Endocrine Abstracts

Introduction: Exposure to air pollution and in particular to nitrogen dioxide (NO₂) or particulate pollutants less than 2.5 µm (PM2.5) or 10 µm (PM10) in diameter has been linked to thyroid (dys)function in pregnant women. The environmental degradation that has occurred in recent years in the region of Athens led us to a local study of air pollution against thyroid function in pregnant women in Athens. We hypothesized that there may be a dose-effect relationship between air pollutants and thyroid function parameters.

Methods: We retrospectively evaluated thyroid function with thyrotropin (TSH) in 293 women, mean ± S.D.: 30.9 ± 5.5 years, vs the mean of the previous 9 months of NO₂, PM2.5 and PM10 levels of five atmospheric air quality measurement stations in the greater Athens area (2013–2017). All the women had no prior thyroid disease and were diagnosed with hypothyroidism for the first time during their pregnancy (mean ± S.D. gestational age at diagnosis 19.4 ± 8.6 weeks, weight gain 5.1 ± 5.6 kg, TSH: 4.54 ± 1.66 mIU/l). We only included women with TSH > 2.5 mIU/l or > 3.0 mIU/l if the initial thyroid assessment was done in the first or the second trimester of pregnancy respectively. Exposure to air pollution for each woman was considered according to her place of residence (permanent residence for at least one year) within a reasonable distance of one of the five air quality measuring stations. Statistical analysis of age, pregnancy weight change, and air pollutants vs TSH was performed with ordinary least squares regression (OLS-R) and quantile regression (Q-R).

Results: Using OLS-R, a significant (positive) correlation for logTSH was found only with PM2.5 (r = +0.13, P = 0.02). Analysis with Q-R showed that each incremental unit increase (for the 10th to the 90th response quantile) in PM2.5 increased TSH (± s.e.) between + 0.029 (0.001) to + 0.025 (0.001) mIU/l (P < 0.01). Other pollutants (PM10 and NO₂) had no significant effect on TSH.

Conclusion: Our results indeed show a relationship between PM2.5 and TSH. The mechanisms involved in the pathophysiological effects of atmospheric pollutants, in particular PM2.5, are being investigated.