Diagnostic Tests For Hyperthyroidism In Cats

The t3 suppression test is used for diagnosing hyperthyroidism in cats that have normal t3 t4 and or free t4 concentrations but appear clinically hyperthyroid.

Diagnostic tests for hyperthyroidism in cats. Hyperthyroidism is a common condition in older cats that is caused by excess release of thyroid hormone resulting in an increased metabolic state. The most common cause of hypothyroidism in cats is due to radioactive iodine i 131 therapy to treat hyperthyroidism and is usually transient. In older cats presenting with clinical features of hyperthyroidism confirmation of a diagnosis of thyroid disease is usually straightforward. As a result tests are run to prove or disprove an abnormal thyroid level.

Diagnosis is made by testing blood thyroid hormone levels. However the potential for false negative and false positive results exists with all thyroid function tests especially in the context of routine screening of asymptomatic cats and leads to clinical dilemmas. Also called thyrotoxicosis hyperthyroidism is caused by an increase in production of thyroid hormones known as t3 and t4 from an enlarged thyroid gland in a cat s neck. Hyperthyroidism can cause weight loss despite a good appetite increased water consumption and urination vomiting diarrhea cardiomyopathy and hypertension.

Hyperthyroid cats may have normal findings on the cbc and urinalysis but the chemistry panel often shows elevation of several liver enzymes. The most important disadvantage of use of the free t 4 determination however is the loss of diagnostic specificity that is occasionally seen in sick euthyroid cats. Up to 12 of cats with nonthyroidal illness that do not have hyperthyroidism have high free t 4 concentrations for reasons that are unclear figure 3 figure 4 11 27 therefore caution is therefore advised in using serum free. Although thyroid tumors can be cancerous the chances are less than 5 percent in cats.

Most hyperthyroid cats have very high levels of hormone but some cats will have signs of hyperthyroidism with normal or only slightly increased levels of thyroid hormone 1. Heart disease vomiting diarrhea anorexia anesthesia hyperthyroidism is a common disease in cats and mostly afflicts cats middle aged and older. Although hyperthyroidism is relatively easy to diagnose in classically presenting cats the increased frequency of testing cats with early mild disease as well as the routine screening of large numbers of asymptomatic cats has had significant implications for the diagnostic performance of many of the routine tests currently used. Suggested articles hypertension chronic kidney disease diagnosis.

A diagnosis of hyperthyroidism is made when the level of thyroid hormone is increased in the blood. T3 suppression test for cats diagnosis of feline hyperthyroidism can usually be accomplished by measuring t3 t4 and or free t4 in a single baseline blood sample. More than 99 of t3 and t4 is bound to protein thyroid binding globulin which prevents the t4 from entering the various tissues.