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Thyroid disruptors

Qinchang Chen, Xiaoxiang Wang, Wei Shi, Hongxia Yu, Xiaowei Zhang, John P Giesy
Some hydroxylated polybrominated diphenyl ethers (HO-PBDEs), that have been widely detected in the environment and tissues of humans and wildlife, bind to thyroid hormone (TH) receptor (TR) and can disrupt functioning of systems modulated by the TR. However, the mechanism of TH disrupting effect is still equivocal. Here, disruption of functions of TH modulated pathways by HO-PBDEs were evaluated by use of assays of competitive binding, coactivator recruitment and proliferation of GH3 cells. In silico simulations considering effects of co-regulators were carried out to investigate molecular mechanisms and predict potencies for disrupting functions of the TH...
October 14, 2016: Environmental Science & Technology
Marcela Dvořáková
The article gives an overview of the circumstances-eating habits, disorders of absorption in the intestinal and other disease, certain drugs and substances occurring in nature affecting the metabolism of thyroid hormones on many levels, thyroid disruptors, for which compensation may be healing broken thyroid function to be unsatisfactory in spite of following the rules of substitution treatment. Knowledge of these conditions and adapting to them timely by adjusting either the eating habits or thyroid hormone by adjusting benefits, allowing the patient to improve his subjective feelings from treatment and improving compliance...
2016: Vnitr̆ní Lékar̆ství
Susanna Wegner, Patience Browne, David Dix
Reference chemicals were selected based on thyroid bioactivity in 'Tier 1' screening assays used by the U.S. EPA's Endocrine Disruptor Screening Program. Active reference chemicals had significant effects on thyroid-responsive endpoints in the amphibian metamorphosis assay, and the male and female pubertal rat assays. In the absence of thyroid weight or histopathological effects, additional published studies providing mechanistic data on thyroid activity were required for active chemicals. Inactive reference chemicals had no significant effects on thyroid-responsive endpoints in Tier 1 assays, or in amphibian or rodent studies from several online databases...
October 2016: Reproductive Toxicology
Satoko Matsui, Sayoko Ito-Harashima, Yuji Sugimoto, Eiji Takada, Kazuhiro Shiizaki, Masanobu Kawanishi, Takashi Yagi
Thyroid hormones (THs) are involved in the regulation of metabolic homeostasis during the development and differentiation of vertebrates, particularly amphibian metamorphosis, which is entirely controlled by internal TH levels. Some artificial chemicals have been shown to exhibit TH-disrupting activities. In order to detect TH disruptors for amphibians, we herein developed a reporter assay using yeast strains expressing the thyroid hormone receptors (TRs) α and β together with the transcriptional coactivator SRC-1, all of which were derived from the frog Xenopus tropicalis (XT)...
December 2016: Toxicology in Vitro: An International Journal Published in Association with BIBRA
Derik E Haggard, Pamela D Noyes, Katrina M Waters, Robert L Tanguay
Triclosan (TCS) is an antimicrobial agent commonly found in a variety of personal care products and cosmetics. TCS readily enters the environment through wastewater and is detected in human plasma, urine, and breast milk due to its widespread use. Studies have implicated TCS as a disruptor of thyroid and estrogen signaling; therefore, research examining the developmental effects of TCS is warranted. In this study, we used embryonic zebrafish to investigate the developmental toxicity and potential mechanism of action of TCS...
October 1, 2016: Toxicology and Applied Pharmacology
Hong-Jie Sun, Ping Xiang, Jun Luo, Huachang Hong, Hongjun Lin, Hong-Bo Li, Lena Q Ma
Due to its toxicity as a carcinogen and wide distribution in the environment, arsenic (As) exposure in humans is of public concern globally. Many studies have manifested that As exposure induces cancers besides pathological effects in humans. Animal studies showed that chronic As exposure induces serious neurological effects. Based on recent studies, researchers proposed that As, including arsenate (AsV) and arsenite (AsIII), is also an endocrine disruptor. This review discusses the mechanisms of As toxicity on three endocrine systems including gonadal, adrenal and thyroid endocrine systems...
October 2016: Environment International
Amira M Aker, Deborah J Watkins, Lauren E Johns, Kelly K Ferguson, Offie P Soldin, Liza V Anzalota Del Toro, Akram N Alshawabkeh, José F Cordero, John D Meeker
INTRODUCTION: Phenols and parabens are ubiquitous environmental contaminants. Evidence from animal studies and limited human data suggest they may be endocrine disruptors. In the current study, we examined associations of phenols and parabens with reproductive and thyroid hormones in 106 pregnant women recruited for the prospective cohort, "Puerto Rico Testsite for Exploring Contamination Threats (PROTECT)". METHODS: Urinary exposure biomarkers (bisphenol A, triclosan, benzophenone-3, 2,4-dichlorophenol, 2,5-dichlorophenol, butyl, methyl and propyl paraben) and serum hormone levels (estradiol, progesterone, sex hormone-binding globulin (SHBG), free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone) were measured at up to two time points during pregnancy (16-20 weeks and 24-28 weeks)...
