Diagnosis of Feline Hyperthyroidism

Feline hyperthyroidism is the result of a benign tumor in one or both of the thyroid lobes.  Diagnostic steps begin with a thorough physical examination.  As part of the examination, the veterinarian will check for all clinical symptoms of feline hyperthyroidism and palpate the thyroid gland. 

A diagnosis of feline hyperthyroidism can be confirmed by conducting a special blood test to measure the thyroid hormone or T4 level.  Although a cat has hyperthyroidism, the test can still show normal results.  This is due to the fluctuation in the thyroid hormone level. 

If hyperthyroidism is still suspected, a more sensitive test can be preformed, this test is known as a T3 suppression test.  A blood chemistry panel can be performed to rule out other diseases with symptoms resembling those seen in hyperthyroidism.  The results can also show if the cat is having problems with other internal organs.  Blood work to test for hyperthyroidism should be done at intervals throughout the cat’s life.  The follow-up blood work will be used to determine if the dosage is still appropriate or if it needs to be increased or decreased.