Urinary Bisphenol A Concentration and Thyroid Function in Chinese Adults:

Exploring the potential of metal-organic framework based composites as key players in bisphenol detection

The extensive usage of bisphenols in the production of plastics and other materials has raised concerns about their potential adverse effects on human and marine ecosystems. This comprehensive review paper aims to provide insights into the various types of bisphenols and their derivatives, as well as the multiple pathways through which human and marine life can be exposed to these compounds. Additionally, it highlights the growing importance of developing effective detection methods for bisphenols and their derivatives due to their potential health and environmental implications. The focus then shifts towards metal-organic frameworks (MOFs) as promising materials for the detection of bisphenols. We delve into the characteristic properties of MOFs and their potential and limitations in the detection of bisphenols and their derivatives. This paper also addresses the significance of pristine MOFs and explores the potential of MOF-based composites for achieving enhanced detection performance. Subsequently, various detection techniques utilizing MOFs and their composites are reviewed. In the final sections, the recent strategic developments and challenges in this field, offering a concise summary of the principal findings of this review, novel approaches, limitations of current methodologies, and emerging trends for future directions, are discussed. This comprehensive exploration of the subject matter not only illuminates the current state of research on the detection of bisphenols but also provides valuable insights into the opportunities and challenges in this evolving field. In conclusion, this review underscores the critical importance of advancing the detection of bisphenols and their derivatives, with MOFs and their composites emerging as promising candidates for more efficient and sensitive detection. The potential for their applications in diverse fields, coupled with ongoing research efforts, suggests a bright future for MOF-based bisphenol detection technologies.

Endocrine Disruptors Chemicals: Impacts of Bisphenol A, Tributyltin and Lead on Thyroid Function

The large-scale industrial production characteristic of the last century led to an increase in man-made compounds and mobilization of natural compounds, many of which can accumulate in the environment and organisms due to their bioaccumulation and biomagnification properties. The endocrine system is especially vulnerable to these compounds that are known as endocrine disruptor chemicals (EDCs). Thyroid hormones (THs) are essential for normal development and growth, besides being the main regulators of basal metabolic rate. Thus, compounds able to affect THs synthesis, transport, and action could produce important deleterious effects, impacting the development of metabolic and endocrine diseases. Herein, we will review the main effects of EDCs on the thyroid axis, with special emphasis on the widely used substances bisphenol A (BPA), employed in the synthesis of polycarbonate plastics and epoxy resins; tributyltin (TBT), an organotin chemical substance widely used in several agro-industrial applications; and lead (Pb), a ubiquitous environmental and occupational polluting heavy metal. Exposure to these EDCs occurs mainly from the ingestion of contaminated food and beverages. Furthermore, there are few epidemiological studies evaluating human risk, and experimental studies employ different exposure models, making it difficult to integrate results. However, even low doses of these EDCs warn of thyrotoxicity. Since THs homeostasis is essential for health and humans are increasingly being exposed to EDCs, it is important to clarify which substances might act as thyroid hormone system disrupting chemicals and how they act in order to try to overcome their deleterious effects and limit the exposure to these compounds.

Perinatal bisphenol A exposure has an age- and dose-dependent association with thyroid allostasis adaptive response, as well as anxiogenic-depressive-like and asocial behaviors in juvenile and adult male rats

Thyroid hormones are essential for brain development, and a shortage throughout the fetal and postnatal periods can result in mood disorders. Perinatal exposure to bisphenol A (BPA) affects thyroid activity and dependent processes indirectly during pregnancy or early postnatal life. This is particularly important because it may cause changes in tissue ontogeny, increasing the risk of developing disorders later in life. The study aimed to investigate the consequences of thyroid hormone deficiency on anxiety, social, and depressive behaviors, as well as disruption in thyroid peroxidase (TPO) gene expression, which influences the NF-κB/Nrf-2/HO-1/iNOS signaling pathway, leading to oxidative stress, inflammation, and DNA fragmentation in perinatal BPA exposure (PND18), and whether these effects can be observed in juvenile (PND60) and adult (PND95) male offspring rats. BPA increased anxiety-like behavior while decreasing sucrose preference and sociability on a choice task between novel conspecific male rats and enhanced immobility on the forced swim test. Perinatal exposure to BPA causes thyroid insult by overproducing ROS, increasing iNOS, and NF-κB levels-these effects, in turn, down-regulate Nrf-2/HO-1 signaling, resulting in DNA fragmentation within thyroid tissues. Furthermore, perinatal BPA exposure for 60 and 95 days resulted in a significant fold decrease in TPO mRNA levels in the thyroid tissues, with an insignificant fold rise in TPO expression levels in BPA 50-60. In conclusion, the present study found that perinatal BPA exposure induced thyroid allostasis-adaptive response by inhibiting the NF-κB/Nrf-2/HO-1/iNOS signaling pathway and altering the transcriptional expression of TPO, where TSH reinforced a possible association with TPO activity, disrupting thyroid hormone synthesis in juvenile rats and gradual deterioration reaching the adult stage.

Bisphenol derivatives in cord blood and association between thyroid hormones and potential exposure sources

Endocrine-disrupting environmental chemicals are a public health concern, particularly fetal exposure to Bisphenol derivatives. This study aimed to assess fetal exposure to Bisphenol derivatives (BPA, BPF, and BPS) by measuring their levels in cord blood and investigating their association with plastic material used in daily life as well as cord blood TSH and free L-thyroxine (fT4) levels. In this descriptive study, a questionnaire with a face-to-face interview was administered before birth, and cord blood samples were taken immediately after delivery. The mean levels of BPA, BPF, TSH, and fT4 were measured as 10.69 ± 2.39 ng/ml, 3.80 ± 0.58 ng/ml; 2.36 ± 0.23 µIU/ml, and 14.18 ± 0.53 pg/ml, respectively, in a total of 104 cord blood samples. All BPS levels remained below the detection limit. Linear regression analysis revealed a positive association between birth weight and cord blood BPA concentration (β = 0.26; p = 0.02). Further research on maternal exposure during the fetal and neonatal period is critical for public health.

The effect of bisphenols on sex and thyroid hormone concentrations in cord blood among newborns

This study aims to investigate the associations of bisphenols with sex and thyroid hormones in cord blood among newborns. Four bisphenols, three hormones related to gonadal function, and four parameters related to thyroid function were measured in umbilical cord blood in 378 mother-newborn pairs. Multivariable linear regression, quantile-based g-computation (QGC), and Bayesian kernel machine regression were used. In the multivariable linear regression, bisphenol A (BPA) was associated with increased testosterone (TT) (regression coefficient, β = 0.049, 95% confidence interval, CI: 0.013,0.085; p = 0.007) and free tri-iodothyronine (FT3) levels (β = 0.019, 95% CI: 0.003, 0.035; p = 0.023), and decreased thyroid peroxidase antibody (TPOAb) (β = -0.053, 95% CI: 0.098, -0.008; p = 0.021). Consistently associations were observed in males, except TT, which was observed in females, and bisphenol AF (BPAF) was associated with decreased follicle-stimulating hormone (FSH) in females. These associations were also observed in a mixture of bisphenols. Moreover, we observed maternal prepregnancy body mass index (BMI) and delivery mode disparity in the relationship between bisphenols and sex and thyroid hormones. This study suggests that bisphenols may exert effects on sex and thyroid hormones in newborns, the effect may vary with sex differences, maternal prepregnancy BMI, and delivery mode.

Effects of crosstalk between steroid hormones mediated thyroid hormone in zebrafish exposed to 4-tert-octylphenol: Estrogenic and anti-androgenic effects

Alkylphenols, such as nonylphenol and 4-tert-octylphenol (OP), are byproducts of the biodegradation of alkylphenol ethoxylates and present substantial ecological and health risks in aquatic environments and higher life forms. In this context, our study aimed to explore the effect of OP on reproductive endocrine function in both female and male zebrafish. Over a period of 21 days, the zebrafish were subjected to varying concentrations of OP (0, 0.02, 0.1, and 0.5 μg/L), based on the lowest effective concentration (EC10 = 0.48 μg/L) identified for zebrafish embryos. OP exposure led to a pronounced increase in hepatic vitellogenin (vtg) mRNA expression and 17β-estradiol biosynthesis in both sexes. Conversely, OP exhibits anti-androgenic properties, significantly diminishes gonadal androgen receptor (ar) mRNA expression, and reduces endogenous androgen (testosterone and 11-ketotestosterone) levels in male zebrafish. Notably, cortisol and thyroid hormone (TH) levels demonstrated concentration-dependent elevations in zebrafish, influencing the regulation of gonadal steroid hormones (GSHs). These findings suggest that prolonged OP exposure may result in sustained reproductive dysfunction in adult zebrafish, which is largely attributable to the intricate reciprocal relationship between hormone levels and the associated gene expression. Our comprehensive biological response analysis of adult zebrafish offers vital insights into the reproductive toxicological effects of OP, thereby enriching future ecological studies on aquatic systems.

