Pets & Animal Pets Cats

Thyroid Disease in Cats


    • Hyperthyroidism occurs when too much thyroid hormone is produced and, according to, is the most common hormonal disorder that affects pet cats. Hypothyroidism is the production of too little thyroid hormone and occurs very rarely in cats. Older animals can sometimes develop the condition, but it is more commonly acquired because of surgery for hyperthyroidism.

    Cause and Occurrence

    • One of the most common causes for the development of hyperthyroidism, according to, is the growth of abnormal cells in the thyroid gland. Most are benign, and only 1 or 2 percent post a threat as cancerous. There is no age, gender or breed bias for developing hyperthyroidism, and most cases appear after the age of 8. Hypothyroidism usually occurs as a side effect of hyperthyroidism treatment, as surgery is often performed to stop the overproduction of thyroid hormone and causes the gland to not produce enough as a result.


    • Symptoms of hyperthyroidism can include weight loss, increased activity and diarrhea. Hypothyroidism symptoms can appear as exact opposites as hyperthyroidism and can include weight gain, lethargy and constipation. Either condition can exhibit symptoms such as poor coat appearance and appetite loss.


    • Your cat's symptoms will be taken into consideration as your veterinarian performs a physical examination. He may be able to feel the cat's thyroid gland because of its larger or irregular size. Blood tests be performed to check your cat's T3 and T4 levels, as higher levels indicate hyperthyroidism and lower levels point to hypothyroidism.


    • Treating hyperthyroidism involves daily medications, surgery or a procedure using radioactive iodine. Medications help to block the production of the thyroid hormone and are used for the rest of the cat's life. Surgery is performed to remove growths or damaged thyroid gland lobes. Radioactive iodine is used to halt the growth of abnormal cells through injection. Synthetic hormones such as levothyroxine and methimazole are administered to those cats suffering from hypothyroidism to mimic the naturally occurring hormone.

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