DefinePK

Research Objective

To assess the epidemiological data and potential connection between different endocrine chemical disruptors and thyroid hormone abnormalities.

Methodology

A systematic review conducted following the 2020 PRISMA standards. Ten research studies were identified and examined. The review included observational studies (prospective or retrospective cohorts) that addressed the relationship between exposure to endocrine disruptors and thyroid hormone imbalance. Inclusion criteria encompassed observational studies, individuals above 15 years of age, research describing endocrine disruptor substances, and papers published in English. Exclusion criteria included critiques, proposals, summaries, laboratory procedures, letters to the editor, edited compositions, information not related to disruptive endocrine substances, data pertaining to children younger than 15, personal thoughts or reflections, and articles in languages other than English. Literature searches were conducted using Scopus, Web of Science, PubMed, Medline, EMBASE, and Science Direct, as well as specific journals. Data extraction and quality appraisal were performed.

Methodology Flowchart

                        graph TD
    A["Literature Search Databases & Journals"] --> B["Identify Relevant Studies"];
    B --> C["Screen Titles & Abstracts"];
    C --> D["Full-Text Review"];
    D --> E["Data Extraction"];
    E --> F["Quality Appraisal"];
    F --> G["Synthesize Findings"];
    G --> H["Conclusion"];                    

Discussion

Endocrine-disrupting chemicals (EDCs) can interfere with thyroid function by affecting hormone transporters, gene expression, and the hypothalamic-pituitary-thyroid axis. Exposure to EDCs can lead to obesity, illness, and cancer. The prevalence of thyroid-related cancers and autoimmune thyroid illnesses has increased, with environmental factors potentially contributing. Cadmium, a notable carcinogen in the thyroid gland, can disrupt DNA repair pathways and promote reactive oxygen species generation. EDCs found in various industrial and agricultural pollutants can disrupt hormonal balance, leading to reproductive health issues, metabolic disorders, and increased cancer risk. The review highlights the challenges in categorizing and retrieving literature in this field due to poor indexing and inconsistent terminology.

Key Findings

Ten studies demonstrated that endocrine-disrupting chemicals, particularly in adulthood, impact thyroid hormone levels and the incidence of thyroid nodules. Metals like mercury were linked to decreased levels of Thyroxine and Triiodothyronine, while Cadmium was related to a decrease in Thyroid-Stimulating Hormone. Cadmium in urine was correlated with increased T3 and T4 hormones. Thallium and barium in urine were linked to decreased Thyroxine and Triiodothyronine. Caesium was associated with decreased TSH, and tungsten with increased TSH. Bisphenols can influence the probability of developing breast cancer, and BPA exposure may negatively affect thyroid function during early pregnancy. Studies indicated that females have a higher likelihood of having thyroid cancer compared to males.

Conclusion

Endocrine-disrupting chemicals can compromise thyroid function by affecting hormone transporters, gene expression, and the hypothalamic-pituitary-thyroid axis. Multiple studies indicate a correlation between obesity and metabolic syndrome, which can also impact hormone levels and lead to the development of autoimmune thyroid disorders and subclinical hypothyroidism.

Fact Check

1. PRISMA Standards: The systematic review followed the 2020 PRISMA standards. (Confirmed in Methodology section).
2. Number of Studies: Ten research studies were found and examined. (Confirmed in Abstract and Results sections).
3. Cadmium and Thyroid: Cadmium is identified as a notable carcinogen in the thyroid gland. (Confirmed in Introduction section).

Mind Map