Preliminary Evidence of Microplastics in the Human Thyroid and Their Potential Association with Autoimmune Thyroiditis.

Abstract

Background: Microplastics (MPs) have been identified in multiple human tissues and are increasingly implicated in systemic health risks. Their presence in the thyroid gland, however, remains unexamined. Autoimmune thyroiditis (AIT) is the most frequent autoimmune thyroid disorder and the leading cause of hypothyroidism. This study aims to detect the presence of MPs in the thyroid and their potential relevance to AIT.

Methods: In this case-control study, thyroid tissues were obtained from 29 patients with histologically confirmed AIT and 29 age- and sex-matched non-AIT controls who underwent thyroidectomy due to thyroid nodules. MP burden was quantified by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Particle-level polymer identity and particle characteristics, including size, shape, and color, were assessed using micro-Raman spectroscopy, whereas scanning electron microscopy (SEM) was employed for morphological observation.

Results: MPs were detected in thyroid tissues from both groups. Py-GC/MS revealed significantly higher total MP concentrations in the AIT group compared to controls (median: 19.9 vs. 1.9 μg/g; p=0.012). This elevation was primarily driven by polyvinyl chloride (PVC), which was significantly higher in AIT patients. Micro-Raman spectroscopy identified particles ranging from 33.9 to 1467 µm. The AIT group contained significantly increased MPs abundance compared with the non-AIT control group (172 vs. 50.2 items/g, p=0.037). Morphological profiling revealed no significant differences in the size, shape and color of MPs between groups.

Conclusion: An increased MPs burden with the particular enrichment of PVC was observed in patients with AIT, suggesting a potential association between environmental MPs exposure and thyroid autoimmunity. Further mechanistic and epidemiological studies to clarify the impacts of chronic MPs exposure are needed.