heterozygously in 10 research subjects (minor allele frequency 13.5%).

CONCLUSION

WT1 mutations were identified in only a few cases of hypospadias and most of these were syndromic. This result implies that mutation of WT1 is not a common cause of hypospadias in the Indonesian population.

Associations of TGFBR1 and TGFBR2 gene polymorphisms with the risk of hypospadias: a case-control study in a Chinese population

This case-control study investigated the association of transforming growth factor-β (TGF-β) receptor type I and II (TGFBR1 and TGFBR2) gene polymorphisms with the risk of hypospadias in a Chinese population. One hundred and sixty two patients suffering from hypospadias were enrolled as case group and 165 children who underwent circumcision were recruited as control group. Single nucleotide polymorphisms (SNPs) in TGFBR1 and TGFBR2 genes were selected on the basis of genetic data obtained from HapMap. PCR-restriction fragment length polymorphism (PCR-RFLP) was performed to identify TGFBR1 and TGFBR2 gene polymorphisms and analyze genotype distribution and allele frequency. Logistic regression analysis was conducted to estimate the risk factors for hypospadias. No significant difference was found concerning the genotype and allele frequencies of TGFBR1 rs4743325 polymorphism between the case and control groups. However, genotype and allele frequencies of TGFBR2 rs6785358 in the case group were significantly different in contrast with those in the control group. Patients carrying the G allele of TGFBR2 rs6785358 polymorphism exhibited a higher risk of hypospadias compared with the patients carrying the A allele (P<0.05). The TGFBR2 rs6785358 genotype was found to be significantly related to abnormal pregnancy and preterm birth (both P<0.05). The frequency of TGFBR2 rs6785358 GG genotype exhibited significant differences amongst patients suffering from four different pathological types of hypospadias. Logistic regression analysis revealed that preterm birth, abnormal pregnancy, and TGFBR2 rs6785358 were the independent risk factors for hypospadias. Our study provides evidence that TGFBR2 rs6785358 polymorphism might be associated with the risk of hypospadias.

Hypospadias, Intrauterine Growth Restriction, and Abnormalities of the Placenta

BACKGROUND

Hypospadias is more common among male infants with growth restriction, defined as a birth weight less than the 10^th centile, than in infants with a normal birth weight. Intrauterine growth retardation (IUGR) has been associated, also, with abnormalities of the placenta, such as maternal vascular malperfusion. In a consecutive sample of newborn infants, the association between hypospadias, IUGR and abnormalities of the placenta could be analyzed.

METHODS

Affected infants were identified among 289,365 liveborn and stillborn infants in the Active Malformations Surveillance Program between 1972 and 2012. The four anatomic locations of the ectopic urethral opening, based on the recorded physical examination findings, were: (1) glandular; (2) subcoronal; (3) penile; (4) penoscrotal. Affected infants with associated malformations, a chromosome abnormality, teratogenic exposure, maternal diabetes mellitus, or multiple gestations were excluded.

RESULTS

Three hundred sixteen affected infants were identified: 52.2% glandular, 11.7% subcoronal, 27.8% penile, and 8.2% penoscrotal. The highest frequency of IUGR (34.6%) was in the infants with the most severe hypospadias (penoscrotal). The 39 reports of placenta findings showed a high frequency of abnormalities.

CONCLUSION

An increased rate of occurrence of hypospadias and abnormalities of the placenta were present in infants with intrauterine growth restriction. The postulated cause of this association is a deficiency in the function of the placenta during weeks 10 to 14 of gestation when normal masculinization occurs due to an increase in the level of placental human chorionic gonadotropin and fetal testosterone. The cause of the placental deficiency has not been established. Birth Defects Research 110:122-127, 2018.© 2017 Wiley Periodicals, Inc.

Association of SRD5A2 gene mutations with risk of hypospadias in the Iranian population

BACKGROUND

Hypospadias is one of the most common forms of congenital malformation of the male external genitalia worldwide. The ratio in the Iranian population is one in 250 live male births. The conversion of testosterone to dihydrotestosterone (DHT) in the presence of steroid 5α-reductase 2, which is encoded by SRD5A2 gene, plays an important role in the normal development of the male reproductive system.

METHODS

We examined whether SRD5A2 gene mutations (V89L and A49T polymorphisms) are associated with the risk of hypospadias in the Iranian population. We performed exons sequencing for SRD5A2 gene in 109 hypospadias patients.

RESULTS

We identified two new mutations in the subgroups of affected cases: including a substitution of the nucleotide T > A in the codon 73 [c.219T > A (p.Leu73_Ser74insHisPro)] and an insertion of an extra A nucleotide in the codon 77 [c.229insA* (p.Gly77*)]. Additionally, we performed PCR-RFLP for the two identified polymorphisms and revealed that V89L [OR = 5.8, 95% CI (3.8-8.8), p value < 0.001] and A49T [OR = 10.16, 95% CI (3.94-26.25), p value < 0.001] are significantly associated with hypospadias occurrence in patients. Our haplotype analysis further indicated that the Leu-Ala haplotype increases risk of hypospadias; conversely, the Val-Ala haplotype decreases the risk of hypospadias in the studied patients.

