Thyroid Tumors in Dogs

Thyroid tumors are rare in canines, but most commonly, the tumors are malignant. The thyroid tumors can hinder the normal function of the thyroid glands and will also spread to other organs, so the tumors need to be removed or their development should be delayed as much as possible.

The Thyroid Glands

Dogs have two thyroid glands which are located in the neck area. The thyroid glands produce the thyroid hormones, which are essential for the normal metabolism of the dog.

The thyroid glands may be affected by tumors, but only in very rare cases. More frequently, the tumors will be carcinomas, which are malignant cell growths. Adenomas, which are benign tumors, are less common in dogs. Thyroid cancers are more common in senior dogs and in certain breeds such as boxers and beagles.

Causes of Thyroid Tumors

The causes of thyroid tumors are not clear. The tumors may form due to an over-stimulation of the thyroid glands. However, the tumors may also be caused by the dog's diet or they may be hereditary.

Symptoms of Thyroid Tumors

The thyroid tumors can be observed as a swelling at the middle or base of the neck. Additional symptoms will include:

  • Coughing and breathing problems, if the tumors press on the air passages
  • Difficulties when swallowing and refusal to eat, if the tumor affects the esophagus
  • Changes in the dog's barking tone
  • Poor skin and coat condition, due to the lack of thyroid hormones
  • Changes in the dog's metabolism

The dog rarely presents symptoms of hyperthyroidism (i.e., oily skin, acne, excessive thirst or agitation), as the tumors will not cause an excessive production of hormones.

Thyroid Tumor Diagnosis

A thyroid tumor can be detected through X-rays and a cell biopsy. However, blood tests will be necessary to establish the extent to which the tumor affects the dog's system. Additional X-rays and ultrasounds may also be necessary, as thyroid tumors often extend to the lungs or to the nearby lymph nodes.

Treatment Options

A full understanding of the dog's condition is essential to establish the best course of treatment. It is important to know how advanced the tumor is.

If the tumor is an adenoma or a carcinoma in its incipient phases, the vet will perform a surgery, which can extract the tumor or even the entire thyroid gland affected by the tumor. In the case of a cancerous tumor, after the surgery, the dog will have to receive chemotherapy, which should hinder the development or occurrence of new cancerous cells. If the thyroid glands are both removed, the dog will have to get a supplementation of thyroid hormones. Medication is available.

If the tumor is larger and more extended, the vet cannot perform surgery. Chemotherapy and radiation therapy are the treatment options in this case. Alternative natural treatments may also be applied, especially if the tumor is not operable and the dog's condition is advanced.