Increased exposure to dioxin-like compounds is associated with endometriosis in a case-control study in women

Endometriosis: Update of Pathophysiology, (Epi) Genetic and Environmental Involvement

Endometriosis is a chronic disease caused by ectopic endometrial tissue. Endometriotic implants induce inflammation, leading to chronic pain and impaired fertility. Characterized by their dependence on estradiol (via estrogen receptor β (ESRβ)) and their resistance to progesterone, endometriotic implants produce their own source of estradiol through active aromatase. Steroidogenic factor-1 (SF1) is a key transcription factor that promotes aromatase synthesis. The expression of SF1 and ESRβ is enhanced by the demethylation of their promoter in progenitor cells of the female reproductive system. High local concentrations of estrogen are involved in the chronic inflammatory environment favoring the implantation and development of endometriotic implants. Similar local conditions can promote, directly and indirectly, the appearance and development of genital cancer. Recently, certain components of the microbiota have been identified as potentially promoting a high level of estrogen in the blood. Many environmental factors are also suspected of increasing the estrogen concentration, especially prenatal exposure to estrogen-like endocrine disruptors such as DES and bisphenol A. Phthalates are also suspected of promoting endometriosis but throughmeans other than binding to estradiol receptors. The impact of dioxin or tobacco seems to be more controversial.

Adipose to serum ratio and mixtures of persistent organic pollutants in relation to endometriosis: Findings from the ENDO Study

BACKGROUND

Endometriosis is an estrogen-dependent disease. Endocrine disrupting chemicals (EDCs) and their mixtures may play an etiologic role.

OBJECTIVES

We evaluated an adipose-to-serum ratio (ASR) of lipophilic EDCs and their mixtures associated with incident endometriosis.

METHODS

We quantified 13 polychlorinated biphenyl (PCB) congeners, 6 polybrominated diphenyl ether (PBDE) congeners, and 11 organochlorine pesticides (OCPs) in serum and omental fat among women from the ENDO Study (2007-2009) aged 18-44 years diagnosed with (n=190) or without (n=283) surgically-visualized incident endometriosis. Odds ratios (OR) and 95% confidence intervals (CI) between ASR and endometriosis were estimated using logistic regression models adjusted for age (years), body mass index (kg/m²), serum cotinine (ng/ml), and breastfeeding conditional on parity. Bayesian hierarchical models (BHM) compared estimated associations for adipose and ASR to serum. Bayesian kernel machine regression (BKMR) estimated change in latent health and 95% posterior intervals (PI) between chemical mixtures and endometriosis.

RESULTS

Select ASR for estrogenic PCBs and OCPs were associated with an increased odds of an endometriosis diagnosis, but not for anti-estrogenic PCBs or PBDEs. Across all chemicals, BHMs generated ORs that were on average 14% (95% PI: 6%, 22%) higher for adipose and 20% (95% PI: 12%, 29%) higher for ASR in comparison to serum. ORs from BHMs were greater for estrogenic PCBs and OCPs, with no differences for PBDEs. BKMR models comparing the 75th to 25th percentile were moderately associated with endometriosis for estrogenic PCBs [adipose 0.27 (95% PI: 0.18, 0.72) and ASR 0.37 (95% PI: 0.06, 0.80)] and OCPs [adipose 0.17 (95% PI: 0.21, 0.56) and ASR 0.26 (95% PI: 0.05, 0.57)], but not for antiestrogenic PCBs and PBDEs.

DISCUSSION

ASR added little insight beyond adipose for lipophilic chemicals. BKMR results supported associations between ASR and adipose estrogenic PCB and OCP mixtures and incident endometriosis. These findings underscore the importance of choice of biospecimen and considering mixtures when assessing exposure-disease relationships.

