Adults and young boys exposed to high levels of phthalates—chemicals found in plastics and some personal care products—tend to have reduced levels of testosterone in their blood compared to those with lower chemical exposure, according to a new University of Michigan study.

[Photo: Dr. John Meeker]

Testosterone, the main sex hormone in men, contributes to a variety of functions in both sexes, including physical growth and strength, brain function, bone density, and cardiovascular health. Animal and cellular studies have found that some phthalates block the effects of testosterone on the body’s organs and tissues. Researchers set out to examine whether these chemicals, which are widely used in flexible PVC plastics and personal care products, had a similar effect in humans.

“We found that reduced levels of circulating testosterone were associated with increased phthalate exposure in several key populations, including boys ages 6-12, and men and women ages 40-60,” said Dr. John Meeker, associate professor of environmental health science at the U-M School of Public Health.

Dr. Meeker and colleague Dr. Kelly Ferguson of the U-M School of Public Health examined phthalate exposure and testosterone levels in 2,208 people who participated in the U.S. National Health and Nutrition Examination Survey, 2011-2012. The researchers found an inverse relationship between phthalate exposure and testosterone levels at various life stages. In women ages 40-60, for example, increased phthalate concentrations were associated with a 10.8-to-24 percent decline in testosterone levels. Among boys ages 6-12, increased concentrations of metabolites of a phthalate called di-(2-ethylhexyl) phthalate, or DEHP, was linked to a 24-to-34.1 percent drop in testosterone levels.

“While the study’s cross-sectional design limit the conclusions we can draw, our results support the hypothesis that environmental exposure to endocrine-disrupting chemicals such as phthalates could be contributing to the trend of declining testosterone and related disorders,” Dr. Meeker said. “With mounting evidence for adverse health effects, individuals and policymakers alike may want to take steps to limit human exposure to the degree possible.”

For more information:  http://ns.umich.edu/new/releases/22339-reduced-testosterone-tied-to-chemical-exposure