Feline Thyroid Cancer

The feline thyroid is a butterfly shaped gland located over the esophagus and at the lower base of the neck. Its primary function is to use iodine ingested from food and to metabolize it into hormones that the thyroid can use—namely T3, or triiodothyronine, and T4, or thyroxine. These hormones are then dispersed to cells throughout a cat's body where metabolic functions are induced so that his body can appropriately use oxygen and calories as energy.

There is no other gland in a cat's body that can produce this effect and thus, every cell in his body needs the hormones released by the thyroid gland to function properly. When there is any interruption in thyroid function, such as increased or decreased thyroid hormones or a cancerous tumor, the entire thyroid gland becomes useless. This is when signs of a thyroid condition or thyroid cancer in cats will start to become visible.

Risk Factors and Symptoms

The most common cause of feline thyroid cancer is hyperthyroidism, which occurs when a cat's thyroid gland produces more thyroid hormone than his body requires. When this occurs, a cat may begin to experience an insatiable appetite but will gain very little, if any, weight. Additionally, a cat will start to become very active, overly alert and seemingly may have trouble sleeping. These symptoms occur because the cells in the cat’s body are being over-stimulated.

Thyroid cancer is typically only seen in older cats or cats who have suffered over the years with a hyperthyroid condition. When the thyroid overproduces thyroid hormone, then nodules, or lumps, can begin to form on the thyroid gland. These nodules can range in size from being very small to being so large that they require surgical removal. These nodules are the breeding ground for thyroid cancer.

Treating Thyroid Cancer in Cats

When an existing condition of hyperthyroidism exists and the presence of a nodule develops on the thyroid gland, thyroid cancer should be suspected. Even if there is no known hyperthyroidism in a cat, the presence of a nodule on the thyroid should always prompt an investigation of thyroid cancer.

Typical diagnosis of thyroid cancer consists of a complete blood count, to check the level of white and red blood cells, a CT scan of the throat and a physical examination. If the tumor on the thyroid appears to look abnormal after viewing it on a CT scan, a biopsy of the tumor will be conducted and a diagnosis can be made.

Treating Thyroid Cancer

There are two treatment options for feline thyroid cancer: surgery or radioactive iodine treatment. The method of treatment will depend on what stage the cancer is in, how rapidly it is expected to grow and how early the cancer was diagnosed.

If the tumor appears to rather small in size and has not yet affected any other portion of the cat's thyroid or nearby glands, radioactive iodine treatment may be appropriate. Radioactive iodine treatment consists of exposing a radioactive iodine element to the tumor, which kills the cancer cells and causes the tumor to shrink when treatment is successful.

However, when thyroid cancer appears to be growing rapidly, or has been allowed to progress for too long, surgery may be the only viable way to rid a cat of thyroid cancer.