CONCLUSIONS

This study demonstrates that polymorphisms in the SRD5A2 gene could be considered as a risk factor for hypospadias disease emergence.

Maternal inflammatory bowel disease and hypospadias in male offspring: a population-based study in Denmark

Background

The occurrence of inflammatory bowel disease (IBD) and hypospadias has been concurrently increasing, possibly through shared environmental risk factors such as endocrine disrupting compounds. Also, maternal IBD may disturb the normal development of the fetal reproductive tract. However, whether maternal IBD increases the risk of hypospadias in male offspring is unknown. We compared hypospadias risk in sons of mothers with and without IBD.

Methods

We used Danish nationwide population-based registries to conduct a longitudinal prevalence study including all live-born boys from 1979 through 2009. We computed HRs, as estimates of prevalence ratios (PRs), with 95% CIs for hypospadias, using Cox proportional hazards regression, while adjusting for measured confounding.

Results

Among 966 038 live-born boys, 4688 (0.5%) had a mother with a history of IBD diagnosis before the relevant childbirth. Among the boys with maternal IBD, 36 (0.8%) were diagnosed with hypospadias any time after birth, whereas 6112 (0.6%) sons of mothers without IBD diagnosis had hypospadias (adjusted PR: 1.20, (95% CI 0.86 to 1.67). Adjusted PRs for maternal Crohn's disease and ulcerative colitis were 1.38 (95% CI 0.83 to 2.29) and 1.10 (95% CI 0.71 to 1.68), respectively. Analyses defining hypospadias diagnosis recorded <6 months postpartum showed similar results.

Conclusions

We found no convincing evidence of an association between maternal IBD and hypospadias.

Prenatal exposure to di-n-butyl phthalate (DBP) differentially alters androgen cascade in undeformed versus hypospadiac male rat offspring

This study was to compare the alterations of androgen cascades in di-n-butyl phthalate (DBP)-exposed male offspring without hypospadias (undeformed) versus those with hypospadias. To induce hypospadias in male offspring, pregnant rats received DBP via oral gavage at a dose of 750mg/kg BW/day during gestational days 14-18. The mRNA expression levels of genes downstream of the androgen signaling pathway, such as androgen receptor (AR) and Srd5a2, in testes of undeformed rat pups were similar to those in controls; in hypospadiac rat pups these levels were significantly lower than those of control pups. In contrast, both undeformed and hypospadiac rats had decreased serum testosterone levels, reduced mRNA expression of key enzymes in the androgen synthetic pathway in the testes, and ablated genes of developmental pathways, such as Shh, Bmp4, Fgf8, Fgf10 and Fgfr2, in the genital tubercle (GT) as compared to those in DBP-unexposed controls, albeit hypospadiac rats had a more severe decrement than those of undeformed rats. Although other possibilities cannot be excluded, our findings suggest that the relatively normal levels of testosterone-AR-Srd5a2 may contribute to the resistance to DBP toxicity in undeformed rats. In conclusion, our results showed a potential correlation between decreased testosterone levels, reduced mRNA expression of AR and Srd5a2 and the occurrence of hypospadias in male rat offspring prenatally exposed to DBP.

The Genetic and Environmental Factors Underlying Hypospadias

Hypospadias results from a failure of urethral closure in the male phallus and affects 1 in 200-300 boys. It is thought to be due to a combination of genetic and environmental factors. The development of the penis progresses in 2 stages: an initial hormone-independent phase and a secondary hormone-dependent phase. Here, we review the molecular pathways that contribute to each of these stages, drawing on studies from both human and mouse models. Hypospadias can occur when normal development of the phallus is disrupted, and we provide evidence that mutations in genes underlying this developmental process are causative. Finally, we discuss the environmental factors that may contribute to hypospadias and their potential immediate and transgenerational epigenetic impacts.

Higher Incidence of Hypospadias in Monochorionic Twins

Background:Hypospadias is associated with twinning. The incidence of hypospadias in monochorionic and dichorionic male twins is, however, yet to be determined.Methods:All medical records of monochorionic and dichorionic twins admitted to our neonatal nursery between January 2004 and August 2013 were reviewed for the presence of hypospadias.Results:A total of 350 monochorionic and 303 dichorionic male twins were included in the study. The incidence of hypospadias in monochorionic and dichorionic groups was 4% (14/350) and 1% (3/303) (p= .016) respectively. In 11 of the 15 twin couples, hypospadias occurred in the twin with the lowest birth weight. The rate of hypospadias in twin infants small-for-gestational-age group was 10% (6/60) compared with 2% (11/593) in the appropriate-for-gestational-age group (p= .002). In a multivariate analysis, both monochorionicity and small-for-gestational-age were independently associated with hypospadias, odds ratio 4.1 (95% confidence interval (CI): 1.1–14.7) and 6.1 (95% CI: 2.2–17.2) respectively.Conclusions: The incidence of hypospadias is four-fold higher in monochorionic twins compared with dichorionic twins. Hypospadias is also independently associated with small-for-gestational-age.

