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

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          Abstract

          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.

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          Most cited references 46

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          Neurodevelopmental and neurophysiological actions of thyroid hormone.

          For over 100 years, thyroid hormones have been known to be essential for neonatal neurodevelopment but whether they are required by the foetal brain remains a matter of controversy. For decades, the prevailing view was that thyroid hormones are not necessary until after birth because circulating levels in the foetus are very low and the placenta forms an efficient barrier to their transfer from the mother. Clinical observations of good neurological outcome following early treatment of congenital hypothyroidism were used to support the view that thyroid hormones are not required early in neurodevelopment. Nevertheless, the issue remained contentious because of findings that the severity of foetal neurological deficit due to maternal iodine deficiency correlated with the degree of maternal thyroxine (T4) deficiency. Furthermore, neurological damage in these cases could be prevented by correction of maternal T4 deficiency before mid-gestation. This observation led to the opposing view, supported by epidemiological studies of neurological cretinism, that maternal thyroid hormones are important and necessary for early foetal neurodevelopment. It is now clear that thyroid hormones are essential for both foetal and post-natal neurodevelopment and for the regulation of neuropsychological function in children and adults. In recent years, this controversial subject has progressed very rapidly following remarkable progress in understanding of the molecular mechanisms of thyroid hormone action. This article reviews the contributions of molecular biology and genetics to our new understanding of the physiological effects of thyroid hormones on neurodevelopment and in the adult brain.
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            Effects of environmental synthetic chemicals on thyroid function.

             Paul Davis (1998)
            Synthetic chemicals are released into the environment by design (pesticides) or as a result of industrial activity. It is well known that natural environmental chemicals can cause goiter or thyroid imbalance. However, the effects of synthetic chemicals on thyroid function have received little attention, and there is much controversy over their potential clinical impact, because few studies have been conducted in humans. This article reviews the literature on possible thyroid disruption in wildlife, humans, and experimental animals and focuses on the most studied chemicals: the pesticides DDT, amitrole, and the thiocarbamate family, including ethylenethiourea, and the industrial chemicals polyhalogenated hydrocarbons, phenol derivatives, and phthalates. Wildlife observations in polluted areas clearly demonstrate a significant incidence of goiter and/or thyroid imbalance in several species. Experimental evidence in rodents, fish, and primates confirms the potentiality for thyroid disruption of several chemicals and illustrates the mechanisms involved. In adult humans, however, exposure to background levels of chemicals does not seem to have a significant negative effect on thyroid function, while exposure at higher levels, occupational or accidental, may produce mild thyroid changes. The impact of transgenerational, background exposure in utero on fetal neurodevelopment and later childhood cognitive function is now under scrutiny. There are several studies linking a lack of optimal neurological function in infants and children with high background levels of exposure to polychlorinated biphenyls (PCBs), dioxins, and/or co-contaminants, but it is unclear if the effects are caused by thyroid disruption in utero or direct neurotoxicity.
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              Arsenic in the aetiology of cancer.

              Arsenic, one of the most significant hazards in the environment affecting millions of people around the world, is associated with several diseases including cancers of skin, lung, urinary bladder, kidney and liver. Groundwater contamination by arsenic is the main route of exposure. Inhalation of airborne arsenic or arsenic-contaminated dust is a common health problem in many ore mines. This review deals with the questions raised in the epidemiological studies such as the dose-response relationship, putative confounders and synergistic effects, and methods evaluating arsenic exposure. Furthermore, it describes the metabolic pathways of arsenic, and its biological modes of action. The role of arsenic in the development of cancer is elucidated in the context of combined epidemiological and biological studies. However, further analyses by means of molecular epidemiology are needed to improve the understanding of cancer aetiology induced by arsenic.
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                Author and article information

                Contributors
                48 717 840 105 , pawelgac@interia.pl
                Journal
                Biol Trace Elem Res
                Biol Trace Elem Res
                Biological Trace Element Research
                Springer US (New York )
                0163-4984
                1559-0720
                19 July 2017
                19 July 2017
                2018
                : 182
                : 2
                : 196-203
                Affiliations
                [1 ]ISNI 0000 0001 1090 049X, GRID grid.4495.c, Department of Internal Medicine, Occupational Diseases and Hypertension, , Wroclaw Medical University, ; Borowska 213, 50-556 Wroclaw, Poland
                [2 ]ISNI 0000 0001 1090 049X, GRID grid.4495.c, Department of Hygiene, , Wroclaw Medical University, ; Mikulicza-Radeckiego 7, 50-368 Wroclaw, Poland
                [3 ]ISNI 0000 0001 1090 049X, GRID grid.4495.c, Department of Pathophysiology, , Wroclaw Medical University, ; Marcinkowskiego 1, 50-368 Wroclaw, Poland
                Article
                1096
                10.1007/s12011-017-1096-x
                5838128
                28726072
                © The Author(s) 2017

                Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                Funding
                Funded by: Wroclaw Medical University
                Award ID: -
                Award Recipient :
                Categories
                Article
                Custom metadata
                © Springer Science+Business Media New York 2018

                Biochemistry

                lead, cadmium, arsenic, occupational exposure, thyroid, thyrotropic hormone

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