Environmental exposures to endocrine disrupting chemicals (EDCs) and their role in endometriosis: a systematic literature review

PURPOSE

Endocrine-related diseases and disorders are on the rise globally. Synthetically produced environmental chemicals (endocrine-disrupting chemicals (EDCs)) mimic hormones like oestrogen and alter signalling pathways. Endometriosis is an oestrogen-dependent condition, affecting 10-15% of women of the reproductive age, and has substantial impacts on the quality of life. The aetiology of endometriosis is believed to be multifactorial, ranging from genetic causes to immunologic dysfunction due to environmental exposure to EDCs. Hence, we undertook a systematic review and investigated the epidemiological evidence for an association between EDCs and the development of endometriosis. We also aimed to assess studies on the relationship between body concentration of EDCs and the severity of endometriosis.

METHOD

Following PRISMA guidelines, a structured search of PubMed, Embase and Scopus was conducted (to July 2018). The included studies analysed the association between one or more EDCs and the prevalence of endometriosis. The types of EDCs, association and outcome, participant characteristics and confounding variables were extracted and analysed. Quality assessment was performed using standard criteria.

RESULTS

In total, 29 studies were included. Phthalate esters were positively associated with the prevalence of endometriosis. The majority (71%) of studies revealed a significant association between bisphenol A, organochlorinated environmental pollutants (dioxins, dioxin-like compounds, organochlorinated pesticides, polychlorinated biphenyls) and the prevalence of endometriosis. A positive association between copper, chromium and prevalence of endometriosis was demonstrated in one study only. Cadmium, lead and mercury were not associated with the prevalence of endometriosis. There were conflicting results for the association between nickel and endometriosis. The relationship of EDCs and severity of endometriosis was not established in the studies.

CONCLUSION

We found some evidence to suggest an association between phthalate esters, bisphenol A, organochlorinated environmental pollutants and the prevalence of endometriosis. Disentangling these exposures from various other factors that affect endometriosis is complex, but an important topic for further research.

Reproductive health research in Australia and New Zealand: highlights from the Annual Meeting of the Society for Reproductive Biology, 2019

The 2019 meeting of the Society for Reproductive Biology (SRB) provided a platform for the dissemination of new knowledge and innovations to improve reproductive health in humans, enhance animal breeding efficiency and understand the effect of the environment on reproductive processes. The effects of environment and lifestyle on fertility and animal behaviour are emerging as the most important modern issues facing reproductive health. Here, we summarise key highlights from recent work on endocrine-disrupting chemicals and diet- and lifestyle-induced metabolic changes and how these factors affect reproduction. This is particularly important to discuss in the context of potential effects on the reproductive potential that may be imparted to future generations of humans and animals. In addition to key summaries of new work in the male and female reproductive tract and on the health of the placenta, for the first time the SRB meeting included a workshop on endometriosis. This was an important opportunity for researchers, healthcare professionals and patient advocates to unite and provide critical updates on efforts to reduce the effect of this chronic disease and to improve the welfare of the women it affects. These new findings and directions are captured in this review.

Environmental risk factors for endometriosis: A critical evaluation of studies and recommendations from the epidemiologic perspective

Purpose of review

Recent studies of environmental chemicals and endometriosis were critically evaluated from the epidemiologic perspective to identify aspects of study design and analyses that may contribute to discrepant results across studies.

Recent findings

Of the 29 studies reviewed, 12 studies used new approaches to population-based sampling. The remaining studies were conducted primarily among patients undergoing pelvic surgery; controls may not represent the exposure experience of the underlying study base, resulting in biased estimates of associations. Most studies used biologic specimens collected near diagnosis and varied in analytic approaches to minimize bias. Few studies investigated ovarian, deep-infiltrating, and peritoneal endometriosis presentations separately.

Summary

Recommendations to move the field forward include: (1) control selection from a defined study base, (2) exposure characterization during the etiologically-relevant window, (3) employment of best practices to minimize bias in analyses, and (4) separate consideration of endometriosis presentations that may be etiologically-distinct entities.

