BPA linked to thyroid hormone changes in pregnant women, newborns

http://www.eurekalert.org/pub_releases/2012-10/uoc--blt100212.php

Public release date: 4-Oct-2012
Contact: Sarah Yang
University of California - Berkeley

Berkeley — Bisphenol A (BPA), an estrogen-like compound that has drawn increased scrutiny in recent years, has been linked to changes in thyroid hormone levels in pregnant women and newborn boys, according to a new study by researchers at the University of California, Berkeley.

Normal thyroid function is essential to the healthy growth and cognitive development of fetuses and children. Yet, until this study, to be published Thursday, Oct. 4, in the journal Environmental Health Perspectives, little was known about the effects of BPA exposure on thyroid hormones in pregnant women and newborns.

The new findings add to growing health concerns about BPA, a chemical found in hard plastics, linings of canned food, dental sealants, and sales receipts on thermal paper, which is coated with a chemical that changes color when exposed to heat. In July, the U.S. Food and Drug Administration officially banned the chemical in baby bottles and cups, something the industry began doing voluntarily in recent years in response to consumer concerns about the potential risks of BPA.

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It was not clear why an association was not found among newborn girls, but animal studies may provide some clues. One study in neonatal rats found a similar hyperthyroidic effect in males, but not females. Another study found that female rats had higher levels of an enzyme important in metabolizing BPA when compared with their male counterparts. Whether that same relationship holds true for humans is not yet clear.

"In addition, studies in rodents are increasingly showing that BPA can have different effects in males and females, particularly in brain development and behavior," said the study's senior author, Kim Harley, adjunct associate professor of public health and associate director of CERCH.

The researchers pointed out that several studies in recent years have linked lower thyroid hormone levels to delays in cognitive and motor development in young children. Two years ago, the same group of UC Berkeley researchers also found links between PBDEs (polybrominated diphenyl ethers), a class of flame retardants, and changes in thyroid hormone levels.