Feline Thyroid Problems

The thyroid gland, consisting of two connected lobes located in the cat's lower neck, regulates metabolism through the production of a hormone known as thyroxine, or T4. When too little hormone is produced, the condition is known as hypothyroidism. When too much of the hormone is secreted, the disorder is called hyperthyroidism. Feline hyperthyroidism is considerably more common. Both hypothyroidism and hyperthyroidism in cats are diagnosed through tests to measure thyroxine levels in the blood. Both thyroid problems are controllable and neither is life-threatening with proper treatment.

Feline Hypothyroidism

While in dogs hypothyroidism may be an inherited condition, in cats it usually results either from an injury to the gland during surgery or from the administration of radioactive iodine during therapy for hyperthyroidism. The disorder may also occur if the cat's diet contains insufficient iodine, but this is rare since most commercial pet foods include the supplement.

Symptoms of Feline Hypothyroidism

Cats with hypothyroidism may exhibit the following symptoms:

  • Weight gain
  • Increased thirst
  • Dull, dry coat
  • Excessive grooming
  • Lethargy

Cats with hypothyroidism are generally sluggish and slow to participate in play or other activities.

Treatment of Feline Hypothyroidism

Feline hypothyroidism is treated with supplemental thyroxine administered orally, usually as a pill or gel. With adequate treatment and regular monitoring, cats are able to live happy, healthy lives with this condition.

Feline Hyperthyroidism

Hyperthyroidism is relatively common in older cats and rarely occurs in dogs. The condition is considerably more common in older cats. Ninety-five percent of cats who develop the disorder are over the age of 10.

Symptoms of Feline Hyperthyroidism

Because the thyroid gland produces hormones affecting many bodily functions, thyroid dysfunction, particularly hyperthyroidism, can produce a wide range of symptoms. The most common Symptoms of this condition include:

  • Weight loss
  • Increased appetite
  • Increased activity, restlessness
  • Unsociable or aggressive behavior
  • Rapid heart rate
  • Increased consumption of water
  • Frequent urination

Less common symptoms of feline hyperthyroidism may include: vomiting, diarrhea, labored breathing, weakness, depression, and a poor coat.

Diagnosis of Feline Hyperthyroidism

Because levels of thyroxine in the blood may vary, the diagnostic test for feline hyperthyroidism is normally repeated three times. Physical examination is also necessary because an enlarged thyroid gland can often be palpated in the neck by the veterinarian. If blood tests are inconclusive, a veterinary specialist with a nuclear medicine scan available may be consulted.

In the process of diagnosing feline hyperthyroidism, the veterinarian may also screen for abnormalities in other organs, particularly if the animal is advanced in age. It is possible for high levels of thyroxine in the blood to affect the heart and lungs are well, causing abnormal electrical activity in the former and creating fluid buildup in the latter. While these associated problems will, of course, require their own treatment, they may recede once the thyroid gland is under control.

Treatment of Feline Hyperthyroidism

There are three basic treatments for feline hyperthyroidism. The veterinarian will choose the most appropriate treatment based on the cat's state of health and whether the animal has any other underlying medical conditions. The possible treatments for feline hyperthyroidism are

  • Ongoing oral medication
  • Surgical removal of the thyroid glands
  • Treatment with radioactive iodine

Many older cats with feline hyperthyroidism have kidney disease as well. When thyroid and kidney problems co-exist, the veterinarian must carefully balance the thyroid medicine to keep both organs functioning properly.

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