Environmental toxins and the impact of other endocrine disrupting chemicals in women's reproductive health

This review aimed to look into agents and mechanisms characterized as endocrine disrupting chemicals (EDCs). These agents are known to cause several harmful effects to the reproductive system of women and wildlife. There is a wide range of chemicals, developed for commercial use mainly in agriculture, which may cause endocrine disruption. Numerous studies show evidence of environmental contamination. However, no one is being held liable for the damages. The most important potentially harmful agents are identified and described, along with the different effects they have on the female genital area. Brazil is a large consumer of pesticides and others chemicals that may interfere with a normal women's life. We analyzed and described the mode of action and the impacts of different EDCs (bisphenols, phthalates, atrazine, polychlorinated and polybrominated biphenyls, DDT-dichlorodiphenyltrichloroethane; DDE-dichlorodiphenyldichloroethylene; DDD-dichlorodiphenyldichloroethane; and DES-diethylstilbestrol) on the genital area, ovarian steroidogenesis, polycystic ovary syndrome, endometriosis, the structure of the uterus and the vagina, and on the formation of leiomyomas.

Human epidemiological evidence about the associations between exposure to organochlorine chemicals and endometriosis: Systematic review and meta-analysis

BACKGROUND

Endometriosis is a gynaecological disease characterized by the presence of ectopic endometrial tissue that affects women during their reproductive years, having a strong impact on their lives, fertility and healthcare costs. The aetiology remains largely unknown, but current evidence suggests that it is multi-causal and oestrogen-dependent. Many epidemiologic studies have explored associations between organochlorine chemicals (OCCs) and endometriosis, but the findings are inconsistent.

OBJECTIVES

A systematic review (SR) and meta-analysis were conducted to gather and synthesize all the available evidence from human epidemiological studies about the associations between OCCs and endometriosis.

DATA SOURCES

The searches were conducted in PubMed and Web of Science in June 2016 with a final follow-up in August 2018.

STUDY ELIGIBILITY CRITERIA

Only human epidemiological studies were considered, independent of participant age, body mass index or life-stage. Studies reporting individual measures of exposure to OCCs were included, considering but not limited to polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), or organochlorine pesticides (OCPs). The primary health outcome was presence of endometriosis, including all sub-types. Eligibility criteria excluded articles not written in English, conference papers, reviews and studies with overlapping information.

STUDY APPRAISAL AND SYNTHESIS METHODS

A SR protocol pre-registered at PROSPERO was applied in duplicate to gather and extract all eligible original papers from PUBMED and Web of Science databases. Odds ratios were pooled using the inverse variance method for random effects meta-analysis for each group of OCCs. Risk of bias was assessed using the National Toxicology Program/Office of Health Assessment and Translation (NTP/OHAT) Risk of Bias Rating Tool for Human and Animal Studies adapted to the review question. The confidence in the body of evidence and related level of evidence was measured by using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) based NTP/OHAT framework. The results were structured and presented in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Of the 51 studies retained for the full-text screening, 17 provided effect sizes and metrics sufficient for pooling estimates through meta-analysis. The overall odds ratios and 95% confidence intervals were 1.65 (1.14; 2.39) for dioxins (n = 10), 1.70 (1.20; 2.39) for PCBs (n = 9), and 1.23 (1.13; 1.36) for OCPs (n = 5). Despite being statistically significant, these estimates should be considered with caution given the notable heterogeneity and small estimated effect size. Misclassification of exposure, due to varying laboratory detection rate capabilities, and disease status, due to varying definitions of endometriosis, were identified as major sources of uncertainty.

LIMITATIONS, CONCLUSIONS, AND IMPLICATIONS OF KEY FINDINGS

The level of evidence was considered to be "moderate" with "serious" risk of bias according the NTP/OHAT criteria, supporting the need for further well-designed epidemiological research to fill lingering data gaps. Given the complexity of endometriosis and lack of known biomarkers suitable for population-based research, carefully designed observational studies play an important role in better understanding the aetiology of endometriosis, as will evolving mixture modeling approaches capable of handling various environmental chemical exposures. Attention to critical windows of exposure will shed further light on the possible developmental origin of endometriosis. Considering the high economic and societal cost associated with endometriosis, further research on this field is urged.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42018080956.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

Epigenetic Therapy: Novel Translational Implications for Arrest of Environmental Dioxin-Induced Disease in Females