Endocrine-disrupting chemicals and autoimmune diseases

Endocrine-disrupting chemicals (EDCs) widely exist in people's production and life which have great potential to damage human and animal health. Over the past few decades, growing attention has been paid to the impact of EDCs on human health, as well as immune system. So far, researchers have proved that EDCs (such as bisphenol A (BPA), phthalate, tetrachlorodibenzodioxin (TCDD), etc.) affect human immune function and promotes the occurrence and development of autoimmune diseases (ADs). Therefore, in order to better understand how EDCs affect ADs, we summarized the current knowledge about the impact of EDCs on ADs, and elaborated the potential mechanism of the impact of EDCs on ADs in this review.

EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP), Lambré C, Barat Baviera JM, Bolognesi C, Chesson A, Cocconcelli PS, Crebelli R, Gott DM, Grob K, Lampi E, Mengelers M, Mortensen A, Rivière G, Silano (until 21 December 2020†) V, Steffensen I, Tlustos C, Vernis L, Zorn H, Batke M, Bignami M, Corsini E, FitzGerald R, Gundert‐Remy U, Halldorsson T, Hart A, Ntzani E, Scanziani E, Schroeder H, Ulbrich B, Waalkens‐Berendsen D, Woelfle D, Al Harraq Z, Baert K, Carfì M, Castoldi AF, Croera C, Van Loveren H. Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs

In 2015, EFSA established a temporary tolerable daily intake (t-TDI) for BPA of 4 μg/kg body weight (bw) per day. In 2016, the European Commission mandated EFSA to re-evaluate the risks to public health from the presence of BPA in foodstuffs and to establish a tolerable daily intake (TDI). For this re-evaluation, a pre-established protocol was used that had undergone public consultation. The CEP Panel concluded that it is Unlikely to Very Unlikely that BPA presents a genotoxic hazard through a direct mechanism. Taking into consideration the evidence from animal data and support from human observational studies, the immune system was identified as most sensitive to BPA exposure. An effect on Th17 cells in mice was identified as the critical effect; these cells are pivotal in cellular immune mechanisms and involved in the development of inflammatory conditions, including autoimmunity and lung inflammation. A reference point (RP) of 8.2 ng/kg bw per day, expressed as human equivalent dose, was identified for the critical effect. Uncertainty analysis assessed a probability of 57-73% that the lowest estimated Benchmark Dose (BMD) for other health effects was below the RP based on Th17 cells. In view of this, the CEP Panel judged that an additional uncertainty factor (UF) of 2 was needed for establishing the TDI. Applying an overall UF of 50 to the RP, a TDI of 0.2 ng BPA/kg bw per day was established. Comparison of this TDI with the dietary exposure estimates from the 2015 EFSA opinion showed that both the mean and the 95th percentile dietary exposures in all age groups exceeded the TDI by two to three orders of magnitude. Even considering the uncertainty in the exposure assessment, the exceedance being so large, the CEP Panel concluded that there is a health concern from dietary BPA exposure.

Association between bisphenol A exposure and thyroid dysfunction in adults: a systematic review and meta-analysis

The occurrence of thyroid dysfunction is affected by environmental factors, and BPA is a ubiquitous environmental pollutant with the potential to cause thyroid dysfunction. However, the limited epidemiological evidence shows an inconsistent association between BPA exposure and thyroid dysfunction. Therefore, the literature on the impact of BPA on thyroid was sorted and analyzed to study the relationship between BPA and adult thyroid function. The studies published on or before 23rd May 2022 from PubMed, Web of Science, and Scopus were collected analyzing the association between BPA exposure and the levels of thyroid hormones. The methodological quality of each study was assessed, the sensitivity analysis and subgroup analysis based on study population and gender were also performed, and publication bias was evaluated. A total of 2969 literature studies were retrieved. Based on inclusion and exclusion criteria, eleven studies were included. Our results showed that BPA concentration was negatively correlated with FT4 and TSH in males. Pooled correlation coefficients between BPA and FT4/TSH were -0.027 (95%CI = -0.030∼-0.024) and -0.058 (95%CI = -0.111∼-0.004). BPA concentration was positively correlated with FT4 in females, and the pooled correlation coefficient was 0.006 (95%CI = 0.003-0.008). The effects of BPA on thyroid hormone levels were significantly different between males and females. BPA may significantly decrease the levels of FT4 and TSH in males but increase the levels of FT4 in females. Considering the high heterogeneity among studies and the limited investigations into subgroups, the relationship between BPA exposure and thyroid dysfunction needs to be further investigated.

Bisphenol A alternatives continuously contribute to the endocrine disruption in cetaceans

The bans on bisphenol A (BPA) have facilitated the widespread use of BPA alternatives and shifted environmental contamination profiles of bisphenols (BPs). However, the continued reports of toxicities of emerging BPA alternatives have raised questions about whether the shifting profiles are contributed to mitigate BPs-mediated endocrine-disruption effects (EDEs). Cetaceans are commonly used as the ideal sentinel species for monitoring marine pollutants of concern and determining potential health effects, but far less is known about BP loads and BPs-mediated EDEs in cetaceans. Here we measured the hepatic concentrations of six BPs in eight stranded cetacean species (n = 41) in the South China Sea, between 2007 and 2020. The large-bodied whales generally showed higher ∑BPs concentrations than the small-bodied dolphins. In Indo-Pacific finless porpoises (Neophocaena phocaenoides) (n = 33), BPA concentrations first increased (2007-2014) and then decreased (2014-2020), while ∑BP_Alternatives concentrations increased from 2007 to 2020. It appears that the alternatives gradually replaced BPA, probably due to the BPA-related bans in China. In order to examine the hormone disruption of BPA and its alternatives in finless porpoises, five blubber hormones (cortisol, progesterone, testosterone, triiodothyronine and tetraiodothyronine), which are proven to be validated endocrine biomarkers, were measured in 21 samples. Tetraiodothyronine, testosterone, and cortisol were significantly and positively correlated with BPA and its alternatives, suggesting that the interference of endocrine hormone homeostasis may continue to occur despite the changes of BP profiles in finless porpoises. This is the first investigation of the relationship between hormone and BP concentrations in cetaceans and represents a substantial advance in understanding BPs-mediated endocrine effects on cetaceans.

Endocrine disrupting chemicals: effects on pituitary, thyroid and adrenal glands

BACKGROUND

In recent years, scientific research has increasingly focused on Endocrine Disrupting Chemicals (EDCs) and demonstrated their relevant role in the functional impairment of endocrine glands. This induced regulatory authorities to ban some of these compounds and to carefully investigate others in order to prevent EDCs-related conditions. As a result, we witnessed a growing awareness and interest on this topic.

AIMS

This paper aims to summarize current evidence regarding the detrimental effects of EDCs on pivotal endocrine glands like pituitary, thyroid and adrenal ones. Particularly, we directed our attention on the known and the hypothesized mechanisms of endocrine dysfunction brought by EDCs. We also gave a glimpse on recent findings from pioneering studies that could in the future shed a light on the pathophysiology of well-known, but poorly understood, endocrine diseases like hormone-producing adenomas.

CONCLUSIONS

Although intriguing, studies on endocrine dysfunctions brought by EDCs are challenging, in particular when investigating long-term effects of EDCs on humans. However, undoubtedly, it represents a new intriguing field of science research.

Associations of bisphenol exposure with thyroid hormones in pregnant women: a prospective birth cohort study in China

Bisphenols are endocrine disruptor chemicals that disrupt thyroid hormone homeostasis. However, evidence on the effects of bisphenol mixtures on thyroid hormones are insufficient. Therefore, the present study aimed to explore the effects of bisphenol substitutes and bisphenol mixtures on thyroid hormones during pregnancy. The study was conducted among 446 pregnant women in the Guangxi Zhuang Birth Cohort (GZBC), China. In multiple linear regressions, compared with the low-exposure group, bisphenol S (BPS) concentrations in the middle-exposure group led to a 10.90% (95% CI: - 18.16%, - 2.99%) decrease in triiodothyronine (T3) levels in the first trimester; tetrabromobisphenol A (TBBPA) levels in the middle-exposure group led to an 8.26% (95% CI: - 15.82%, - 0.01%) decrease in T3 levels in the first trimester; bisphenol B (BPB) levels in the middle-exposure group led to higher free thyroxine (FT4) levels (9.84%; 95% CI: 1.73%, 18.60%) in the second trimester; bisphenol F (BPF) in the middle-exposure group led to higher FT4 levels (8.59%, 95% CI: 0.53%, 17.31%) in the second trimester; and TBBPA levels in the high-exposure group led to a 9.39% (95% CI: 1.46%, 17.93%) increase in FT4 levels in the second trimester. The Bayesian kernel machine regression (BKMR) and restricted cubic spline (RCS) models showed a U-shaped dose-response relationship between bisphenol A (BPA) and free triiodothyronine (FT3) (p < 0.01) as well as BPS and FT4 (p < 0.05). Nonlinear relationships were also observed between the bisphenol mixture and FT3. Overall, maternal bisphenol exposure affected thyroid hormone levels during pregnancy. This study provides evidence that BPB, BPF, BPS, and TBBPA are unsafe substitutes for BPA, as well as the overall effect of bisphenols on adverse health in human beings.

