Feline Hyperthyroidism - a technical bulletin

摘要

Feline hyperthyroidism is the most common endocrinopathy diagnosed in domestic cats and is one of the most frequently diagnosed disorders in small animal practice, affecting approximately one in 300 cats in the UK. The prevalence of the disease in cats in Ireland was recently investigated by Dr. Carmel Mooney in a study, partially funded by MSD Animal Health. Preliminary results suggest that more than one in five older cats (> 10 years old) were affected by the disease. The previous low rate of diagnosis/prevalence may be due to low testing rates and an acknowledged difficulty for the study practitioners to palpate goitre in hyperthyroid animals. Feline hyperthyroidism is a multi-systemic disorder resulting from excessive levels of the circulating thyroxine (T4) and triiodothyronine (T3). Ninety-nine per cent of cases result from benign nodular hyperplasia, adenomatous hyperplasia or adenoma with both glands affected in 70-75% of cats. Only 1-3% of cases are caused by mild to moderately malignant thyroid carcinoma; as such, the disease carries a favorable prognosis with effective therapy. Although the incidence of feline hyperthyroidism has increased steadily since the early 1980s, the cause is still unknown. A number of theories have been proposed including:Diet - high levels of iodine and goitrogenic compounds, such as phthalates;Environmental factors- regular exposure to pesticides and fertilisers;Genetic mutation;Abnormal immune responses; and,Abnormal hormonal responses.