Many owners get excited when their older, usually lethargic feline companion suddenly starts racing around the house every night. They think that their cat has found a second kittenhood. However, this increased hyperactivity is most likely caused by a disease called hyperthyroidism.
Hyperactive behavior, a common sign: Hyperthyroidism occurs when the thyroid gland, located in the neck, begins to overproduce hormones (T3, or triiodothyronine, and T4, or thyroxine), which are important for metabolism. The reason for the hormone overproduction is most commonly goiter, a swelling of the thyroid gland, which is usually due to the presence of a benign thyroid tumor.
Hyperthyroidism is extremely common in cats eight (8) years old and over. The behavioral manifestations are so typical that veterinarians will screen older cats who show marked behavioral changes for hyperthyroidism right away. This is done by taking blood samples to measure T4 levels.
The insidious aspect of the disease is that most owners assume the increased activity is merely a new lease on life. They also often don't notice that their cat is losing lots of weight-another result of the disease-since they see the cat every day.
Behavior signs: Hyperthyroidism affects the cat's behavior in two ways. The disease causes physiological hunger to the extent that the cat may even jump on the table to eat the owner's food or break into a cupboard. It also has a direct effect on nerve tissue-essentially, the overabundance of hormone is toxic to the nervous system.
Typical behavioral changes include restlessness and, in some cats, aggression. Most hyperthyroid cats can't tolerate being restrained, may pace and look at you (as if staring) but not quite seeing you.
In a few cases, the cat may become extremely listless. This may occur after the other more typical behavioral changes. The degree of thyrotoxicity may vary from cat to cat, so the behavioral effects may not be exactly the same.
Watch for these signs in your older (8 + years) cat:
Weight loss, often with extreme hunger
Irritability
Hyperactivity
Unkempt appearance
Increased urine volume
Vomiting
Diarrhea
See your veterinarian to confirm the presence of hyperthyroidism or another disease with a blood test.
Complications/Treatment: The
physiological effects of hyperthyroidism include enlargement of the heart and hypertension. Essentially, thyrotoxicity causes the whole body to go into overdrive. To treat this, veterinarians may prescribe an antithyroid drug such as methimazole. This drug is not always the answer for long-term use though. Curative measures include surgical removal of the thyroid gland and treatment with radioactive iodine, which destroys the hormone-manufacturing tissue of the gland.
Hyperthyroidism and Kidney
Failure
An interesting side effect is that hyperthyroidism compensates for kidney failure, another plague of elderly cats. When hyperthyroidism is treated, the kidney failure becomes evident. This is something veterinarians watch closely when treating a hyperthyroid cat and may mean additional therapy to help kidneys function better.
If left untreated, hyperthyroidism can lead to congestive heart failure, intractable diarrhea, kidney damage, blindness (from retinal detachment) and death.
