Low-Dose Ionizing Radiation and Thyroid Diseases and Functional Modifications in Exposed Workers: A Systematic Review

Background/Objectives: With technological development, ionizing radiation has found applications in numerous occupations. However, the determination and quantification of the damage resulting from exposure to it remains rather unclear, along with the damage to particular organs. The aim of this systematic review was to investigate the relationship between low-dose ionizing radiation (LDIR) in exposed workers and possible functional changes and cancer development in the thyroid gland. Methods: We included observational studies evidencing the correlation under study. Data extraction and analysis was conducted on all included studies. The research strategy included three electronic databases (PubMed, Scopus, and Web of Science). The systematic review followed PRISMA guidelines, and the research protocol was submitted to PROSPERO (CRD:42023425839). Results: The search initially yielded 166 articles and, once duplicates and irrelevant articles were removed, a total of 15 useful articles were reviewed. Qualitative analysis of the studies showed that the TSH value does not change following exposure, while a reduction in fT3 and an increase or reduction in fT4 can be observed. Furthermore, the correlation between thyroid cancer and occupational exposure to radiation was not shown with certainty, but there was some evidence of increased gland volume and nodule formation. Conclusions: Even at low doses, ionizing radiation adversely affects thyroid activity. In this regard, new studies should be carried out in order to further investigate and define this issue and, consequently, outline useful measures to ensure the protection of workers in contact with this particular physical agent.