The associations between concentrations of gestational bisphenol analogues and thyroid related hormones in cord blood: A prospective cohort study

The effect of bisphenols on sex and thyroid hormone concentrations in cord blood among newborns

This study aims to investigate the associations of bisphenols with sex and thyroid hormones in cord blood among newborns. Four bisphenols, three hormones related to gonadal function, and four parameters related to thyroid function were measured in umbilical cord blood in 378 mother-newborn pairs. Multivariable linear regression, quantile-based g-computation (QGC), and Bayesian kernel machine regression were used. In the multivariable linear regression, bisphenol A (BPA) was associated with increased testosterone (TT) (regression coefficient, β = 0.049, 95% confidence interval, CI: 0.013,0.085; p = 0.007) and free tri-iodothyronine (FT3) levels (β = 0.019, 95% CI: 0.003, 0.035; p = 0.023), and decreased thyroid peroxidase antibody (TPOAb) (β = -0.053, 95% CI: 0.098, -0.008; p = 0.021). Consistently associations were observed in males, except TT, which was observed in females, and bisphenol AF (BPAF) was associated with decreased follicle-stimulating hormone (FSH) in females. These associations were also observed in a mixture of bisphenols. Moreover, we observed maternal prepregnancy body mass index (BMI) and delivery mode disparity in the relationship between bisphenols and sex and thyroid hormones. This study suggests that bisphenols may exert effects on sex and thyroid hormones in newborns, the effect may vary with sex differences, maternal prepregnancy BMI, and delivery mode.

Association between maternal age and sex-based neonatal free triiodothyronine levels

BACKGROUND

Advanced maternal age may affect the intrauterine environment and increase the risk of neurodevelopmental disorders in offspring. Thyroid hormones are critical for fetal neurological development but whether maternal age influences fetal thyroid hormone levels in euthyroid mothers is unknown.

OBJECTIVE

This study evaluated the association between cord blood thyroid hormones and maternal age, fetal sex, maternal thyroid function, and other perinatal factors.

METHODS

The study population consisted of 203 healthy women with term singleton pregnancies who underwent elective cesarean section. Maternal levels of free T3 (fT3), free T4 (fT4) and TSH before delivery, and cord levels of fT3, fT4 and TSH were measured. Spearman's correlation coefficient and multiple linear regression analyses were performed to determine the correlation between cord thyroid hormone parameters and maternal characteristics.

RESULTS

There were no significant differences in maternal serum or cord blood thyroid hormone levels between male and female births. In multivariate linear regression analysis, maternal age and maternal TSH values were negatively associated with the cord blood levels of fT3 in all births, after adjusting for confounding factors. Maternal age was more closely associated with the cord blood levels of fT3 in female than in male births.

CONCLUSION

The inverse association between maternal age and cord blood levels of fT3 in euthyroid pregnant women suggested an impact of maternal aging on offspring thyroid function.

Screening for endocrine disrupting chemicals inhibiting monocarboxylate 8 (MCT8) transporter facilitated thyroid hormone transport using a modified nonradioactive assay

Early neurodevelopmental processes are strictly dependent on spatial and temporally modulated of thyroid hormone (TH) availability and action. Thyroid hormone transmembrane transporters (THTMT) are critical for regulating the local concentrations of TH, namely thyroxine (T4) and 3,5,3'-tri-iodothyronine (T3), in the brain. Monocarboxylate transporter 8 (MCT8) is one of the most prominent THTMT. Genetically induced deficiencies in expression, function or localization of MCT8 are associated with irreversible and severe neurodevelopmental adversities. Due to the importance of MCT8 in brain development, studies addressing chemical interferences of MCT8 facilitated T3 uptake are a crucial step to identify TH system disrupting chemicals with this specific mode of action. Recently a non-radioactive in vitro assay has been developed to rapidly screen for endocrine disrupting chemicals (EDCs) acting upon MCT8 mediated transport. This study explored the use of an UV-light digestion step as an alternative for the original ammonium persulfate (APS) digestion step. The non-radioactive TH uptake assay, with the incorporated UV-light digestion step of TH, was then used to screen a set of 31 reference chemicals and environmentally relevant substances to detect inhibition of MCT8-depending T3 uptake. This alternative assay identified three novel MCT8 inhibitors: methylmercury, bisphenol-AF and bisphenol-Z and confirmed previously known MCT8 inhibitors.