Thyroid Treatment for Cats

Updated April 17, 2017

A cat's thyroid gland is butterfly in shape, with each lobe located on either side of the trachea. This critical gland maintains the feline's metabolic rate and harnesses the power to affect all bodily function. Consequently, should complications arise with the thyroid gland, any of the cat's systematic functions may be impacted, making thyroid treatment critical for the overall health of the feline.

Expert Insight

Doctors Foster and Smith teaches that the thyroid gland produces two types of hormones in the cat: T3 (triiodothyronine) and T4 (thyroxine). The brain-based pituitary gland is responsible for stimulating T3 and T4 production by controlling the thyroid-stimulating hormone. When the thyroid gland produces excess hormones, the cat suffers from hyperthyroidism (the most common thyroid condition in cats), which can lead to further complications such as kidney failure. Therefore, treatment is critical to bring hormone production back down to normal levels.


Treatment to regulate thyroid function is also critical because the symptoms of hyperthyroidism are uncomfortable for the feline and detrimental to the cat's overall health. Despite being hungry all the time, the cat will lose severe amounts of weight and muscle tissue. The feline may also experience hyperactivity to the point of suffering from muscle spasms. Thyrotoxic heart disease is another inherited condition resulting from an untreated thyroid condition, says Dr. Michael Bernstein. Increased hormone production compromises the cat's heart function, resulting in symptoms of heart failure and difficulty breathing.


The severity of the feline's thyroid problem dictates the type of treatment prescribed. In most cases, medication helps regulate thyroid hormone production. Website Vetinfo indicates the most commonly prescribed medication for hyperthyroidism is methimazole. This treatment is fairly inexpensive and reversible, according to Doctors Foster and Smith If the methimazole brings the feline's thyroid hormone production down too low, the veterinarian can adjust the dosage.

Invasive Treatment

More severe cases of hyperthyroidism might require irreversible treatments such as surgery or radiation. Surgery, or a thyroidectomy as website Vetinfo calls it, involves the removal of the actual thyroid tissue that is overgrowing and causing the thyroid condition.

Radiation, known as radioactive iodine therapy, is less invasive, involving an injection into the "malfunctioning parts of the thyroid gland," states Besides sparing the cat from surgery, this procedure is also advantageous because it us usually considered very effective.


As with all treatment options, treatment of a thyroid condition in cats does not come without side effects. If the veterinarian prescribed methimazole for the cat, side effects range in severity from loss of appetite, nausea, vomiting and diarrhoea to liver disease, the neuromuscular disease myasthenia gravis, high fevers and tendencies to bruise or bleed abnormally.

Both surgery and radioactive iodine therapy share the possible side effect of hypothyroidism, where the thyroid hormone production is actually decreased to levels that are too low, rather than normal. Additionally, the veterinarian might need to perform both procedures a second time if the abnormal thyroid tissue continues to develop.

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