Association of Polybrominated Diphenyl Ethers (PBDEs) and Polychlorinated Biphenyls (PCBs) with Hyperthyroidism in Domestic Felines, Sentinels for Thyroid Hormone Disruption

Abstract

BackgroundHyperthyroidism is the most common endocrine disorder observed in domestic felines; however, its etiology is largely unknown. Two classes of persistent organic pollutants, polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are known to interfere with thyroid hormone (TH) signaling and regulation; thus, it is postulated that they contribute to the etiopathogenesis of feline hyperthyroidism and pose a risk to humans and other species. In this case-control study, the concentrations of 13 PBDE and 11 PCB congeners were measured by gas chromatography mass spectrometry in serum or plasma samples from 20 hyperthyroid and 31 control cats in order to investigate the association between concentration of PBDE and PCB congeners and feline hyperthyroidism. Logistic regression analysis was used to determine whether elevated concentrations of individual congeners were associated with a higher risk of feline hyperthyroidism.ResultsHyperthyroid cats had higher concentrations of four PBDE congeners (BDE17, BDE100, BDE47, and BDE49) and five PCB congeners (PCB131, PCB153, PCB174, PCB180, and PCB196), compared to control cats. In addition, the sum of both PBDE and PCB congener concentrations were elevated in the hyperthyroid group compared to control cats; however, only the increased PCB concentrations were statistically significant. The sum total PBDE concentrations in our feline samples were approximately 50 times greater than concentrations previously reported in human populations from a geographically similar area, whereas sum total PCB concentrations were comparable to those previously reported in humans.ConclusionsThese observational findings support the hypothesis that PBDEs and PCBs may contribute to the etiopathogenesis of hyperthyroidism in felines. As domestic house cats are often exposed to higher concentrations of PBDEs than humans, they may serve as sentinels for the risk of TH disruption that these pollutants pose to humans and other species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-017-1031-6) contains supplementary material, which is available to authorized users.

Comparison of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the serum of hypothyroxinemic and euthyroid dogs

“…Our data agrees with these trends with the Bay Area having the highest concentrations of BDE-47, -99, and -100. Our results also agree with a recent study investigating PBDE congener profiles in felines from California ( Walter et al, 2017 ). In contrast, a feline study conducted in Sweden identified BDE209 and BDE207 as the most prevalent BDE congeners with BDE99 accounting for only 13% total body burden, compared to 44% in a US population ( Kupryianchyk et al, 2009 ).…”

“…Domestic pets, such as cats and dogs, share much of their environment with humans, thus they may serve as biosentinels of potential human health hazards by providing data on the contaminants within a defined area and serving as a proxy of human exposure to these environmental contaminants ( Venier & Hites, 2011 ; Walter et al, 2017 ). Even though pets and their owners share the same air, water, and housing, pets are usually free of lifestyle factors that may confound associations with true risk factors in humans, such as tobacco use, alcohol and caffeine consumption, poor diet, insufficient physical activity, and low social class ( Schmidt, 2009 ).…”

Prevalence and risk factors for hyperthyroidism in Irish cats from the greater Dublin area

“…Their involvement in the aetiology of hyperthyroidism has recently been disputed, at least in Australian cats [ 46 ]. However, several other studies have suggested that PBDEs may be involved in the aetiopathogenesis of the disease, at least in Europe and California [ 31 – 33 ]. Alternatively, clients owning cats that are kept predominantly indoors may be more observant of clinical signs associated with hyperthyroidism and thus more likely to present for veterinary attention.…”

“…Undoubtedly, there are many potential thyroid disruptors that cats may be exposed to, either through their diet or from the environment. Several factors have since been implicated in the development of hyperthyroidism including dietary iodine intake [ 27 ], soy isoflavone excess [ 28 , 29 ], exposure to bisphenol A from pop top or ring pull cans [ 8 , 30 ] and polybrominated diphenyl ethers (PBDEs) from the environment [ 31 – 33 ]. Overall the association between diet and development of hyperthyroidism is controversial and exemplified by the presence of the same potential dietary risk factors in areas of low prevalence of the disease [ 13 ].…”

Altered hepatic cytochrome P450 expression in cats after chronic exposure to decabromodiphenyl ether (BDE-209)

“…The studies have suggested that pet cats are suitable bio-sentinel for human exposure to household chemicals including PBDEs [ 7 , 8 , 19 , 26 ]. Feline hyperthyroidism associated with increased PBDE levels in cat serum have been reported worldwide [ 26 , 30 , 40 ], but the information on CYP expression in cat exposed to PBDE has not been provided. The objective of this study was therefore to investigate the CYP mRNA expression in cats treated BDE-209 for long-term exposure.…”