Thyroid Cancer (Adenocarcinoma) in Cats

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Thyroid Gland Adenocarcinoma in Cats

The importance of the thyroid gland is many fold. It is responsible for a variety of bodily functions, most notably the coordination of hormones and normal metabolism. Adenocarcinoma of the thyroid gland is like other adenocarcinomas: it grows rapidly and can metastasize to other parts of body. Adenocarcinoma of the thyroid is more commonly seen in older cats, but young cats may also suffer from this neoplasm.

The element iodine is also suspected of playing a role in the dysfunction of the thyoid gland. Because iodine is essential for the thyroid to work properly, cats living in iodine deficient areas may be at higher risk of developing these neoplasms.

Symptoms and Types

Following are some of the symptoms commonly related to adenocarcinoma of the thyroid.

  • Large fixed or movable mass over cat’s trachea covering the larynx
  • Dyspnea (difficult breathing)
  • Dysphagia (difficulty in swallowing)
  • Weight loss
  • Dysphonia (hoarseness)
  • Polydipsia (increased thirst)
  • Polyuria (increased amount and/or frequency of urine passing)


The cause of thyroid adenocarcinoma is still unknown.


Your veterinarian will perform a thorough physical exam on your cat, with blood tests, biochemistry profile, and urinalysis. You will need to give a thorough history of your cat's health and onset of symptoms. The most informative and helpful test is the T4 (thyroxine) and/or free T4 concentration determination. Thyroxine is a primary hormone produced by the thyroid gland. Its level tends to increase in some patients with adenocarcinoma of the thyroid gland. Thyroid Stimulating Hormone (TSH) levels will also be determined, along with T4. TSH is another hormone released from the brain which controls the release of T4 hormone. X-ray and ultrasound imaging, computed tomography (CT) scan, and magnetic resonance imaging (MRI) are some of the diagnostic tools your veterinarian can use to confirm the diagnosis and to determine whether the tumor has metastasized. Your veterinarian may also perform a biopsy of the thyroid tissue to see if malignant cells are present in the thyroid gland.

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