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Your Environment. Your Health.

BPA Exposure Linked to Thyroid Level Changes for Pregnant Women and Newborns

Kim Harley, Ph.D., Brenda Eskenazi, Ph.D.
University of California, Berkeley
NIEHS Grants RC2ES018792, P01ES009605


A new study from NIEHS grantees links levels of urine bisphenol A (BPA) in pregnant women with changes in thyroid hormone levels for the women and their newborn boys. Thyroid hormone is necessary for healthy brain development, and the new findings add to growing health concerns about BPA.


The researchers studied 476 women participating in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) longitudinal study, which is examining environmental exposures and health among pregnant women and children. They measured BPA concentration in urine samples collected during the first and second half of pregnancy and also measured free and total levels of the thyroxine thyroid hormone as well as thyroid-stimulating hormone in the women. The investigators measured thyroid-stimulating hormone in the newborns.


The BPA measurement taken closest in time to the thyroid hormone measurement was significantly associated with reduced maternal total thyroxine (β=-0.13 Hg/dL per log2 unit; 95 percent CI=-0.25, 0.00). The average maternal BPA concentration was associated with reduced thyroid-stimulating hormone in boys (-9.9 percent per log2 unit; 95 percent CI=-15.9 percent, -3.5 percent) but not in girls. Among boys, the link was stronger for BPA measurements taken in the third trimester of pregnancy and decreased with increasing time between BPA and thyroid hormone measurements. Some animal studies suggest that males may not metabolize BPA as efficiently as females.


The researchers say that their results suggest that maternal BPA either has a transient effect on thyroid-stimulating hormone in the newborn or the existence of a developmental window of susceptibility. Further studies are needed to better understand the relationship.


Citation: Chevrier J, Gunier RB, Bradman A, Holland NT, Calafat AM, Eskenazi B, Harley KG. 2012. Maternal Urinary Bisphenol A during Pregnancy and Maternal and Neonatal Thyroid Function in the CHAMACOS Study. Environ Health Perspect; doi:10.1289/ehp.1205092 [Online 4 Oct. 2012].

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