An investigation of per- and polyfluoroalkyl concentrations in dogs and cats with endocrine disorders.

INTRODUCTION: Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with endocrine-disrupting and potential carcinogenic effects in humans. Data on PFAS exposure in companion animals are limited. This study quantified PFAS concentrations in dog and cat serum and investigated associations with endocrine disorders. METHODS: This retrospective study included 179 dogs from the Universities of Bologna and Utrecht, and 84 cats from the University of Bologna, sampled between 2021 and 2025. The population comprised 23 healthy dogs, 35 healthy cats, and animals with endocrine disorders, including 49 cats with hyperthyroidism, 64 dogs with pituitary-dependent hypercortisolism, 16 with primary hyperparathyroidism, and 85 with adrenal tumors. Eleven PFAS were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Between-group differences were evaluated using nonparametric tests, associations with disease status using age-adjusted generalized linear models, and correlations with age and body condition score using Spearman's rank correlation. RESULTS: Eight PFAS were detected in dogs and nine in cats. The most frequently detected compounds were perfluorooctanesulfonic acid (PFOS, 99.5%), perfluorohexanesulfonic acid (PFHxS, 69.0%), and perfluorooctanoic acid (PFOA, 68.5%) in dogs, and PFOS (99.0%) and PFOA (96.0%) in cats. Dogs from Utrecht had higher PFOS concentrations than dogs from Bologna. Unadjusted between-group differences varied by species, with higher PFAS concentrations in healthy cats but higher concentrations of some PFAS in certain canine diseased groups. After adjustment for age, no PFAS was independently associated with disease status in either species. A weak negative correlation between ∑PFAS and age was observed in dogs (r = -0.206, p = 0.005) and cats (r = -0.234, p = 0.032), and diseased animals were older than healthy controls, suggesting that age contributed to the observed between-group differences. No significant associations were found with body condition score. DISCUSSION AND CONCLUSIONS: PFAS exposure was widespread in both species, with higher PFOS concentrations in dogs from the Dutch cohort. The inverse association between PFAS concentrations and age, together with the older age of diseased animals, suggests that age substantially contributed to the observed between-group differences. Further longitudinal studies, including minimally exposed control populations, are warranted to clarify the health implications of PFAS exposure in companion animals.