Multiple metals predict prolactin and thyrotropin (TSH) levels in men

Hormonal, liver, and renal function associated with electronic waste (e-waste) exposure in Dhaka, Bangladesh

Electronic waste (e-waste) contains numerous metals and organic pollutants that have detrimental impacts on human health. We studied 199 e-waste recycling workers and 104 non-exposed workers; analyzed blood, urine, and hair samples to measure heavy metals, hormonal, liver, and renal function. We used quantile regression models to evaluate the impact of Pb, Cd, and Hg on hormonal, liver and renal function, and the role of DNA oxidative damage in mediating the relationship between exposures and outcomes. Exposed workers had higher blood lead (Pb) (median 11.89 vs 3.63 µg/dL), similar blood cadmium (Cd) (1.04 vs 0.99 µg/L) and lower total mercury (Hg) in hair (0.38 vs 0.57 ppm) than non-exposed group. Exposed workers also had elevated median concentrations of total triiodothyronine (TT3), aspartate aminotransferase (AST), alanine aminotransferase (ALT), urinary albumin, albumin creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) were significantly higher than non-exposed group (p≤0.05). Sex hormones including luteinizing hormone, follicle stimulating hormone, estrogen, progesterone and testosterone concentrations were not significantly different between exposed and non-exposed (all p≥0.05). The median concentration of ALT was 4.00 (95% CI: 0.23, 7.77), urinary albumin was 0.09 (95% CI: 0.06, 0.12) and ACR was 1.31 (95% CI: 0.57, 2.05) units higher in the exposed group compared to non-exposed group. Pb was associated with a 3.67 unit increase in the ALP (95% CI: 1.53, 5.80), 0.01 unit increase in urinary albumin (95% CI: 0.002, 0.01), and 0.07 unit increase in ACR (95% CI: 0.01, 0.13). However, no hormonal, renal, and hepatic parameters were associated with Cd or Hg. Oxidative DNA damage did not mediate exposure-outcome relationships (p≥0.05). Our data indicate e-waste exposure impairs liver and renal functions secondary to elevated Pb levels. Continuous monitoring, longitudinal studies to evaluate the dose-response relationship and effective control measure are required to protect workers from e-waste exposure.

Cadmium exposure and thyroid hormone disruption: a systematic review and meta-analysis

INTRODUCTION

This meta-analysis aimed to analyze the effect of cadmium (Cd) exposure on thyroid hormone disruption.

CONTENT

Databases including PubMed, Embase, Cochrane Library, and Scopus were searched for studies published up to December 14, 2022. Studies evaluating the association between Cd exposure (blood Cd [BCd] or urine Cd [UCd]) and thyroid function (thyroid-stimulating hormone [TSH], free thyroxine [FT4], total triiodothyronine [TT3]) or thyroid autoimmunity (thyroglobulin antibody [TgAb] or thyroperoxidase Ab [TPOAb]) were included.

SUMMARY AND OUTLOOK

This systematic review included 12 cross-sectional studies. Cd exposure showed a neutral association with TSH (pooled correlation=0.016, 95 % confidence interval [CI]=-0.013 to 0.045, p=0.277), FT4 (pooled correlation=0.028, 95 % CI=-0.005 to 0.061, p=0.098), and thyroid autoimmunity (pooled odds ratio=1.143, 95 % CI=0.820-1.591, p=0.430). However, Cd exposure showed a positive association with TT3 (pooled correlation=0.065, 95 % CI=0.050-0.080, p<0.001), which was consistent with the BCd and UCd subgroup analyses (pooled correlation=0.053 and 0.081, respectively, both p<0.001). Cd exposure was not associated with TSH, FT4, or thyroid autoimmunity but tended to increase with TT3.

Correlations Among Maternal and Infant Factors, Lead Exposure, and Serum Prolactin Levels During Lactation: A Cross-sectional Study in Indonesia

OBJECTIVES

Prolactin is vital for breastfeeding and milk production, and its secretion is influenced by factors related to the mother, infant, and environment. To date, no study has concurrently investigated the correlation of these factors with serum prolactin levels during lactation. Therefore, the objective of this study was to investigate the correlations among maternal and infant factors, lead exposure, and serum prolactin levels during lactation.

METHODS

A cross-sectional approach was employed in Surabaya, Indonesia, among 110 exclusively lactating mothers. The mothers' daily diets were determined using multiple 24-hour recalls, while blood lead levels were measured with inductively coupled plasma mass spectrometry. Serum prolactin levels were assessed using the electrochemiluminescence immunoassay. For bivariate analysis, we employed the Spearman correlation, Mann-Whitney, and Kruskal-Wallis tests, while for multivariate analysis, we utilized multiple linear regression.

RESULTS

The average serum prolactin level of the lactating mothers was 129.19±88.96 ng/mL. Positive correlations were found between serum prolactin levels and breastfeeding frequency (p < 0.001), protein intake (p < 0.001), and calcium intake (p = 0.011) but had negative correlation with blood lead levels (p < 0.001) and vitamin B6 intake (p = 0.003). Additionally, prolactin levels were not significantly associated with maternal age; parity; intake of calories, vitamin D, vitamin E, zinc, folic acid, magnesium, or iron; infant age; or infant sex.

CONCLUSIONS

Breastfeeding frequency had a stronger positive relationship with serum prolactin levels than protein and calcium intake. However, lead exposure was associated with reduced serum prolactin levels during lactation. Consequently, specific interventions from policymakers are necessary to manage breastfeeding in mothers exposed to lead.

Associations between multiple heavy metals exposure and neural damage biomarkers in welders: A cross-sectional study

BACKGROUND

Both occupational and environmental exposure to heavy metals are associated with various neurodegenerative diseases. However, limited evidence is available on the potential effects of exposure to metallic mixtures and neural damage.

OBJECTIVES

This study aimed to evaluate the association between metal mixtures in urine and neural damage biomarkers in welders.

METHODS

In this cross-sectional study, a total of 186 workers were recruited from steel mills. Twenty-three metals in urine were measured by inductively coupled plasma mass spectrometry. Serum neural damage biomarkers, including neurofilament light chain (NfL), sphingosine-1-phosphate (S1P), prolactin (PRL), and dopamine (DA) were detected using enzyme-linked immunosorbent assay kits. Multivariable linear regression, Bayesian kernel machine regression (BKMR), and Quantile g-computation (QG-C) were employed to estimate the association between metals exposure and neural damage biomarkers.

RESULTS

Inverted u-shaped associations of nickel with NfL, S1P, and DA were observed in the BKMR model. A non-linear relationship was also found between Fe and PRL. Urinary cobalt was positively associated with serum PRL and had the strongest positive weights in the QG-C model. Urinary lead was associated with higher serum S1P levels. We also found the interaction among nickel, zinc, arsenic, strontium, iron, and lead with the neural damage biomarkers.

CONCLUSION

This study provides new evidence of a direct association between metal mixture exposure and the serum biomarkers of neural damage. Several metals Ni, Co, Pb, Sr, As and Fe, may have adverse effects on the nervous system, while Zn may have neuroprotective effects.

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.

Low-Dose Occupational Exposure to Nickel and Thyroid Hormones

INTRODUCTION

The aim of this study was to evaluate the effects of a low-dose exposure to nickel, as it is present in urban air, on thyroid hormones and on thyrotropin in outdoor workers exposed to urban pollutants.

MATERIALS AND METHODS

A total of 164 outdoor workers were studied and divided by sex and smoking habit. Each worker underwent measurement of urinary nickel and of blood triiodothyronine, L-thyroxine, and thyrotropin levels. The statistical analysis was performed.

RESULTS

Statistical analysis shows a significant and positive correlation between urinary nickel and L-thyroxine, both in total sample and in males.

DISCUSSION AND CONCLUSION

The study suggests that occupational exposure to a low dose of nickel may affect thyroid function in municipal police workers. These data may provide information on other categories of outdoor workers with similar exposure.

Associations of exposure to metal and metal mixtures with thyroid hormones: Results from the NHANES 2007-2012

BACKGROUND

Disrupted thyroid homeostasis plays a role in neurocognitive dysfunction and metabolic disorders. Since individuals are exposed to multiple metals simultaneously, it is important to assess the effects of metal mixtures on thyroid hormone status. This study aimed to investigate the associations of metal mixtures and individual metals with thyroid hormone levels.

