Hyperthyroidism and Chronic Renal Failure in Older Cats
What are some of the most common diseases we encounter in middle-aged and older cats? Just ask Lynda H. and her 15-year-old cat Ripley. They have experience with two of these diseases: feline hyperthyroidism and chronic renal (kidney) failure.
Poll several of your friends with geriatric cats and one of them is sure to say they are dealing with chronic renal failure or hyperthyroidism. As with Ripley, it’s not uncommon to see both of these diseases simultaneously.
Symptoms of Hyperthyroidism in Cats
About five years ago, Ripley began vomiting and losing weight. She still had a great appetite, but she just couldn’t seem to maintain her weight. On her physical exam, Ripley was underweight, had a fast heart rate, and her thyroid gland, located in her neck near the trachea, was enlarged. All of these are hallmark signs of hyperthyroidism. A simple blood test determined that Ripley’s thyroid hormone was, in fact, high.
Changes in thyroid can affect many body systems. One of the biggest effects is on metabolism. An increased thyroid hormone level speeds the metabolism, causing weight loss and an increase in heart rate.
Treating Feline Hyperthyroidism
Fortunately, treatment for hyperthyroidism is usually fairly simple. Options include medication, surgery and radiation. Medication may be either oral or a transdermal, which is a gel absorbed through the skin. Surgery and radiation offer permanent solutions. Because radiation treatment gives such good results without the risk of surgery, it has become our “gold standard” for permanent treatment.
In Lynda’s case, she was able to take Ripley to the Feline Hyperthyroid Treatment Center for Iodine-131 radiation treatment, thus curing her of her hyperthyroidism. Ripley was soon back to her old self and even gained over 2 pounds in a matter of months.
A Common Secondary Issue: Renal (Kidney) Failure
Sometimes treating hyperthyroidism can be a little more challenging. High thyroid hormone levels increase metabolism. This, in turn, increases blood flow to the kidneys, which can mask signs of kidney disease.
Thus when we initially treat hyperthyroidism and bring the patient’s metabolism back down to normal, we sometimes uncover renal failure that had been hidden by the elevated thyroid hormone. In these cases, medication is often the treatment of choice because we can adjust the medication to appropriately balance the two diseases.
Luckily, at the time of Ripley’s diagnosis, she showed no signs of kidney disease. However roughly four years after the thyroid treatment, Lynda noticed Ripley’s water consumption was increasing. Annual blood panels in the previous years had indicated that Ripley’s kidneys were functioning normally. However, this year, blood tests revealed slight increases in BUN and creatinine, the values we use to assess kidney function. These elevated values in conjunction with a low urine specific gravity (concentration) mean that Ripley’s kidneys were slowly losing their function.
By the time that we are able to detect kidney disease in a blood panel, approximately 2/3 of the kidneys have lost their normal function. Although we can’t reverse this damage, fortunately there are a few things we can do to slow the progression—including a low protein diet and fluid therapy.
Little Miss Ripley still has mildly elevated kidney values, so her main treatment at this point is a prescription diet. We know her disease will be progressive, but now that we know what to watch for, we are able to slow its progression as best we can.
Lynda and Ripley are still looking forward to many golden years together!
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