Fish-flavored cat food could contribute to feline hyperthyroidism, study suggests

Hyperthyroidism is a hormonal disorder that can cause weight loss, hyperactivity, aggression, vomiting and other symptoms in cats. No one knows for sure what causes it. But some studies have suggested a connection between environmental pollutants including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), which have been banned in many countries because they could potentially harm humans. Previous studies have detected these compounds and their byproducts in blood samples from cats. But the byproducts, which can also have toxic effects, could come naturally from other sources such as fish, a common ingredient in cat food. Hazuki Mizukawa, Kei Nomiyama and colleagues wanted to investigate whether cats were getting exposed from their fish-flavored food.

The researchers tested cat food and blood samples from cats. They also simulated how a feline's body would process various PCB- and PBDE-related compounds. Based on their results, the team concluded that the byproducts that were detected at high levels in cats' blood samples likely came from fish-flavored food and not exposure to PCBs or PBDEs. The researchers say further work is needed to clarify whether these metabolites specifically contribute to hyperthyroidism.

The authors acknowledge funding from the Japan Society for the Promotion of Science.