Endocrine Abstracts

Objective: Recent reports have suggested that air pollution may impact thyroid function, although the evidence is still scarce and inconclusive. In this study we evaluated the association of exposure to air pollutants to thyroid function parameters in a nationwide sample representative of the adult population of Spain.

Methods: The [email protected] study is a national, cross-sectional, population-based survey which was conducted in 2008-2010 using a random cluster sampling of the Spanish population. The present analyses included 3846 individuals, free of thyroid disease, with negative thyroid peroxidase antibodies (TPO Abs) and TSH levels 0.1-20 mIU/l. Participants were assigned air pollution concentrations for particulate matter <2.5μm (PM2.5) and Nitrogen Dioxide (NO2), corresponding to the health examination year, obtained by means of modeling combined with measurements taken at air quality stations (CHIMERE chemistry-transport model). TSH, FT4, FT3 and TPO Abs concentrations were analyzed using an electrochemiluminescence immunoassay (Modular Analytics E170 Roche).

Results: There was a significant association between PM2.5 concentrations and the odds of presenting lower FT4 [OR 1.30 (1.08-1.57) P=0.006] and FT3 levels [OR 1.34 (1.11-1.62) P=0.002] per each IQR increase in PM2.5 (4.86 μg/m3). The association remained after the multivariate adjustment of the data. There was no association between NO2 concentrations and thyroid hormone levels. No significant heterogeneity was seen in the results between groups of men, pre-menopausal and post-menopausal women.

Conclusions: Exposures to PM2.5 in the general population were associated with a mild thyroid dysfunction consisting of lowered levels of FT4 and FT3 without any significant changes in TSH. The nature of this association remains unknown. Additional studies are warranted to expand the data in this field.