Risk factors for hypospadias in China

This case-controlled study was designed to evaluate the association between various baseline parental factors and the risk of hypospadias in China. Patients were selected from tertiary referral hospitals in Anhui, a province in mid-eastern China. A questionnaire was given to the parents of each patient. The final database included 193 cases and 835 controls. The incidence of additional coexistent anomalies was 13.0%, primarily cryptorchidism (9.8%). Ten patients (5.1%) were from families with genital anomaly, including five families (2.6%) with hypospadias. The risks of hypospadias was higher for children of mothers > 35 (odds ratio [OR] =1.47) and < 18 (OR = 2.95) years of age, and in mothers who had consumed alcohol (OR = 2.67), used drugs (OR = 1.53) and had an infection (OR = 1.87) during pregnancy. The risk of hypospadias was also higher when mothers (OR = 1.68) and fathers (OR = 1.74) were engaged in agriculture. Other factors assessed were not associated with the risk of hypospadias.

Diacylglycerol kinase κ (DGKK) variants and hypospadias in Han Chinese: association and meta-analysis

OBJECTIVE

To investigate whether diacylglycerol kinase κ (DGKK) is a susceptibility gene for hypospadias in the Han Chinese population as has been suggested by previous publications.

PATIENTS SUBJECTS AND METHODS

A case-control study involving 466 patients with hypospadias and 402 healthy subjects was conducted to assess the relationship between DGKK single nucleotide polymorphisms (SNPs) and hypospadias risk in the Han Chinese population. The 466 hypospadias patients were further divided into mild, moderate and severe subgroups for analysis.

RESULTS

Six SNPs (rs1934179, rs4143304, rs9969978, rs1934188, rs4826632 and rs4599945) were marginally associated with mild and moderate hypospadias [odds ratios (ORs) > 1, P = 0.05 to P < 0.1), whereas no significant relationship was seen with the severe cases (ORs >1, P > 0.1). After correcting for multiple testing, it was determined that neither individual SNPs nor individual haplotypes were associated with hypospadias. To evaluate this relationship in multiple populations, we performed a meta-analysis on six SNPs, using combined data from our present results and those of previous studies of different races (including 1966 patients and 2492 controls). Six SNPs (rs1934179, rs4143304, rs9969978, rs1934188, rs7063116 and rs1934190) were significantly associated with mild/moderate hypospadias (ORs >1, P < 0.05), and rs1934179 was significantly associated with severe hypospadias (OR > 1, P < 0.05).

CONCLUSIONS

DGKK gene variants do not appear to play a major role in hypospadias susceptibility in the Chinese Han population. Our meta-analysis supports the hypothesis that DGKK is a common risk gene for hypospadias, particularly in cases of mild or moderate hypospadias in Caucasian populations.

Environmental, parental and gestational factors that influence the occurrence of hypospadias in male patients

OBJECTIVE

Hypospadias is a congenital defect, which affects normal development of the male urogenital external tract. In this malformation, the urethral orifice of the penis is positioned ventrally, thus interfering with normal urination and creating, in some adults, problems during sexual intercourse. Heritability of hypospadias has been shown in some reports, and the abnormality has been associated with the presence of mutations in one of the genes involved in urogenital development. However, even for patients who were born in families with a higher incidence rate of this defect, no evident genetic alteration could be identified in known genes, indicating that the list of loci involved is still incomplete. To further complicate matters, recent reports also underline that epigenetic changes, without any identifiable gene sequence mutation, may be involved in gene function impairment. Therefore, the inheritance of most hypospadias cases is not evident, suggesting that the genetic background is not the only cause of this malformation; indeed, the majority of hypospadias cases are classified as sporadic and idiopathic.

MATERIALS AND METHODS

Evidence has accumulated highlighting the role of the environment and of its relationships with the genome in the etiology of this abnormality. In particular, the interaction between some chemicals, which are able to mimic endogenous molecules such as sexual hormones--for this reason called endocrine disrupting compounds (EDC)--and specific receptors has been extensively investigated during the pregnancy. Additionally, several articles have shown that parental and gestational factors play a significant role too. Indeed, physiological alterations, such as body weight of the mother and/or of the newborn, mother's diabetes, impaired father fertility, and exposure of one parent to job-related pollutants, show in many cases a direct correlation with hypospadias incidence. The overall prevalence of this condition has been studied in many countries, suggesting that at least in some periods and/or in specific populations there are detectable fluctuations, probably mirroring the different natural environments. However, many articles present data that do not agree with these findings and, consequently, most causes of hypospadias are still highly debated.

