Thyroid dysfunction caused by exposure to environmental endocrine disruptors and the underlying mechanism: A review

Thyroid Endocrine Disrupting Potential of Fluoxetine in Zebrafish Larvae

Fluoxetine (FLX), a typical selective serotonin reuptake inhibitors, has been frequently detected in aquatic environment and wild fish. However, little is known about its effect on thyroid endocrine system. In the present study, zebrafish (Danio rerio) embryos were exposed to 1, 3, 10, and 30 μg/L of FLX for 6 days. Chemical analysis demonstrated that FLX and its metabolic product (nonfluoxetine, NFLX) were accumulated in zebrafish larvae. The exposure resulted in decreased thyroid hormones (THs) levels, indicating thyroid endocrine disruption. Moreover, thyroid-stimulating hormone (TSH) content was significantly inhibited in a concentration-dependent manner after exposure to FLX. Gene transcription in the hypothalamic-pituitary-thyroid (HPT) axis was further examined, and the results showed that the genes encoding corticotrophin-releasing hormone (crh) and thyrotropin-releasing hormone (trh) were significantly up-regulated as a compensatory mechanism for the decreased TH contents accompanied with decreased tshβ mRNA expression. In addition, genes involved in thyroid hormone synthesis (sodium/iodide symporter, nis, thyroglobulin, tg) and transport (transthyretin, ttr) were down-regulated after exposure to FLX in a concentration-dependent manner. The increased gene transcription of deiodinases (dio2) and uridinediphosphate-glucuronosyltransferase (ugt1ab) might be responsible for the decrease of TH contents. In addition, a significant inhibition in thyroid hormone receptors (trα and trβ) gene expression was observed upon treatment with FLX. All these results demonstrated that FLX could alter THs and TSH content as well as gene transcription in the HPT axis, exerting an endocrine disruption of the thyroid system in zebrafish larvae.

Exposure profiles to Benzophenones and their impacts on thyroid hormones in pregnant women

PURPOSE

Benzophenones are ubiquitous compounds widely used in various industrial and consumer products including sunscreens, plastics, and personal care items. Their presence as emerging pollutants has raised concerns due to their potential adverse health effects, particularly as endocrine disrupting chemicals (EDCs). The aim of this study was to identify exposure profiles to Benzophenones in pregnant women living in Algiers and to explore associations between urinary levels of these compounds and disruptions of thyroid hormones levels during pregnancy.

METHODS

This study was carried out on 384 pregnant women. After gathering necessary information using a questionnaire, blood and urine samples were collected. Thyroid hormones (TSH, FT3, and FT4) were measured by electrochemiluminescence while Benzophenones (BP-1, BP-2, and BP-3) were detected by LC-MS/MS.

RESULTS

BP-1, BP-2, and BP-3 were detected in 91.9%, 56.5%, and 88.3% of the analyzed samples, respectively. Mean concentrations were 2.250, 0.178, and 2.067 µg/g creatinine for BP-1, BP-2, and BP-3, respectively. Significant negative associations were found between plasma levels of FT3 and urinary concentrations of both BP-1 (β = -0.101) and BP-3 (β = -0.110). Moreover, significant positive associations were recorded between urinary concentrations of both BP-1 and BP-3 and the application of makeup.

CONCLUSION

In conclusion, exposure of pregnant women to Benzophenones may affect levels of thyroid hormones resulting in possible adverse health effects on the mother and the development of the child. Therefore, preventive measures limiting exposure to these EDCs are recommended.

A Scoping Review on the Prevalence of Hashimoto's Thyroiditis and the Possible Associated Factors

BACKGROUND

Hashimoto's thyroiditis (HT) is the most common autoimmune thyroid disease (AITD) and is characterized by the presence of thyroid autoantibodies against thyroid peroxidase and/or thyroglobulin. Several studies have found that the global prevalence of HT has increased in recent decades, while others show the opposite.

