Effect of short-term and long-term traffic noise exposure on the thyroid gland in adult rats: a sexual dimorphic study

Association of prolonged occupational co-exposures to electromagnetic fields, noise, and rotating shift work with thyroid hormone levels

The purpose of this study was to determine the association of prolonged occupational co-exposure to extremely low-frequency electromagnetic fields (ELF-EMFs), noise, and rotating shift work with the levels of thyroid hormones (triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH). From 2016 to 2017, we enrolled all male workers without a history of thyroid disorders and followed them until 2020. To measure ELF-EMFs and noise exposures, we calculated the 8-hour equivalent sound pressure levels (Leq) and the 8-hour average of ELF-EMFs, respectively. Shift work schedules involved 8-hr fixed day and 8-hr clockwise 3-rotating night schedules. The participant's thyroid hormone levels were obtained from blood test results in their medical records. The percentage change in the levels of T3, T4, and TSH was estimated by using different mixed-effects linear regression models. The TSH levels were significantly elevated per a 10-dB increment of noise. The levels of T4 hormone were significantly changed per a unit increase in the levels of ELF-EMFs. Compared to the fixed-day workers, we observed workers exposed to shift work had a significantly lower T4 level. For T4 and TSH hormones, we found significant interactions among noise, ELF-EMFs, and shift work variables. In summary, this study warranted that prolonged exposure to ELF-EMFs, noise, and rotating shift work might be associated with thyroid dysfunction.

[Disruptors of thyroid hormones: Which consequences for human health and environment?]

Endocrine disruptors (EDs) of chemical origin are the subject of numerous studies, some of which have led to measures aimed at limiting their use and their impact on the environment and human health. Dozens of hormones have been described and are common to all vertebrates (some chemically related messengers have also been identified in invertebrates), with variable roles that are not always known. The effects of endocrine disruptors therefore potentially concern all animal species via all endocrine axes. These effects are added to the other parameters of the exposome, leading to strong, multiple and complex adaptive pressures. The effects of EDs on reproductive and thyroid pathways have been among the most extensively studied over the last 30 years, in a large number of species. The study of the effects of EDs on thyroid pathways and brain development goes hand in hand with increasing knowledge of 1) the different roles of thyroid hormones at cellular or tissue level (particularly developing brain tissue) in many species, 2) other hormonal pathways and 3) epigenetic interactions. If we want to understand how EDs affect living organisms, we need to integrate results from complementary scientific fields within an integrated, multi-model approach (the so-called translational approach). In the present review article, we aim at reporting recent discoveries and discuss prospects for action in the fields of medicine and research. We also want to highlight the need for an integrated, multi-disciplinary approach to studying impacts and taking appropriate action.

Noise-induced hormonal & morphological malformations in breeding pigeons

Environmental pollution has the potential to have a significant impact on animal's health especially on birds due to daily exposure and habitat. This experimental study was carried out for a 60 days period in which, a total of 24 pigeon birds with suitable weight (80-100 g) were kept in Animal house with suitable environmental conditions viz, controlled temperature, humidity & light source to minimize any other stress. Out of twenty-four, eighteen birds were divided into three treatment groups (6 birds in each group). Whole experiment was run in triplicate manner in breeding season. One served as Control (Group 1) and remaining three were experimental groups including Road traffic noise (Group 2), Military noise (Group 3) & Human activities noise (Group 4). Noise was applied as recorded high intensity music (1125 Hz/ 90 dB) through speakers for 5-6 hrs. daily. Blood sampling was done after 20, 40 and 60 days by sacrificing treatment birds. Noise stress significantly (p<0.05) increase the serum levels of corticosterone and thyroid stimulating hormone (TSH) in Group 2 while significantly (p<0.05) decrease the serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) of Group 3 birds. Moreover, major fault bars formation was seen both in Group 2 and Group 3. It was concluded as that Noise stress caused rise in serum levels of Corticosterone and TSH but fall in LH and FSH. Along with fault bars formation was also prominent in all treatment groups due to stress hormone.