Increased toxicant exposure and resultant environmentally induced diseases are a tradeoff of industrial productivity. Dioxin [2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD)], a ubiquitous byproduct, is associated with a spectrum of diseases including endometriosis, a common, chronic disease in women. TCDD activates cytochrome (CYP) p450 metabolic enzymes that alter organ function to cause disease. In contrast, the transcription factor, Krüppel-like factor (KLF) 11, represses these enzymes via epigenetic mechanisms. In this study, we characterized these opposing mechanisms in vitro and in vivo as well as determining potential translational implications of epigenetic inhibitor therapy. KLF11 antagonized TCDD-mediated activation of CYP3A4 gene expression and function in endometrial cells. The repression was pharmacologically replicated by selective use of an epigenetic histone acetyltransferase inhibitor (HATI). We further showed phenotypic relevance of this mechanism using an animal model for endometriosis. Fibrotic extent in TCDD-exposed wild-type animals was similar to that previously observed in Klf11-/- animals. When TCDD-exposed animals were treated with a HATI, Cyp3 messenger RNA levels and protein expression decreased along with disease progression. Fibrotic progression is ubiquitous in environmentally induced chronic, untreatable diseases; this report shows that relentless disease progression can be arrested through targeted epigenetic modulation of protective mechanisms.

Associations between internal exposure levels of persistent organic pollutants in adipose tissue and deep infiltrating endometriosis with or without concurrent ovarian endometrioma

Endometriosis is a gynaecological disease characterized by the presence of ectopic endometrial tissue. Histologically, it appears as different sub-types, being peritoneal endometriosis, ovarian endometrioma (OvE) and deep infiltrating endometriosis (DIE), which are of major relevance due to their varying clinical presentations. A number of persistent organic pollutants (POPs) have been associated with the onset of endometriosis, yet the overall set of existing studies remains fairly divergent. In this preliminary case-control study we aimed to assess the potential associations between the internal exposure to POPs and the presence of DIE with or without concurrent OvE. Adipose tissue and serum samples were collected from surgically confirmed cases (n=55) and controls (n=44) enrolled during 2013 and 2015 in Pays de la Loire, France. Targeted pollutants (76 historical or more emerging POPs including dioxins, polychlorobiphenyls (PCB), polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), hexabromocyclododecanes (HBCDs) and organochlorine pesticides (OCPs) were quantified by chromatography coupled to mass spectrometry. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated from unconditional logistic regression adjusted for known confounding variables. The results showed significant associations between DIE and adipose tissue levels of 1.2.3.7.8 - PeCDD, OCDF, PCB 105, 114, 118 and 123, PBDE 183, PBB 153, and several OCPs including trans‑nonachlor, cis‑heptachlor epoxide, dieldrin, β-hexachlorocyclohexane and hexachlorobenzene. The largest associations were observed for OCDF followed by cis‑heptachlor epoxide, exhibiting adjusted ORs (95% CI) of 5.42 (2.73-12.85) and 5.36 (2.44-14.84) per 1-SD increase, respectively. The stratified analysis comparing both disease sub-types suggested that adipose tissue exposure markers may be more associated with DIE concurrent with OvE, however these results need to be confirmed in a larger population.

Polychlorinated biphenyls and its potential role in endometriosis

With the progress of global industrialization and environmental deterioration, the relationship between human health and the living environment has become an increasing focus of attention. Polychlorinated biphenyls (PCBs, including dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls), as part of the organic chlorine contaminants, have been suspected as playing a role in the etiopathogenesis of endometriosis. Several population-based studies have proposed that exposure to PCBs may increase the risk of developing endometriosis, while some epidemiological studies have failed to find any association between PCBs and endometriosis. The purpose of this review is to discuss the potential pathophysiological relationship between endometriosis and PCBs with a focus on both dioxin-like polychlorinated biphenyls and non-dioxin-like polychlorinated biphenyls.