METHODS

Data included 2399 men and 1988 women from the 2007-2012 National Health and Nutrition Examination Survey (2007-2012). Thyroid hormones measured included total triiodothyronine (T3), total thyroxine (T4), free forms of T3 (FT3) and T4 (FT4), and thyroid stimulating hormone (TSH). We included twelve metals (arsenic, barium, cobalt, cesium, molybdenum, antimony, thallium, tungsten, and uranium from urine; cadmium, lead, and mercury from blood) in traditional linear regression models controlling for 12 metals simultaneously and in quantile-based g-computation (QGC) to assess the relative contribution of each metal as well as the overall association with thyroid hormones as a metal mixture.

RESULTS

There were associations of the total metal mixture with thyroid hormones for T3 (beta: -0.023, 95% CI: -0.04, -0.01, in women), T4 (beta: -0.03, 95% CI: -0.05, -0.01, in men; beta: -0.026, 95% CI: -0.04, -0.01, in women), and the T3:T4 ratio (beta: 0.026, 95% CI: 0.01, 0.05, in men). Arsenic had negative contributions to T3 and T4. Cadmium had a positive contribution to T4 but negative contributions to T3 and T3:T4. Lead had a positive contribution to T3 and T3:T4, but a negative contribution to T4.

CONCLUSION

Multiple metals as a mixture were associated with thyroid hormone levels. Arsenic, cadmium, and lead were individually associated with multiple thyroid hormones. Examination of associations of metal mixtures and individual metals with thyroid hormones can contribute to an understanding of thyroid hormone homeostasis and provide evidence for developing intervention and guidance for health promotion.

Geophagia: Benefits and potential toxicity to human—A review

Geophagy is the habit of consuming clay soil such as chalk or kaolin. Though it is globally practiced, the safety of those involved is yet to be fully established. It is thought to be highly prevalent in pregnant women because of its antinausea or therapeutic effects. This practice is also thought to be provoked by some nutritional needs, but in modern society its etiology is obscure. The mineralogical and chemical compositions of clay may vary from one region to another and even in all form of rocks clay constitutes. Published articles in geophagy indicate lack of adequate investigations into the toxicity of geophagy, though it is globally practiced and more prevalent in Africa (as a continent) or in Africans migrants. Some studies have helped to identify some minerals that are toxic to human if ingested. In most cases, the potential toxicity emphasized by these studies is based on the detection of the presence of these nuisance elements in the geophagic materials. Scientifically, a lot has been done in the light of detection of toxic matter, but more investigations on metabolic studies are still necessary. The variability of clay content with respect to source motivated this review on geophagy and its potential toxicity to human. This review is aimed at bringing out findings that would enable a better understanding of the toxicity potential of geophagy across context and taxa.

Environmental arsenic exposure and its toxicological effect on thyroid function: a systematic review

OBJECTIVES

This study was performed to review epidemiological evidence related to Arsenic (As) effects on the thyroid function by focusing on the serum thyroid hormone concentration.

CONTENT

As, one of the main pollutants, has been recognized as an endocrine-disrupting agent that may affect the function of thyroid as shown by experimental studies.

SUMMARY

This systematic study indicates the association between As exposure and thyroid dysfunction. The studies have shown an association between serum and urine concentration of arsenic and thyroid dysfunction. Most of them reported the association between increase in the serum or urine As levels and decrease in the triiodothyronine (T3) and thyroxine (T4), and also elevation in the thyrotropic hormone (TSH) levels.

OUTLOOK

Our findings related to the effects of As on the function of thyroid in humans are still limited and future studies should be done to address this question.

Are ethnic differences, urinary iodine status, lead and cadmium exposure associated with thyroid autoimmunity and hypothyroid status? A cross-sectional study

OBJECTIVE

We aimed to evaluate the effects of different ethnicities and potential environmental exposure on the prevalence of thyroid autoimmune status and hypothyroid status.

DESIGN

The data were obtained from two cross-sectional studies.

PARTICIPANTS

2105 participants in Shanghai (Han) and 772 participants in Yunnan Honghe Prefecture (Han, Yi, Miao and Hani), aged 18-75 were enrolled.

METHODS

Participants underwent several checkups, including urinary iodine concentration, blood lead (BPb) and blood cadmium (BCd), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), thyroid stimulating hormone (TSH) as well as thyroid ultrasonography (US). Thyroid autoimmune status was defined as: antithyroid antibody positive (ATA+): TPOAb + or TgAb+; and ATA + and US+: TPOAb + or TgAb + together with characteristic US features.

RESULTS

The standardised prevalence of thyroid autoimmune positivity in Yunnan were higher than those in Shanghai (TPOAb+: 13.56% vs 8.27%, p<0.001; TgAb+: 9.28% vs 7.09%, p=0.045; ATA+: 16.96% vs 11.10%, p<0.001; ATA + and US+: 8.96% vs 6.64%, p=0.036). For urinary iodine-to-creatinine ratio (UI/Cr), compared with the level of 100.00-199.99 µg/g, the level of ≥300.00 µg/g had a 1.5-fold risk for ATA + and US+ (OR 1.455, p=0.041). The levels of 200.00-299.99 µg/g and ≥300.00 µg/g were positively associated with hypothyroid status (OR 1.509, p=0.002 and OR 1.338, p=0.043). Compared with the first quartiles, the fourth quartiles of BPb were positively associated with TPOAb+: (OR 1.637, p=0.006), ATA+ (OR 1.435, p=0.025), ATA + and US+ (OR 1.641, p=0.013), hypothyroid status (OR 1.467, p=0.013) and TSH levels (B 0.092, p=0.021). The fourth quartile of BCd was positively associated with the prevalence of ATA+ (OR 1.427, p=0.036).

CONCLUSIONS

Higher levels of UI/Cr, BPb and BCd may be associated with thyroid autoimmunity and hypothyroid status.

Associations of exposure to cadmium, antimony, lead and their mixture with gestational thyroid homeostasis

Maintaining thyroid homeostasis during pregnancy is vital for fetal development. The few studies that have investigated associations between metal exposure and gestational thyroid function have yielded mixed findings. To evaluate the association of exposure to a mixture of toxic metals with thyroid parameters in 824 pregnant women from the Rhea birth cohort in Crete, Greece. Concentrations of three toxic metals [cadmium (Cd), antimony (Sb), lead (Pb)] and iodine were measured in urine using inductively coupled plasma mass spectrometry and thyroid hormones [Thyroid Stimulating Hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3)] were measured in serum in early pregnancy. Associations of individual metals with thyroid parameters were assessed using adjusted regression models, while associations of the metal mixture with thyroid parameters were assessed using Bayesian Kernel Machine Regression (BKMR).Women with high (3rd tertile) concentrations of urinary Cd, Sb and Pb, respectively, had 13.3 % (95%CI: 2.0 %, 23.2 %), 12.5 % (95%CI: 1.8 %, 22.0 %) and 16.0 % (95%CI: 5.7 %, 25.2 %) lower TSH compared to women with low concentrations (2nd and 1st tertile). In addition, women with high urinary Cd had 2.2 % (95%CI: 0.0 %, 4.4 %) higher fT4 and 4.0 % (95%CI: -0.1 %, 8.1 %) higher fT3 levels, and women with high urinary Pb had 4 % (95%CI: 0.2 %, 8.0 %) higher fT3 levels compared to women with low exposure. The negative association of Cd with TSH persisted only when iodine sufficiency was unfavorable. BKMR attested that simultaneous exposure to toxic metals was associated with decreased TSH and increased fT3 and revealed a potential synergistic interaction of Cd and Pb in association with TSH. The present results suggest that exposure to toxic metals even at low levels can alter gestational thyroid homeostasis.

