Hyperthyroidism in Cats - The Fact Sheet

Hyperthyroidism in Cats
by Dr. Arnold Plotnick

Section: Overview

Hyperthyroidism is a multisystemic metabolic disorder that occurs as a result of excessively high concentrations of thyroid hormones in the bloodstream. It is the most common glandular disorder in cats. Untreated hyperthyroidism results in increased cardiac output, and increased blood flow to the kidneys. Although the disease is treatable, in recent years it has become apparent that previously undetected kidney disease may suddenly be unmasked, and that known kidney disease may worsen in some cats after correction of their hyperthyroidism.

The disease is caused by excessive secretion of thyroid hormones by hyperplastic (overly large), usually benign thyroid glands. Although extensively studied, it is still not known why some cats develop hyperthyroidism while others do not.

There is no breed or sex predisposition for the disorder, but it occurs almost exclusively in older cats. Less than 6 percent of cases are younger than 10 years old. The average age of onset is 12 to 13 years.

The impact of the disease can be significant, as hyperthyroidism can affect many body systems, especially the heart.

What to Watch For

Weight loss
Ravenous appetite
Excessive drinking and urinating
Hyperactivity (restlessness, excessive vocalization)
Intermittent vomiting
Intermittent diarrhea
Panting

Diagnosis

Complete blood count
Chemistry panel
Urinalysis
Thyroid hormone level
Radiographs
Scintigraphy

Treatment

Antithyroid medication (tapazole)
Possible cardiac medication
Surgical removal of the thyroid glands (rarely done anymore)
Radioactive iodine therapy
Hill’s Prescription Diet Y/D

Consequences involving the kidneys can be minimized or prevented in hyperthyroid cats by assessing kidney function before undertaking therapy to treat the hyperthyroidism. Cats are then given oral medication to bring the thyroid hormone levels back into the normal range slowly, temporarily controlling the condition. Kidney function is then re-evaluated. If kidney function remains stable, a more permanent method of therapy (surgery, radioactive iodine) can be undertaken. If kidney function worsens, the veterinarian is faced with the dilemma of balancing the two disorders so that the most severe clinical signs of either disorder are kept to a minimum.

Home Care and Prevention

Consistently administer any prescribed anti-thyroid and/or cardiac medication if necessary. Treat for kidney failure (subcutaneous fluids, prescription diets, phosphate binders, gastric protectants, vitamin D supplements) if warranted and prescribed.

It is still not understood why some cats develop hyperthyroidism while others do not. Thus, there are no measures that can be taken to prevent the development of hyperthyroidism.

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Pocket of Fluid on Leg, Part Two

Pocket of Fluid on Leg, Part Two
(continued from Part 1)

Okay, so I left you all hanging on this weird case of Percy, the cat with the unusual cystic thingy on her front leg. There’s more to the story, so here’s the update

Percy’s owner went to Blue Pearl Veterinary Partners for a second opinion and saw one of their surgeons, Dr. Andrew Kyles. He examined Percy and was equally puzzled. He basically agreed with my assessment and he recommended that Percy have a CT scan performed to evaluate the full extent of this cyst/swelling and see if there’s any solid tissue associated with it at all. Depending on the CT findings, they would probably schedule the cat for surgery. If it was just a cyst, they would try to remove it. If it was a more solid type of mass, depending on how infiltrative it was, they would either try to biopsy and remove the mass, or in the worst case scenario, consider amputation of the leg.

Percy’s owner decided to pursue yet another opinion, and I don’t blame her, especially when the word amputation is mentioned. She went to the Animal Medical Center. They discussed surgery, and she decided to have the surgeons at AMC do the procedure. They opted not to go for a CT scan. The surgeons there felt it was very likely to be a cyst, and that they would try to remove it first and see what happens.

The surgeons at the AMC removed the cyst. There was some solid tissue associated with the cyst, at the base. They submitted a biopsy specimen. The diagnosis: “suspected synovial myxoma”.
Synovial myxomas are tumors of the synovium – the membrane that lines the joints. They are mainly seen in middle-aged large-breed dogs. The pathologist had never seen one in a cat. She felt that this tumor was likely to grow back at the surgical site, but was not very likely to spread to other parts of the body.

AMC sent the sample to a different pathologist, for a second opinion on the biopsy. A second pathologist agreed that a synovial myxoma is a plausible diagnosis. It’s never been diagnosed in cats, though. In May 2010, a review of 39 cases of canine synovial myxoma was published. Because this hasn’t been described before in a cat, the AMC is probably going to try to publish this as a case report. They are having special stains done on the biopsy specimen to try to characterize it further. They are also contacting the author of that review article to help with the definitive identification of the tumor.

If synovial myxomas behave in cats the same way that they behave in dogs, then things might not be so bad for Percy. In that review article, the average survival time in dogs was 2.5 years, even if the tumor wasn’t completely removed. The tumor regrew at the incision site in a few dogs, but the tumor never spread to any other organs or directly resulted in any dog’s death.

After the special staining is done, we should have the truly final diagnosis.

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21 Vintage Cat Advertisements

21 Vintage Cat Advertisements
Cats sell. And we're not just talking cat food here; historically, companies have used cats in advertisements for wares ranging from cod liver oil to Corvettes. So without further ado, here's a sampling of twenty one products hawked by cats.(via Buzzfeed)