METHODS AND RESULTS

The objective of this scoping review was to synthesize and analyze the different studies that have evaluated the prevalence of HT (in adults) and the possible associated factors. The following databases were consulted, as follows: MEDLINE, Web of Science, PubMed, and Scopus. The search terms "epidemiology", "prevalence", and "Hashimoto disease" and "Hashimoto thyroiditis" were used. The search was limited to articles published between January 1965 and October 2024, and only articles in English were considered. In order to reduce selection bias, each article was scrutinized using the JBI Critical Appraisal Checklist independently by two authors. Studies were included if the number of participants (study population and/or cases and controls, depending on the study design) was clearly described and duplicate studies were excluded. A total of 59 studies were identified, the vast majority of them used a cross-sectional design, using different methods of disease assessment.

CONCLUSIONS

Globally, the prevalence of HT is estimated to be between 5-10%; some areas with prevalences > 20% and others < 0.5% were identified. Prevalence is also higher in women than in men. Multiple underlying factors (genetic, epigenetic, environmental, and lifestyle), together with socioeconomic, nutritional, overdiagnosis, inter alia, may explain (at least in part) the wide variability in the prevalence of HT.

Exploring the relationships between prenatal phthalate exposure and neonatal thyroid function: A prospective cohort study

Previous studies have reported the thyroid disruptive effects of prenatal phthalate exposure; however, evidence on the impact of prenatal phthalate alternative exposure on neonatal thyroid function is still limited. We aimed to investigate the associations between prenatal exposure to phthalates and phthalate alternatives (individually and as a mixture) and neonatal thyroid function, based on longitudinal data from the Wuhan Healthy Baby Cohort Study. We measured concentrations of phthalate and phthalate alternative metabolites (mPAEs) in urine samples, provided by 1202 mothers at three trimesters, and neonatal thyroid stimulating hormone (TSH) levels in heel-prick blood samples. The results suggested higher levels of some mPAEs, particularly monomethyl phthalate (MMP) and mono-2-ethyl-5-Carboxypentyl terephthalate (MECPTP), were associated with increased neonatal TSH. Interquartile range (IQR) increases of mPAEs were associated with an increase in TSH ranging from 8.21 % to 13.5 %, and the associations were more likely to occur in girls. Quantiles g-computation models revealed that joint exposure to phthalates was significantly associated with increased TSH in three trimesters, MEOHP and MMP were the most predominant contributors to the positive associations. The research results imply that prenatal phthalate exposure may interfere with thyroid hormone homeostasis, which warrants further replication.

Biodegradation of Xenoestrogens by the Green Tide Forming Seaweed Ulva: A Model System for Bioremediation

Anthropogenic xenoestrogens pose serious threats to humans and the environment. Ulva (Chlorophyta), a green macroalga that can propagate in environments of various salinities, is a potential candidate for efficient wastewater treatment and bioremediation. In this study, we tested the class of bisphenols and ethinylestradiol and investigated the underlying removal mechanisms of these xenoestrogens. The model organism Ulva mutabilis demonstrated over 99% removal efficiency for bisphenols A, B, E, F, P, and Z, and partial removal of bisphenol S. Ulva showed complete removal capabilities even under axenic conditions, while its associated bacteria were not involved. Complete removal of 6.6 mg L-1 of bisphenol A was achieved within 2 days and a half-time of 1.85 h. Biodegradation was the leading cause of removal, whereas bioaccumulation was minimal. The model substance bisphenol A underwent various reactions, and 20 transformation products were detected using stable isotope labeling. While most of the bisphenol A was completely biodegraded, the primary transformation products were monobromobisphenol A, bisphenol A bisulfate, and 4-hydroxypropanylphenol. This study highlights the potential of the green seaweed Ulva to provide a pathway for more effective and sustainable bioremediation strategies to tackle the environmental pollution caused by xenoestrogens.

Evaluating the Spectrum of Sleep Abnormalities in Patients With Primary Hypothyroidism

Introduction and aim: Primary hypothyroidism is a common endocrine disorder. While thyroid dysfunction is recognized for impacting numerous bodily systems, the connection between thyroid disorders and sleep function remains unclear. Since sleep disorders seldom manifest as the sole presenting symptom of thyroid dysfunction, it is crucial to examine the interplay between thyroid function and sleep when implementing a comprehensive treatment approach for these individuals. This study aimed to assess sleep dysfunction in patients with primary hypothyroidism using validated questionnaires.

