Hyperthyroidism is a condition that can be seen in both senior and middle-aged cats. Today, our Palmyra vets share the causes, symptoms, and treatments of hyperthyroidism in cats.
Hyperthyroidism in Cats
Cats develop hyperthyroidism when they have overactive thyroid glands. It’s a very common disorder caused by an increase in the production of thyroid hormones by the thyroid glands, which are located in the neck.
Thyroid hormones are used to regulate many processes in the body and to control the metabolic rate, and when too much of the hormone is produced, clinical symptoms can be quite dramatic and make cats severely sick.
Cats suffering from hyperthyroidism tend to burn energy too quickly, which results in weight loss, despite eating more food and experiencing an increase in appetite. We’ll discuss more symptoms below.
Signs & Symptoms of Hyperthyroidism in Cats
Hyperthyroidism is generally seen in middle-aged or senior cats. Most kitties are older than 10 (usually between 12 and 13 years old) when the disease becomes a problem. It's equally probable for female and male cats to develop this condition.
The most common signs of hyperthyroidism are:
- Increase in thirst
- Increased irritability or restlessness
- Increase in heart rate
- Poor grooming habits
- Typically a healthy or increased appetite
Some cats will also have mild to moderate diarrhea and/or vomiting, while others will seek cooler places to lounge and have a low tolerance for heat.
In advanced situations, some cats might pant when they become stressed (an unusual behavior in cats). While most kitties are restless and have a good appetite, some might feel lethargic, weaker, or have a lack of appetite. It's essential to monitor for any significant changes in your pet and have them attended to as quickly as possible.
These symptoms are usually subtle to start and gradually become more severe as the underlying disease gets worse. Other diseases can also complicate and mask these symptoms, so it’s important to see your vet early.
The Causes of Hyperthyroidism in Cats
This condition can be triggered by benign (non-cancerous) changes in a cat's body. Both thyroid glands are most often involved and become enlarged (the clinical change is nodular hyperplasia, and it resembles a benign tumor).
While we don't know the exact causes of this change, it's very similar to hyperthyroidism in humans (clinically named toxic nodular goitre). Rarely, a cancerous (malignant) tumor called thyroid adenocarcinoma is the underlying cause of this disease.
The Long-Term Complications of Hyperthyroidism
If hyperthyroidism goes untreated it can affect the function of your cat's heart, changing the organ’s muscular wall and increasing heart rate. Eventually, this can result in heart failure.
High blood pressure (hypertension), is another possible complication. While this is seen less often, it could lead to damage in various organs such as the heart, kidneys, brain, and eyes. If your cat is diagnosed with hypertension on top of their hyperthyroidism, your kitty will require medication to control their blood pressure.
Hyperthyroidism and kidney disease often occur at the same time, as they are both commonly seen in older cats. When both these conditions are present, they need to be closely monitored and managed as managing hyperthyroidism may sometimes adversely affect kidney function.
Diagnosing Cats With Hyperthyroidism
It can be tricky to diagnose hyperthyroidism in elderly cats. Your vet will conduct a comprehensive physical assessment and palpate the area of your cat’s neck to see if they have an enlarged thyroid gland. At Palmyra Animal Clinic our vets are trained in internal medicine and have access to a range of diagnostic tests and treatment options.
A battery of tests will likely be needed to diagnose hyperthyroidism in your cat, as many other common diseases experienced by senior cats (intestinal cancer, chronic kidney failure, diabetes, inflammatory bowel disease, and more) share clinical symptoms with hyperthyroidism.
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, however, this isn't true for 100% of cats because of concurrent illnesses or mild cases of hyperthyroidism, which can result in fluctuating levels of T4 or showing elevated T4 levels if another illness is influencing the result.
If they can, your vet might also check your kitty’s blood pressure and conduct an ultrasound, chest X-ray, or electrocardiogram.
The Treatments for Hyperthyroidism in Cats
There are several treatment options your vet may use to treat your kitty's hyperthyroidism. The one they select will be determined by your cat's specific circumstances and the pros and cons of each method. The treatments available are:
- Surgery to remove the thyroid gland
- Radioactive iodine therapy (likely the safest and most effective treatment option)
- Dietary therapy
- Antithyroid medication, administered orally, to control the disease for either the short-term or long-term
The Prognosis for Cats With Hyperthyroidism
Cats that have hyperthyroidism generally have a good prognosis when the appropriate therapy is administered early. Sometimes, problems with other organs can make the prognosis worse.
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.