Hyperthyroidism, a New Disease in Cats – Is It Caused by Exposure to Environmental Organic Pollutants?

Kupryianchyk D., Hovander L., Jones B., et al.

Organohalogen Compounds, 2009. 71: p.002720-002725.


Feline hyperthyroidism has been observed to increase all over the world since the end of 1970s. It has been suggested that increased risk of developing hyperthyroidism in cats is associated with indoor living and consumption of canned food. In 2007 a group of American scientists hypothesized that the high incident of feline hyperthyroidism is associated with intensive use of brominated flame retardants, in particular PBDEs, which cats are exposed to through diet, inhalation of house dust and direct contact with flame-retarded materials. The results of their study did not show any association between hyperthyroid cats and levels of PBDEs. The present study was performed to evaluate levels of halogenated (including chlorinated, brominated and fluorinated) contaminants in cat serum from Sweden and, to determine whether body burdens of these compounds differ depending on thyroid status.

One hundred thirty eight serum samples from Swedish cats were obtained from client-owned cats around Sweden, pooled into 21 pools in accordance with cat thyroid status and age. The samples were analyzed for organohalogen pesticides, PCBs, PBDEs and PFCs. Totally ten PCB congeners, dominated by CB-138, -153 and -180, were detected in the Swedish cat serum samples. Likewise, 10 PBDE congeners were detected and quantified in the serum, with BDE-209 present at the highest levels. Among the PFCs, PFOS and PFOA dominated, but at far lower concentrations than e.g. 4,4’-DDE, PCB and PBDE congeners.

The results of the study showed that pet cats from Sweden are exposed to a wide range of organohalogen contaminants. Since they share living environment with their owners, they can serve as indicators and be used in assessment of human exposure to various pollutants. Further research is required to evaluate if chronic exposure to PBDEs may have any health consequences for pet cats.