Gestational Perfluoroalkyl Concentrations and Thyroid Hormone Levels in Faroese Pregnant Women and Neonates: A Prospective Cohort Study

Abstract

Background: Exposure to perfluoroalkyl substances (PFASs) may disrupt maternal and neonatal endocrine function. Adequate thyroid hormone (TH) levels during pregnancy are essential for fetal and early childhood development.Objective: To assess the relationship between gestational PFAS exposures and maternal and cord TH levels.Methods: Data was collected from a cohort of 182 mother-child pairs from 1994-1995 in the Faroe Islands. The concentrations of 17 PFASs, including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were measured in maternal serum. Maternal and cord serum were measured for THs such as thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroxine (T4), free triiodothyronine (FT3), free triiodothyronine resin uptake (T3RU), and free T4 index (FTI). We examined relationships between PFAS concentrations and TH levels using multivariable regression models and effect measure modification in sex-stratified analyses.Results: PFAS concentrations were mostly positively associated with both maternal and fetal TSH. PFOS and PFOA had the strongest estimates; doubling PFOS and PFOA concentrations were associated with 49% (95% CI: 18, 87%) and 33% (95% CI: 11, 59%) increase in cord TSH concentrations respectively. Perfluorooctanesulfonamide (PFOSA) was negatively associated with maternal FT4 and T3RU but positively associated with cord T4 and FTI levels. In mothers carrying female fetuses, doubling PFOS concentrations was associated with a 54% (95% CI: 14, 109%) increase in maternal TSH, but not in mothers bearing male neonates (-5%; 95% CI: -27, 24%). We did not observe consistent patterns for sex-stratified associations between gestational PFAS concentrations and cord TH levels.Conclusions: Prenatal exposure to several PFASs during pregnancy, such as PFOS and PFOA, is associated with increases in infant TSH levels. PFOS may also affect maternal TSH levels depending on the fetus’s sex, the implications of which are still to be understood.