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Hyperthyroidism in Cats

by DR. SHERI SIME on MARCH 21, 2011 in ARTICLES (Updated 20 November 2013)

Hyperthyroidism in Cats

Middle-aged to older cats are commonly affected by an overactive thyroid gland. In rare cases, it is a consequence of a malignant tumour of the thyroid gland. Symptoms are reflective of an overall increase in metabolism. Dogs are rarely affected.

Historically the cats have lost weight, despite having an increased appetite initially. Increased vocalization, diarrhea, vomiting and increases in both urination and water consumption have been reported. Eventually the appetite may be decreased. Some cats have reportedly become aggressive. The symptoms seen with hyperthyroid cats can mimic those animals with cancers, liver or kidney disease.

On a physical examination hyperthyroid cats may have a large nodule palpable in their neck, and may have developed a rapid heart rate or a murmur.

Diagnosis involves blood tests. It is recommended that further diagnostics are carried out to evaluate a pet’s overall health and identify concurrent disease. This may influence treatment options and ultimately, the pet’s prognosis.

Left untreated, irreversible kidney, liver and cardiac changes can develop. High blood pressure, congestive heart failure, and ultimately death may ensue.

With early detection and treatment, the prognosis for cats with hyperthyroidism is excellent. A number of treatment modalities are available. Radioiodine treatment is a safe and effective treatment and is becoming more readily available. The affected thyroid gland can be surgically removed. (If associated with a malignancy, surgery is not curative.)

Some aged patients are medically managed for years. They require ongoing monitoring through blood testing and again the prognosis can be excellent.