Overactive Thyroid Symptoms in Dogs

Overactive thyroid symptoms are not very specific in dogs, so your veterinarian will have to combine observation of symptoms with blood tests to reach a viable diagnosis. Overactive thyroid gland syndrome rarely occurs in dogs. Its most common causes are carcinomas or hypothyroidism medication.

Overactive Thyroid Symptoms in Dogs

Hyperactive thyroid, or hyperthyroidism, is a condition caused by an excess of thyroid hormones which stimulate the dog's metabolism. This causes hyperactivity in most dogs, followed by extreme lethargy due to exhaustion. The symptoms vary from one case to the other and may often be similar to the symptoms of hypothyroidism. Hyperthyroidism is a slow, progressive disease, but it is treatable, so check with your veterinarian as soon as you observe any of these symptoms:

  • The thyroid gland is enlarged and can be felt as a lump on the neck
  • An increased heart rate, also known as gallop rhythm
  • Appetite might vary and may be excessive or lacking
  • Increased water intake and urination
  • Hyperactivity
  • Weakness
  • Lack of muscle strength
  • Weight loss
  • Difficulty breathing
  • Rapid and shallow breathing
  • Irritability
  • Dog's coat is coarse
  • Vomiting and diarrhea

Causes of Overactive Thyroid in Dogs

Hyperactive thyroid in dogs usually occurs due to cancer. A tumor interferes with the gland's normal function, causing it to produce an increased amount of T3 and T4 thyroid hormones. The administration of hypothyroidism medication can also cause symptoms of hyperthyroidism.

Diagnosing Overactive Thyroid Symptoms in Dogs

As thyroid conditions influence metabolism and all organs become affected, the symptoms can often be misleading and the vet may suspect hypothyroidism. Correlating symptoms and tests will help your veterinarian find the correct diagnosis.

The vet will palpate the thyroid glands, which can be felt on the neck. Your veterinarian will run a chemical blood profile, a complete blood count and a urine test. If T4 is concentrated in the dog's blood, the diagnosis of overactive thyroid is confirmed. Thyroid gland scintigraphy is another means of diagnosing hyperthyroidism (radioisotopes are used to obtain a two-dimensional image).

Treatment of Overactive Thyroid in Dogs

The overactive thyroid can be treated effectively, and the treatment can range from medication to surgery. Older dogs might be too weak for traditional treatment, so you could discuss alternative solutions. Homeopathic cures can have a calming effect on the dog, so your veterinarian might combine them with traditional ones.

In dogs with hyperthyroidism, medication is prescribed to control the production of hormones. While under treatment, your dog's hormone levels will be monitored. If the hyperthyroidism is caused by a tumor, surgery will be performed. The vet will remove the cancer-affected thyroid gland. After the surgery, your dog will receive thyroxine to replace the production of hormones.

Radioactive iodine can also be administered. This treatment is only performed in vet clinics. The dog has to remain under observation until the radioactive material is cleared from his body.