Association between perfluoroalkyl and polyfluoroalkyl substances and maternal thyroid-related hormones in pregnant women

Background Exposure to perfluoroalkyl and polyfluoroalkyl substances (PFAS) during pregnancy might affect thyroid-related hormone levels in pregnant women. However, most previous studies focused on the effects of PFAS containing 8-10 carbon atoms, and few studies have estimated the associations between PFAS with longer carbon chain and thyroid-related hormone levels.

Objective To examine the associations between PFAS exposure and thyroid-related hormones in pregnant women.

Methods The present study was based on the Jiashan Birth Cohort from September 2016 to April 2018. We analyzed 13 PFAS in maternal blood samples (n=781) by high-performance liquid chromatography-tandem mass spectrometry, as well as total triiodothyronine (T3), total thyroxine (T4), free T3 (FT3), free T4 (FT4), thyroid stimulating hormone (TSH), thyroglobulin antibody (TG-Ab), and thyroid peroxidase antibody (TPOAb) by electrochemiluminescence immunoassay. PFAS were divided into three groups:low concentration, medium concentration and high concentration according to the tertile of their concentrations. We estimated the associations between PFAS concentrations and thyroid-related hormones in pregnant women by multiple linear regression.

Results In the multiple linear regression models, a change in perfluorododecanoic acid (PFDoA) concentrations from the low concentration group to the high concentration group was associated with a −0.10 (95%CI: −0.20, 0) nmol·L⁻¹ change in T3, −0.15 (95%CI: −0.28, −0.02) pmol·L⁻¹ change in FT3, and −3.02 (95%CI: −5.66, −0.39) pmol·L⁻¹ change in FT4, respectively. A change in perfluorotridecanoic acid (PFTrDA) concentrations from the low concentration group to the high concentration group was associated with a −0.10 (95%CI: −0.20, 0) nmol·L⁻¹ change in T3. Compared with the low concentration group, the concentration of T4 in the medium concentration group of perfluorohexane sulfonate (PFHxS) increased by 6.10 (95%CI: 0.44, 11.75) nmol·L⁻¹. No statistically significant associations were found between PFAS and TSH concentration. The negative associations of PFAS with thyroid-related hormones were more pronounced in pregnant women with positive TG-Ab and/or TPOAb.

Conclusion Exposure to PFAS during pregnancy may affect thyroid-related hormone homeostasis in pregnant women, and the effect is stronger in TG-Ab and/or TPOAb-positive pregnant women.