Relation Between Zinc and Thyroid Hormones in Humans: a Systematic Review

The aim of this study was to systematically evaluate the relation between zinc and the thyroid hormones in humans. The search for articles was conducted using the Pubmed, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL), and ScienceDirect databases on October 21 and 22, 2019, by two authors independently. The recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) were followed in the conduct of this review. The Cochrane Collaboration tool was used to assess the risk of bias of the trials included in this review. After the screening of the articles, eight studies that assessed the effects of zinc supplementation on thyroid hormone concentrations and ten studies that assessed the relationship between blood zinc concentrations and thyroid hormones were included in this systematic review. Although cross-sectional and case-control studies have shown a relationship between zinc deficiency and thyroid, the data from this systematic review provides inconclusive evidence with respect to the effects of zinc supplementation on thyroid hormone concentrations due to the divergence of the research found by the authors that only reports findings in patients suffering from some kind of disease, which cannot be generalized to the average human population.

Heavy Metals in the Environment and Thyroid Cancer

In recent decades, the incidence of thyroid cancer has increased more than most other cancers, paralleling the generalized worldwide increase in metal pollution. This review provides an overview of the evidence supporting a possible causative link between the increase in heavy metals in the environment and thyroid cancer. The major novelty is that human thyroid stem/progenitor cells (thyrospheres) chronically exposed to different metals at slightly increased environmentally relevant concentrations show a biphasic increase in proliferation typical of hormesis. The molecular mechanisms include, for all metals investigated, the activation of the extracellular signal-regulated kinase (ERK1/2) pathway. A metal mixture, at the same concentration of individual metals, was more effective. Under the same conditions, mature thyrocytes were unaffected. Preliminary data with tungsten indicate that, after chronic exposure, additional abnormalities may occur and persist in thyrocytes derived from exposed thyrospheres, leading to a progeny population of transformation-prone thyroid cells. In a rat model predisposed to develop thyroid cancer, long-term exposure to low levels of metals accelerated and worsened histological signs of malignancy in the thyroid. These studies provide new insight on metal toxicity and carcinogenicity occurring in thyroid cells at a low stage of differentiation when chronically exposed to metal concentrations that are slightly increased, albeit still in the "normal" range.

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.

Association between mercury exposure and thyroid hormones levels: A meta-analysis

BACKGROUND

The relationship between mercury (Hg) exposure and thyroid hormones (THs) levels in the general population has been inconclusive. We conducted a random effects model meta-analysis to identify the association between Hg exposure and THs levels in the general population.

METHODS

This meta-analysis were performed based on the PECO questions (P = general population; E =1ug/L Hg in blood and urine; C =1ug/L incremental increase on; and O = variation of THs levels). We searched four electronic databases including PubMed, Web of Science, Embase, and Cochrane Library for studies published on or before 20th July 2020. Prospective and cross-sectional studies that evaluated the association between Hg exposure and the levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3), and free thyroxine (FT4) were included. We also assessed aggregate risks for the reliability of the included studies.

RESULTS

Initially, we retrieved 4889 articles. 18 studies met our inclusion criteria after screening and 13 articles were eligible to be included in the meta-analysis. The meta-analysis results suggest that blood Hg may be significantly associated with THs levels. The presence of Hg in blood may significantly increase the levels of TSH (β=0.55; 95%CI: 0.20,0.90; p < 0.001) and FT4 (β=0.47; 95%CI: 0.11,0.82; p < 0.001), with the opposite association in T4 (β=-0.02; 95%CI: 0.02, -0.01; p < 0.001). For the subgroup analysis, blood Hg was positively correlated with TSH levels in children and adolescents (β=0.62; 95%CI: 0.09, 1.15; p < 0.001) and FT4 levels in pregnant women (β=1.00; 95%CI: 0.99, 1.00; p < 0.001) respectively.

CONCLUSIONS

This meta-analysis indicates that exposure to Hg in blood could significantly corrrelate with the levels of TSH, T4, and FT4 in the general population. Therefore, it is crucial to control the use of Hg and strengthen protection of the thyroid.

Association of exposure to polycyclic aromatic hydrocarbons and heavy metals with thyroid hormones in general adult population and potential mechanisms

Air pollution and fuel emissions are the common sources of human exposure to polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Several studies have suggested potential associations between PAHs/heavy metals and thyroid hormones, however, reports have been inconsistent. In this study, we employed a subpopulation of the adults (n = 1254) who participated in the Korean National Environmental Health Survey 2015-2017, and investigated the association of PAHs and major heavy metals with thyroid hormones, and explored the underlying mechanisms of thyroid disruption. Four PAH metabolites and three heavy metals of lead (Pb), mercury (Hg), and cadmium (Cd) were measured either in urine or in total blood. In addition, thyroid hormones (T3 and T4), TSH, thyroxine-binding globulin (TBG), and thyroid autoantibodies were measured, and peripheral deiodinase activity (G_D) and thyroid's secretory capacity (G_T) were calculated. Urinary Hg was negatively associated with total T3 in both males and females, while it was positively associated with total T4 among females only. Urinary Hg was related to decreased G_D and increased G_T in both sexes. In contrast, urinary Cd was positively associated with total T3 and G_D in both male and female populations. Urinary Cd also showed a positive association with thyroid autoantibodies, but only in males. A multi-factor model considering co-exposure to multiple chemicals also resulted in similar associations. Among the measured PAH metabolites, only urinary 1-hydroxypyrene showed a negative association with total T3 in males. However, this association was marginal, and disappeared in a multi-chemical model. The present observations are suggestive that exposures to Hg and Cd might disrupt thyroid hormones, possibly through an alteration of deiodinase activity. Association of PAH exposure with thyroid hormone appears to be insignificant.

Impact of groundwater samples and leachates from Gbagede dumpsite, Amoyo, Kwara State, Nigeria, on testes and prostate of male Wistar rats: A biochemical and histological study

This study evaluated the impact of groundwater samples and leachate from Gbagede dumpsite in Amoyo, Kwara State, on the testicular and prostatic function indices of male rats. The groundwater sample 1 (GW1), groundwater sample 2 (GW2), 2.5%, 5.0%, 7.5% and 10.0% leachate progressively reduced (p < .05) feed intake, groundwater and leachate intake, body weight, weights of testes and prostate, and testes-body weight ratio. The groundwater and leachates significantly (p < .05) reduced the sperm count, motility, normal morphology and testicular volume; activities of semen acid phosphatase (ACP) and α-glucosidase, testicular alkaline phosphatase, ACP, ᵧ-GT, lactate dehydrogenase, glutathione reductase, catalase and superoxide dismutase; testicular total protein, glycogen, total cholesterol, sialic acid, testosterone, reduced glutathione, total antioxidant capacity, zinc, iron and copper; serum LH and FSH; prostatic calcium and phosphate. Treatments increased testicular malondialdehyde, prostate-specific antigen and ACP whilst prostatic pH remained significantly unaltered. Only the leachates reduced prostate-body weight ratio. The treatments induced distortions of seminiferous tubules, destroyed spermatogonic cells and degenerated prostatic acinus. The study concluded that metals in the groundwater and leachate samples have adversely impacted on the testes and prostates of the male rats via endocrine disruption and oxidative stress, with attendant implications on reproductive capacity.

Assessment of Thyroid Function and Oxidative Stress State in Foundry Workers Exposed to Lead

BACKGROUND

Exposure to lead (Pb) has been associated with endocrine, hematological, gastrointestinal, renal and neurological problems in humans. However, effects on the thyroid gland are controversial.

OBJECTIVES

The aim of the present study was to assess thyroid function in foundry workers occupationally exposed to Pb and the mechanism of oxidative-antioxidant imbalance.

METHODS

Thyroid function parameters and markers of oxidative stress were examined in 59 adult males who had been occupationally exposed to Pb. The results were then compared to those of 28 male subjects who had no history of Pb exposure or thyroid abnormalities and served as a control group.

RESULTS

Mean blood lead levels (16.5±1.74 μg/dl) were significantly higher among the exposed workers compared to those of the control group (12.8±1.16 μg/dl, (p <0.001)). The exposed group had significantly increased free triiodothyronine (FT3), free thyroxine (FT4) and significantly decreased thyroid stimulating hormone (TSH) (1.77±0.44 μIU/ml), whereas the control group had a TSH level of 2.61±0.94 μIU/ml (p< 0.0001). A state of oxidative stress was indicated by the significant increase in mean levels of malondialdehyde (MDA) and significant decrease in glutathione (GSH) (p < 0.0001). There was a significant positive correlation (r=0.358, p <0.05) between blood lead levels (BLL) and duration of employment, while BLL showed a significant negative correlation with TSH (r =-0.486, p <0.001), and GSH (r =-0.336, p <0.05). Of the occupationally exposed workers, 32.76% had elevated thyroid hormones. The results showed a significant positive relationship between GSH and TSH (β coefficient=0.274, p < 0.05), MDA with FT3 (β coefficient=0.355, p < 0.05) and FT4 (β coefficient = 0.491, p < 0.0001) among exposed workers.

