From MedPage Today
Perfluorinated chemicals (PFCs), a class of chemicals used in products ranging from stain-resistant fabrics to fire extinguishers, may increase levels of thyroid hormones, particularly among women, researchers reported.
In an analysis of NHANES data, there was a significant positive relationship between perfluorooctanoate (PFOA)
and total T3 and between perfluorohexane sulfonate (PFHxS) and total T3 and total T4
among women, Chien Yu Lin, MD, PhD, of En Chu Kong Hospital in New Taipei City in Taiwan, and colleagues reported online in the Journal of Clinical Endocrinology and Metabolism.
For men, they saw an inverse association between PFHxS and free T4.
"These findings suggest an effect of low-dose PFOA and PFHxS in humans, although the potential biological significance of this effect is small and subclinical in the general U.S. population," they wrote.
PFCs are widely used in consumer and industrial goods, including fabrics, carpets, surfactants, lubricants, paper coatings, cosmetics, and fire-fighting foams. They are characterized by highly stable carbon-fluoride bonds.
In addition to PFOA and PFHxS, other PFCs include perfluorooctane sulfonate (PFOS) and perfluorononanoic acid (PFNA). The researchers noted that PFOA and PFOS are largely being phased out and replaced with short-chain PFCs such as PFHxS.
Although further study is needed to clarify whether there's a causal relationship between PFC concentrations and thyroid function -- the study was limited by its observational nature and by its cross-sectional design -- the researchers said the findings "provide clues about where to focus future epidemiologic and toxicology research."