Researchers from the University of California, Berkeley found a significant association between maternal urinary bisphenol A (BPA) concentrations during pregnancy and the serum thyroid stimulating hormone (TSH) levels of male neonates (Chevrier et al. 2013). Maternal urinary BPA was also negatively associated with maternal total T4, but free T4 levels remained unaffected. T4 is the thyroid hormone synthesized by the thyroid which needs to be metabolized to T3 in order to become effective. Only free T4 can be metabolized by the liver. The authors evaluated maternal urinary BPA and maternal as well as neonatal serum thyroid hormones of 364 mother-child pairs. Urinary conjugated and free BPA was measured in two spot measurements in the first and second half of pregnancy. BPA is used as a monomer in polycarbonate plastics and in epoxy resins for food packaging, amongst other uses (thermal paper etc). The disruption of thyroid function observed in the study could be relevant for effects on cognition, behavior and growth, but further research is necessary. In particular it is not clear what health effects in children are linked to reduced total T4 in pregnant women.
Chevrier, J., R. B. et al. (2013). “Maternal Urinary Bisphenol A during Pregnancy and Maternal and Neonatal Thyroid Function in the CHAMACOS Study.” Environ Health Perspect 121, 138-144.