Feline Hyperthyroidism Information

Feline Hyperthyroidism - General Information

  • The feline hyperthyroid condition was first diagnosed in 1979
  • Feline hyperthyroidism is caused by a benign tumor of thyroid gland called an adenoma
  • It is a disease of older cats
  • The disease occurs in all cats but females may be more at risk
  • Siamese cats and Himalayans seem to be less predisposed to hyperthyroidism
  • Feline hyperthyroidism is very treatable and has a good prognosis if caught early

Your Cat's Thyroid Hormones

Hyperthyroidism in cats is caused by excessive production of circulating thyroid hormones. Thyroid hormone regulates the body's metabolic rate and affects all tissues and every system in the cat's body.

Symptoms of Feline Hyperthyroidism

  • Increased appetite - very often is the first noticeable symptom of feline hyperthyroidism.
  • Weight loss - also occurs early.
  • High blood pressure, vomiting, increased body temperature.
  • Increased heart rate, thirst and urination.
  • Increased levels of thyroid hormones cause hyperactivity of all body functions.
  • Poor appearance is very common in cats with feline hyperthyroidism.
  • During a physical exam, enlarged thyroid gland is often palpable in cats.

Testing for Feline Hyperthyroidism

  • Blood testing for Total T4 levels is diagnostic.
  • About 6% of cats with feline hyperthyroidism have normal T4 levels.
  • Elevated liver enzymes are common and can help with the diagnosis of this condition.

Causes of Feline Hyperthyroidism

Environmental factors appear to be the most important cause of feline hyperthyroidism

Possible causes:

  • Too much Iodine in cat food.
  • Canned food increased likelihood of feline hyperthyroidism.
  • Fire-retardant chemicals called PBDEs (polybrominated diphenyl ethers) that are used in fabric - carpets, upholstery, mattresses and electronics - appear to be associated with increased numbers of cats diagnosed with feline hyperthyroidism.
  • High levels of PBDEs also found in dry and canned cat food.
  • Exposure to secondhand cigarette smoke has been linked to the feline hyperthyroid condition.

Treatment Options for Feline Hyperthyroidism

Medication for feline hyperthyroidism - necessitates daily lifelong treatment with pills. Medical treatment does not cause a cure. Side effects are also present - vomiting, allergic reaction. The medication used to treat cat hyperthyroidism is potentially toxic. Blood levels must be monitored regularly.

Surgery for feline hyperthyroidism - Hyperthyroid cats are in poor medical condition and surgery is very risky. Surgical complications are also possible. The surgery requires the expertise of a very skilled and experienced surgeon. After surgery, the cat needs thyroid hormone therapy for the rest of its life.

Radioactive Iodine ( I-131 ) Therapy - This is the best treatment option for feline hyperthyroidism.

  • No anesthesia or surgery is necessary when treating hyperthyroidism with Radioactive Iodine ( I-131 ) therapy
  • No medication is necessary for Radioactive Iodine ( I-131 ) therapy.
  • One injection of Radioactive Iodine ( I-131 ) cures the condition.
  • Radioactive Iodine ( I-131 ) treatment is well-tolerated by hyperthyroid cats.
  • Thyroid supplementation is rarely needed after Radioactive Iodine ( I-131 ) therapy.

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