Environmental chemical links to hyperthyroidism in cats

Abstract

Feline hyperthyroidism (FH) is the most common endocrine disorder affecting cats and poses significant health challenges to domestic cats and veterinary professionals. This disease is caused by the effects of excess thyroid hormone production and causes a variety of symptoms including weight loss, increased urination, and increased appetite. Despite its prevalence, the underlying cause of this condition remains unclear. While many factors have been extensively studied, there isn't conclusive evidence linking hyperthyroidism to diet, litter, and indoor lifestyle. Recent research has suggested an association between FH and exposure to flame retardants in consumer products. Many consumer products also contain other endocrine-disrupting chemicals (EDCs) and potential endocrine-disrupting chemicals (pEDCs) in addition to flame retardants that could be linked to FH. To investigate this further, silicone passive sampling devices (PSDs) in the form of pet tags were used to measure the environmental chemical exposure of 78 cats, aged seven years and older, in Oregon and New York using a chemical screening method containing hundreds of EDCs/pEDCs. The objective of this study was to compare exposure frequencies and concentrations between hyperthyroid and non-hyperthyroid cats. While no statistically significant associations were identified, this study found higher concentrations of butyl benzyl phthalate (BBP), galaxolide, lilial, and tonalide in the tags worn by cats with FH compared to euthyroid cats. TCPP, b-ionone, lilial, cinnamal, benzyl salicylate, and tonalide have not been previously mentioned in past feline exposure studies. These chemicals are found in various personal care and consumer products such as vinyl tiles, fragrances, furniture, and cosmetics. Their presence in PSDs worn by cats that develop hyperthyroidism may indicate a potential role of these environmental chemicals in FH etiology.