Prevalence of thyroid disorders in inland and coastal populations: A systematic review.

Endocrine conditions such as thyroid disorders can significantly impact maternal and child health. Key determinants such as environmental setting and presence of iodine can influence the incidence of thyroid disorders. Individuals living in coastal regions are exposed to iodine rich foods in comparison to those residing in inland areas, which is a possible differentiating factor in the occurrence of thyroid based diseases in these individuals. Despite this possible relationship, very few studies have investigated the burden of thyroid diseases amongst coastal and inland populations. The study aims to systematically explore the prevalence of thyroid disorders in coastal and inland regions to understand the impact of differences in diet, environmental determinants, demographic variation and access to healthcare services on thyroid disease occurrence. Databases such as PubMed, Google Scholar and Scopus were used to identify articles in accordance with the PRISMA 2020 guidelines. Twenty three articles were selected based on them being in the English language, full length studies published between January 2017 and September 2023 and had reported on prevalence of thyroid diseases in inland and/or coastal areas. The review identified that a higher prevalence of thyroid cancer and thyroid nodules were seen amongst coastal populations, while goiter and hypothyroidism were seen in inland and mountainous areas. These differences were influenced by the iodine status of the region, consumption of seafood, presence of environmental pollutants like bisphenol A and polychlorinated biphenyls, iodization of salt, socioeconomic conditions and healthcare access. Female gender and older age was found to be significantly associated with greater burden of disease in both areas of study. The geographical location or setting is a vital determinant of the distribution of thyroid disorders, mainly through the influence of iodine intake and exposure to environmental pollutants. Regular monitoring of environmental pollutants, early detection of cases, universal iodization of salt and proactive supplementation of iodine may lead to decreased prevalence of thyroid disorders and its consequences. Longitudinal studies in this field can help identify the causal pathways emerging from socioeconomic factors and environmental determinants to thyroid disorders.