Impact of Chemical Endocrine Disruptors and Hormone Modulators on the Endocrine System

There is growing concern regarding the health and safety issues of endocrine-disrupting chemicals (EDCs). Long-term exposure to EDCs has alarming adverse health effects through both hormone-direct and hormone-indirect pathways. Non-chemical agents, including physical agents such as artificial light, radiation, temperature, and stress exposure, are currently poorly investigated, even though they can seriously affect the endocrine system, by modulation of hormonal action. Several mechanisms have been suggested to explain the interference of EDCs with hormonal activity. However, difficulty in quantifying the exposure, low standardization of studies, and the presence of confounding factors do not allow the establishment of a causal relationship between endocrine disorders and exposure to specific toxic agents. In this review, we focus on recent findings on the effects of EDCs and hormone system modulators on the endocrine system, including the thyroid, parathyroid glands, adrenal steroidogenesis, beta-cell function, and male and female reproductive function.

Derivation of a Human In Vivo Benchmark Dose for Bisphenol A from ToxCast In Vitro Concentration Response Data Using a Computational Workflow for Probabilistic Quantitative In Vitro to In Vivo Extrapolation

A computational workflow which integrates physiologically based kinetic (PBK) modelling; global sensitivity analysis (GSA), Approximate Bayesian Computation (ABC), Markov Chain Monte Carlo (MCMC) simulation and the Virtual Cell Based Assay (VCBA) for the estimation of the active, free in vitro concentration of chemical in the reaction medium was developed to facilitate quantitative in vitro to in vivo extrapolation (QIVIVE). The workflow was designed to estimate parameter and model uncertainty within a computationally efficient framework. The workflow was tested using a human PBK model for bisphenol A (BPA) and high throughput screening (HTS) in vitro concentration-response data, for estrogen and pregnane X receptor activation determined in human liver and kidney cell lines, from the ToxCast/Tox21 database. In vivo benchmark dose 10% lower confidence limits (BMDL10) for oral uptake of BPA (ng/kg BW/day) were calculated from the in vivo dose-responses and compared to the human equivalent dose (HED) BMDL10 for relative kidney weight change in the mouse derived by European Food Safety Authority (EFSA). Three from four in vivo BMDL10 values calculated in this study were similar to the EFSA values whereas the fourth was much smaller. The derivation of an uncertainty factor (UF) to accommodate the uncertainties associated with measurements using human cell lines in vitro, extrapolated to in vivo, could be useful for the derivation of Health Based Guidance Values (HBGV).

The Impact of Bisphenol A on Thyroid Function in Neonates and Children: A Systematic Review of the Literature

Background: Bisphenol A (BPA) is an endocrine-disrupting chemical widely used in plastic products that may have an adverse effect on several physiologic functions in children. The aim of this systematic review is to summarize the current knowledge of the impact of BPA concentrations on thyroid function in neonates, children, and adolescents. Methods: A systematic search of Medline, Scopus, Clinical Trials.gov, Cochrane Central Register of Controlled Trials CENTRAL, and Google Scholar databases according to PRISMA guidelines was performed. Only case–control, cross-sectional, and cohort studies that assessed the relationship between Bisphenol A and thyroid function in neonates and children aged <18 years were included. Initially, 102 articles were assessed, which were restricted to 73 articles after exclusion of duplicates. A total of 73 articles were assessed by two independent researchers based on the title/abstract and the predetermined inclusion and exclusion criteria. According to the eligibility criteria, 18 full-text articles were selected for further assessment. Finally, 12 full-text articles were included in the present systematic review. Results: The presented studies offer data that suggest a negative correlation of BPA concentrations with TSH in children, a gender-specific manner of action, and a potential effect on proper neurodevelopment. However, the results are inconclusive with respect to specific thyroid hormone concentrations and the effect on thyroid autoimmunity. Conclusion: The potential negative effect of BPA in the developing thyroid gland of children that may affect proper neurodevelopment, suggesting the need to focus future research on designing studies that elucidate the underlying mechanisms and the effects of BPA in thyroid function in early life.

Internal exposure of Chinese children from a typical coastal city to bisphenols and possible association with thyroid hormone levels

Bisphenols (BPs) are widely used in consumer products, and human exposure to BPs is nearly ubiquitous. However, human biomonitoring data are scarce, especially for children. In this study, we quantified eight BPs in the serum of 345 children from a typical coastal city in China. Bisphenol A (BPA), bisphenol F (BPF), and bisphenol S (BPS) were frequently detected (63% BPA, 68% BPF, 43% BPS), with geometric mean (GM) concentrations of 1.6, 0.08, and 0.04 ng/mL, respectively. The other five BPs had low detection frequencies (<5%). The distribution of BPA, BPF, and BPS in children's serum samples was independent of sex whereas the concentrations of BPS and BPF both significantly increased with age (P < 0.01). The GM values of estimated daily intake for BPA and BPS were 0.61 and 0.014 μg/kg body weight (bw)/day, respectively, indicating a relatively higher exposure risk of BPA in comparison with BPS. Compared with the population with euthyroid or nonhyperthyroid thyroid dysfunction, children with hyperthyroidism suffered higher exposure to BPA. By multiple linear regression analysis, thyroid-stimulating hormone showed a significantly negative relationship with log₁₀-BPA concentration for euthyroid children (R² = 0.477, P < 0.001), whereas a significantly positive correlation (R² = 0.753, P = 0.033) was found for hyperthyroid children.

Endocrine disrupting chemicals and thyroid hormone action

Thyroid hormones (predominantly thyroxine, T4, and triiodothyronine, T3) are essential for normal development and for adult physiology. There are several challenges, however, that make identifying chemicals that produce adverse effects by interfering with the thyroid system difficult. First, individual variability in serum concentrations of thyroid hormones represent only about 10% of the population reference range that is considered to be "normal." This means that populations studies evaluating the relationship between chemical exposure and serum thyroid hormones must be large enough to overcome this internal variance. In addition, we know that there are chemicals that do not produce changes in thyroid hormone levels, but nevertheless impact thyroid signaling in target tissues. A good example is that of polychlorinated biphenyls (PCBs). PCB exposure during development are clearly associated with cognitive deficits in humans. But PCB exposure isn't uniformly associated with a reduction in serum thyroid hormone in human populations despite mechanistic studies showing that PCBs reduce serum T4 in animals. In contrast, perchlorate is a chemical that inhibits iodide uptake, thereby reducing thyroid hormone synthesis and serum hormone levels. Human studies have been variable in identifying a relationship between thyroid hormone and perchlorate exposure, but studies also show that dietary iodine, cigarette smoking and other factors can modify this relationship. The conclusion is that identifying chemicals that interfere with thyroid hormone could depend on in vitro analysis of chemicals that interact with different proteins important for thyroid hormone to function properly.

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene-environment interactions underlying the pathology of thyroid diseases.

Bisphenol A as a Factor in the Mosaic of Autoimmunity

The population worldwide is largely exposed to bisphenol A (BPA), a commonly used plasticizer, that has a similar molecular structure to endogenous estrogens. Therefore, it is able to influence physiological processes in human body, taking part in the pathophysiology of various endocrinopathies, as well as, cardiovascular, neurological and oncological diseases. BPA has been found to affect the immune system, leading to the development of autoimmunity and allergies, too. In the last few decades, the prevalence of autoimmune diseases has significantly increased, that could be explained by a rising exposure of the population to environmental factors, such as BPA. BPA has been found to play a role in the pathogenesis of systemic autoimmune diseases and also organ-specific autoimmunity (thyroid autoimmunity, diabetes mellitus type 1, myocarditis, inflammatory bowel disease, multiple sclerosis, encephalomyelitis etc), but the results of some studies remain still controversial, so further research is needed.

Dietary Intake of Endocrine Disrupting Substances Presents in Environment and Their Impact on Thyroid Function

According to the available data, environmental pollution is a serious problem all over the world. Between 2015 and 2016, pollution was responsible for approximately nine million deaths worldwide. They also include endocrine disrupting chemicals (EDCs) that can interfere with the functioning of the thyroid gland. They are characterized by high persistence in the environment. These substances can enter the body through the gastrointestinal tract, respiratory system, as well as contact with the skin and overcome the placental barrier. EDC can be found in food, water, and personal care products. They can get into food from the environment and as a result of their migration to food products and cosmetics from packaging. EDCs can disrupt the functioning of the thyroid gland through a number of mechanisms, including disrupting the activation of thyroid receptors and the expression of genes that are related to the metabolism, synthesis, and transport of thyroid hormones (HT). There is a need to strengthen the food safety policy that aimed at the use of appropriate materials in direct contact with food. At the same time, an important action is to reduce the production of all waste and, when possible, use biodegradable packaging, which may contribute to the improvement of the quality of the entire ecosystem and the health of food, thus reducing the risk of developing thyroid diseases.