CONCLUSIONS

Workers exposed to Pb dust proved to be at risk for hyperthyroidism, which was found to have a significant role in oxidative-antioxidant imbalance present among workers with increasing duration of exposure.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

This study was approved by the Ethical Committee of the National Research Centre in Egypt (NRC) under the registration number 15225.

COMPETING INTERESTS

The authors declare no competing financial interests.

Sex differences in the effects of lead exposure on growth and development in young children

The adverse effects of lead exposure on children's health have been widely investigated. Physical growth is a central indicator of health in early childhood. However, studies on the associations between lead exposure and the physical growth of young children are still equivocal. This study aimed to investigate the effects of lead exposure on young children's growth. A cross-sectional survey was conducted, and a total of 1678 young children were recruited. Blood lead levels were determined by graphite furnace atomic absorption spectrophotometry and anthropometric measurements were obtained by nurses. The weight-for-age Z-score (WAZ), height-for-age Z-score (HAZ) and BMI for-age Z-score (BMIZ) of the children were calculated according to World Health Organization standards. Multivariable linear models after adjustment for potential confounders were used to evaluate the associations between lead exposure and childhood anthropometric characteristics. Meanwhile, the sex differences in these associations were also examined. The median blood lead levels in total subjects, in boys and in girls were 46.44, 49.00 and 43.27 μg/L, respectively. After adjusting for confounders, a significantly negative association of blood lead levels with WAZ and HAZ was observed. After stratification by sex, the blood lead levels in children were negatively associated with WAZ and HAZ in boys but not in girls. Meanwhile, we further provide evidence that blood lead levels below 50 μg/L may also have adverse effects on young children's HAZ. Our findings suggest that lead exposure may have sex-specific effects on physical growth in young children and that blood lead level in a low levels may also have adverse effects on children's physical growth and development.

Exploring the role of copper and selenium in the maintenance of normal thyroid function among healthy Koreans

BACKGROUND

Selenium and iodine are trace elements well known to have important roles in the synthesis and metabolism of thyroid hormones. However, the effects of other trace elements on thyroid hormones are still inconclusive. We investigated the association between several trace elements and thyroid hormones.

METHODS

The data of 448 subjects who were measured for both, trace elements and TSH/free T4, at the Heath Checkup Center were retrospectively reviewed. The presence of thyroiditis (from thyroid echogenicity) and thyroid nodules were reviewed in the subjects who underwent thyroid ultrasonography.

RESULTS

Blood concentrations of manganese, copper, selenium, and molybdenum were associated with TSH or free T4. After adjusting for age, sex, BMI, smoking, and alcohol consumption, blood copper levels were positively associated with free T4 in both sexes and selenium levels were positively associated with free T4 in women. There was no association between trace elements and thyroiditis. Blood copper concentration had a weak non-linear association with the presence of thyroid nodules.

CONCLUSIONS

This study demonstrated that blood concentrations of copper and selenium were significantly associated with free T4 in healthy Korean subjects with sufficient iodine intake suggesting their role in maintaining normal thyroid function.

Association of urinary metal concentrations with blood pressure and serum hormones in Spanish male adolescents

OBJECTIVE

To examine the association of urinary concentrations of arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), manganese (Mn), and chromium (Cr) with blood pressure (BP) and serum hormone levels in male adolescents.

METHODS

Participants were selected from the INMA (Environment and Childhood)-Granada cohort at their follow-up visit when aged 15-17 years. Metal concentrations were measured in urine samples using inductively coupled plasma mass spectrometry. Outcomes were BP measurements (systolic, diastolic, and pulse pressure) recorded during the visit and concurrent serum levels of thyroid hormones, sex hormones, and adrenal hormones. Associations were assessed by regression analysis in a sub-sample of 133 boys with available data on urinary metals, outcomes, and relevant covariates.

RESULTS

Models simultaneously adjusted for all metals and other potential confounders showed that urinary As and Cd were both associated with slight elevations in systolic BP (0.70 mmHg, 95%CI = 0.11; 1.29 and 1.47, 95%CI = 0.30; 2.63, respectively, per each 50% increase in metal concentrations), and urinary As was also associated with an increased risk of elevated systolic BP (≥120 mmHg) (OR = 1.28, 95%CI = 1.04; 1.56). The presence of detectable levels of 4 and 5 versus 2-3 non-essential metals (As, Cd, Hg, Ni, Pb) per boy was associated with elevations in systolic BP of 5.84 mmHg (95%CI = 0.40; 11.3) and 7.01 mmHg (95%CI = 1.01; 13.0), respectively (p-trend = 0.05). Significant associations were also found between Hg and increased testosterone and luteinizing hormone (LH) and decreased thyroid-stimulating hormone (TSH); between the combination of As and Hg and increased LH and insulin-like growth factor 1; between Cr and decreased TSH; and between Cd and increased adrenocorticotropic hormone.

CONCLUSIONS

These findings suggest that combined exposure to toxic metals, especially As and Cd, may contribute to BP elevation in male adolescents and that exposure to Hg, As, Cd, and Cr may affect their hormone levels.

Thyroid dysfunction: how concentration of toxic and essential elements contribute to risk of hypothyroidism, hyperthyroidism, and thyroid cancer

This study was conducted to evaluate the levels of trace metals Fe, Cr, Co, Cd, Cu, Ni, Hg, Zn, and Pb in healthy individuals and patients with thyroid disease (hyperthyroidism, hypothyroidism, and cancerous). The serum levels of 110 participants living in Birjand City, east of Iran, were collected and analyzed using ICP-MS (Agilent 7900). Results showed that the concentration levels of Cr, Co, Zn, Cd, and Pb were significantly higher at case-patients (p < 0.05), but the levels of Fe, Ni, and Hg were similar between healthy and patient subjects (p > 0.05). In patients with high or low thyroid activity, strong mutual correlations between Cr, Ni, and Fe were noticeable (p < 0.05). In hypothyroid patients, no significant correlation between Zn and Hg, Co, and Cd was found, but Zn was moderately and positively correlated with other trace metals. The moderate negative correlations between Cd-Cr (p = - 0.46) and Cd-Fe (p = - 0.43) were also observed. Logistic regression analysis showed that the effect of Cr, Co, Pb, Cu, Zn, and Cd was significant in developing hyperthyroidism and hypothyroidism; whereas, in patients with thyroid cancer, the effect of Cr, Cd, and Pb was found to be significant. In conclusion, our findings suggest that toxic metals such as Pb, Cd, and Cr can increase the risk of developing hypothyroidism and thyroid cancer, but more research is needed to evaluate the potential toxicity mechanisms of Pb, Cd, and Cr.

Thyroid hormones and neurobehavioral functions among adolescents chronically exposed to groundwater with geogenic arsenic in Bangladesh

Groundwater, the major source of drinking water in Bengal Delta Plain, is contaminated with geogenic arsenic (As) enrichment affecting millions of people. Children exposed to tubewell water containing As may be associated with thyroid dysfunction, which in turn may impact neurodevelopmental outcomes. However, data to support such relationship is sparse. The purpose of this study was to examine if chronic water As (WAs) from Holocene alluvial aquifers in this region was associated with serum thyroid hormone (TH) and if TH biomarkers were related to neurobehavioral (NB) performance in a group of adolescents. A sample of 32 healthy adolescents were randomly drawn from a child cohort in the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh. Half of these participants were consistently exposed to low WAs (<10 μg/L) and the remaining half had high WAs exposure (≥10 μg/L) since birth. Measurements included serum total triiodothyronine (tT₃), free thyroxine (fT₄), thyrotropin (TSH) and thyroperoxidase antibodies (TPOAb); concurrent WAs and urinary arsenic (UAs); and adolescents' NB performance. WAs and UAs were positively and significantly correlated with TPOAb but were not correlated with TSH, tT₃ and fT₄. After accounting for covariates, both WAs and UAs demonstrated positive but non-significant relationships with TSH and TPOAb and negative but non-significant relationships with tT₃ and fT₄. TPOAb was significantly associated with reduced NB performance indicated by positive associations with latencies in simple reaction time (b = 82.58; p < 0.001) and symbol digit (b = 276.85; p = 0.005) tests. TSH was significantly and negatively associated with match-to-sample correct count (b = -0.95; p = 0.05). Overall, we did not observe significant associations between arsenic exposure and TH biomarkers although the relationships were in the expected directions. We observed TH biomarkers to be related to reduced NB performance as hypothesized. Our study indicated a possible mechanism of As-induced neurotoxicity, which requires further investigations for confirmatory findings.