RESULTS

In this review, we summarize the developmental steps involved in urogenital tract formation, with a particular emphasis on the genes that most frequently are associated with this condition, or that are subject to environmental stress, or that may be the targets of hormone-like, exogenous molecules. Then, we make an overview of the identified factors able to impair the function of important genes, even in the absence of their mutations, including those for which contradictory reports have been published. Finally, we propose an explanation of sporadic cases of hypospadias that reconciles these contradictions and suggest some steps for moving forward in the research focused on this condition.

CONCLUSION

We hypothesize that most patients develop hypospadias because of gene-environment interactions acting on polymorphic genes that, in the absence of environmental stimuli, would otherwise cause no developmental anomaly during urogenital development.

Geographic analysis of individual and environmental risk factors for hypospadias births

BACKGROUND

Hypospadias is a relatively common birth defect affecting the male urinary tract. We explored the etiology of hypospadias by examining its spatial distribution in North Carolina and the spatial clustering of residuals from individual and environmental risk factors.

METHODS

We used data collected by the North Carolina Birth Defects Monitoring Program from 2003 to 2005 to estimate local Moran's I statistics to identify geographic clustering of overall and severe hypospadias, using 995 overall cases and 16,013 controls. We conducted logistic regression and local Moran's I statistics on standardized residuals to consider the contribution of individual variables (maternal age, maternal race/ethnicity, maternal education, smoking, parity, and diabetes) and environmental variables (block group land cover) to this clustering.

RESULTS

Local Moran's I statistics indicated significant clustering of overall and severe hypospadias in eastern central North Carolina. Spatial clustering of hypospadias persisted when controlling for individual factors, but diminished somewhat when controlling for environmental factors. In adjusted models, maternal residence in a block group with more than 5% crop cover was associated with overall hypospadias (odds ratio = 1.22; 95% confidence interval = 1.04-1.43); that is living in a block group with greater than 5% crop cover was associated with a 22% increase in the odds of having a baby with hypospadias. Land cover was not associated with severe hypospadias.

CONCLUSION

This study illustrates the potential contribution of mapping in generating hypotheses about disease etiology. Results suggest that environmental factors including proximity to agriculture may play some role in the spatial distribution of hypospadias. Birth Defects Research (Part A) 100:887-894, 2014. © 2014 Wiley Periodicals, Inc.

[Questions and dilemmas in the management of hypospadias]

Hypospadias is the second most common congenital malformation in males. Etiology remains unknown in about 70% of the cases. Distal hypospadias is considered not only developmental abnormality of the urethra in males, but it may also constitute a mild form of sexual development disorder in 46,XY males. Most urologists and endocrinologists consider that it is necessary to perform a detailed investigation of children presenting with proximal hypospadias associated with a small phallus or poorly developed scrotum and undescended testes. Currently, there is no generally accepted recommendation for the preoperative evaluation of hypospadias and, therefore, masculinizing surgery without preoperative evaluation is performed in these children. The authors summarize the international literature data and their own experience for the assessment and management of hypospadias concerning questions and problems related to preoperative investigation, masculinizing surgery and additional surgery. A detailed algorithm is presented for preoperative evaluation of both proximal and distal hypospadias.

Review of genetic and environmental factors leading to hypospadias

Hypospadias is one of the most common congenital malformations, affecting about 4-6 males per 1000 male births, and ranging in severity from a urethral meatus that is slightly off-center to a meatus in the perineal area. Over the past three decades its prevalence may have increased due to changes in reporting of mild cases and/or increased survival of low birth weight infants due to improved neonatal care. However, despite the increasing numbers of males with hypospadias, the overall etiology remains unclear and likely multifactorial in nature. The purpose of this review article is to provide a comprehensive overview of the various factors implicated in hypospadias etiology, including genetic and environmental factors. In addition, we list syndromes in which hypospadias is a relatively common association and delineate the areas that require further investigation in an effort to understand this condition.

Hypospadias and variants in genes related to sex hormone biosynthesis and metabolism

We examined whether variants in genes related to sex hormone biosynthesis and metabolism were associated with hypospadias in humans. We examined 332 relatively common tag single-nucleotide polymorphisms (tagSNPs) in 20 genes. Analyses included 633 cases (84 mild, 322 moderate, 212 severe and 15 undetermined severity) and 855 population-based non-malformed male controls born in California from 1990 to 2003. We used logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (CI) for each SNP. Several of the 332 studied SNPs had p < 0.01: one in CYP3A4, four in HSD17B3, one in HSD3B1, two in STARD3, 10 in SRD5A2 and seven in STS. In addition, haplotype analyses gave several associations with p < 0.01. For HSD17B3, 14-SNP and 5-SNP blocks had ORs of 1.5 (95% CI 1.1, 2.0, p < 0.001) and 2.8 (95% CI 1.6, 4.8, p < 0.001) respectively. For SRD5A2, 9-SNP, 3-SNP and 8-SNP blocks had ORs of 1.7 (95% CI 1.3, 2.2, p < 0.001), 1.4 (95% CI 1.1, 1.8, p = 0.008) and 1.5 (95% CI 1.2, 1.9, p = 0.002) respectively. Our study indicates that several genes that contribute to sex hormone biosynthesis and metabolism are associated with hypospadias risk.

