Thyroid Test in Cats

A thyroid test is a blood test to evaluate the function of the thyroid gland. This gland is responsible for producing thyroid hormone, an important hormone in the regulation and maintenance of body functions. A thyroid test is indicated in any ill animal, including cats. Normal cats, especially the elderly, can benefit from thyroid test results and this test is often used as a screening test for underlying illness or disease. Normal results help determine health or exclude certain diseases.

There are no real contraindications to performing this test but care should be taken if the cat has a tendency toward excessive bleeding. After obtaining the sample, extra care should be taken to make sure there is no hemorrhaging from the site where the sample was obtained.

What Does a Thyroid Test Reveal in Cats?

A thyroid test reveals the levels of circulating thyroid hormone in the blood. High levels of thyroid hormone indicate an overproduction by the thyroid gland, typically related to a thyroid tumor. Low levels indicate a poorly functioning thyroid gland, usually associated with immune system disorders that result in destruction of the thyroid gland by the body.

How Is a Thyroid Test Done in Cats?

In order to perform a thyroid test, your veterinarian must draw a blood sample, which is placed in a special glass tube and allowed to clot. It is then placed in a centrifuge, where it is divided into two parts: serum and a blood clot. The serum is removed and submitted to a laboratory for analysis. The blood clot is discarded. Some veterinary hospitals are able to perform thyroid tests in their clinic. Most veterinarians rely on outside laboratories.

If performed in the veterinary hospital, a thyroid test generally takes about 40 to 60 minutes to complete. If the sample is submitted to an outside laboratory, results may take 1 to 2 days.

Is a Thyroid Test Painful to Cats?

The pain involved is associated with the collection of the blood sample. A needle is used to pierce the skin and enter a blood vessel to draw the sample. As with people, the pain experienced from a needle will vary from individual to individual.

Is Sedation or Anesthesia Needed for a Thyroid Test?

Neither sedation nor anesthesia is needed in most patients; however, some cats resent needle sticks and may need tranquilization or ultrashort anesthesia.