The Putative Adverse Effects of Bisphenol A on Autoimmune Diseases

Bisphenol A (BPA) is a monomer that is widely used in the manufacture of polycarbonate plastics including storage plastics and baby bottles, and is considered one of the most widely used synthetic compounds in the manufacturing industry. Exposure to BPA mainly occurs after oral ingestion and results from leaks into food and water from plastic containers and according to epidemiological data exposure is widespread and estimated to occur in 90% of individuals. BPA exertspleiotropiceffects and demonstrates estrogen like effects, thus considered an endocrine disrupting chemical. Growing body of evidence highlight the role of BPA in modulating immune responses and signaling pathways resulting in a proinflammatory response by enhancing the differential polarization of immune cells and cytokine production profile to one that is consistent with proinflammation. Indeed, epidemiological studies have uncovered associations between several autoimmune diseases and BPA exposure. Data from animal models provided consistent evidence highlighting the role of BPA in the pathogenesis, exacerbation and perpetuation of various autoimmune phenomena including neuroinflammation in the context of multiple sclerosis, colitis in inflammatory bowel disease, nephritis in systemic lupus erythematosus, and insulitis in type 1 diabetes mellitus. Given the wide spread of BPA use and its effects in immune systemdysregulation, a call for careful assessment of patients' risks and for public health measures are needed to limit exposure and subsequent deleterious effects. The purpose of this paper is to explore the autoimmune triggering mechanisms and present the current literature supporting the role of BPA in the pathogenesis of autoimmune diseases.

Serum concentration of bisphenol A in elderly cats and its association with clinicopathological findings

OBJECTIVES

Bisphenol A (BPA) has been mentioned as a possible factor contributing to feline hyperthyroidism. Nevertheless, there are no previous studies reporting on the concentration of BPA in feline serum and its association with thyroid function. The objectives of this study were to measure serum BPA concentration in cats aged ⩾7 years, considered as healthy by their owners, and to compare the results with clinicopathological findings.

METHODS

Sixty-nine cats aged ⩾7 years considered as healthy by their owners were enrolled in the study. The concentration of BPA in feline serum was measured using liquid chromatography-tandem mass spectrometry. In all cats, signalment, living environment, diet history, and the results of haematological and biochemical analysis, including thyroxine levels, were available.

RESULTS

The mean serum BPA concentration in feline serum was 1.06 ± 0.908 ng/ml. Significant correlation was found between BPA concentration and haemoglobin (r = 0.3397; P = 0.0043), haematocrit (r = 0.3245; P = 0.0065) and the number of red blood cells (r = 0.2916; P = 0.0151), concentration of total protein (r = 0.2383; P = 0.0486), concentration of calcium (r = 0.3915; P = 0.0009) and level of bilirubin (r = 0.3848; P = 0.0011). No other significant correlations were found. Significant differences (P <0.01) were found between mature (1.28 ± 0.994 ng/ml) and geriatric cats (0.420 ± 0.240 ng/ml), between strictly indoor cats (1.27 ± 0.992 ng/ml) and cats with outdoor access (0.660 ± 0.529 ng/ml), and between cats fed canned food (1.23 ± 0.935 ng/ml) and cats fed non-canned food (0.774 ± 0.795 ng/ml).

CONCLUSIONS AND RELEVANCE

Measurable serum BPA levels were found in all examined samples. The age of the cats was revealed as a significant factor affecting BPA concentration and mature cats had the highest levels. A significantly higher concentration of BPA was found in cats living strictly indoors and in cats fed canned food. No association was found between BPA and thyroid function. Further studies are needed that focus on hyperthyroid cats for better evaluation of this relationship.

Maternal and childhood urinary phenol concentrations, neonatal thyroid function, and behavioral problems at 10 years of age: The SMBCS study

BACKGROUND

Environmental phenols, bisphenol A (BPA), triclosan (TCS), and benzophenone-3 (BP-3), are known as emerging endocrine-disrupting chemicals; however, their impacts on thyroid hormones and children's neurobehaviors are still unclear.

OBJECTIVES

We aimed to examine the associations of prenatal and childhood exposure to phenols with neonatal thyroid function and childhood behavioral problems aged 10 years.

METHODS

A total of 386 mother-singleton pairs were included from Sheyang Mini Birth Cohort Study (SMBCS), a longitudinal birth cohort in China. We quantified urinary BPA, TCS and BP-3 concentrations in maternal and 10-year-old children's urine samples using gas chromatography tandem mass spectrometry and thyroid function parameters in cord serum samples. Caregivers completed the Strength and Difficulties Questionnaire (SDQ) for their children at 10 years of age. Multivariable linear regression models and logistic regression models were applied to estimate associations of urinary phenol concentrations with thyroid hormones and risks of children's behavioral problems, respectively.

RESULTS

The median values of urinary BPA, TCS and BP-3 concentrations for pregnant women were 1.75 μg/L, 0.54 μg/L and 0.37 μg/L, while 1.29 μg/L, 6.64 μg/L and 1.39 μg/L for children, respectively. Maternal urinary BPA concentrations were in associations with 1.00% [95% confidence interval (CI): 0.20%, 1.92%] increases in cord serum FT4 concentrations and significantly associated with increased risks of total difficulties [odds ratio (OR): 1.45, 95% CI: 1.07, 1.97], while maternal urinary levels of BP-3 were significantly related to poorer prosocial behaviors (OR: 1.58, 95% CI: 1.04, 2.39) of children at 10 years of age. In sex-stratified analyses, maternal urinary BPA concentrations were related to increased total difficulty subscales only in boys.

CONCLUSIONS

The findings indicated that higher prenatal urinary BPA concentrations were associated with increased risks of total difficulties, especially in boys and maternal urinary BP-3 concentrations were related to poorer prosocial behaviors at 10 years.

Bisphenol A and thyroid hormones: Bibliometric analysis of scientific publications

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical which can cause potential health risks and interfere with thyroid hormones through multiple avenues. This study aimed to evaluate the hotspots and emerging trends on BPA and thyroid hormones by using a bibliometric method.Publications related on BPA and thyroid hormones were downloaded from Science Citation Index-Expanded database. Annual outputs, high yield journals, countries, institutions, authors and their cited times were summarized. In addition, keywords co-occurrence, burst references and citation networks were bibliometric analyzed.From 2000 to 2019, 418 articles were published. Both of the Environment International and Environmental Health Perspectives, United States, Chinese Academy of Sciences and Antonia M. Calafat were the most recorded journals, countries, institutions and authors, respectively. The main research area was Toxicology. In addition of the retrieve term "bisphenol-a" and "thyroid-hormone", "in-vitro", "exposure" and "endocrine disruptors", were the hotspot keywords and "triclosan", "oxidative stress" and "united-states" were the most recent trends keywords. "Thyroid hormone action is disrupted by Bisphenol A as an antagonist" published on The Journal of Clinical Endocrinology & Metabolism by Kenji Moriyama in 2002 got both the highest burst score and citation score. Six groups were clustered and the mechanism of BPA's effect on thyroid hormones, and the exposure of BPA and potential risks in children and pregnant women were the two main large fields.The number of publications in the field of BPA and thyroid hormones has increased tremendously since 2000. The research hotspot ranged from mechanism researches in animal models to epidemiological studies. "Thyroid hormone action is disrupted by bisphenol A as an antagonist" of Kenji Moriyama provided important building blocks in the field. The impact of BPA on thyroid hormones, especially pregnant women and children, was the latest research frontiers and might be the future direction of this filed in the following years.

Bisphenol A and its analogues: A comprehensive review to identify and prioritize effect biomarkers for human biomonitoring

Human biomonitoring (HBM) studies have demonstrated widespread and daily exposure to bisphenol A (BPA). Moreover, BPA structural analogues (e.g. BPS, BPF, BPAF), used as BPA replacements, are being increasingly detected in human biological matrices. BPA and some of its analogues are classified as endocrine disruptors suspected of contributing to adverse health outcomes such as altered reproduction and neurodevelopment, obesity, and metabolic disorders among other developmental and chronic impairments. One of the aims of the H2020 European Human Biomonitoring Initiative (HBM4EU) is the implementation of effect biomarkers at large scales in future HBM studies in a systematic and standardized way, in order to complement exposure data with mechanistically-based biomarkers of early adverse effects. This review aimed to identify and prioritize existing biomarkers of effect for BPA, as well as to provide relevant mechanistic and adverse outcome pathway (AOP) information in order to cover knowledge gaps and better interpret effect biomarker data. A comprehensive literature search was performed in PubMed to identify all the epidemiologic studies published in the last 10 years addressing the potential relationship between bisphenols exposure and alterations in biological parameters. A total of 5716 references were screened, out of which, 119 full-text articles were analyzed and tabulated in detail. This work provides first an overview of all epigenetics, gene transcription, oxidative stress, reproductive, glucocorticoid and thyroid hormones, metabolic and allergy/immune biomarkers previously studied. Then, promising effect biomarkers related to altered neurodevelopmental and reproductive outcomes including brain-derived neurotrophic factor (BDNF), kisspeptin (KiSS), and gene expression of nuclear receptors are prioritized, providing mechanistic insights based on in vitro, animal studies and AOP information. Finally, the potential of omics technologies for biomarker discovery and its implications for risk assessment are discussed. To the best of our knowledge, this is the first effort to comprehensively identify bisphenol-related biomarkers of effect for HBM purposes.