Hypospadias and residential proximity to pesticide applications

BACKGROUND

Experimental evidence suggests pesticides may be associated with hypospadias.

OBJECTIVE

Examine the association of hypospadias with residential proximity to commercial agricultural pesticide applications.

METHODS

The study population included male infants born from 1991 to 2004 to mothers residing in 8 California counties. Cases (n = 690) were ascertained by the California Birth Defects Monitoring Program; controls were selected randomly from the birth population (n = 2195). We determined early pregnancy exposure to pesticide applications within a 500-m radius of mother's residential address, using detailed data on applications and land use. Associations with exposures to physicochemical groups of pesticides and specific chemicals were assessed using logistic regression adjusted for maternal race or ethnicity and age and infant birth year.

RESULTS

Forty-one percent of cases and controls were classified as exposed to 57 chemical groups and 292 chemicals. Despite >500 statistical comparisons, there were few elevated odds ratios with confidence intervals that excluded 1 for chemical groups or specific chemicals. Those that did were for monochlorophenoxy acid or ester herbicides; the insecticides aldicarb, dimethoate, phorate, and petroleum oils; and adjuvant polyoxyethylene sorbitol among all cases; 2,6-dinitroaniline herbicides, the herbicide oxyfluorfen, and the fungicide copper sulfate among mild cases; and chloroacetanilide herbicides, polyalkyloxy compounds used as adjuvants, the insecticides aldicarb and acephate, and the adjuvant nonyl-phenoxy-poly(ethylene oxy)ethanol among moderate and severe cases. Odds ratios ranged from 1.9 to 2.9.

CONCLUSIONS

Most pesticides were not associated with elevated hypospadias risk. For the few that were associated, results should be interpreted with caution until replicated in other study populations.

Lower urinary tract development and disease

Congenital anomalies of the lower urinary tract (CALUT) are a family of birth defects of the ureter, the bladder, and the urethra. CALUT includes ureteral anomaliesc such as congenital abnormalities of the ureteropelvic junction (UPJ) and ureterovesical junction (UVJ), and birth defects of the bladder and the urethra such as bladder-exstrophy-epispadias complex (BEEC), prune belly syndrome (PBS), and posterior urethral valves (PUVs). CALUT is one of the most common birth defects and is often associated with antenatal hydronephrosis, vesicoureteral reflux (VUR), urinary tract obstruction, urinary tract infections (UTI), chronic kidney disease, and renal failure in children. Here, we discuss the current genetic and molecular knowledge about lower urinary tract development and genetic basis of CALUT in both human and mouse models. We provide an overview of the developmental processes leading to the formation of the ureter, the bladder, and the urethra, and different genes and signaling pathways controlling these developmental processes. Human genetic disorders that affect the ureter, the bladder and the urethra and associated gene mutations are also presented. As we are entering the postgenomic era of personalized medicine, information in this article may provide useful interpretation for the genetic and genomic test results collected from patients with lower urinary tract birth defects. With evidence-based interpretations, clinicians may provide more effective personalized therapies to patients and genetic counseling for their families.

Minor hypospadias: the "tip of the iceberg" of the partial androgen insensitivity syndrome

BACKGROUND

Androgens are critical in male external genital development. Alterations in the androgen sensitivity pathway have been identified in severely undermasculinized boys, and mutations of the androgen receptor gene (AR) are usually found in partial or complete androgen insensitivity syndrome (AIS).

OBJECTIVE

The aim of this study was to determine whether even the most minor forms of isolated hypospadias are associated with AR mutations and thus whether all types of hypospadias warrant molecular analysis of the AR.

MATERIALS AND METHODS

Two hundred and ninety-two Caucasian children presenting with isolated hypospadias without micropenis or cryptorchidism and 345 controls were included prospectively. Mutational analysis of the AR through direct sequencing (exons 1-8) was performed. In silico and luciferase functional assays were performed for unreported variants.

RESULTS

Five missense mutations of the AR were identified in 9 patients with glandular or penile anterior (n = 5), penile midshaft (n = 2) and penile posterior (n = 2) hypospadias, i.e., 3%: p.Q58L (c.173A>T), 4 cases of p.P392S (c.1174C>T), 2 cases of p.A475V (c.1424C>T), p.D551H (c.1651G>C) and p.Q799E (c.2395C>G). None of these mutations was present in the control group. One mutation has never been reported to date (p.D551H). It was predicted to be damaging based on 6 in silico models, and in vitro functional studies confirmed the lowered transactivation function of the mutated protein. Three mutations have never been reported in patients with genital malformation but only in isolated infertility: p.Q58L, p.P392S, and p.A475V. It is notable that micropenis, a cardinal sign of AIS, was not present in any patient.

