ETA2022 Oral Presentations Oral Session 2: Pregnancy (5 abstracts)
Phthalate exposure is associated with thyroid function during pregnancy through a novel pathway as a hCG disruptor.
Objectives: hCG stimulates thyroid function in pregnancy and phthalates are known thyroid disruptors. We investigated if phthalate exposure could act as a thyroid disruptor through affecting hCG.
Methods: This study was embedded in the prospective Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study. Pregnant women were enrolled at median gestational week of 10 (with 95% recruited before week 14). Urinary concentrations of phthalate metabolite, serum thyroid function measurements and hCG were measured. We used linear regression and causal mediation analysis to investigate the potential mediation by hCG in the association of phthalates with maternal FT4.
Results: In total, 2004 women were included. Out of the 14 phthalate metabolites, higher MEP, MBP, MBzP and all metabolites of DEHP (MEHP, MEHHP, MEOHP, MECPP and MCMHP) were associated with lower hCG concentrations, with the largest effect estimate corresponding to a 0.15 IU/l decrease in hCG concentrations per 1 log-unit increase in urinary MBP concentrations (µg/g creatinine). We identified that of the 5 phthalate metabolites (MEP, MBP, MEHHP, MEOHP and MECPP) which were previously shown to be negatively associated with FT4 concentrations, hCG mediated 34% (MEOHP, P=0.004) to 60% (MBP, P=0.03) of the association of all five phthalate metabolites with FT4.
Conclusions: This is the first study to suggest phthalates act as a hCG disruptor. We also show that higher phthalate exposure during early pregnancy is associated with lower hCG concentrations, resulting in lower FT4 concentrations which is likely mediated through reduced stimulation of the thyroid gland.
10 Sep 2022 - 13 Sep 2022