Diagnostic Tests For Hyperthyroidism In Cats

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.

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. Heart disease vomiting diarrhea anorexia anesthesia hyperthyroidism is a common disease in cats and mostly afflicts cats middle aged and older. In the vast majority of cases a definitive diagnosis of hyperthyroidism is based on a simple blood test that shows elevated t 4 levels in the bloodstream. A diagnosis of hyperthyroidism is made when the level of thyroid hormone is increased in the blood.

In older cats presenting with clinical features of hyperthyroidism confirmation of a diagnosis of thyroid disease is usually straightforward. 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. More than 99 of t3 and t4 is bound to protein thyroid binding globulin which prevents the t4 from entering the various tissues. 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.

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. Hyperthyroid cats may have normal findings on the cbc and urinalysis but the chemistry panel often shows elevation of several liver enzymes. 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. Although thyroid tumors can be cancerous the chances are less than 5 percent in cats.

Hypothyroidism is a rare endocrine disorder in cats which occurs when there is an underproduction of thyroid hormones. As a result tests are run to prove or disprove an abnormal thyroid level. 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. 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.

Diagnosis is made by testing blood thyroid hormone levels. Hyperthyroidism also known as hyperthyroid disease occurs when the thyroid gland enlarges and starts producing excess amounts of thyroid hormone thyrotoxicosis in cats thyrotoxicosis is usually caused by a benign tumor on one or both thyroid glands. Hyperthyroidism can cause weight loss despite a good appetite increased water consumption and urination vomiting diarrhea cardiomyopathy and hypertension.