CONCLUSION

AR mutations may play a role in the cause of isolated hypospadias, even in the most minor forms. Identification of this underlying genetic alteration may be important for proper diagnosis and longer follow-up is necessary to find out if the mutations cause differences in sexual function and fertility later in life.

Acrania-anencephaly associated with hypospadias. Prenatal ultrasound and MRI diagnosis and molecular folate metabolism pathway analysis

Acrania may occur as a single isolated malformation or associated with extracranial defects. Hypospadias is one of the most common congenital abnormalities of the genitalia frequently missed on prenatal sonograms. Second trimester two- and three-dimensional ultrasound and MRI diagnosis with necropsy and folate metabolism pathway analysis. The mechanisms leading to closure of both neural and urethral tubes, are far from being demonstrated, and molecular studies of this very rare association are lacking although it might be based on a common genetic mechanism, leading to a disturbed development pathway at the molecular level.

A nested case-control study of intrauterine exposure to persistent organochlorine pollutants and the risk of hypospadias

Background

Environmental exposures to endocrine disrupting chemicals have been suggested as a risk factor for male genital abnormalities such as hypospadias. The aim of this case-control study was to investigate the association between fetal exposure to persistent organochlorine pollutants (POP) and the risk for hypospadias.

Methodology/Principal Findings

The Southern Sweden Maternity Cohort (SSMC) contains serum samples collected in early pregnancy among women in Southern Sweden. Linkages with the Medical Birth Register, the Malformation Register and the In-patient Register resulted in 390 SSMC mothers who had given birth to a boy with hypospadias in year 1986–2002 (mean 1995). For 237 of these (cases) sufficient amounts of serum for the chemical analyses were available. For each case, a control boy from the SSMC was randomly selected, matched for maternal age, birth year, parity and maternal smoking. PCB-153, p,p’-DDE and hexachlorbenzene (HCB) were used as biomarkers for POP exposure. The exposures were categorized into quartiles based on the distributions among the controls. There were no statistically significant trends between the a priori categorisation of the exposure variables and the risk for hypospadias. However, when the upper HCB quartile (>26 ng/ml) was compared to the other quartiles an odds ratio of 1.65 (95% CI 1.02 to 2.69) was obtained. p,p′-DDE levels above median (>1.0 ng/ml) compared to levels below 0.1 ng/ml gave an OR of 1.69 (95% CI 0.97 to 2.93).

Conclusions

The present study suggests that fetal exposure to HCB and p,p’-DDE may be a risk factor for hypospadias.

Environmental and genetic contributors to hypospadias: a review of the epidemiologic evidence

This review evaluates current knowledge related to trends in the prevalence of hypospadias, the association of hypospadias with endocrine-disrupting exposures, and the potential contribution of genetic susceptibility to its etiology. The review focuses on epidemiologic evidence. Increasing prevalence of hypospadias has been observed, but such increases tend to be localized to specific regions or time periods. Thus, generalized statements that hypospadias is increasing are unsupported. Owing to the limitations of study designs and inconsistent results, firm conclusions cannot be made regarding the association of endocrine-disrupting exposures with hypospadias. Studies with more rigorous study designs (e.g., larger and more detailed phenotypes) and exposure assessment that encompasses more breadth and depth (e.g., specific endocrine-related chemicals) will be critical to make better inferences about these important environmental exposures. Many candidate genes for hypospadias have been identified, but few of them have been examined to an extent that enables solid conclusions. Further study is needed that includes larger sample sizes, comparison groups that are more representative of the populations from which the cases were derived, phenotype-specific analyses, and more extensive exploration of variants. In conclusion, examining the associations of environmental and genetic factors with hypospadias remain important areas of inquiry, although our actual understanding of their contribution to hypospadias risk in humans is currently limited.

A pilot study of the association between genetic polymorphisms involved in estrogen signaling and infant male genital phenotypes

Single nucleotide polymorphisms (SNPs) in genes that influence development of the male reproductive tract have been associated with male genitourinary abnormalities. However, no studies have tested the relationship between SNPs and intermediate phenotypes such as anogenital distance (AGD), anoscrotal distance (ASD) and penile width (PW). We tested whether 24 common SNPs in eight genes that influence male genital development were associated with intermediate phenotypes in 106 healthy male infants from the Study for Future Families. We used DNA from buccal smears and linear regression models to assess the relationship between anogenital measurements and SNP genotypes with adjustment for covariates. We found that the rs2077647 G allele, located in the coding region of estrogen receptor alpha (ESR1), was associated with a shorter AGD (P=0.02; -7.3 mm, 95% confidence interval (CI): -11.6 to -3.1), and the rs10475 T allele, located in the 3' untranslated region of activating transcription factor 3 (ATF3), was associated with a shorter ASD (-4.3 mm, 95% CI: -7.2 to -1.4), although this result was not significant (P=0.07) after controlling for multiple comparisons. We observed no association between PW and the SNPs tested. Minor alleles for two SNPs in genes that regulate estrogen signaling during male genital development were associated with AGD and ASD, although the significance of the association was marginal. Our findings suggest that AGD and ASD are influenced by heritable factors in genes known to be associated with frank male genital abnormalities such as hypospadias and cryptorchidism.