The relationships between blood lead levels and serum thyroid stimulating hormone and total thyroxine in the third National Health and Nutrition Examination Survey

Regression analysis was used to estimate and test for relationships between the blood lead concentration and the concentrations of serum thyroid stimulating hormone and serum total thyroxine in adults, 20 years and older, participating in the third National Health and Nutrition Examination Survey. No relationship was found between the blood lead level and the concentration of serum thyroid stimulating hormone. The serum total thyroxine concentration decreased as the blood lead level increased in women, but not in men. The lowest concentration of blood lead at which a relationship could be detected was 2.1 μg/dL and 3.9 μg/dL for the non-pregnant and pregnant women, respectively. Hypothetical mechanisms of the action of lead are discussed.

Associations of blood metal exposure with thyroid hormones in Chinese pregnant women: A cross-sectional study

BACKGROUND

Few epidemiological studies have investigated associations of exposure to multiple metals with thyroid hormone homeostasis, especially for the pregnant women.

METHODS

Among all the 1644 participants enrolled in Hangzhou Birth Cohort Study (HBCS) at baseline, a total of 915 pregnant women with complete data of interest were analyzed. Eleven metals were measured in blood samples collected around 25 weeks gestation. Serum levels of thyroid hormones including free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), total thyroxine (TT4) and thyroid-stimulating hormone (TSH) were abstracted from the medical records. Relationships between tertiles of metal levels (setting the lowest tertile as the reference) and percent changes in thyroid hormones were estimated by multivariable adjusted linear regression models.

RESULTS

Five metals [arsenic (As), selenium (Se), manganese (Mn), nickel (Ni), antimony (Sb)] were significantly linked to decreased levels of one or more thyroid hormones based on trend tests in the single-metal models. Percent changes [95% confidence intervals (CIs)] in thyroid hormones for the third tertiles of metals remained significant between FT3 and As [-3.53% (-5.48%, -1.54%)]; and between TT3 and As [-4.19% (-7.00%, -1.31%)]; and between FT4 and Mn [-2.05% (-3.49%, -0.58%)], Sb [-1.99% (-3.44%, -0.52%)] in the multiple-metal models.

CONCLUSIONS

Thyroid hormone concentrations were reversely related to the levels of blood metals of As, Mn and Sb among Chinese pregnant women. Additional prospective studies are warranted to confirm the causality. Paper capsule: Exposure to multiple metals was reversely associated with one or more thyroid hormones in the Chinese pregnant women.

Dietary determinants of urinary molybdenum levels in Mexican women: a pilot study

OBJECTIVE

This study determined the main dietary sources of urinary molybdenum (Mo) concentrations in a sample of 124 pregnant women in Mexico.

MATERIALS AND METHODS

Dietary data was collected during pregnancy, through a semi-qualitative food frequency questionnaire, with information of 84 foods. Urine Mo levels were determined by atomic absorption spectrometry, for at least two trimesters of pregnancy. The associations with Mo levels were estimated by generalized mixed effect regression models.

RESULTS

Between 5.8 to 12.7% of the samples were above the 95th percentile of urinary Mo distribution reported by National Health and Nutrition Examination Survey (NHANES) 2009-2010 for women (151 μg/L and 148 μg/g creatinine). After bootstrap resampling was conducted, women with high-consumption of hot peppers (β=1.34μg/g; 95% CI: 1.00-1.80; p= 0.05) had marginally higher urinary Mo concentration levels, creatinine adjusted, compared to women with low-consumption.

CONCLUSION.

Hot chili pepper consumption may contribute to body burden Mo levels in this population.

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland.

Concentration of Thyrotropic Hormone in Persons Occupationally Exposed to Lead, Cadmium and Arsenic

Thyroid hormones are essential for body homeostasis. The scientific literature contains restricted proofs for effects of environmental chemical factors on thyroid function. The present study aimed at evaluating the relationship between toxicological parameters and concentration of thyrotropic hormone in persons occupationally exposed to lead, cadmium and arsenic. The studies were conducted on 102 consecutive workers occupationally exposed to lead, cadmium and arsenic (mean age 45.08 ± 9.87 years). The estimated parameters characterizing occupational exposure to metals included blood cadmium concentration (Cd-B), blood lead concentration (Pb-B), blood zinc protoporphyrin concentration (ZnPP) and urine arsenic concentration (As-U). Thyroid function was evaluated using the parameter employed in screening studies, the blood thyrotropic hormone concentration (TSH). No differences were disclosed in mean values of toxicological parameters between the subgroup of persons occupationally exposed to lead, cadmium and arsenic with TSH in and out of the accepted normal values. Logistic regression demonstrated that higher blood total bilirubin concentrations (ORu = 4.101; p = 0.025) and higher Cd-B (ORu = 1.532; p = 0.027) represented independent risk factors of abnormal values of TSH in this group. In conclusion, in the group of workers exposed to lead, cadmium and arsenic, higher blood cadmium concentration seems to augment the risk of abnormal hormonal thyroid function.

Copper influence on bank vole's (Myodes glareolus) sexual behavior

The impact of human activity on the environment has led to a steady increase of the amounts of copper in the ecosystems. This element accumulates in plants and water, potentially exposing rodents to its harmful effects. In industrial districts, a decrease in the density of small rodent populations has been observed. This decline may be caused by many factors, including mortality, decreased fertility, or impaired sexual behavior. The decline in the reproductive abilities of small rodents after copper exposure was demonstrated in our previous work (Miska-Schramm A, Kruczek M, Kapusta J, Ecotoxicology 23:1546-1554, 2014). The aim of the presented research was to determine how copper administered at concentrations similar to those recorded in industrial districts (Cu I-150 mg/kg, Cu II-600 mg/kg, C-control) affects the sexual behavior of small rodents. The model species was the bank vole (Myodes glareolus). The behavior and vocalizations of male-female pairs were recorded during open-field tests: ♂C vs. ♀C; ♂Cu I vs. ♀C; ♂Cu II vs. ♀C while in preference tests, female behavior was assessed in the following combinations: ♀C vs. ♂C & ♂Cu I; ♀C vs. ♂C & ♂Cu II. In the presented work, we show that copper decreased the males' sexual attractiveness. Females showed suppressed preference towards males treated with 600 mg/kg copper. The number of sniffs and a number of approaches towards Cu II males was significantly lower than towards control individuals. Also, in preference test with 150 mg/kg treated animals, total activity was lower towards copper treated animals. At the same time, copper did not influence intra-sexual interactions.

Effects of Combined Exposure to Chronic High-Fat Diet and Arsenic on Thyroid Function and Lipid Profile in Male Mouse

The thyroid is one of the major endocrine glands that contribute to body and fat metabolism. The present study evaluated the effects of combined exposure to chronic high-fat diet (HFD) and arsenic on thyroid function and lipid profile. In this experimental study, 72 male Naval Medical Research Institute mice were divided into six groups and fed HFD or low-fat diet (LFD) while being exposed to 25 or 50 ppm of arsenic in drinking water for 20 weeks. After 24 h of the last experimental day, blood samples were collected for hormonal and biochemical measurements. The data indicated that exposure to HFD alone increased the levels of triiodothyronine (T3), thyroid-stimulating hormone (TSH), leptin, lipid profile, reactive oxygen species (ROS), and malondialdehyde (MDA) and decreased the levels of high-density lipoprotein, albumin, adiponectin, and glutathione sulfhydryl reductase (GSH), whereas exposure to arsenic alone decreased the levels of T3 and GSH and increased the levels of TSH, leptin, ROS, MDA, and T4/T3 ratio compared to those in the control LFD group. Furthermore, concomitant administration of HFD and arsenic decreased the lipid profile and levels of T4, albumin, total protein, T3, and GSH and increased the levels of TSH, adiponectin, leptin, ROS, MDA, and T4/T3 ratio compared to those in the control LFD or HFD group. In conclusion, combined exposure to HFD and arsenic induced hypothyroidism via reduction of thyroid hormones and enhancement of plasma TSH and T3 uptake levels concomitant with hypolipidemia, hyperleptinemia, hyperadiponectinemia, induction of oxidative stress, and reduction of GSH levels.

