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How Vets Diagnose Thyroid Problems in Pets: Symptoms & More

A dog with symptoms of thyroid problems for the NHV pet health blog.

A pet’s thyroid gland is a small but important organ that regulates metabolism, growth, and energy levels. When problems in the thyroid occur, it can affect many organs in their body. While thyroid problems in pets can be common, especially as pets age, early detection can make a significant difference in the treatment outcomes.

Why Diagnosing Thyroid Problems in Pets Matters

In both dogs and cats, the thyroid gland is located in the neck and produces hormones that help control metabolism, heart rate, temperature regulation, etc. When this hormone production is too low (hypothyroidism) or too high (hyperthyroidism), your little one’s body falls out of balance.

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Hypothyroidism is much more common in dogs than in cats. It may cause a characteristic “sad-looking” face. This occurs because the condition affects the skin and facial muscles, making their expression appear droopy or tired.

Some of the most common symptoms of hypothyroidism are:

Reduced activity and lethargy
Gain weight despite no change in diet
Hair loss, especially on the tail and trunk
Dry, flaky skin or recurrent ear or skin infections
Slow heart rate

On the other hand, hyperthyroidism is more common in felines. This includes unexplained weight loss despite a good or increased appetite, irritability (including restlessness or hyperactivity), diarrhea and vomiting, increased thirst and urination, and a rapid or irregular heartbeat.

While those symptoms are common in cats with hyperthyroidism, they can also overlap with other conditions. Therefore, diagnostic testing is extremely important.

Causes of Thyroid Disorders

Hypothyroidism in dogs can be a result of autoimmune destruction of the thyroid gland or natural shrinkage (atrophy) of thyroid tissue. However, in cats, hyperthyroidism is usually due to a benign growth (adenoma) in the thyroid that produces excess hormones. In very rare cases, thyroid cancer can be involved. Thus, genetics, environment, and underlying diseases may also play a role.

How Vets Diagnose Thyroid Issues in Dogs and Cats

Physical Exams: Your vet will start with a thorough physical exam. For hyperthyroid cats, sometimes the thyroid gland can be felt as a small lump in the neck.
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Blood Tests: Bloodwork is the best tool for diagnosis. Three qualities of the blood can help provide a diagnosis. Total T4 (thyroxine) is a first-line test that measures the main thyroid hormone in the blood. Free T4 is a more sensitive test that looks at the active form of T4. This is especially useful if a total T4 is borderline. TSH (Thyroid Stimulating Hormone) can also be measured. In dogs, a HIGH TSH along with a LOW T4 normally confirms hypothyroidism. In cats, TSH is not often used as it does not provide a clear diagnosis.
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Additional Diagnostics: Full blood panels can check for other diseases that can be similar to thyroid problems, such as kidney or liver disease. Imaging (ultrasound or nuclear scintigraphy) is sometimes recommended for complex cases, especially if there are concerns for cancer. According to the American College of Veterinary Internal Medicine (ACVIM), combining multiple tests can give a more accurate diagnosis than relying on a single test.

When to See Your Veterinarian

If you notice changes in body weight, appetite, activity level, or hair condition, don’t wait. Early testing for thyroid issues in pets is minimally invasive and can prevent complications.

Key Takeaway

With regular checkups, lab testing, and a combined traditional veterinary and holistic approach, thyroid issues in dogs and cats can be diagnosed early and effectively managed.