Exploring the causal relationship between long-term exposure to particulate matter 2.5 and risk of thyroid disorders:...

Area of Science:

• Environmental Health
• Endocrinology
• Genetic Epidemiology

Background:

• Particulate matter 2.5 (PM2.5) exposure is linked to thyroid dysfunction, but causal evidence is limited.
• Understanding the causal impact of PM2.5 on thyroid health is critical for public health initiatives.

Purpose of the Study:

• To investigate the causal relationship between long-term PM2.5 exposure and thyroid disorders using a two-sample Mendelian Randomization approach.
• To identify specific thyroid subtypes affected by PM2.5 exposure.

Main Methods:

• Utilized genetic variants associated with PM2.5 exposure from UK Biobank as instrumental variables.
• Employed inverse-variance weighted (IVW) analysis, supported by MR-Egger, weighted median, and mode methods, using FinnGen consortium data for thyroid outcomes.
• Assessed pleiotropy and heterogeneity using MR-Egger intercept, MR-PRESSO, and Cochran's Q test.

Main Results:

• A significant causal association was found between PM2.5 exposure and an increased risk of thyroid disorders (OR=1.77).
• Autoimmune hypothyroidism showed a strong causal link to PM2.5 exposure (OR=1.83).
• No significant causal associations were detected for autoimmune hyperthyroidism or other thyroid subtypes. Sensitivity analyses confirmed no significant pleiotropy or heterogeneity.

Conclusions:

• PM2.5 exposure has a causal role in the development of thyroid dysfunction, especially autoimmune hypothyroidism.
• Findings underscore the importance of air pollution reduction strategies for safeguarding thyroid health.