Heavy metals in the volcanic environment and thyroid cancer

In the last two decades thyroid cancer incidence has increased worldwide more than any other cancer. Overdiagnosis of subclinical microcarcinomas has certainly contributed to this increase but many evidences indicate that a true increase, possibly due to environmental factors, has also occurred. Thyroid cancer incidence is markedly increased in volcanic areas. Thus, the volcanic environment is a good model to investigate the possible factors favoring thyroid cancer. In the volcanic area of Mt. Etna in Sicily, as well as in other volcanic areas, a non-anthropogenic pollution with heavy metals has been documented, a consequence of gas, ash and lava emission. Soil, water and atmosphere contamination, via the food chain, biocontaminate the residents as documented by high levels in the urines and the scalp hair compared to individuals living in adjacent non-volcanic areas. Trace amounts of metals are essential nutrients but, at higher concentrations, can be toxic for living cells. Metals can behave both as endocrine disruptors, perturbing the hormonal system, and as carcinogens, promoting malignant transformation. Similarly to other carcinogens, the transforming effect of heavy metals is higher in developing organisms as the fetus (contaminated via the mother) and individuals in early childhood. In the last decades environment metal pollution has greatly increased in industrialized countries. Although still within the "normal" limits for each single metal the hormesis effect (heavy metal activity at very low concentration because of biphasic, non linear cell response) and the possible potentiation effect resulting from the mixture of different metals acting synergistically can explain cell damage at very low concentrations. The effect of metals on the human thyroid is poorly studied: for some heavy metals no data are available. The scarce studies that have been performed mainly focus on metal effect as thyroid endocrine disruptors. The metal concentration in tissues has been rarely measured in the thyroid. Heavy metal accumulation and metabolism in the thyroid or the carcinogenic activity of different doses and different speciation of metals has not been investigated. These studies are now warranted to better understand thyroid biology and heavy metal role in human thyroid carcinogenesis.

Arsenic in seafood is associated with increased thyroid-stimulating hormone (TSH) in healthy volunteers - A randomized controlled trial

BACKGROUND

Exposure to exogenous elements like arsenic (As) may influence thyroid enzymes, thyroid-stimulating hormone (TSH), and the two principal thyroid hormones, free thyroxine (FT4) and free triiodothyronine (FT3), but little is known about how this is related to organic arsenicals, the main form in seafood.

AIM

To investigate whether a high intake of dietary arsenic from seafood can impact thyroid function and thyroid hormones by examining possible associations with changes in TSH, FT4, FT3 and the FT4:FT3-ratio in plasma.

METHODS

Thirty-eight healthy subjects were randomized into four groups. During a 14-day semi-controlled dietary study, the subjects ingested daily portions of either 150g cod, salmon, blue mussels or potato (control). Plasma concentrations of total As, FT3, FT4, TSH and selenium (Se), and urinary concentrations of iodine were monitored.

RESULTS

Plasma concentrations of TSH increased significantly in all seafood groups. The change in plasma As, with different coefficients for each seafood group, was the dominant factor in the optimal multiple regression model for change in TSH (R²=0.47). Plasma Se and iodine were negative and positive factors, respectively. There were also indications of changes in FT4, FT3 and the FT4:FT3 ratio consistent with a net inhibiting effect of As on FT4 to FT3 conversion.

CONCLUSION

Ingestion of seafood rich in various organic As species was strongly associated with an increase of the TSH concentrations in plasma. Change in TSH was positively associated with total plasma As, but varied with the type of seafood ingested. These findings indicate that organic dietary As, apparently depending on chemical form, may influence thyroid hormones and function.

The influence of chronic and subacute exposure to lead on the levels of prolactin, leptin, osteopontin, and follistatin in humans

This study was designed to determine the levels of prolactin, leptin, osteopontin, and follistatin in workers chronically and subacutely exposed to lead compounds. The examined population consisted of three groups. The first group was composed of 56 male workers who were chronically exposed to lead for 13.38 ± 10.38 years. The second group served as a control group and consisted of 24 male administrative workers, while the third group included 32 male workers exposed to lead for 40 ± 3 days. The levels of leptin, osteopontin, and prolactin were significantly lower in the group of workers chronically exposed to lead than in the control group by 42%, 26%, and 41%, respectively. The levels of follistatin did not differ between those groups. The levels of all measured hormones did not change after a short-term exposure to lead compared to baseline. Chronic lead exposure is associated with significantly decreased level of prolactin, leptin, and osteopontin. Lead-induced changes in the levels of these hormones may disturb many functions of the human body, including the immune response, metabolism, reproduction, and bone turnover.

A meta-analysis of studies investigating the effects of occupational lead exposure on thyroid hormones

INTRODUCTION

Investigations of the effects of occupational exposure to lead on the concentrations of thyroid hormones in the blood have not produced consistent results. A meta-analysis was performed to assess the effect of occupational exposure to lead on thyroid hormone concentrations using the results from published studies.

METHODS

Group means from studies of the thyroid function of persons occupationally exposed to lead were used in a meta-analysis. Differences between the control and exposed groups, and the slopes between thyroid hormone concentrations and log10 blood lead concentrations or duration of exposure to lead were estimated using mixed models. The hormones analyzed were thyroid stimulating hormone, total and free thyroxine, and total and free triiodothyronine.

RESULTS

No differences in mean thyroid hormone concentrations were found between the exposed and control groups. No relationships were found between blood lead or the duration of exposure to lead and thyroid hormone concentrations.

CONCLUSION

The results of the analysis do not provide evidence for an effect of occupational lead exposure on thyroid function in men. Am. J. Ind. Med. 59:583-590, 2016. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

In Vivo and In Vitro Arsenic Exposition Induces Oxidative Stress in Anterior Pituitary Gland

Inorganic arsenic (iAs) is at the top of toxic metalloids. Inorganic arsenic-contaminated water consumption is one of the greatest environmental health threats worldwide. Human iAs exposure has been associated with cancers of several organs, neurological disorders, and reproductive problems. Nevertheless, there are no reports describing how iAs affects the anterior pituitary gland. The aim of this study was to investigate the mechanisms involved in iAs-mediated anterior pituitary toxicity both in vivo and in vitro. We showed that iAs administration (from 5 to 100 ppm) to male rats through drinking water increased messenger RNA expression of several oxidative stress-responsive genes in the anterior pituitary gland. Serum prolactin levels diminished, whereas luteinizing hormone (LH) levels were only affected at the higher dose tested. In anterior pituitary cells in culture, 25 µmol/L iAs significantly decreased prolactin release in a time-dependent fashion, whereas LH levels remained unaltered. Cell viability was significantly reduced mainly by apoptosis evidenced by morphological and phosphatidylserine externalization studies. This process is characterized by early depolarization of mitochondrial membrane potential and increased levels of reactive oxygen species. Expression of some key oxidative stress-responsive genes, such as heme oxygenase-1 and metallothionein-1, was also stimulated by iAs exposure. The antioxidant N-acetyl cysteine prevented iAs-induced effects on the expression of oxidative stress markers, prolactin release, and apoptosis. In summary, the present work demonstrates for the first time that iAs reduces prolactin release both in vivo and in vitro and induces apoptosis in anterior pituitary cells, possibly resulting from imbalanced cellular redox status.

