A recent University of Michigan study has reportedly suggested that phthalates and bisphenol A (BPA) could affect thyroid functioning in humans. John Meeker and Kelly Ferguson, “Relationship Between Urinary Phthalate and Bisphenol A Concentrations and Serum Thyroid Measures in U.S. Adults and Adolescents from NHANES 2007-08,” Environmental Health Perspectives, July 11, 2011. Researchers apparently used thyroid serum measures from 1346 adults and 329 adolescents enrolled in the U.S. National Health and Nutrition Examination Survey to determine that “[g]enerally speaking, greater concentrations of urinary phthalate metabolites and BPA were associated with greater impacts on serum thyroid measures.” In particular, the study found that as urinary metabolite concentrations for di(2-ethylhexyl) phthalate (DEHP) and BPA increased, certain thyroid hormones decreased.

“The current study showed the strongest relationship between thyroid disruption and DEHP,” explained a July 12, 2011, University of Michigan press release, which noted that “urine samples in the highest 20 percent of exposure to DEHP were associated with as much as a 10 percent decrease in certain thyroid hormones compared to urine samples at the lowest 20 percent of exposure.”

“This seems like a subtle difference,” study author Meeker was quoted as saying. “But if you think about the entire population being exposed at this level you’d see many more thyroid related effects in people.”