Phenols and Parabens Affect Thyroid Hormones in Pregnant Women

The “Trainee Publication Spotlight Series” aims to provide PROTECT trainees with opportunities to practice translating their research in a manner that would be understandable to non-scientific laypeople. Today’s trainee spotlight was written by Amira M. Aker on the publication “Associations between maternal phenol and paraben urinary biomarkers and maternal hormones during pregnancy: A repeated measures study.”

Authors: Amira M. Aker, Lauren Johns, Thomas F. McElrath, David E. Cantonwine, Bhramar Mukherjee, John D. Meeker

There are many chemicals in every day consumer products. Phenols and parabens are examples of such chemicals that are found in a variety of products, including plastics, personal care products (such as shampoos, soaps, creams, make-up, etc.) and pesticides. These chemicals have also been detected in urine and blood samples in the majority of the U.S. population, and concerns have been raised as to whether or not these chemicals in our bodies can affect our health. We were particularly interested in the effect of these chemicals on a mother’s thyroid hormone levels during pregnancy, since pregnancy is a sensitive time period with a lot of hormone changes. In addition, a fetus is dependent on the mother’s thyroid hormone levels during early pregnancy for development, in particular to brain development.

We followed a group of 439 pregnant women that were part of a larger study in Boston, MA. The women were visited at up to four time points during pregnancy to gather data and collect urine and blood samples (Visit 1: 5-19 weeks into the pregnancy; Visit 2: 15-30 weeks into the pregnancy; Visit 3: 23-26 weeks into the pregnancy; and Visit 4: 33-38 weeks into the pregnancy). After analyzing the levels of 10 phenols and parabens in the study participants’ urine, and analyzing the levels of four thyroid hormones in the study participants’ blood, we modeled the levels of hormones against the level of phenols and parabens to look for any potential relationships between them. Our results showed a relationship between four phenols and parabens (benzophenone-3, triclosan, triclocarban and butyl-paraben) and a decrease in the hormone total triiodothyronine (T3). Whereas, another paraben, methyl-paraben was associated with an increase in T3. Propyl-paraben was related to a decrease in the hormone, free thyroxine (FT4). We then re-ran the models to look at the relationships separately during visits 1-4, and found that the timing during pregnancy also made a difference in the relationships we found between these chemicals and hormones. This study provides evidence that phenols and parabens could affect thyroid hormones in pregnant women. However, additional research is required to replicate our results and add confidence to our results.