Diagnosing thyroid hormone diseases in dogs requires valid testing. In this article, our Santa Cruz County vets explain what thyroid testing is, how it is done, and the common types of thyroid tests for dogs.
What Is A Dog's Thyroid Gland?
The production of thyroxine (T4), a crucial thyroid hormone, takes place in the thyroid gland, situated near the trachea. The metabolic rate of the body is regulated by these hormones, thereby having a broad impact on various bodily functions. The thyroid gland function is regulated by the pituitary gland located at the base of the brain, which produces TSH (thyroid stimulating hormone).
What Is Thyroid Testing?
Dogs with low thyroid levels may experience signs like hair loss, lack of energy and dull coats. To measure low thyroid in dogs, vets use a blood test called the thyroid test is conducted. It is suggested for any ill animal and is commonly employed as a screening procedure to detect any underlying health issues or ailments. Normal outcomes of this test help determine the animal's overall health and exclude specific diseases. If the animal tends to have excessive bleeding, extra care should be taken after obtaining the sample to ensure no hemorrhaging from the site where the sample was obtained.
How Is Thyroid Testing Done In Dogs?
To perform a thyroid test, a blood sample is drawn and collected in a specialized glass tube. The collected blood is then divided into two parts, namely serum and blood clot. The serum portion is sent to a laboratory for testing, while the blood clot is discarded. While some veterinary hospitals offer in-house thyroid tests, most rely on external laboratories.
Typically, a thyroid test performed at a veterinary hospital takes approximately 40-60 minutes. If the test is conducted at an external laboratory, results can be expected within 1-2 days.
The majority of dogs do not require sedation or anesthesia for this procedure. However, some dogs may be uneasy with needles and require anesthesia.
What Are The Types Of Thyroid Tests?
It is important to test for low thyroid in dogs. The following are some of the most common thyroid tests done for dogs.
T4 & T3
Total T4 (Thyroxine) and Total T3 (Triiodothyronine) testing can be used to screen for hypothyroidism in dogs. Unexpectedly high levels of either hormone may be indicative of autoantibodies, and T3 and T4 concentrations can be influenced by a variety of factors including medications, disease states, and nutrition.
Free T4 By lmmulite Or By Equilibrium Dialysis
A valid assay for measuring free T4 (FT4) can be used to distinguish true hypothyroidism from the euthyroid sick condition. The non-protein bound thyroxine, FT4, is found in lower concentrations in the blood than total T4. A method should be used to separate the protein-bound hormone from the free (unbound) hormone for accurate FT4 testing.
The Equilibrium Dialysis (ED) method is the standard test for dogs, requiring an overnight incubation in buffer and dialysis cells to separate bound T4 from free T4. The Immulite method is less expensive and faster than the ED method, producing results comparable to dialysis. Thyroid supplementation should be monitored using FT4 in any dog known or suspected to have thyroid autoantibodies, as these tests remove the autoantibody effects.
Thyroglobulin Autoantibody (TgAA) Test
The TgAA test is a canine-specific test for detecting autoimmune thyroiditis. For a more accurate diagnosis, it should be used in conjunction with other thyroid tests. Thyroglobulin autoantibodies are involved in the synthesis of T4 and T3.
TSH Measurement
The endogenous thyroid stimulating hormone (TSH) can be measured in dogs. High levels of endogenous thyroid-stimulating hormone levels suggest hypothyroidism, but normal or low endogenous thyroid-stimulating hormone levels in dogs do not necessarily rule it out. This test should be used in conjunction with other thyroid tests to make a diagnosis.
