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Hyperthyroidism in Cats - A Progressive Disease?

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    • 26 posts
    April 20, 2015 11:53 AM EDT

    Hyperthyroidism is a common endocrine disease in geriatric cats. In the late 1980s it was reported to be a rare disease, however it is now estimated that up to 10% of senior and geriatric cats develop hyperthyroidism. It is unknown whether this increase in prevalence over the years is because of better screening methodologies or due to an increase in actual disease incidence. The majority of affected cats have benign thyroid or multifocal adenomas, and up to 2% of affected cats develop thyroid carcinomas.

    Standard of medical care for hyperthyroid cats includes the oral administration of methimazole. Radioiodine therapy and surgery are definitive treatment options. Many cats with hyperthyroidism are medically managed with methimazole chronically - only to seek referral for I-131 treatment when methimazole no longer maintains control of serum T4 concentrations. 
    A recently published paper reports on the effect of disease duration on the prevalence and degree of thyroid pathology in hyperthyroid cats. This study included data from 2096 cats referred for radioiodine therapy and examined the effect of disease duration on:

    • Serum T4 concentrations in cats
    • Distribution of lesions seen on scintigraphy
    • Tumor size and burden
    • Risk for suspected malignancy
    The discussion of those findings and the clinical significance including:
    • Why to consider early referral of patients for definitive therapy 
    • Why this may be considered a progressive disease
    • Why chronic use of methimazole might not be so good

    is availble for viewing on demand in the Evidence Based Updates (running time 11 mins). (Approved for CE credit in New York and by the NJVMA, pending approval for CE credit by AAVSB RACE).



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    Prevalence and degree of thyroid pathology in hyperthyroid cats increases with disease duration: a cross-sectional analysis of 2096 cats referred for radioiodine therapy - Journal of Feline Medicine and Surgery (2015)