Exposure to endocrine disruptors during adulthood: consequences for female fertility

Endocrine disrupting chemicals are ubiquitous chemicals that exhibit endocrine disrupting properties in both humans and animals. Female reproduction is an important process, which is regulated by hormones and is susceptible to the effects of exposure to endocrine disrupting chemicals. Disruptions in female reproductive functions by endocrine disrupting chemicals may result in subfertility, infertility, improper hormone production, estrous and menstrual cycle abnormalities, anovulation, and early reproductive senescence. This review summarizes the effects of a variety of synthetic endocrine disrupting chemicals on fertility during adult life. The chemicals covered in this review are pesticides (organochlorines, organophosphates, carbamates, pyrethroids, and triazines), heavy metals (arsenic, lead, and mercury), diethylstilbesterol, plasticizer alternatives (di-(2-ethylhexyl) phthalate and bisphenol A alternatives), 2,3,7,8-tetrachlorodibenzo-p-dioxin, nonylphenol, polychlorinated biphenyls, triclosan, and parabens. This review focuses on the hypothalamus, pituitary, ovary, and uterus because together they regulate normal female fertility and the onset of reproductive senescence. The literature shows that several endocrine disrupting chemicals have endocrine disrupting abilities in females during adult life, causing fertility abnormalities in both humans and animals.

Endometriosis: a disease that remains enigmatic

Endometriosis, a gynecologic pathology, is defined by the presence of a tissue similar to uterine endometrium, which is located in places other than physiologically appropriate. These endometrial heterotopic islets contain glands and stroma and are functionally capable of responding to exogenous, endogenous, or local hormonal stimuli. Endometriosis affects 8%-10% of women of reproductive age; in 30% of the women, the condition is associated with primary or secondary infertility. In several instances, endometriosis persists as a minimal or mild disease, or it can resolve on its own. Other cases of endometriosis show severe symptomatology that ends when menopause occurs. Endometriosis can, however, reactivate in several postmenopausal women when iatrogenic or endogenous hormones are present. Endometriosis is occasionally accompanied by malignant ovarian tumors, especially endometrioid and clear cell carcinomas. Its pathogenesis is widely debated, and its variable morphology appears to represent a continuum of individual presentations and progressions. Endometriosis has no pathognomonic signs or symptoms; it is therefore difficult to diagnose. Because of its enigmatic etiopathogenesis, there is currently no satisfactory therapy for all patients with endometriosis. Treatments include medications, surgery, or combined therapies; currently, the only procedures that seem to cure endometriosis are hysterectomy and bilateral salpingo-oophorectomy. In this paper, we review the most controversial and enigmatic aspects of this disease.

Bisphenol A and phthalates and endometriosis: the Endometriosis: Natural History, Diagnosis and Outcomes Study

OBJECTIVE

To explore the relation between bisphenol A and 14 phthalate metabolites and endometriosis.

DESIGN

Matched cohort design.

SETTING

Fourteen clinical centers.

PATIENT(S)

The operative cohort comprised 495 women undergoing laparoscopy/laparotomy, whereas the population cohort comprised 131 women matched on age and residence.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Surgically visualized or pelvic magnetic resonance imaging diagnosed endometriosis in the two cohorts, respectively.

RESULT(S)

Odds ratios (OR) and 95% confidence intervals (CIs) were estimated using logistic regression adjusting for age, body mass index, and creatinine. In the population cohort, six phthalate metabolites-mono-n-butyl phthalate, mono-[(2-carboxymethyl) hexyl] phthalate, mono (2-ethyl-5-carboxyphentyl) phthalate, mono (2-ethylhexyl) phthalate, mono (2-ethyl-5-hydroxyhexyl) phthalate, and mono (2-ethyl-5-oxohexyl) phthalate-were significantly associated with an approximately twofold increase in the odds of an endometriosis diagnosis. Two phthalates were associated with endometriosis in the operative cohort when restricting to visualized and histologic endometriosis (monooctyl phthalate; OR 1.38; 95% CI 1.10-1.72) or when restricting comparison women to those with a postoperative diagnosis of a normal pelvis [mono (2-ethylhexyl) phthalate; OR 1.35; 95% CI 1.03-1.78].