Thyroxine-binding globulin, peripheral deiodinase activity, and thyroid autoantibody status in association of phthalates and phenolic compounds with thyroid hormones in adult population

Exposure to consumer chemicals such as phthalates and phenolic compounds has been associated with thyroid hormone disruption in humans. However, information related to factors that may influence such associations, e.g., transport and activation of the hormones, and autoimmunity status, is limited. In the present study, we employed a subpopulation of adults (n = 1,254) who participated in the Korean National Environmental Health Survey (KoNEHS) 2015-2017, and associated urinary concentrations of major phthalate metabolites, bisphenol A (BPA), and parabens, with thyroid hormone-related measures, including free and total T3 and T4, TSH, thyroxine-binding globulin (TBG), calculated peripheral deiodinase (DIO) activity, and thyroid autoantibodies of thyroperoxidase (TPO) and thyroglobulin (Tg). Phthalate metabolites were negatively associated with total T4 and free T3, and positively associated with total T3. These observations could be explained by TBG levels and calculated peripheral DIO activity that were positively associated with phthalates exposure. In contrast, BPA was positively associated with total T4 and negatively associated with total T3, without any changes in TBG concentration. Serum TPO and Tg antibodies were not associated with urinary phthalate metabolites and BPA. However, thyroid autoantibody status appeared to modulate the association of some phthalates with thyroid hormones. For parabens, little to negligible association was observed. The results of our observation show potential underlying mechanisms of phthalates-induced thyroid hormone disruption, and suggests the importance of consideration of thyroid autoimmunity status in association studies for thyroid disrupting chemicals.

Molecular interactions of thyroxine binding globulin and thyroid hormone receptor with estrogenic compounds 4-nonylphenol, 4-tert-octylphenol and bisphenol A metabolite (MBP)

AIM

Endocrine disruption due to environmental chemical contaminants is a global human health issue. The aim of present study was to investigate the structural binding aspects of possible interference of commonly detected environmental contaminants on thyroid function.

MATERIAL AND METHODS

Three compounds, 4-tert-octylphenol (4-tert-OP), 4-nonylphenol (4-NP), and 4-methyl-2,4-bis(4-hydroxypentyl)pent-1-ene (MBP) were subjected to induced fit docking (IFD) against thyroxine binding globulin (TBG) and thyroid hormone receptor (THR). Structural analysis included molecular interactions of the amino acid residues and binding energy estimation between the ligands and the target proteins.

KEY RESULTS

All the ligands were successfully placed in the ligand binding pocket of TBG and THR using induced fit docking (IFD). The IFD results revealed high percentage of commonality in interacting amino acid residues between the aforementioned compounds and the native ligand for both TBG and THR. The results of our study further revealed that all the compounds have the potential to interfere with thyroid transport and signaling. However, MBP showed higher binding affinity for both TBG and THR, suggesting higher thyroid disruptive potential as compared to 4-t-OP and 4-NP. Furthermore, our results also suggest that the reported disruptive effects of BPA could actually be exerted through its metabolite; MBP.

SIGNIFICANCE

This work implies that all the three compounds 4-NP, 4-t-OP and especially MBP have the potential to interfere with thyroid hormone transport and signaling. This potentially leads to disruption of thyroid hormone function.

Bisphenols as Environmental Triggers of Thyroid Dysfunction: Clues and Evidence

Bisphenols (BPs), and especially bisphenol A (BPA), are known endocrine disruptors (EDCs), capable of interfering with estrogen and androgen activities, as well as being suspected of other health outcomes. Given the crucial role of thyroid hormones and the increasing incidence of thyroid carcinoma in the last few decades, this review analyzes the effects of BPS on the thyroid, considering original research in vitro, in vivo, and in humans published from January 2000 to October 2019. Both in vitro and in vivo studies reported the ability of BPs to disrupt thyroid function through multiple mechanisms. The antagonism with thyroid receptors (TRs), which affects TR-mediated transcriptional activity, the direct action of BPs on gene expression at the thyroid and the pituitary level, the competitive binding with thyroid transport proteins, and the induction of toxicity in several cell lines are likely the main mechanisms leading to thyroid dysfunction. In humans, results are more contradictory, though some evidence suggests the potential of BPs in increasing the risk of thyroid nodules. A standardized methodology in toxicological studies and prospective epidemiological studies with individual exposure assessments are warranted to evaluate the pathophysiology resulting in the damage and to establish the temporal relationship between markers of exposure and long-term effects.

Ginger extract ameliorates bisphenol A (BPA)-induced disruption in thyroid hormones synthesis and metabolism: Involvement of Nrf-2/HO-1 pathway

Environmental exposure to BPA is alarming because of the potential health threats for example those concerning the thyroid glands which may show signs of oxidative stress. This original study aimed to investigate the possible antioxidant protective effects of ginger extract (GE) against BPA-induced thyroid injury in male rats, focusing on its effect on Nrf-2/HO-1 signaling and thyroid hormone synthesis regulating genes. The cascade of events in thyroid injury induced by chronic exposure to BPA (200 mg/kg b.w/day for 35 days) involved a preliminary overproduction of ROS followed by significant (p ≤ 0.05) depletion of reduced glutathione (GSH) levels and superoxide dismutase (SOD) activity as well as significant increases of malondialdehyde (MDA) contents, myeloperoxidase (MPO) activity and inducible nitric oxide synthase (iNOS) gene expression. These actions consequently down-regulate the Nrf-2/HO-I signaling which eventually resulting in the DNA fragmentation within the thyroid tissues. Moreover, BPA administration caused a reduction of thyroid iodide uptake evidenced by significant inhibitions (p ≤ 0.05) of sodium-iodide symporter (NIS), thyroid peroxidase (TPO) and thyroid-stimulating hormone receptor (TSHR) mRNA expressions within the thyroid glands. A subsequent significant decreased serum levels of T3 and T4 accompanied by a significantly increased serum TSH level were also detected. These findings were confirmed by the severe pathological changes detected in the thyroid tissue of BPA treated rats. These biochemical and histological alterations were significantly alleviated with ginger administration (250 mg/kg b.w/day for 35 days) plus BPA. In conclusion, ginger extract is a potent antioxidant that can effectively protect against BPA-induced thyroid oxidative damage by activating the Nrf-2/HO-1 gene expressions and enhancing the thyroid hormones synthesis. This is the first study to show the contribution of Nrf-2/HO-1 pathway to the protective effect of ginger extract against BPA-induced thyroid oxidative damage and thyroid hormonal disruption.

Association of bisphenol A and its alternatives bisphenol S and F exposure with hypertension and blood pressure: A cross-sectional study in China

Epidemiological studies have investigated the associations of bisphenol A (BPA) exposure with hypertension risk or blood pressure levels, but findings are inconsistent. Furthermore, the association between its alternatives bisphenol S and F (BPS and BPF) and hypertension risk are not yet known. We conducted a cross-sectional study in 1437 eligible participants without hypertension-related diseases, with complete data about blood pressure levels, hypertension diagnosis, and urinary bisphenols concentrations. Multivariable logistic and linear models were respectively applied to examine the associations of urinary bisphenols concentrations with hypertension risk and blood pressure levels. The dose-response relationship was explored by the restricted cubic spline model. Compared with the reference group of BPA, individuals in the middle and high exposure group had an adjusted odds ratio (OR) of 1.30 and 1.40 for hypertension, had a 3.08 and 2.82 mm Hg higher systolic blood pressure (SBP) levels, respectively, with an inverted "U" shaped dose-response relationship. Compared with the reference group of BPS, individuals in the second and third tertile had an adjusted OR of 1.49 and 1.48 for hypertension, had a 2.61 and 3.89 mm Hg increased levels of SBP, respectively, with a monotonic curve. No significant associations of BPF exposure with hypertension risk or blood pressure levels were found. BPA and BPS exposure were suggested to be associated with increased hypertension risk and blood pressure levels, with different dose-response relationships. Our findings have important implications for public health but require confirmation in prospective studies.

Urinary bisphenol A and thyroid function by BMI in the Korean National Environmental Health Survey (KoNEHS) 2012-2014

Bisphenol A (BPA) is one of the largest amounts of chemicals in daily life and source of polycarbonate plastics, epoxy resins, medical equipment, plastic consumer products. Recent studies reported that the effects of BPA on human health in the thyroid hormone. Therefore, this study aimed to indicate the association between urinary BPA concentration and thyroid function in total triiodothyronine (T3), thyroxine (T4), thyroidal stimulating hormone (TSH) and stratified the population by body mass index (BMI). This study was performed on 6478 adults aged 19 years and older based on the Second Korean National Environmental Health Survey (KoNEHS, 2012-2014). We measured BPA in urine and total T3, T4 and TSH in serum from the 2nd KoNEHS study. The multiple regression analysis was performed to assess the association of urinary BPA concentrations with thyroid hormone after BMI stratification. Urinary BPA associated with thyroid hormone. Especially, BPA is related to T3 (-0.627) in all group, and T4 (-0.060, -0.098) in all group and the group of BMI 25.0kg/m2 or more negatively. When stratified by BPA, T3 and T4 were significantly decreased with the high BPA exposure compared with the low BPA exposure for BMI more than 25.0kg/m2 (adjusted β = -3.402, 95% CI: 4.942, -1.862, adjusted β = -0.209, 95% CI: 0.328, -0.090). However, no obvious associations were found between BPA concentration and TSH. The results of urinary BPA decrease with T3 and T4 levels increase in the higher BMI group is a new finding which does not exist in recent studies of Korea.

