Phthalates Linked to Disruption of Pregnancy Hormone

  • Jennifer Adibi is an assistant professor of epidemiology the University of Pittsburgh, and she recently presented new findings from her research into phthalates and early pregnancy. Photo: Kara Holsopple

March 13, 2015

Phthalates are chemicals used to make plastic products pliable, and they’re found in food packaging, shampoos and even baby products. Phthalates have also been fingered as endocrine disruptors, impacting normal hormonal function. 

Jennifer Adibi, MPH Sc.D., an assistant professor of epidemiology the University of Pittsburgh, recently presented new findings from her research into phthalates and early pregnancy. The research, presented at the Endocrine Society's annual meeting in San Diego, looks at early pregnancy and how phthalates affect sex differentiation in fetuses. Adibi found that phthalates can disrupt an essential pregnancy hormone, human chorionic gonadotropin (hCG), and affect the masculinization of male genitals in babies.

The research piggy-backed on an existing study of pregnant women—in their first trimesters—in four cities. Urine samples were collected, phthalates measured, and then babies were measured at birth. Adibi’s study added on the hCG pregnancy hormone. 

“We found that the mother's concentrations, in her urine, of a very common chemical, called phthalates, was associated with levels in her blood of a pregnancy hormone called human chorionic gonadotropin,” Adibi says. “ And the association actually differs depending on whether or not she was carrying a male baby or a female baby. So in the case of female babies, higher phthalates was associated with higher hormone level, and in the male it was the opposite.”

Adibi says hCG is made in the placenta and plays an important role in many aspects of pregnancy, though with respect to the fetal development, there's less known.

“...it has been shown that hCG does bind to a receptor in the male fetal testis, that is essential for initiating the production of the male hormone testosterone, and testosterone is required for normal male development,” she explains.

So how could phthalates disruption of this hormone impact the development and later life of boy babies? Adibi says it’s still unclear in humans, but experiments with rodents tell a different story.

“There are in the rodents very well worked out experimental models, where if you give the pregnant mother the phthalate, you get a whole constellation of effects in the males related to testicular development, so lower testosterone certainly, malformations in the genitalia. Over the life of that male there will be lower sperm count, lower fertility, eventually maybe a higher risk of testicular cancers,” she says.

But the measure the researchers took in the newborn babies in the study—AGD, or anogenital distance, the measure from the anus to the bottom of the genitalia—could hold a clue. Adibi says lower AGD is “correlated to reproductive health and function of that child as he or she goes through life.”

Adibi says researchers won’t know if phthalates are causing an adverse effect in babies until there is more study in humans.

“We would need to know how those babies are different given their shorter anogenital distance at birth. We don't know that for sure, “ she says. “I think that what the strength of this study is that we’re getting our first real signal that there’s a physiologic thing...we can measure early in pregnancy that is correlated with these exposures, which means that we can...shine the light early in pregnancy in terms of how the placenta and the fetus are responding to environmental exposures and also how that might be related to the health of the baby longterm.”

Adibi says her research is unique in studies of endocrine disruptors because it tries to identify and characterize the role of the placenta.

“The placenta is this major and fascinating organ that’s basically produced by the fetus. Without placenta, you don’t get life. It’s carrying out all kinds of functions essential for the pregnancy and for the baby’s development, yet it is often overlooked,” she says.

Though the study doesn’t identify ways the data could be used by healthcare providers to treat pregnant women and babies who have been exposed to phthalates, Adibi says it adds to concern over the pervasiveness of phthalates.

“They’re just everywhere, to the point where a lot of us just throw up our hands because you can shop at Whole Foods everyday and do your best to eliminate your phthalates, but they’re generally still going to show up in your urine,” she says. “I think that the take-home message really is more to the makers of the products, to the government regulatory agencies—how can we as a society think about these exposures and do we want to endure these risks, and are there options, maybe potential for innovation, to think of ...still having our plastics, but better, safer plastics that are not going to harm our fetuses."