2016 ACVIM Forum Research Abstract Program

To authors' knowledge this is the first study to report increased risk of hyperthyroidism in long haired, non-purebred, domestic cats. Consistent with a number of previous studies, increased risk of hyperthyroidism was found with increased age and female sex, and reduced risk in Burmese, Siamese and Persian breeds. However, this study also newly identified two further purebreds, Abyssinian and British shorthair, at reduced risk of hyperthyroidism, neither of which were exclusively colourpoint. Coat colouration was not found to be associated with risk of hyperthyroidism in the analysis of domestic cats, however, reliance on secondary data may have resulted in misclassification errors and coat phenotype may be a poor surrogate marker for melanin concentrations. Further studies are required to evaluate tyrosine availability as a potential factor in the aetiology of feline hyperthyroidism, and to investigate the apparent protective effect in certain purebreds and associations between hyperthyroidism and hair length. Medical records were searched for cats receiving 131-I therapy after documented feeding of the prescription diet for at least 14 days. Cats were excluded if the prescription diet had been supplemented with other foods, or if methimazole had been administered concurrently with, or subsequent to, the prescription diet. Owners were contacted directly to provide missing dietary information.