Development of the penile urethra in the tammar wallaby

Hypospadias is increasingly common, and requires surgery to repair, but its aetiology is poorly understood. The marsupial tammar wallaby provides a unique opportunity to study hypospadias because penile differentiation occurs postnatally. Androgens are responsible for penile development in the tammar, but the majority of differentiation, in particular formation and closure of the urethral groove forming the penile urethra in males, occurs when there is no measurable sex difference in the concentrations of testosterone or dihydrotestosterone in either the gonads or the circulation [corrected]. Phalluses were examined morphologically from the sexually indifferent period (when androgens are high) to well after the time that the phallus becomes sexually dimorphic. We show that penile development and critical changes in the positioning of the urethra occur in the male phallus begin during an early window of time when androgens are high. Remodelling of the urethra in the male occurs between days 20-60. The critical period of time for the establishment urethral closure occurs during the earliest phases of penile development. This study suggests that there is an early window of time before day 60 when androgen imprinting must occur for normal penile development and closure of the urethral groove.

Prenatal two- and three-dimensional imaging in two cases of severe penoscrotal hypospadias

We present the prenatal two- and three-dimensional (3D) ultrasound (US) findings in two cases of severe penoscrotal hypospadias. 3D sonography was used for better definition of ambiguous genitalia. The images were compared with postnatal clinical features. Despite hypospadias being the most common urogenital anomaly of male neonates, the diagnosis is often missed before birth. Performing prenatal ultrasound should include the study of genitals, not only determining the sex.

Hypospadias in Istanbul: incidence and risk factors

BACKGROUND

The aim of the present prospective study was to determine the incidence of hypospadias in newborns in one of the busiest teaching hospitals of Istanbul, and to investigate the risk factors.

METHODS

All live-born boys delivered between September 2007 and December 2008 were screened for hypospadias. A questionnaire was given to the parents of the hypospadias and control subjects for investigation.

RESULTS

Out of 1750 boys examined, 34 had hypospadias, that is, the frequency was 19.4 per 1000 male live-births and 93.7 per 10,000 total live-born deliveries. The incidence of additional coexistent anomalies was 29.4%, predominantly urogenital (17.6%), the majority of which were cryptorchidism (14.7%). Twelve (35.3%) of the 34 hypospadiac boys had a second family member with a genital anomaly, nine (26.5%) of whom had hypospadias, three (8.8%) being the fathers. Mean birthweight, length and head circumference were significantly lower in the hypospadiac infants than the control group (P= 0.003, P= 0.025, P= 0.002). Although parity, parental consanguinity, hypospadias in family members, and low birthweight also varied significantly among the groups, logistic regression analysis indicated that maternal age, prematurity, coexistence of cryptorchidism and presence of genital anomaly among family members were independent risk factors for hypospadias (P= 0.016, P= 0.0001, P= 0.041, P= 0.0001, respectively).

CONCLUSIONS

Genetic predisposition and placental insufficiency in early gestation might play a role in the etiology of hypospadias.

Maternal occupational pesticide exposure and risk of hypospadias in the National Birth Defects Prevention Study

BACKGROUND

Hypospadias is a common congenital malformation among men in which the urethral opening is ventrally displaced. Pesticide exposure has been suggested as a possible etiologic factor, but previous epidemiologic studies have produced inconsistent results.

METHODS

We used data from the National Birth Defects Prevention Study (NBDPS), a population-based case-control study, to examine maternal occupational exposure to fungicides, insecticides, and herbicides among 647 hypospadias case infants and 1496 unaffected male control infants with estimated delivery dates from October 1997 to December 2002. Periconceptional (1 month before conception through the first trimester of pregnancy) pesticide exposures were assigned by an expert rater, assisted by a job-exposure matrix (JEM), from a job history completed by mothers during a telephone interview. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated with multivariable logistic regression, and adjusted for relevant covariates.

RESULTS

Maternal periconceptional occupational exposure to any pesticides (yes/no) was not associated with an increased risk of hypospadias (OR = 0.78; 95% CI = 0.61-1.01). Maternal occupational periconceptional pesticide exposure type (insecticides, fungicides, and herbicides) and estimated quantity also showed no significantly increased risk of hypospadias and no evidence of a dose-response relationship; however, the estimated pesticide exposure levels in this population were low.

CONCLUSION

Using broad classes of insecticides, herbicides, and fungicides, we found no evidence that low intensity maternal periconceptional occupational pesticide exposure was a risk factor for hypospadias.