Correlation Analysis of Exercise-Induced Changes in Plasma Trace Element and Hormone Levels During Incremental Exercise in Well-Trained Athletes

This study analyzes the relationship between hormonal changes induced by exercise and variations in trace elements associated with oxidative stress during incremental exercise. Nineteen well-trained endurance athletes performed a cycle ergometer test: after a warm-up of 10 min at 2.0 W kg(-1), workload increased by 0.5 W kg(-1) every 10 min until exhaustion. The analysis was controlled for prior diet and activity patterns, levels of exercise training, and time of day (circadian rhythms). Whole blood lactate concentration and plasma concentrations of ions (Zn, Se, Mn, and Co), insulin, glucagon, aldosterone, thyroid stimulating hormone (TSH), calcitonin, and parathyroid hormone (PTH) were measured at rest; at the end of each stage; and 3, 5, and 7 min post-exercise. The statistical analysis involved paired non-parametric tests and correlation coefficients. No significant differences were found in Mn or Co levels as a function of exercise intensity. Zn and Se levels at the end of the exercise protocol and over the recovery time were significantly different to baseline. Further, Zn levels were significantly correlated with aldosterone, calcitonin, and PTH levels, while Se levels were associated with aldosterone, calcitonin, and TSH levels. Our results indicate several different patterns of association between acute changes in hormone concentrations and variations in trace element concentrations related to oxidative stress during submaximal exercise.

Endocrine activities and cellular stress responses in the marsh frog Pelophylax ridibundus exposed to cobalt, zinc and their organic nanocomplexes

Metal-containing materials are extensively used in industry, personal care products and medicine, and their release in the environment causes concern for the potential impacts on aquatic organisms. We assessed endocrine disrupting potential of N-vinyl-2-pyrrolidone-based nanoparticles (Me-PSs) containing cobalt (Co(2+)) or zinc (Zn(2+)), using the marsh frog Pelophylax ridibundus as a model. Adult males were exposed for 14 days to waterborne Co(2+) (50μg/L), Zn(2+) (100μg/L) or corresponding concentrations of Co-PS, Zn-PS, or parental polymeric compound (PS). The indices of thyroid activity, vitellogenesis, cytochrome P450-dependent monooxygenases activity (EROD) and cytotoxicity markers were evaluated. Exposure to Co(2+) led to the elevation of serum thyrotropin (TSH) and hepatic deiodinase activities accompanied by the up-regulation of EROD activity. In contrast, the action of the polymer-containing substances (Co-PS, Zn-PS and PS) as well as free Zn(2+) caused a prominent decrease of EROD activity and a decrease in serum cortisol and TSH concentrations. Exposures to Zn(2+), Zn-PS and PS upregulated vitellogenesis in males. All exposures except Co(2+) caused neurotoxicity as indicated by the depletion of cholinesterase. These results demonstrate toxicity of Co- and Zn-containing Me-PSs and their parental compounds (Zn(2+) and PS) in frogs and indicate distinct mechanisms of Co(2+) action. Broad disruption of the hormonal pathways and reduced capacity for organic xenobiotic detoxification may have deleterious impacts on amphibian populations from habitats exposed to metallorganic pollution.

Evaluation of calcium and lead interaction, in addition to their impact on thyroid functions in hyper and hypothyroid patients

There is compelling evidence in support of interaction between calcium (Ca) and lead (Pb) in thyroid disorders. The aim of present study was to compare the level of Ca and Pb with thyroid hormones such as thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxin (FT4) in serum samples of hyperthyroid (HPRT) and hypothyroid (HPOT) patients of both genders. For comparative purpose, age-matched (25-50 years) subjects having no thyroid disorders were selected as referents/controls. The serum samples were acid-digested prior to analysis by atomic absorption spectrometry. The validity and accuracy of the methodology were checked by certified reference materials. The resulted data indicates that the mean values of Ca in serum samples of HPRT patients were significantly higher than those of referent subjects (p < 0.01), while reverse pattern was observed in the case of HPOT patients. The level of Pb was higher in the serum samples of both types of thyroid patients, but difference was significant in case of HPOT patients as compare to referent subjects (p < 0.01). A negative correlation was observed between serum Ca levels and TSH of HPRT patients (-r = 0.37-0.39, p < 0.01), while FT3 and FT4 have positive correlation (r = 0.49-0.52 and r = 0.46-0.47), p values <0.01. The Pb in serum had positive correlation with TSH (r = 0.48-0.51, p < 0.005), while negative correlation was observed for FT3 and FT4 (-r = 0.55-0.56, 0.5-0.54, p < 0.05) in HPRT patients. On the other hand, a reverse pattern was observed, for correlation of Ca and Pb with thyroid functions in HPOT patients.

Lead, Arsenic, and Manganese Metal Mixture Exposures: Focus on Biomarkers of Effect

The increasing exposure of human populations to excessive levels of metals continues to represent a matter of public health concern. Several biomarkers have been studied and proposed for the detection of adverse health effects induced by lead (Pb), arsenic (As), and manganese (Mn); however, these studies have relied on exposures to each single metal, which fails to replicate real-life exposure scenarios. These three metals are commonly detected in different environmental, occupational, and food contexts and they share common neurotoxic effects, which are progressive and once clinically apparent may be irreversible. Thus, chronic exposure to low levels of a mixture of these metals may represent an additive risk of toxicity. Building upon their shared mechanisms of toxicity, such as oxidative stress, interference with neurotransmitters, and effects on the hematopoietic system, we address putative biomarkers, which may assist in assessing the onset of neurological diseases associated with exposure to this metal mixture.

Association of hypothyroidism with low-level arsenic exposure in rural West Texas

It has been reported recently that a higher airborne arsenic level was correlated with higher urinary arsenic concentration and lower serum thyroxin level among urban policemen and rural highway workmen in Italy. The current study was to determine whether exposure to low-level arsenic groundwater (2-22µg/L) is associated with hypothyroidism among 723 participants (118 male and 267 female Hispanics; 108 male and 230 female non-Hispanic whites, NHW) living in rural West Texas counties. Arsenic and iodine levels in their groundwater used for drinking and or cooking were estimated by the inverse distance weighted (IDW) interpolation technique. Groundwater arsenic was ≥8µg/L in 36% of the subjects' wells while iodine concentration was <1µg/L in 91% of their wells. Logistic regression analysis showed that arsenic in groundwater ≥8µg/L and cumulative arsenic exposure (groundwater arsenic concentration multiplied by the number of years living in the current address) but not groundwater iodine concentration were significant predictors for hypothyroidism among Hispanics (p<0.05) but not NHW after adjusting for covariates such as age, gender, annual household income and health insurance coverage. The ethnic difference may be due to a marginally higher percentage of Hispanics (p=0.0622) who lived in areas with groundwater arsenic ≥8µg/L compared with NHW. The prevalence of hypothyroidism was significantly higher in Hispanics or NHW of this rural cohort than the national prevalence. Measures should be taken to reduce arsenic in drinking water in order to prevent hypothyroidism in rural areas.

Interacting effects of selected trace and toxic metals on thyroid function

Interacting effects of blood levels of manganese (Mn), selenium, cadmium (Cd), lead (Pb), and mercury, and serum levels of iron (Fe), zinc (Zn), and copper (Cu) on thyroid function in general US population were evaluated. Data from the National Health and Nutrition Examination Survey for 2011-2012 were used for this evaluation. The variables used to evaluate thyroid function were as follows: thyroid-stimulating hormone, free and total triiodothyronine (FT3, TT3), free and total thyroxine (FT4, TT4), and thyroglobulin (Tg). Levels of FT4 were positively associated with the levels of copper and negatively associated with the levels of Fe for males only. Elevated levels of Mn and Fe were associated with increased levels of FT3 for both males and females. TT4 had a positive association with the levels of Cu and a negative association with the levels of Fe for both males and females.

