What is hyperthyroidism in cats?
The thyroid glands are located in your cat's neck and produce a variety of hormones that help to regulate many processes in the body and control your cat's metabolic rate. If the thyroid produces too much or too little of these hormones your cat will either show symptoms of hypothyroidism (low levels of hormone) or hyperthyroidism (too much hormone).
If your cat is suffering from hyperthyroidism their metabolism will speed up. This means that your cat will tend to burn energy too quickly, resulting in weight loss even if you notice that your kitty is eating considerably more food than usual.
Symptoms of Hyperthyroidism in Cats
While any breed of cat can suffer from hyperthyroidism, most cats diagnosed with this condition are older. Typically between 12 and 13 years old. Female and male cats are equally impacted.
Often, the symptoms of hyperthyroidism in cats are subtle in the early days but gradually become more severe over time. Other underlying health issues can also complicate or mask symptoms of hyperthyroidism, so it’s important to see your vet early if your cat shows any of the symptoms listed below. Cats producing too much thyroid hormone may show one or more of the following symptoms:
- Increase in thirst
- Mild diarrhea and vomiting
- Increase in heart rate
- Poor grooming habits
- Hearty or increased appetite
- Low heat tolerance
When the condition becomes more advanced, some cats will pant when they are stressed which is unusual for cats. Although most cats suffering from hyperthyroidism have a good appetite and are restless, others may feel weak, lethargic or experience a lack of appetite.
Causes of Hyperthyroidism
Hyperthyroidism is most often caused by a non-cancerous tumor located somewhere on the thyroid gland. In some rare cases, however, the tumor can develop into thyroid cancer.
Long-Term Complications Related to Cat Hyperthyroidism
Left untreated, hyperthyroidism can impact the function of your cat's heart and possibly lead to heart failure.
Your cat may also develop high blood pressure as a result of hyperthyroidism. Though we see this less often, high blood pressure in cats is linked to other serious health concerns such as damage to the brain, kidneys, heart and eyes. If your kitty is diagnosed with hypertension in addition to hyperthyroidism, medication will be required to their control blood pressure.
Hyperthyroidism and kidney disease often occur at the same time in older cats. When both these conditions are present, they need to be closely monitored and managed as managing hyperthyroidism can sometimes adversely affect kidney function.
Diagnosing Hyperthyroidism in Cats
Diagnosing hyperthyroidism in older cats can be somewhat tricky. Your vet will complete a physical exam and palpate your cat’s neck area to look for signs of an enlarged thyroid gland. At North Boulder Companion Animal Hospital our veterinary internal medicine team uses state-of-the-art diagnostic testing to help diagnose your pet's condition and provide advanced care.
Because there are a range of conditions that share the clinical symptoms of hyperthyroidism, a variety of tests may be used to diagnose your cat's condition. A complete blood count (CBC) urinalysis and chemistry panel can help rule out kidney failure and diabetes. A simple blood test showing elevated T4 levels in the bloodstream may be enough for a definitive diagnosis. Your vet may also check your kitty’s blood pressure or perform an electrocardiogram, chest x-ray or ultrasound.
Treatment for Cats with Hyperthyroidism
Depending on the results of your cat's tests, your vet may choose one of several treatment options for your cat’s hyperthyroidism. They may include:
- Radioactive iodine therapy (likely the safest and most effective treatment option)
- Antithyroid medication
- Surgery to remove the thyroid
- Modified diet
Modified Diet to Treat Hyperthyroidism in Cats
Hyperthyroidism in cats can often be managed through an iodine-restricted prescription diet from your vet. Iodine intake is necessary for the production of thyroid hormones, so the goal of an iodine restricted therapeutic diet is to help reduce the production thyroid hormones by reducing iodine in your cat's diet.
Strict adherence to the low-iodine diet is necessary for this treatment to be effective, which can prove challenging for some pet parents and their cats. Along with feeding your cat a prescription food, you will need to strictly monitor your cat's treats, and prevent your cat from hunting for their own meal while outside.
Some studies show that after three weeks of following a prescription hyperthyroidism diet, levels of thyroid hormones begin to decrease, and within a few months, they may even return to normal levels.
Prognosis for Cats with Hyperthyroidism
If the condition is diagnosed and treated early, the prognosis for cats suffering from hyperthyroidism are generally good. In some cases where the condition has become more advanced, complications with other organs can worsen prognosis.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.