Bisphenol A and Phthalates Exhibit Similar Toxicogenomics and Health Effects

Bisphenol A and phthalates are most frequently detected organic pollutants found in our surroundings because of their regular use as plasticizers in daily use polymeric products. BPA is used in manufacturing baby feeding bottles, water pipes, canned food linings, and food packaging materials. Phthalates are used in polyvinyl chloride products including clothing, toys, medical devices, and food packaging. These chemicals are not bound to the matrix and leach out into the surroundings on slight change in the environment, like alteration in pH, temperature, and pressure. Humans are continuously exposed to these chemicals through skin contact, inhalation, or ingestion when the leachates enter food, drinks, air, water, or soil. The Comparative Toxicogenomics Database (CTD) revealed that Bisphenol A has 1932 interactions with genes/proteins and few frequently used phthalates (DEHP, MEHP, DBP, BBP, and MBP) showed 484 gene/protein interactions. Similar toxicogenomics and adverse effects of Bisphenol A and phthalates on human health are attributed to their 89 common interacting genes/proteins.

Bisphenols as a Legacy Pollutant, and Their Effects on Organ Vulnerability

Bisphenols are widely used in the synthesis of polycarbonate plastics, epoxy resins, and thermal paper, which are used in manufacturing items of daily use. Packaged foods and drinks are the main sources of exposure to bisphenols. These chemicals affect humans and animals by disrupting the estrogen, androgen, progesterone, thyroid, and aryl hydrocarbon receptor functions. Bisphenols exert numerous harmful effects because of their interaction with receptors, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial dysfunction, and cell signal alterations. Both cohort and case-control studies have determined an association between bisphenol exposure and increased risk of cardiovascular diseases, neurological disorders, reproductive abnormalities, obesity, and diabetes. Prenatal exposure to bisphenols results in developmental disorders in animals. These chemicals also affect the immune cells and play a significant role in initiating the inflammatory response. Exposure to bisphenols exhibit age, gender, and dose-dependent effects. Even at low concentrations, bisphenols exert toxicity, and hence deserve a critical assessment of their uses. Since bisphenols have a global influence on human health, the need to discover the underlying pathways involved in all disease conditions is essential. Furthermore, it is important to promote the use of alternatives for bisphenols, thereby restricting their uses.

Bisphenols and Thyroid Hormone

In recent decades, attention has been directed toward the effects of bisphenol A (BPA) on human health. BPA has estrogenic activity and is regarded as a representative endocrine disruptor. In addition, mounting evidence indicates that BPA can disrupt thyroid hormone and its action. This review examined human epidemiological studies to investigate the association between BPA exposure and thyroid hormone levels, and analyzed in vivo and in vitro experiments to identify the causal relationship and its mechanism of action. BPA is involved in thyroid hormone action not only as a thyroid hormone receptor antagonist, but also through several other mechanisms. Since the use of bisphenols other than BPA has recently increased, we also reviewed the effects of other bisphenols on thyroid hormone action.

CLARITY-BPA: Bisphenol A or Propylthiouracil on Thyroid Function and Effects in the Developing Male and Female Rat Brain

The CLARITY-BPA experiment, a large collaboration between the National Institute of Environmental Health Sciences, the National Toxicology Program, and the US Food and Drug Administration, is designed to test the effects of bisphenol A (BPA) on a variety of endocrine systems and end points. The specific aim of this subproject was to test the effect of BPA exposure on thyroid functions and thyroid hormone action in the developing brain. Timed-pregnant National Center for Toxicological Research Sprague-Dawley rats (strain code 23) were dosed by gavage with vehicle control (0.3% carboxymethylcellulose) or one of five doses of BPA [2.5, 25, 250, 2500, or 25,000 µg/kg body weight (bw) per day] or ethinyl estradiol (EE) at 0.05 or 0.50 µg/kg bw/d (n = 8 for each group) beginning on gestational day 6. Beginning on postnatal day (PND) 1 (day of birth is PND 0), the pups were directly gavaged with the same dose of vehicle, BPA, or EE. We also obtained a group of animals treated with 3 ppm propylthiouracil in the drinking water and an equal number of concordant controls. Neither BPA nor EE affected serum thyroid hormones or thyroid hormone‒sensitive end points in the developing brain at PND 15. In contrast, propylthiouracil (PTU) reduced serum T4 to the expected degree (80% reduction) and elevated serum TSH. Few effects of PTU were observed in the male brain and none in the female brain. As a result, it is difficult to interpret the negative effects of BPA on the thyroid in this rat strain because the thyroid system appears to respond differently from that of other rat strains.

Dose exposure of Bisphenol- A on female Wistar rats fertility

Background 2, 2-Bis (4-hydroxyphenyl propane [bisphenol A (BPA)] is one of the major environmental pollutants and has the adverse effects on human health. BPA mimics the structure of estrogen and binds to estrogen receptors and alters the secretion of the hormone. It is ingested in humans through the regular use of plastic containers, bottles and food cans. Materials and methods Female Wistar rats were exposed orally to 5, 50, 300, 600 and 800 mg BPA/kg body weight (bd. wt.)/week mixed in olive oil and administered every 168 h for 3 months continuing through the mating, gestation and lactation and its effects on fertility, reproductive organ weight and hormones [LH (luteinizing hormone), FSH (follicle stimulating hormone), estradiol (E2), progesterone (PROG) and PRL (prolactin)] were evaluated. Results The findings revealed that females exposed to BPA exhibited a decrease in female fertility rate and weight of reproductive organs (ovary and uterus) with significant decreased levels of LH, FSH, E2, PROG and PRL in the non-pregnancy phase whereas in cesarean and post-term females, no significance difference was found in fertility rate, reproductive organ weight and hormonal levels. Conclusions These data indicate an increased sensitivity to BPA needs careful evaluation of the current levels of exposure.

Bisphenol A exposure and risk of thyroid nodules in Chinese women: A case-control study

BACKGROUND

Thyroid nodules (TNs) are highly prevalent worldwide and have a pattern of female predominance. Bisphenol A (BPA) is an endocrine disruptor that can lead to adverse effects in human health. However, epidemiologic studies revealing the association between BPA exposure and TNs are limited and the results are inconsistent. We aimed to examine the association between urinary BPA and TNs in women who are more susceptible to TNs.

METHODS

We conducted a case-control study with 1416 women aged 18 years or older (705 cases, 711 controls). All participants underwent thyroid ultrasonography. Urinary total BPA (free and conjugated) concentration was quantified using the HPLC-MS/MS. We analyzed the association between urinary BPA concentration and the risk of TNs using crude and multivariable logistic regression models. Participants were further stratified into thyroid autoantibody positive group (at least one positive) and thyroid autoantibody negative group (both negative) according to the thyroglobulin antibody (TGAb) and thyroid peroxidase antibody (TPOAb) levels, and restricted cubic spline regression was also applied to determine the possible nonlinear relationship between urinary BPA and TNs.

RESULTS

Compared with women in the first quartile, the odds of TNs was 72% (adjusted OR = 1.72, 95% CI: 1.25 to 2.35) higher for those in the second quartile, 54% (adjusted OR = 1.54, 95% CI: 1.12 to 2.12) higher for those in the third quartile, and 108% (adjusted OR = 2.08, 95% CI: 1.50 to 2.90) higher for those in the fourth quartile after adjusting for age, BMI, education, HDL-C, LDL-C, triglyceride, total cholesterol, urinary iodine, TGAb and TPOAb. When the study population was stratified into thyroid autoantibody positive group and thyroid autoantibody negative group, we found that only in the positive group, the association was significant in model 1 (crude OR = 2.80; 95% CI = 1.90 to 4.12), model 2 (adjusted OR = 2.84; 95% CI = 1.91 to 4.22), model 3 (adjusted OR = 4.01; 95% CI = 2.57 to 6.27) and model 4 (adjusted OR = 3.71; 95% CI = 2.36 to 5.83). Multivariable-adjusted restricted cubic spline analysis demonstrated a similar result that in the thyroid autoantibody positive group, the association between urinary BPA and TNs risk was near linear (P-overall <0.001; P-non-linear = 0.054).

CONCLUSION

In Chinese women, higher urinary BPA concentration was associated with increased risk of TNs only in those with positive thyroid autoantibodies. Moreover, this association was near linear, indicating that any rise in BPA exposure was associated with elevated TNs risk.