METHOD

This cross-sectional study included 81 participants attending the endocrinology outpatient department. The participants included those with both overt and subclinical primary hypothyroidism who were drug-naive or had a thyroid-stimulating hormone (TSH) level >4.5 µIU/L while on treatment. The study subjects were assessed based on various validated questionnaires for sleep disturbance.

RESULTS

The study predominantly comprised 64 (79%) female participants. Overall, poor sleepers in subclinical and overt hypothyroidism were 66.7 and 60.8%. The Berlin Risk Score Questionnaire showed the occurrence of sleep apnea to be 26.7% and 27.5% in subclinical and overt groups, respectively. However, the occurrence of sleep dysfunction did not correlate with TSH values alone.

CONCLUSION

Our findings demonstrate that sleep dysfunction is prevalent in patients with both overt and subclinical primary hypothyroidism. Furthermore, the severity of sleep disruption appears independent of the degree of thyroid dysfunction.

Characterization of a human thyroid microtissue model for testing thyroid disrupting chemicals

Perturbation of thyroid hormone (T4) synthesis is known to cause numerous developmental, metabolic, and cognitive disorders in humans. Due to species differences in sensitivity to chemical exposures, there is a need for human-based in vitro approaches that recapitulate thyroid cellular architecture and T4 production when screening. To address these limitations, primary human thyrocytes, isolated from healthy adult donor tissues and cryopreserved at passage one (p'1) were characterized for cellular composition, 3D follicular architecture, and thyroglobulin (TG)/T4 expression and inhibition by prototype thyroid disrupting chemicals (TDC). Flow analysis of the post-thaw cell suspension showed >80% EpCAM-positive cells with 10%-50% CD90-positive cells. When seeded onto 96-well Matrigel®-coated plates and treated with bovine thyroid stimulating hormone (TSH), thyrocytes formed 3D microtissues during the initial 4-5 days of culture. The microtissues exhibited a stable morphology and size over a 14-day culture period. TG and T4 production were highest in microtissues when the proportion of CD90-positive cells, seeding density and thyroid stimulating hormone concentrations were between 10%-30%, 6K-12K cells per well, and 0.03-1 mIU/mL, respectively. At maximal TG and T4 production levels, average microtissue diameters ranged between 50 and 200 µm. The T4 IC50 values for two prototype TPO inhibitors, 6-propyl-2-thiouracil and methimazole, were ∼0.7 µM and ∼0.5 µM, respectively, in microtissue cultures treated between days 9 and 14. Overall, p'1 cryopreserved primary human thyrocytes in 3D microtissue culture represent a promising new model system to prioritize potential TDC acting directly on the thyroid as part of a weight-of-evidence hazard characterization.

The Role of Endocrine Disruption Chemical-Regulated Aryl Hydrocarbon Receptor Activity in the Pathogenesis of Pancreatic Diseases and Cancer

The aryl hydrocarbon receptor (AHR) serves as a ligand-activated transcription factor crucial for regulating fundamental cellular and molecular processes, such as xenobiotic metabolism, immune responses, and cancer development. Notably, a spectrum of endocrine-disrupting chemicals (EDCs) act as agonists or antagonists of AHR, leading to the dysregulation of pivotal cellular and molecular processes and endocrine system disruption. Accumulating evidence suggests a correlation between EDC exposure and the onset of diverse pancreatic diseases, including diabetes, pancreatitis, and pancreatic cancer. Despite this association, the mechanistic role of AHR as a linchpin molecule in EDC exposure-related pathogenesis of pancreatic diseases and cancer remains unexplored. This review comprehensively examines the involvement of AHR in EDC exposure-mediated regulation of pancreatic pathogenesis, emphasizing AHR as a potential therapeutic target for the pathogenesis of pancreatic diseases and cancer.