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.
Highlights
Hyperthyroidism is the most common endocrine disorder observed in domestic felines; its etiology is largely unknown
A Mann-Whitney rank sum test indicated that age varied significantly between study groups (p = 0.040); age was controlled for in subsequent logistic regression analyses to assess the influence of Polybrominated diphenyl ether (PBDE) and Polychlorinated biphenyl (PCB) congener concentration on the risk of hyperthyroidism
The sum of concentrations for PBDE and PCB congeners in all samples, the control, and the hyperthyroid group was calculated for all the congeners measured (ƩPBDEs and ƩPCBs) and for those with detection frequency (DFR) of greater than 40% (ƩPBDE40 and ƩPCB40) (Additional file 1: Table S1)
Summary
Hyperthyroidism is the most common endocrine disorder observed in domestic felines; 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; 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. As domestic cats and their human owners share their environment, it is probable that environmental factors that contribute to FH may adversely impact the thyroid health of humans and other animal species
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