What is the thyroid gland?
The thyroid gland is found near the trachea and produces thyroxine (T4), a major thyroid hormone. Thyroid hormones can impact many processes throughout the body, as they regulate metabolic rate. The pituitary gland, situated at the base of the brain, regulates the function of the thyroid gland with a hormone called TSH (thyroid stimulating hormone).
What is a thyroid test for dogs?
This is a type of blood test that evaluates how the thyroid gland is functioning. A thyroid test is recommend for any sick pet and is often used as a screening test for underlying disease or illness. Normal results help to establish your dog's health status and exclude certain diseases.
If your dog tends to bleed excessively, extra care should be taken after the vet has obtained the sample to prevent hemorrhaging from the area where the sample was obtained.
How will the vet perform a thyroid test on my dog?
To perform a thyroid test for dogs, your vet will obtain a blood sample, place it in a glass tube, and use a centrifuge to separate it into different parts, mainly blood cells and plasma/serum. After the plasma is extracted, it's sent to a laboratory for testing, while the blood clot is discarded. While some veterinary hospitals are able to perform thyroid tests in an in-house veterinary diagnostic lab, most rely on outside labs.
If performed at the animal hospital where your pet is examined, a thyroid test typically takes about 40-60 minutes. If sent to an outside laboratory, you can expect the results within 1-2 days.
Most dogs will not need anesthesia or sedation to have this test done. However, some dogs who dislike needles may require anesthesia.
What are the different types of thyroid testing?
Here are some of the different types of thyroid tests we do for dogs:
T4 & T3 Hormone Testing
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 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 gold 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. This test should be used along with others to confirm diagnosis. Thyroglobulin autoantibodies are involved in the synthesis of T4 and T3.
The endogenous thyroid stimulating hormone (TSH) can be measured in dogs. High levels of endogenous thyroid-stimulating hormone suggest hypothyroidism, but normal or low endogenous thyroid-stimulating hormone levels in dogs do not necessarily rule it out. Your vet will perform other types of thyroid testing along with this one to ensure accuracy.
Veterinary Diagnostic Lab & Pharmacy at Columbia River Veterinary Specialists
When your pet needs high-quality specialty veterinary care, they may also require advanced diagnostic testing and have ongoing medication needs.
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Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.