Human Study Shows Thyroid Hormone Levels Impacted by BPA, Phthalates

<"">Phthalates have been linked in a recent first-of-its-kind, large-scale study to impacts to thyroid function in humans. The nationally representative study was conducted by University of Michigan School of Public Health (U-M SPC) researchers. Science Daily also reported that the new study found consistencies with a prior report linking BPA (bisphenol A) and thyroid hormone levels.

The team utilized publicly available data derived from the U.S. National Health and Nutrition Examination Survey and compared urine metabolites and serum thyroid measures from 1,346 adults and 329 adolescents, said Science Daily. The research revealed that larger urinary phthalate metabolite levels and BPA were linked with increased impacts on serum thyroid measures, according to John Meeker, assistant professor at U-M SPH and the study’s lead author, said Science Daily. The study appears in the recent edition of the journal Environmental Health Perspectives.

The researchers discovered an “inverse” relationship between urine exposure markers and thyroid hormone levels, which means that increased urinary metabolite concentrations pointed to decreased serum levels of specific thyroid hormone levels, explained Science Daily.

BPA, a polycarbonate plastics chemical is present in a growing number of consumer products including food and beverage can linings, CDs and DVDs, dental sealants, plastic drink bottles and sippy cups, nautical resins, and thermal receipt paper. An estrogenic compound and hormone interrupter, BPA presents a potentially significant health issue. Consider this: BPA, with its hormone-mimicking properties, interrupts sexual development and processes, especially in developing fetuses, infants, and children and has been linked to toxic injury and implications in cardiovascular disease, intestinal problems, brain cell connection interference, increased risks of reproductive and immune system diseases and disorders, problems with liver function testing, interruptions in chemotherapy treatment, premature puberty, Polycystic Ovarian Syndrome (PCOS) and other female fertility and endocrine issues, and erectile dysfunction and male sexual problems. All frightening prospects, considering the chemical’s legendary ubiquity.

The chemicals that make plastics and vinyls more flexible—phthalates—have long been linked to health events. Phthalates are also part of a group of endocrine disruptor disorders, interfering with the body’s endocrine, or hormone system. Phthalates can be found in many consumer products including nail polishes, cosmetics, perfumes, lotions, and shampoos and are used to carry fragrance, increase product flexibility and durability, and coat medications or supplements to enable time-release delivery.

The new study found the most significant link between thyroid disruption and a plasticizer phthalate, DEHP, which is typically received through food, said Science Daily. The team found that urine samples with the greatest DEHP exposure—the highest 20 percent—were linked with decreases as high as 10 percent in some thyroid hormones, said Science Daily. “This seems like a subtle difference,” Meeker said, “but if you think about the entire population being exposed at this level you’d see many more thyroid related effects in people,” quoted Science Daily. Thyroid hormones are significant to reproduction, metabolism, and “energy balance,” said Science Daily.

Research has revealed that exposure to phthalates in young girls, can result in adverse physical effects, including disruption in pubertal development, which can lead to later complications; can cause negative behaviors in young children; have been linked to breast enlargement in boys; have been linked to ADHD; and, in pregnancy, to the birth of boys who express less typically masculine behaviors and to an increase in premature births. Phthalates have also been found to exacerbate dermatitis in tests with mammals. Some studies linked phthalate exposure to effects on the development of the male reproductive system: Infertility, undescended testes, and testicular development; penis and other reproductive tract malformations, such as hypospadias; and reduced testosterone levels. Some phthalates have been associated with liver cancer and problems with the developing fetus and are known to interfere with androgens.

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