No association between maternal pre-pregnancy obesity and risk of hypospadias or cryptorchidism in male newborns

BACKGROUND

Hypospadias and cryptorchidism, two relatively common male genital anomalies, may be caused by altered maternal hormone levels, blood glucose levels, or nutritional deficiencies. Maternal obesity, which increases risk of diabetes and could influence hormone levels, may, therefore, be associated with risk of hypospadias and cryptorchidism. The purpose of this study was to assess the association between pre-pregnancy maternal obesity and hypospadias and cryptorchidism.

METHODS

We conducted a case-control study of hypospadias and cryptorchidism in male singleton newborns using Washington State birth records from 1992 to 2008 linked to birth-hospitalization discharge records. Maternal pre-pregnancy body mass index (BMI) was calculated from pre-pregnancy weight and height. Adjusted odds ratios (aORs) and 95% confidence intervals (95% CIs) for hypospadias or cryptorchidism were estimated by fitting multivariable logistic regression models adjusted for year of birth, and maternal age, education, parity, race, and cigarette smoking during pregnancy.

RESULTS

The complete-case analysis included 2219 hypospadias cases, 2563 cryptorchidism cases, and 32,734 controls. Maternal obesity (BMI ≥30 kg/m(2) ) was not associated with risk of hypospadias or cryptorchidism in male offspring: hypospadias (aOR, 1.07; 95% CI, 0.95-1.21); cryptorchidism (aOR, 0.99; 95% CI, 0.89-1.11), and no trend in risk with increasing maternal BMI was found. There was little indication of risk associated with BMI among any subgroup of mothers examined, including women with pre-existing diabetes or hypertension, women who developed preeclampsia, non-Hispanic white women, first-time mothers, or mothers aged ≥30 years.

CONCLUSIONS

The results of this study do not support the hypothesis that pre-pregnancy maternal obesity is a cause of hypospadias or cryptorchidism in male infants.

Hypospadias: interactions between environment and genetics

Hypospadias is one of the most common congenital malformations. It is considered to be a mild form of the 46,XY disorders of sex development (DSD), but its precise etiology remains to be elucidated. Compromised androgen synthesis or effects can cause this frequent malformation, although the mutational analyses of the genes involved in androgen actions have identified abnormalities in only a very small portion of patients. The overwhelming majority of cases remain unexplained and hypospadias may be a highly heterogeneous condition subject to multiple genetic and environmental factors. We here review the recent advances in this field and discuss the potential interactions between the environment and genetics.

Embryonic expression of the cysteine rich protein 61 (CYR61) gene: A candidate for the development of human epispadias

BACKGROUND

Isolated epispadias is the mildest phenotype of the exstrophy-epispadias complex, a urogenital birth defect of variable severity. The androgen receptor antagonist flutamide (FLU) is known to cause malformations in the rat genital and reproductive tract, and single-dose prenatal FLU exposure can induce epispadias in rat offspring. The Cyr61 gene exhibited the highest response to FLU in rat fetal testis, and we suggested it a promising candidate gene for epispadias in humans, because its protein product promotes proliferation, migration, and adhesion of endothelial cells and fibroblasts.

METHODS

We used whole mount in situ analysis in mice to investigate ventrocaudal expression of the Cyr61 transcript at gestational days 9.5 to 11.5, which is the equivalent of human gestational weeks 4 to 6 (postulated time of epispadias organogenesis in humans). We also performed mutational analysis of the CYR61 gene in 11 patients with isolated epispadias and in additional eight patients with the related classic bladder exstrophy phenotype.

RESULTS

Expression of Cyr61 was detected in endothelial cells of vessels surrounding the cloaca and the umbilical cord on gestational days 10 and 11.5. The mutation screening, however, revealed no alterations in the coding region of human CYR61.

CONCLUSIONS

The spatiotemporal expression pattern observed suggests a role for Cyr61 in the development of the external genitalia. Our mutation screening study, however, could not confirm that mutations affecting the CYR61 gene are a frequent cause of epispadias or classic bladder exstrophy, although rare mutations might be detectable in larger patient samples.

Genetic pathway of external genitalia formation and molecular etiology of hypospadias

Hypospadias is one of the most common congenital disorders in males. Impaired fetal androgen action interferes with masculinization, including external genitalia formation, and can result in this anomaly; however, the molecular etiology remains unknown. Recent molecular approaches, including gene-targeting approaches in mice and single nucleotide polymorphisms analyses in humans, might provide an opportunity to identify the causative and risk factors of this anomaly. Several genes, such as sonic hedgehog, fibroblast growth factors, bone morphogenetic proteins, homeobox genes, and the Wnt family regulate external genitalia formation. Mastermind-like domain containing 1/chromosome X open reading frame 6 mutation and activating transcription factor 3 variants have been shown to be associated with the incidence of isolated hypospadias. In addition, this anomaly may be associated with a specific haplotype of the gene for estrogen receptor alpha, which mediates the estrogenic effects of environmental endocrine disruptors, and the effects of these disruptors on external genitalia formation might depend on individual genetic susceptibility. These molecular studies will refine our knowledge of the genetic mechanism involved in external genitalia formation, and lead to new strategies for the clinical management of hypospadias.