Effects of ionizing radiation on the thyroid gland and systemic inflammatory response in occupationally exposed nuclear medicine personnel

Background/Aim. Low-dose ionizing radiation (IR) can cause subtle biological effects with clinical implications after chronic occupational exposure. The aim of the study was to examine the effect of low-dose IR occupational exposure on female nuclear medicine personnel (NMP). Methods. The study was conducted by analyzing medical data from mandatory periodic health examinations of 45 female NMP exposed to IR for an average of 14 years (exposed group - EG) and 43 age-matched female healthcare workers who were not occupationally exposed to IR (control group - CG). Based on peripheral blood count values, systemic inflammatory indices were calculated: neutrophil-to-lymphocyte ratio (NLR), derived NLR (dNLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), systemic-immune-inflammation index (SII), systemic inflammation response index (SIRI), along with platelet indices, such as mean platelet volume (MPV). Thyroid function was assessed using free thyroxine (fT4) and thyroid-stimulating hormone (TSH). Ultrasonographic thyroid gland anatomy was classified as normal or abnormal (nodules, cysts, or diminished echogenicity). Results. Compared with CG, a significantly higher absolute number of monocytes (p = 0.006) and higher values of the SIRI (p = 0.046) were found in EG. SIRI had a borderline negative association (p = 0.057) with IR exposure duration, while LMR had a substantial positive correlation (p = 0.026). EG had significantly decreased fT4 values (p<0.001), with no significant difference in TSH values (p = 0.858) compared with CG. EG had more abnormal thyroid ultrasonography findings, and occupational IR exposure significantly enhanced the risk of abnormal findings in several logistic regression models (p<0.05). Conclusion. Chronic occupational exposure to low-dose IR in female NMP is associated with parallel effects-both systemic and thyroid-related-including altered inflammatory response indices, lower fT4 values within the reference range, and higher structural thyroid abnormalities. These findings imply that radiation-related thyroid abnormalities are accompanied by systemic immunological alterations; however, they should be interpreted as associative and hypothesis-generating.