Kennedy R.L. and Thoday K.L.
Hyperthyroidism, although common in Man, is relatively uncommon in other species. The only animal with an appreciable incidence of hyperthyroidism is the domestic cat. Benign thyroid swellings have long been recognised in the cat, but hyperthyroidism has only been described and characterised in recent years. It is a disease of older cats with no particular breed or sex predisposition. The clinical and biochemical features of the condition are entirely analogous to those of hyperthyroidism in Man. Histologically, the glands excised from such animals usually resemble the toxic nodular goiter found in Man rather than Graves’ disease. However, in a series previously reported by us, there were features in some cases which would be compatible with an autoimmune aetiology: many of the glands were infiltrated with lymphocytes, there were cases which recurred within a few months of successful surgical treatment and 34.5% of cases had circulating thyroid autoantibodies.