Comparison of thyroid hormone disruption potentials by bisphenols A, S, F, and Z in embryo-larval zebrafish

Several structural analogues of bisphenol A (BPA), e.g., bisphenol F (BPF), bisphenol S (BPS), and bisphenol Z (BPZ), have been used as its substitutes in many applications and consequently detected in the environment, and human specimen such as urine and serum. While BPA has been frequently reported for thyroid hormone disruption in both experimental and epidemiological studies, less is known for the BPA analogues. In the present study, thyroid hormone disrupting effects of BPF, BPS and BPZ, were investigated, and compared with those of BPA, using embryo-larval zebrafish (Danio rerio). At 120 hpf, significant increases in T3 and/or T4 were observed in the larval fish following exposure to BPA, BPF, or BPS. Moreover, transcriptional changes of the genes related to thyroid development (hhex and tg), thyroid hormone transport (ttr) and metabolism (ugt1ab) were observed as well. Thyroid hormone (T4) disruption by BPF was observed even at the concentration (2.0 mg/L) lower than the effective concentration determined for BPA (>2.0 mg/L). Delayed hatching was observed by all tested bisphenols. Our results clearly show that these BPA analogues can disrupt thyroid function of the larval fish, and their thyroid hormone disruption potencies could be even greater than that of BPA. The concentrations which disrupt thyroid function of the larval fish were orders of magnitude higher than those occurring in the ambient environment. However, thyroid hormone disruption by longer term exposure and its consequences in the fish population, deserve further investigation.

Thyroid function disruptors: from nature to chemicals

The modern concept of thyroid disruptors includes synthetic chemicals and bioactive compounds from food that interfere with any aspect of the hypothalamus-pituitary-thyroid axis, thyroid hormone biosynthesis and secretion, blood and transmembrane transport, metabolism and local actions of thyroid hormones. This review highlights relevant disruptors that affect populations through their diet: directly from food itself (fish oil and polyunsaturated fatty acids, pepper, coffee, cinnamon and resveratrol/grapes), through vegetable cultivation (pesticides) and from containers for food storage and cooking (bisphenol A, phthalates and polybrominated diphenyl ethers). Due to the vital role of thyroid hormones during every stage of life, we review effects from the gestational period to adulthood, including evidence from in vitro studies, rodent models, human trials and epidemiological studies.

Exposure of environmental Bisphenol A in relation to routine sperm parameters and sperm movement characteristics among fertile men

Although several human studies have examined bisphenol A (BPA) exposure in relation to routine sperm parameters, evidence of BPA’s effects on sperm movement characteristics is limited. We examined associations of BPA exposure with sperm parameters including sperm movement characteristics among fertile men. The cross-sectional study was conducted in Sandu County, Guizhou Province, China. Subjects provided semen samples analyzed by computer-aided sperm analysis (CASA) system and urine samples for BPA assay. They were invited to complete an in-person interview with a structured questionnaire to obtain demographics, lifestyle factors, etc. In final analyses, 500 subjects were included. We used multivariate linear regression analyses to estimate associations between BPA and sperm parameters after adjusting for potential confounders. BPA was detected in 73.6% of urine samples, with a geometric mean of 0.44 μg/gCreatinine. Compared with subjects of undetected BPA, subjects with detected BPA had increased Linearity (LIN, β: 2.19, 95% confidence interval (CI): 0.37, 4.0), Straightness (STR, β: 1.47, 95% CI: 0.19, 2.75), Wobble (WOB, β: 1.75, 95% CI: 0.26, 3.25), reduced Amplitude of lateral head displacement (ALH, β: −0.26, 95% CI: −0.5, −0.02) and Mean angular displacement (MAD, β: −2.17, 95% CI: −4.22, −0.11). Subjects in the highest tertile of creatinine-adjusted BPA group had lower sperm concentration than those with undetected BPA. Dose-response relationships of BPA with LIN, WOB, ALH, MAD and sperm concentration were demonstrated by statistically significant trends across tertiles of creatinine-adjusted BPA concentrations. Similar results were obtained using unadjusted BPA concentrations. Exposure to environmental BPA would decrease sperm concentration and sperm swing characteristics (ALH and MAD), and increase sperm velocity ratios (LIN, STR and WOB), which might mediate further effects on impaired male fecundity.

The Role of Polybrominated Diphenyl Ethers in Thyroid Carcinogenesis: Is It a Weak Hypothesis or a Hidden Reality? From Facts to New Perspectives

In the last decades, the incidence of thyroid cancer has increased faster than that of any other malignant tumor type. The cause of thyroid cancer is likely multifactorial and a variety of both exogenous and endogenous has been identified as potential risk factors. Polybrominated diphenyl ethers (PBDEs), used since the 1970s as flame retardants, are still widespread and persistent pollutants today, although their production was definitely phased out in the western countries several years ago. Polybrominated diphenyl ethers are known endocrine disruptors, and the endocrine system is their primary target. Whereas animal studies have ascertained the ability of PBDEs to affect the normal functionality of the thyroid, evidence in humans remains inconclusive, and only a few epidemiological studies investigated the association between exposure to PBDEs and thyroid cancer. However, a number of clues suggest that a prolonged exposure to these chemicals might act a trigger of the most common malignancy of the endocrine system, whereas further studies with an advanced design are suggested.

Associations of female exposure to bisphenol A with fecundability: Evidence from a preconception cohort study

BACKGROUND

Human exposure to bisphenol A (BPA) is common. The reproductive toxicity of BPA has been well characterized. However, the impact of BPA exposure on fecundability in healthy women is less clear, and evidence from eastern countries is lacking.

OBJECTIVES

We aimed to prospectively assess the associations of BPA with female fecundability, as measured by time to pregnancy (TTP).

METHODS

From 2013 to 2015, we included 700 Chinese couples attempting pregnancy in two preconception care clinics and followed for 12 months or until a pregnancy occurred. The concentrations of BPA were determined in preconception urine samples of female partners. Cox's proportional models for discrete survival time were used to estimate fecundability odds ratios (FORs). Odds ratios (ORs) for infertility (TTP > 12 months) were estimated using logistic regression models.

RESULTS

After adjusting for potential confounders, each ln-unit increase in urinary concentrations of BPA was associated with a 13% reduction in fecundability (FOR = 0.87; 95% CI: 0.78, 0.98) and a 23% increase in odds of infertility (OR = 1.23; 95% CI: 1.00, 1.50). Women in the highest quartile of urinary BPA had a 30% reduction in fecundability (FOR = 0.70, 95% CI: 0.51, 0.96) and a 64% increase in odds of infertility when compared to those in the lowest quartile (OR = 1.64, 95% CI: 0.90, 2.98). The associations of urinary BPA concentrations with fecundability (FOR = 0.80, 95% CI: 0.67, 0.95) and infertility (OR = 1.43, 95% CI: 1.05, 1.93) were strengthened among women over 30 years of age.

CONCLUSIONS

Our results suggest that preconception concentrations of BPA in female urine were associated with decreased fecundability, particularly among women at older ages. These findings should be confirmed in future human studies.

Cord Blood Bisphenol A Levels and Reproductive and Thyroid Hormone Levels of Neonates: The Hokkaido Study on Environment and Children's Health

BACKGROUND

Bisphenol A (BPA) is widely used and BPA exposure is nearly ubiquitous in developed countries. While animal studies have indicated adverse health effects of prenatal BPA exposure including reproductive dysfunction and thyroid function disruption possibly in a sex-specific manner, findings from epidemiologic studies have not been enough to prove these adverse effects. Given very limited research on human, the aim of this study was to investigate associations between cord blood BPA levels and reproductive and thyroid hormone levels of neonates and whether associations differed by neonate sex.

METHODS

The study population included 514 participants of the Hokkaido study recruited from 2002 to 2005 at one hospital in Sapporo, Japan. The BPA level in cord blood was determined by ID-LC/MS/MS, and the limit of quantification was 0.040 ng/ml. We measured nine types of reproductive hormone levels in cord blood, and thyroid hormone levels were obtained from neonate mass screening test data. There were 283 subjects, who had both BPA and hormone levels measurements, included for the final analyses.

RESULTS

The geometric mean of cord blood BPA was 0.051 ng/ml. After adjustment, BPA level was negatively associated with prolactin (PRL) (β = -0.38). There was an interaction between infant sex and BPA levels on PRL; a weak negative association was found in boys (β = -0.12), whereas a weak positive association was found in girls (β = 0.14). BPA level showed weak positive association with testosterone, estradiol, and progesterone levels in boys. No association was found between BPA and thyroid hormone levels.

CONCLUSIONS

Our findings suggested that fetal BPA levels might be associated with changes in certain reproductive hormone levels of neonates in a sex-specific manner, though further investigations are necessary.

Prenatal phenolic compounds exposure and neurobehavioral development at 2 and 7years of age

BACKGROUND

Phenolic compounds such as bisphenol A (BPA), nonylphenol (NP), and octylphenol (OP) are known as endocrine-disrupting compounds and are commonly used. Their impacts on the neurodevelopment of children are inconclusive. The current study aims to investigate the association between umbilical cord blood levels of BPA, NP, OP and neurodevelopmental outcomes at 2 and 7years of age.

METHODS

The study was based on the Taiwan Birth Panel Study, a prospective birth cohort. We collected cord blood plasma to measure phenolic compound levels using ultra-performance liquid chromatography-tandem mass spectrometry. In the follow-up, 208 mother-child pairs with 2-year-old children and 148 mother-child pairs with 7-year-old children were recruited in this study. We used the Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT) and the Wechsler Intelligence Scale for Children (WISC-IV) for neurodevelopmental assessments at 2 and 7years of age, respectively. Multiple linear regressions were used for statistical analysis.

