Hyperthyroidism & Liver Function in Cats
Older cats are prone to hyperthyroidism. It's most often caused by a benign tumor that enlarges the thyroid and makes it produce excess amounts of a hormone called thyroxine, which then goes into the bloodstream. This sends the cat's metabolism into overdrive and can cause problems for many other organs, including the liver.
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Hyperthyroidism Symptoms
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A cat with hyperthyroidism might eat, drink and urinate more and still lose weight. It may vomit or have diarrhea, and its fur will start looking shabby. Labored breathing and accelerated heart rate are other signs. Since older cats tend to exhibit some of these symptoms, they might be dismissed as normal aging, but the cat should see a veterinarian. Untreated hyperthyroidism can lead to heart failure and death.
Diagnosis
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A vet will run a blood panel to detect hyperthyroidism, and it will reveal the status of the other organs. Red and white blood cell counts might be elevated, and the cat might show abnormally high liver enzymes.
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Liver Function
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All liver cells (hepatocytes) contain a bit of fat from the cat's diet in the form of fatty acids, triglycerides and cholesterol. The liver processes these into the bloodstream as energy. A healthy liver doesn't need to store fat.
Hyperthyroidism contributes to hepatic lipidosis, where more fat than the liver can process gets stored, causing triglyceride buildup. No one knows exactly what causes unbalanced liver function in cats, but it's often secondary to hyperthyroidism, particularly if they are obese. The result is a chain reaction affecting insulin and glucose levels that can lead to diabetes mellitus. But it doesn't lead to complete liver failure.
Fortunately, liver cells are among few in the body with the ability to regenerate. Once the hyperthyroidism is under control, the liver heals itself and regains its balance.
Non-Invasive Treatments
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Hyperthyroidism can be treated with radioactive iodine that destroys only the diseased thyroid tissue. It's done without anesthesia and is highly successful. It's also very expensive, and the cat must remain at the vet's up to 10 days so no one else is exposed to the radiation. The cat needs excellent kidney function going in because if the kidneys have been failing, the excess thyroxine that was actually aiding them with increase blood flow will be cut off, and it could result in a serious kidney situation.
An alternative to radiation is Tapazole, an inexpensive drug used to treat hyperthyroidism and chronic renal failure. It's a dual approach that cuts production of thyroxine just enough so the kidneys can function as well as possible. Tapazole's side effects can include loss of appetite, vomiting and depression.
Invasive Treatment
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A surgical thyroidectomy removes the diseased thyroid tissue. It's an instant cure and usually effective, but it's invasive and can rebound into hypothyroidism (too little thyroxine production) and paralysis of the throat muscles.
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