July 20, 2016: Environmental Research
Jin Zhang, Yaozong Li, Arun A Gupta, Kwangho Nam, Patrik L Andersson
Thyroid hormone disrupting chemicals (THDCs), often found abundantly in the environment, interfere with normal thyroid hormone signaling and induce physiological malfunctions, possibly by affecting thyroid hormone receptors (THRs). Indoor dust ingestion is a significant human exposure route of THDCs, raising serious concerns for human health. Here, we developed a virtual screening protocol based on an ensemble of X-ray crystallographic structures of human THRβ1 and the generalized Born solvation model to identify potential THDCs targeting the human THRβ1 isoform...
August 15, 2016: Chemical Research in Toxicology
Ann M Petersen, Nathanial C Earp, Mandy E Redmond, John H Postlethwait, Frank A von Hippel, C Loren Buck, William A Cresko
Perchlorate is a common aquatic contaminant that has long been known to affect thyroid function in vertebrates, including humans. More recently perchlorate has been shown to affect primordial sexual differentiation in the aquatic model fishes zebrafish and threespine stickleback, but the mechanism has been unclear. Stickleback exposed to perchlorate from fertilization have increased androgen levels in the embryo and disrupted reproductive morphologies as adults, suggesting that perchlorate could disrupt the earliest stages of primordial sexual differentiation when primordial germ cells (PGCs) begin to form the gonad...
2016: PloS One
Katie Paul Friedman, Sabitha Papineni, M Sue Marty, Kun Don Yi, Amber K Goetz, Reza J Rasoulpour, Pat Kwiatkowski, Douglas C Wolf, Ann M Blacker, Richard C Peffer
The US Environmental Protection Agency Endocrine Disruptor Screening Program (EDSP) is a tiered screening approach to determine the potential for a chemical to interact with estrogen, androgen, or thyroid hormone systems and/or perturb steroidogenesis. Use of high-throughput screening (HTS) to predict hazard and exposure is shifting the EDSP approach to (1) prioritization of chemicals for further screening; and (2) targeted use of EDSP Tier 1 assays to inform specific data needs. In this work, toxicology data for three triazole fungicides (triadimefon, propiconazole, and myclobutanil) were evaluated, including HTS results, EDSP Tier 1 screening (and other scientifically relevant information), and EPA guideline mammalian toxicology study data...
October 2016: Critical Reviews in Toxicology
Julia Blanco-Muñoz, Marina Lacasaña, Inmaculada López-Flores, Miguel Rodríguez-Barranco, Beatriz González-Alzaga, Susana Bassol, Mariano E Cebrian, Lizbeth López-Carrillo, Clemente Aguilar-Garduño
Several studies have suggested that exposure to DDT may be related to changes in thyroid hormone levels in animals and humans, even though results across studies are inconsistent. The aim of this study was to assess the association between exposure to p,p'-DDE (a stable metabolite of DDT) and serum levels of thyroid hormones in floriculture workers. A longitudinal study was conducted on 136 male subjects from the States of Mexico and Morelos, Mexico, who were occupationally exposed to pesticides, during agricultural periods of high (rainy season) and low (dry season) levels of pesticide application...
October 2016: Environmental Research
Vesna Zadnik, Mateja Krajc
The incidence of hormone-related cancers tends to be higher in the developed world than in other countries. In Slovenia, six hormone-related cancers (breast, ovarian, endometrial, prostate, testicular, and thyroid) account for a quarter of all cancers. Their incidence goes up each year, breast and prostate cancer in particular. The age at diagnosis is not decreasing for any of the analysed cancer types. The risk of breast cancer is higher in the western part of the country, but no differences in geographical distribution have been observed for other hormone-related cancers...
June 1, 2016: Arhiv za Higijenu Rada i Toksikologiju
Iveta Bartonkova, Aneta Grycova, Zdenek Dvorak
Variety of xenobiotics, including therapeutically used vitamin D analogues or environmental and alimentary endocrine disruptors, may interfere with vitamin D receptor (VDR) signaling, with serious physiological or pathophysiological consequences. Therefore, it is of topical interest to have reliable and efficient in vitro screening tools for the identification of agonists and activators of human VDR. We present here two novel stably transfected human reporter cell lines allowing rapid, high-throughput, and selective identification of VDR agonists and activators...