RESULTS

The detection rates of BPA, NP, and OP were 55.9%, 77.6%, and 68.3%, respectively. In this study, the median BPA, NP, and OP levels in 2-year-olds were 3.3, 72.6, and 3.3 (ng/ml), respectively. However, the median levels of BPA, NP, and OP were 3.2, 49.3, and 6.6 (ng/ml), respectively. The levels of phenolic compounds were log₁₀-transformed for statistical analysis. Gender stratification was performed. In the WISC-IV neurocognitive assessment, we found both a significant negative association and a trend between cord blood plasma BPA levels and full-scale IQ (p for trend<0.01), the verbal comprehension index (p for trend<0.01), and the perceptual reasoning index (p for trend<0.01) in the study population. After stratification by sex, significant associations were found in full-scale IQ (p for trend=0.03) and the verbal comprehension (p for trend<0.01) index in boys. In girls, prenatal BPA exposure had adverse effects on full-scale IQ (p for trend=0.02), perceptual reasoning index (p for trend<0.01), and working memory index (p for trend=0.02). None of the developmental quotients (DQs) of the CDIIT analysis were significantly associated with phenolic compound levels in cord blood based on continuous or categorical measures.

CONCLUSION

Prenatal exposure to BPA affects neurocognitive development, and this effect differs between 7-year-old boys and girls. More studies are needed to elucidate the relationship between phenolic compound exposure in utero and children's neurobehavioral development.

Primordial and Primary Preventions of Thyroid Disease

BACKGROUND

Primordial and primary preventions of thyroid diseases are concerned with avoiding the appearance of risk factors, delaying the progression to overt disease, and minimizing the impact of illness.

SUMMARY

Using related key words, 446 articles related to primordial and primary, preventions of thyroid diseases published between 2001-2015 were evaluated, categorized and analyzed. Prevention and elimination of iodine deficiency are major steps that have been successfully achieved and maintained in many countries of the world in last 2 decades. Recent investigations related to the effect of cigarette smoking, alcohol consumption, and autoimmunity in the prevention of thyroid disorders have been reviewed.

CONCLUSIONS

The cornerstone for successful prevention of thyroid disease entails timely implementation of its primordial and primary preventions, which must be highly prioritized in related health strategies by health authorities.

Considering common sources of exposure in association studies - Urinary benzophenone-3 and DEHP metabolites are associated with altered thyroid hormone balance in the NHANES 2007-2008

Epidemiological studies have shown that thyroid hormone balances can be disrupted by chemical exposure. However, many association studies have often failed to consider multiple chemicals with possible common sources of exposure, rendering their conclusions less reliable. In the 2007-2008 National Health and Nutrition Examination Survey (NHANES) from the U.S.A., urinary levels of environmental phenols, parabens, and phthalate metabolites as well as serum thyroid hormones were measured in a general U.S. population (≥12years old, n=1829). Employing these data, first, the chemicals or their metabolites associated with thyroid hormone measures were identified. Then, the chemicals/metabolites with possible common exposure sources were included in the analytical model to test the sensitivities of their association with thyroid hormone levels. Benzophenone-3 (BP-3), bisphenol A (BPA), and a metabolite of di(2-ethylhexyl) phthalate (DEHP) were identified as significant determinants of decreased serum thyroid hormones. However, significant positive correlations were detected (p-value<0.05, r=0.23 to 0.45) between these chemicals/metabolites, which suggests that they might share similar exposure sources. In the subsequent sensitivity analysis, which included the chemicals/metabolite with potentially similar exposure sources in the model, we found that urinary BP-3 and DEHP exposure were associated with decreased thyroid hormones among the general population but BPA exposure was not. In association studies, the presence of possible common exposure sources should be considered to circumvent possible false-positive conclusions.

Occupational Exposure to Bisphenol A (BPA): A Reality That Still Needs to Be Unveiled

Bisphenol A (BPA), 2,2-bis(4-hydroxyphenyl) propane, is one of the most utilized industrial chemicals worldwide, with the ability to interfere with/or mimic estrogenic hormones with associated biological responses. Environmental human exposure to this endocrine disruptor, mostly through oral intake, is considered a generalized phenomenon, particularly in developed countries. However, in the context of occupational exposure, non-dietary exposure sources (e.g., air and contact) cannot be underestimated. Here, we performed a review of the literature on BPA occupational exposure and associated health effects. Relevantly, the authors only identified 19 studies from 2009 to 2017 that demonstrate that occupationally exposed individuals have significantly higher detected BPA levels than environmentally exposed populations and that the detection rate of serum BPA increases in relation to the time of exposure. However, only 12 studies performed in China have correlated potential health effects with detected BPA levels, and shown that BPA-exposed male workers are at greater risk of male sexual dysfunction across all domains of sexual function; also, endocrine disruption, alterations to epigenetic marks (DNA methylation) and epidemiological evidence have shown significant effects on the offspring of parents exposed to BPA during pregnancy. This overview raises awareness of the dramatic and consistent increase in the production and exposure of BPA and creates urgency to assess the actual exposure of workers to this xenoestrogen and to evaluate potential associated adverse health effects.

Determination of Highly Sensitive Biological Cell Model Systems to Screen BPA-Related Health Hazards Using Pathway Studio

Bisphenol-A (BPA) is a ubiquitous endocrine-disrupting chemical. Recently, many issues have arisen surrounding the disease pathogenesis of BPA. Therefore, several studies have been conducted to investigate the proteomic biomarkers of BPA that are associated with disease processes. However, studies on identifying highly sensitive biological cell model systems in determining BPA health risk are lacking. Here, we determined suitable cell model systems and potential biomarkers for predicting BPA-mediated disease using the bioinformatics tool Pathway Studio. We compiled known BPA-mediated diseases in humans, which were categorized into five major types. Subsequently, we investigated the differentially expressed proteins following BPA exposure in several cell types, and analyzed the efficacy of altered proteins to investigate their associations with BPA-mediated diseases. Our results demonstrated that colon cancer cells (SW480), mammary gland, and Sertoli cells were highly sensitive biological model systems, because of the efficacy of predicting the majority of BPA-mediated diseases. We selected glucose-6-phosphate dehydrogenase (G6PD), cytochrome b-c1 complex subunit 1 (UQCRC1), and voltage-dependent anion-selective channel protein 2 (VDAC2) as highly sensitive biomarkers to predict BPA-mediated diseases. Furthermore, we summarized proteomic studies in spermatozoa following BPA exposure, which have recently been considered as another suitable cell type for predicting BPA-mediated diseases.

Evidence for bisphenol A-induced disruption of maternal thyroid homeostasis in the pregnant ewe at low level representative of human exposure

Many uncertainties remain regarding the potential of bisphenol A (BPA) as a thyroid disruptor in mammals and the relevance of experimental data to humans. The relevance of the exposure schemes used in experimental in vivo studies is also a major source of uncertainty when analysing the risk of BPA exposure for human health. In this context, the goals of our study, conducted in an ovine model relevant to human gestation and thyroid physiologies, were to: 1) determine the equivalence of subcutaneous and dietary exposures and 2) determine if environmentally relevant doses of BPA can alter gestational and newborn thyroid functions. The difference between the two routes of exposure was mainly related to the overall BPA exposure and much less to the peak serum concentrations. Interestingly, BPA-GLUC (the main metabolite of BPA) internal exposure via both routes was almost identical. The decrease in thyroid hormones concentration overtime was more accentuated in ewes treated with BPA, particularly with the medium dose (50 μg/(kg.d); SC) for which the maximum BPA concentrations were predicted to be within the 1-10 ng/mL range i.e. very similar to the highest blood concentrations reported in humans. The balance between TT4 and rT3 varied differently between the vehicle and the medium dose group. The mechanisms underlying those modifications of maternal thyroid homeostasis remain to be determined. Our study did not evidence significant modification of TSH secretion or binding to serum proteins but might suggest an effect at the level of deiodinases.

Higher urinary bisphenol A concentration and excessive iodine intake are associated with nodular goiter and papillary thyroid carcinoma

In the present study, we investigated whether bisphenol A (BPA) levels and excessive iodine intake were associated with papillary thyroid carcinoma (PTC) and nodular goiter (NG). We determined total BPA concentrations (TBC) in paired serum and urine samples, and urinary iodine concentrations (UIC) in urine samples collected from PTC patients, NG patients, and healthy individuals, then compared BPA concentrations and UIC within and between each patient group. The results showed that there were no gender-specific differences in serum TBC and UIC in each group, and no differences across all patient groups. Urinary BPA concentrations (UBC) were higher in the NG and PTC groups compared with the control group. UBC showed gender-specific differences in the NG and PTC group. Furthermore, UIC were higher in the NG and PTC groups compared with the control group. Higher UBC and excessive iodine intake were risk factors for NG and PTC according to multivariate logistic regression analysis. There was a significant correlation between UBC and UIC in each group. These data suggested that higher UBC and excessive iodine intake are associated with NG and PTC. The metabolic and functional pathways between BPA and iodine are potentially linked to the pathogenesis and progression of NG and PTC.