Inhibition of key markers linked with spermatogenesis and cellular ATP by subchronic exposure to leachate in a rat model

Few or no studies have measured the toxic effects of subchronic exposure to leachate using key markers linked with spermatogenesis and cellular adenosine triphosphate (ATP) in an experimental rat model. This study was undertaken to evaluate the toxic effects of leachate obtained from the Elewi Odo municipal battery-recycling site (EOMABRL) on male reproductive function using testicular hormones and biomarker of cellular ATP. EOMABRL was administered at 0, 20, 40, 60, 80, and 100% concentrations to adult male rats for 60 days. After exposure, serum was collected for hormonal biochemistry assays, and testes were collected to determine the activity of xanthine oxidase (XO) and lactate dehydrogenase (LDH). Exposure of animals to EOMABRL resulted in a 519.7, 285.7, 569.1, 606.1, and 1,793.2% increase in XO activity with a sequential decrease in LDH activity (marker of cellular ATP) by 44.1, 55.9, 61.4, 69.3, and 89.7%, respectively, compared with the control. Furthermore, EOMABRL caused a significant inhibitory effect on serum luteinizing hormone, follicle-stimulating hormone, and testosterone levels. We conclude that some possible mechanisms by which EOMABRL elicits toxicity in male rat testes could be through inhibition of LDH activity and depletion of serum hormone levels.

Effects of the presence of indium on the mammary gland ultrastructure, body weight, food intake and plasmatic prolactin concentration

Several studies have demonstrated the toxic effect of indium. This element induces impairments in many organs such as spleen, lungs and testicles after its systemic administration. Teratogenic and embryotoxic effects of this element have also been established. In the present study, we attempt to investigate the histological and the ultrastructural consequences of the presence of this element in mammary gland tissue using conventional transmission electron microscopy and to evaluate the incidences of its presence on the food intake, body weight and prolactin plasmatic concentration of lactating female rats. Our study showed that this element induced a significant decrease in food intake and body weight, and caused some cellular damage in the glandular epithelial cell such as cytoplasmic vacuolization and expansion of the ergastoplasm. The ultrastructural observations also showed many electron-dense surcharges in the lysosomes of the glandular epithelial cells. The electron probe microanalysis showed that these deposits are composed of indium and phosphorus. The lysosomes, known for their protective role of sequestrating foreign elements to avoid their diffusion in the blood, failed to stop the toxic effect of indium.

Thyroid function and serum copper, selenium, and zinc in general U.S. population

Association of the levels of serum selenium (Se), zinc (Zn), and copper (Cu) with thyroid function was assessed by analyzing data from National Health and Nutrition Examination Survey for the cycle 2011-2012. Thyroid function variables analyzed were as follows: thyroid-stimulating hormone (TSH), free and total triiodothyronine (FT3, TT3), free and total thyroxine (FT4, TT4), and thyroglobulin (TGN). Regression models with log-transformed values of thyroid hormones as independent variables and age, race/ethnicity, smoking and iodine sufficiency status, respondents' education, and levels of Se, Zn, and Cu as dependent variables were fitted. For males, levels of Zn were associated with decreased levels of FT4 and TT4, and levels of Cu were associated with increased levels of FT4 and TT4. For females, levels of Cu were associated with increased levels of TT3 and TT4. Smoking was found to be associated with lower levels of TSH and higher levels of TGN in males. Smoking was found to be associated with lower levels of TT4 in females. Males had about 5-10% higher levels of both Se and Zn, but as much as 20% lower levels of Cu than females. Smoking was associated with lower levels of Zn, but higher levels of Cu in males.

Low blood lead concentrations and thyroid function of American adults

Lead is often present in our environment, but its effect on thyroid function is still unclear. In this study, multiple linear regressions were performed between log-transformed blood lead levels and thyroid function parameters of 4652 adults from the 2007-2008 National Health and Nutrition Examination Survey. The models were adjusted for age, gender, race/ethnicity, smoking, alcohol consumption, body mass index, physical activity, iodine intake, medications, and bone mineral density. Blood lead concentrations (mean: 1.52 ± 1.20 μg/dL [range 0.18-33.12]) were inversely associated with total thyroxine (regression coefficients [β]: -0.22 [95% CI: -0.34, -0.09] in the general population, but were not correlated with thyroid stimulating hormone, total or free triiodothyronine, nor free thyroxine. Blood lead may have no effect on the thyroid function; however, it could be associated with decreased concentrations in thyroid-binding proteins.

Thyroid hormones in relation to lead, mercury, and cadmium exposure in the National Health and Nutrition Examination Survey, 2007-2008

BACKGROUND

Heavy metals, such as lead (Pb), mercury (Hg), and cadmium (Cd), are known toxicants, but their associations with the thyroid axis have not been well quantified at U.S. background levels.

OBJECTIVES

We investigated the relationships between thyroid hormones (total and free thyroxine [TT4 and FT4], total and free triiodothyronine [TT3 and FT3], thyroid-stimulating hormone [TSH], and thyroglobulin [Tg]) and levels of Pb, Hg, and Cd in blood and Cd in urine.

METHODS

We separately analyzed a sample of 1,109 adolescents (12-19 years of age) and a sample of 4,409 adults from the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2008. We estimated associations after adjusting for age, sex, race, urinary iodine, body mass index, and serum cotinine.

RESULTS

The geometric mean (GM) levels of blood Pb (BPb), total Hg, and Cd were 0.81 µg/dL, 0.47 µg/L, and 0.21 µg/L in adolescents and 1.43 µg/dL, 0.96 µg/L, and 0.38 µg/L in adults, respectively. The GMs of urinary Cd were 0.07 and 0.25 µg/g creatinine in adolescents and adults, respectively. No consistent pattern of metal and thyroid hormone associations was observed in adolescents. In adults, blood Hg was inversely related to TT4, TT3, and FT3 and urinary Cd was positively associated with TT4, TT3, FT3, and Tg, but there were no associations with Pb. Associations were relatively weak at an individual level, with about 1-4% change in thyroid hormones per interquartile range increase in Hg or Cd.

CONCLUSIONS

Our analysis suggests an inverse association between Hg exposure and thyroid hormones, and a positive association between Cd exposure and thyroid hormones in adults.

TSH and Thyrotropic Agonists: Key Actors in Thyroid Homeostasis

This paper provides the reader with an overview of our current knowledge of hypothalamic-pituitary-thyroid feedback from a cybernetic standpoint. Over the past decades we have gained a plethora of information from biochemical, clinical, and epidemiological investigation, especially on the role of TSH and other thyrotropic agonists as critical components of this complex relationship. Integrating these data into a systems perspective delivers new insights into static and dynamic behaviour of thyroid homeostasis. Explicit usage of this information with mathematical methods promises to deliver a better understanding of thyrotropic feedback control and new options for personalised diagnosis of thyroid dysfunction and targeted therapy, also by permitting a new perspective on the conundrum of the TSH reference range.

Exposure to arsenic in urban and rural areas and effects on thyroid hormones

CONTEXT

Arsenic is a ubiquitous element present in urban air as a pollutant, and it may interfere with thyroid hormones.

OBJECTIVE

To evaluate the association between the personal exposure to arsenic and levels of TSH, fT4, fT3, and Tg in urban and rural workers.

MATERIALS AND METHODS

Total urinary arsenic and thyroid markers were obtained from 108 non-smoking traffic policemen and 77 subjects working as roadmen in a rural area. Fifty subjects were monitored to evaluate airborne exposure to arsenic.

RESULTS

The mean value of exposure to arsenic was 2.9 µg/m(3) in traffic policemen, while the mean value was less than 0.1 µg/m(3) in roadmen. The mean values of urinary arsenic (10.4 μg/g creatinine vs. 5.2 μg/g creatinine; p = 0.000), TSH (1.6 µlU/ml vs. 1.3 µlU/ml; p = 0.006), fT3 (3.5 pg/ml vs. 3.7 pg/ml; p = 0.000), fT4 (1.2 ng/dl vs. 1.3 ng/dl; p = 0.000) and Tg (42.8 ng/ml vs. 36.1 ng/ml; p = 0.04) were significantly different between traffic policemen and roadmen. In traffic policemen, urinary arsenic and arsenic in the air were correlated to the airborne arsenic and TSH values, respectively. Urinary arsenic was correlated to TSH, Tg, fT3, and fT4 values. The multiple linear regression models showed the following associations: i) among urinary arsenic, arsenic in the air and job title; ii) among TSH, fT3, Tg and urinary arsenic; and iii) between fT4 and both urinary arsenic and alcohol intake.

CONCLUSION

These results provide information about the relationship between exposure to arsenic and thyroid markers and may be useful for other categories of outdoor workers who are similarly exposed.