CONCLUSION(S)

Select phthalates were associated with higher odds of an endometriosis diagnosis for women with magnetic resonance imaging-diagnosed endometriosis. The lack of consistency of findings across cohorts underscores the impact of methodology on findings.

The influence of endocrine disruptors in a selected population of infertile women

Several studies report that endocrine disrupting chemicals (EDC) able to interfere with endocrine homeostasis may affect women's reproductive health. We analyzed EDC serum levels and nuclear receptors (NRs) expression in order to have an indication of the internal dose of biologically active compounds and a measurement of indicators of their effects, as a result of the repeated uptake from environmental source. The percentage of patients with detectable bisphenol A (BPA) concentrations was significantly higher in the infertile patients compared with fertile subjects. No significant difference was found between the groups with regard to perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), mono-ethylhexyl phthalate (MEHP) and di-(2-ethylhexyl) phthalate (DEHP) concentrations. Among infertile women, the mean expression of estrogen receptor alpha (ERα) and beta (Erβ), androgen receptor (AR) and pregnane X receptor (PXR) was significantly higher than fertile patients. The mean expression of aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor gamma (PPARγ) did not show significant differences between two groups. Patients with endometriosis had higher levels of PPARγ than all women with other causes of infertility. This study led further support to EDC exposure as a risk factor for women's fertility.

Genetic susceptibility to dioxin-like chemicals' induction of cytochrome P4501A2 in the human adult linked to specific AhRR polymorphism

BACKGROUND

Dioxin-like chemicals are known to exert their effect by binding to aryl hydrocarbon receptor (AhR), forming complexes with aryl hydrocarbon nuclear translocator (ARNT), and binding to dioxin responsive elements (DREs) in promoter region to regulate the transcription of specific genes. In a previous study of the Yucheng cohort of humans who were exposed to high toxic levels of dioxin-like chemicals (PCDFs and PCBs), we reported marked induction of cytochrome P450 1A2 (CYP1A2) activity and this induction was an excellent biomarker of the exposure and adverse human health effects seen in the Yucheng cohort.

OBJECTIVES

The goal of this study was to determine the relationship between inducibility of CYP1A2 and genetic polymorphisms of AhR, ARNT, and AhRR in human.

METHODS

The Yucheng victims who completed blood sample collecting in 1994-1995 for serum concentrations of PCB, PCDF, and PCDD congeners, and also completed the caffeine breath tests for CYP1A2 activity were identified. From the collected blood samples, six single nucleotide polymorphisms were selected for genotyping, including AhR (rs2066853), AhRR (rs2292596), ARNT (rs7517566), ARNT (rs3820541), ARNT (rs3768016), and ARNT (rs2228099).

RESULTS

AhRR (rs2292596) polymorphism was significantly related to CYP1A2 inducibility (p=0.01). A linear trend test was observed between people with AhRR (rs2292596) GG, GC, and CC genotype (p=0.0014).

CONCLUSION

Overall, AhRR (rs2292596) genotypes predict the inducibility of CYP1A2 in people highly exposed to toxic dioxin-like chemicals. Future studies and analysis will determine to what degree these polymorphisms can predict a human's susceptibility to dioxin-related adverse human health effects.

Perfluorochemicals and endometriosis: the ENDO study

BACKGROUND

Environmental chemicals may be associated with endometriosis. No published research has focused on the possible role of perfluorochemicals (PFCs) despite their widespread presence in human tissues.

METHODS

We formulated two samples. The first was an operative sample comprising 495 women aged 18-44 years scheduled for laparoscopy/laparotomy at one of 14 participating clinical sites in the Salt Lake City or San Francisco area, 2007-2009. The second was a population-based sample comprising 131 women matched to the operative sample on age and residence within a 50-mile radius of participating clinics. Interviews and anthropometric assessments were conducted at enrollment, along with blood collection for the analysis of nine PFCs, which were quantified using liquid chromatography-tandem mass spectrometry. Endometriosis was defined based on surgical visualization (in the operative sample) or magnetic resonance imaging (in the population sample). Using logistic regression, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) for each PFC (log-transformed), adjusting for age and body mass index, and then parity.

