Cal study links BPA to thyroid hormone changes


Bisphenol A, or BPA, is a chemical found in hard plastics. It's hard to avoid -- researchers say 95 percent of the U.S. population has detectable levels in their bodies. Animal studies have shown that females are better at metabolizing BPA, which could explain why the UC Berkeley study found the relationship between the chemical and hormone levels only in the baby boys.

UC Berkeley researchers found that pregnant women with higher levels of BPA had lower levels of an important thyroid hormone. While that in itself doesn't hurt the woman, it could hurt their baby boys.

"The important thing about looking at thyroid hormone levels during pregnancy is you need proper thyroid hormone levels during pregnancy for proper brain development," said Tracey Woodruff, Ph.D., director of UCSF's program on Reproductive Health and the Environment. Woodruff says they do research similar to the new Berkeley study, "The developing fetus is completely dependent on the maternal thyroid hormone levels during the first part of pregnancy. So if mom has decreased thyroid hormone level then that means the fetus is getting less thyroid hormone."

Lead author of the Berkeley study, Jonathon Chevrier, Ph.D., says that at this point there's no cause for panic. He says it's important to remember it's the first study of its kind, and the results need to be confirmed, "I wouldn't say at this point that this is alarming. I would say that it is cause for concern. These hormones, as I said, are very important for child development."

Chevrier says the main sources of exposure for the women in his study were canned food and beverages, and use of hard clear plastic like reusable water bottles. In July of this year, California banned BPA in baby bottles and sippy cups, but it can still be found in canned baby formula.

Now Chevrier will look at the effect on the children of the women in his study. Those baby boys are now 12-years-old, "This is our next step. So right now we've looked at the hormone and we are in the process of looking at potential relationship with outcomes like obesity, brain development, and child growth as well."

The American Chemistry Council, a plastics industry group, says the bulk of research shows BPA is safe as used now. About the Berkeley study, the group says, quote, "The speculation that BPA is linked to health effects caused by thyroid hormone levels in woman and newborns is not supported by the data."

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