July 18, 2016: Chemical Research in Toxicology
A Pinson, J P Bourguignon, A S Parent
The developing brain is remarkably malleable as neural circuits are formed and these circuits are strongly dependent on hormones for their development. For those reasons, the brain is very vulnerable to the effects of endocrine-disrupting chemicals (EDCs) during critical periods of development. This review focuses on three ubiquitous endocrine disruptors that are known to disrupt the thyroid function and are associated with neurobehavioral deficits: polychlorinated biphenyls, polybrominated diphenyl ethers, and bisphenol A...
July 2016: Andrology
R G Ahmed
This study tested whether the maternal transport of dexamethasone (DEXA) may affect the development of the neuroendocrine system. DEXA (0.2mg/kg b.w., subcutaneous injection) was administered to pregnant rats from gestation day (GD) 1-20. In the DEXA-treated group, a decrease in maternal serum thyroxine (T4), triiodothyronine (T3), and increase in thyrotropin (TSH) levels (hypothyroid status) were observed at GDs 15 & 20 with respect to control group. The reverse pattern (hyperthyroid status) was observed in their fetuses at embryonic days (EDs) 15 & 20...
September 6, 2016: Toxicology Letters
A Tammaro, F Pigliacelli, A Fumarola, S Persechino
Background. Mandatory iodine fortification of salt was introduced in Italy in 2005. The purpose of our study is to estimate the trend of thyroid diseases in Italy before and after mandatory iodization in Italy. Methods. 7976 patients (6802 females; 1174 males) were examined between 2003 and 2010. We divided the patients into categories according to their clinical diagnosis. Later, we evaluated for each patient if there was the positivity for antibodies anti TPO. Finally, we collected data about TSH values of all patients who did not use therapy for thyroid disease at the time of the examination...
May 2016: European Annals of Allergy and Clinical Immunology
Ablikim Abliz, Chen Chen, Wenhong Deng, Weixing Wang, Rongze Sun
PCBs, widespread endocrine disruptors, cause the disturbance of thyroid hormone (TH) homeostasis in humans and animals. However, the exact mechanism of thyroid dysfunction caused by PCBs is still unknown. In order to clarify the hypotheses that NADPH oxidase (NOX) and subsequent NF-κB pathway may play roles in thyroid dysfunction, sixty Sprague-Dawley rats were randomly divided into four groups: control group, PCB153 treated (PCB) group, received apocynin with PCB153 treatment (APO + PCB) group, and drug control (APO) group...
2016: International Journal of Endocrinology
Deborah Molehin, Marloes Dekker Nitert, Kerry Richard
Background. Thyroid hormones (THs) are essential for normal human fetal development and play a major role in the regulation of glucose and lipid metabolism. Delivery of TH to target tissues is dependent on processes including TH synthesis, transport, and metabolism. Thyroid hormone endocrine disruptors (TH-EDCs) are chemical substances that interfere with these processes, potentially leading to adverse pregnancy outcomes. Objectives. This review focuses on the effects of prenatal exposures to combinations of TH-EDCs on fetal and neonatal glucose and lipid metabolism and also discusses the various mechanisms by which TH-EDCs interfere with other hormonal pathways...
2016: Journal of Thyroid Research
N V Yaglova, V V Yaglov
Changes in secretion of thyroid autoantigenes and production of antithyroid autoantibodies after long-term exposure to low doses of DDT were studied. Changes in serum levels of antithyroid peroxidase antibodies and thyroid peroxidase, attributed to disruption of thyroxine production by DDT were found. Long-term exposure of rats to low doses of DDT revealed no specific impact on serum autoantibodies to all thyroid autoantigenes studied. The increase of the ratio of autoantibody/autoantigen for thyroid peroxidase and thyroglobulin was rather small and thus could not be considered as a significant symptom of thyroid autoimmunity...
January 2016: Biomedit︠s︡inskai︠a︡ Khimii︠a︡
Alba Quesada-García, Paloma Encinas, Ana Valdehita, Lisa Baumann, Helmut Segner, Julio M Coll, José M Navas
In mammals, numerous reports describe an immunomodulating effect of thyroid-active compounds. In contrast, only few reports have been published on this subject in fish. We previously demonstrated that immune cells of rainbow trout (Oncorhynchus mykiss) possess thyroid hormone receptors (THRs) and that exposure of trout to the thyroid hormone 3,3',5-triiodo-l-thyronine (T3) or the antithyroid drug propylthiouracil (PTU) alters immune cell transcript levels of THR and several immune genes. The present study aims to further characterize the immunomodulating action of thyroid-active compounds in trout immune cells...
May 2016: Aquatic Toxicology
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