Feline hyperthyroidism is the most common endocrinopathy in cats. Several epidemiological studies suggest that hyperthyroidism is a common disease in countries such as UK (11.9%), Germany (11.4%), Portugal (9%), Poland (20.4%) and Ireland (21%). However, in Spain it has been historically considered a rare disease. A retrospective study in 2005 found a prevalence of 1.53% and 10% in a second prospective study in 2015 in 207 geriatric cats. The aims of this study were to assess the overall and regional prevalence of feline hyperthyroidism in Spain, to determine the age of hyperthyroid and non-hyperthyroid cats and to evaluate the percentage of animals with more than one measurement of total thyroxine (tT4) and the time between these. The study was performed retrospectively, including serum blood samples submitted to a reference laboratory during a 3-year period (January 2016 to December 2018). Prevalence in this population referred to the total number of hyperthyroid cats divided by the total number of individual cats tested. Serum tT4 concentrations were determined in all cats by use of a chemiluminescent competitive immunoassay (Immulite 2000 feline tT4). A cat was considered hyperthyroid when the tT4 concentration was greater than 4.7 μg/dL (reference range 0.8–4.7 μg/dL). A total of 27,893 client-owned cats from different regions of Spain were included in the study. The overall prevalence of feline hyperthyroidism was 6.35%. The prevalence was variable according to the area, with a lower prevalence in Castilla Leon (3.17%) and a higher prevalence in Balearic Islands (9%). Age data was available from 6,470 cats. The mean age of the hyperthyroid cats was 14 years (range 2–25) and 11.7 years (range 1–27) in non-hyperthyroidism group. Total thyroxine measurement was repeated in 8.5% of the cats. Average of repeated measurements in the hyperthyroid group was 4 months compared to 8.6 months in the non-hyperthyroid cats. The number of cats in which tT4 was measured increased from 2016 to 2018 (from 7,652 to 10,345 cats tested per year) which might suggest a more thorough follow-up or greater effort in challenging cases. The overall prevalence of feline hyperthyroidism was 6.35% in a population of 27,893 cats in Spain, but these results were variable according to the area. To the authors’ knowledge this has been the largest prevalence study performed in Spain about feline hyperthyroidism.

Disclosures

Disclosures to report
Raquel Santiago residence program has been sponsored by IDEXX laboratories.