RESULTS

Serum perfluorooctanoic acid (PFOA; OR = 1.89 [95% CI = 1.17-3.06]) and perfluorononanoic acid (2.20 [1.02-4.75]) were associated with endometriosis in the operative sample; findings were moderately attenuated with parity adjustment (1.62 [0.99-2.66] and 1.99 [0.91-4.33], respectively). Perfluorooctane sulfonic acid (1.86 [1.05-3.30]) and PFOA (2.58 [1.18-5.64]) increased the odds for moderate/severe endometriosis, although the odds were similarly attenuated with parity adjustment (OR = 1.50 and 1.86, respectively).

CONCLUSIONS

Select PFCs were associated with an endometriosis diagnosis. These associations await corroboration.

Environmental Influences on the Development of Endometriosis

Purpose

Several environmental toxicants (ETs), including dioxins and dioxin-like compounds (DLCs), perfluorochemicals, organochlorine pesticides, phthalates, and heavy metals (especially cadmium with its estrogen-like properties in animal models) have been investigated as possibly being related to endometriosis.

Methods

Systematic review of pertinent literature.

Results

DLCs have been the most investigated ETs. DLCs are persistent organic pollutants with highly toxic potential and include three types of compounds: polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) or furans, and polychlorinated biphenyls (PCBs). The most toxic is 2, 3, 7, 8- tetrachlorodibenzo-p-dioxin (TCDD). The connection mechanism between dioxins and endometriosis is still unclear. However, dioxins and DLCs are endocrine-disrupting compounds that can affect the pathobiology of endometriosis at multiple levels. Part of the dioxin and DLCs toxic effects can be accounted for by their interaction with the aryl hydrocarbon receptor (AhR). It has been proposed that dioxin can initiate or promote endometriosis by means of interaction with estrogen receptors or by suppressing the expression of progesterone receptors. Furthermore, TCDD alters the expression of cytokines and growth factors, remodeling enzymes and cytochrome P450 expression and activity.

Conclusions

Studies in rhesus models have revealed a correlation between dioxin exposure and endometriosis. However, evidence from epidemiologic studies is inconclusive.

Persistent lipophilic environmental chemicals and endometriosis: the ENDO Study

BACKGROUND

An equivocal literature exists regarding the relation between persistent organochlorine pollutants (POPs) and endometriosis in women, with differences attributed to methodologies.

OBJECTIVES

We assessed the association between POPs and the odds of an endometriosis diagnosis and the consistency of findings by biological medium and study cohort.

METHODS

Using a matched cohort design, we assembled an operative cohort of women 18-44 years of age undergoing laparoscopy or laparotomy at 14 participating clinical centers from 2007 to 2009 and a population-based cohort matched on age and residence within a 50-mile catchment area of the clinical centers. Endometriosis was defined as visualized disease in the operative cohort and as diagnosed by magnetic resonance imaging in the population cohort. Logistic regression analysis was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for each POP in relation to an endometriosis diagnosis, with separate models run for each medium (omental fat in the operative cohort, serum in both cohorts) and cohort. Adjusted models included age, body mass index, breast-feeding conditional on parity, cotinine, and lipids.

RESULTS

Concentrations were higher in omental fat than in serum for all POPs. In the operative cohort, γ-hexachlorocyclohexane (γ-HCH) was the only POP with a significant positive association with endometriosis [per 1-SD increase in log-transformed γ-HCH: adjusted OR (AOR) = 1.27; 95% CI: 1.01, 1.59]; β-HCH was the only significant predictor in the population cohort (per 1-SD increase in log-transformed β-HCH: AOR = 1.72; 95% CI: 1.09, 2.72).

CONCLUSIONS

Using a matched cohort design, we found that cohort-specific and biological-medium-specific POPs were associated with endometriosis, underscoring the importance of methodological considerations when interpreting findings.