Prevalence of Feline Hyperthyroidism in Osaka and the Chugoku Region

Random tests for serum thyroxine (T4) concentration were performed on 112 aged cats brought to hospitals in Osaka and the Chugoku region. Of them, 10 (8.9%) were diagnosed as having feline hyperthyroidism (FHT) with high concentrations of T4 at 4.0 μg/dl or greater. Cats with FHT lost weight, vomited, had poor appetites, and suffered from tachycardia. The thyroid gland was not palpated in any of the cats. Blood-chemistry investigations revealed high ALT and ALP values in cats with FHT. No specific relationship between the development of FHT and food type was observed in the present study. These results suggest that FHT is not rare in this area and that T4 should be evaluated as a thyroid-function test in aged cats demonstrating weight loss, vomiting, decreased appetite and tachycardia or elevated ALT and ALP values.