Hyperthyroidism is a common hormonal condition in older cats where an overactive thyroid speeds up the body. Classic signs are weight loss despite a big appetite, increased thirst, restlessness, and a poor coat. It is very treatable, especially when caught early. PoCo West Animal Hospital can help diagnose and manage it.
What hyperthyroidism is
The thyroid glands, in the neck, produce hormones that set the body’s metabolic rate. In hyperthyroidism, the glands become overactive, usually due to a benign enlargement, and pour out too much hormone. This puts the body into overdrive, burning energy too fast and straining several organs. It is one of the most common hormonal conditions in cats, and it almost always affects middle-aged and senior cats rather than young ones.
Why it is so common in older cats
Hyperthyroidism is primarily a disease of aging cats, typically those over about ten years old. Because the signs come on gradually and overlap with normal aging, the condition is easy to miss in its early stages. It is also frequently found alongside other conditions common in senior cats, such as kidney disease, which can complicate the picture. This is exactly why routine senior screening is so valuable, since it can catch hyperthyroidism before a cat becomes very unwell.
Signs to watch for
The hallmark is a cat who is losing weight despite eating well, even ravenously. Other signs include:
- Weight loss in a cat with a normal or increased appetite
- Increased thirst and urination
- Restlessness, hyperactivity, or irritability
- A poor, unkempt, or greasy coat
- Increased vocalizing, especially at night
- Occasional vomiting or diarrhea
- A faster heart rate
Why hyperthyroidism matters
Left untreated, the strain of an overactive thyroid damages the body over time. It commonly causes high blood pressure, which can harm the eyes, kidneys, and brain, and it makes the heart work too hard, which can lead to heart disease. It can also mask or worsen kidney problems. Because these complications develop quietly, diagnosing and managing hyperthyroidism early protects the rest of your cat’s body, not just their weight.
How it is diagnosed
Hyperthyroidism is usually straightforward to diagnose. Your veterinarian will examine your cat, sometimes feeling an enlarged thyroid gland, and check the heart rate and blood pressure. A blood test that measures thyroid hormone, often as part of broader bloodwork through our pet diagnostics and medical services, confirms the diagnosis and checks for related conditions like kidney disease. Establishing these values gives a clear baseline for treatment and monitoring.
Treatment and ongoing care
The good news is that hyperthyroidism is very treatable, and there are several options your veterinarian can discuss based on your cat’s needs, including daily medication, a special therapeutic diet, and other treatments. Our nutrition counselling can help if a dietary approach is chosen. Whatever the path, treated cats usually feel dramatically better, regaining weight and calm. Ongoing monitoring through our wellness services is important, since treatment is adjusted over time and other senior conditions are watched for.
Why senior cat screening matters
Hyperthyroidism is a strong example of why regular checkups matter for older cats. Because the early signs are easy to mistake for normal aging, many cases are caught through routine senior bloodwork before a cat becomes seriously unwell. Many veterinarians recommend wellness screening for cats from middle age onward, often yearly and sometimes more frequently, precisely so conditions like this are found early.
Screening does more than catch one disease. Senior cats often have more than one condition developing at once, such as hyperthyroidism alongside kidney disease, and testing helps untangle them so each is managed properly. Establishing baseline values while your cat is well also makes it far easier to spot meaningful changes later. For an older cat who seems fine, screening is one of the kindest, most practical things you can do.
Frequently asked questions
My cat is eating well but losing weight. What does that mean?
That combination is a classic sign of hyperthyroidism, though other conditions can cause it too. It is a clear reason to have your cat checked, since the cause needs a veterinary exam and blood test to confirm.
At what age does hyperthyroidism usually appear?
It almost always affects middle-aged and senior cats, typically those over about ten years old. This is why regular screening of older cats is recommended, even when they seem healthy.
Is hyperthyroidism treatable?
Yes, very. There are several effective treatment options, and most cats improve significantly. Your veterinarian will help you choose the approach that best fits your cat and monitor it over time.
Can hyperthyroidism affect my cat’s heart or kidneys?
Yes. Untreated, it strains the heart and raises blood pressure, and it can mask or worsen kidney disease. Treating it early helps protect these organs, which is why prompt diagnosis matters.
Will my cat need treatment for life?
Often yes, depending on the treatment chosen, since some options manage the condition long term while others can be curative. Your veterinarian will explain the choices and what ongoing care each involves.
How often should my treated cat be rechecked?
Regularly, especially early on, so your veterinarian can fine-tune treatment and monitor the heart, kidneys, and blood pressure. Your team will set a recheck schedule suited to your cat.
Can diet alone manage hyperthyroidism?
For some cats a special iodine-restricted diet can control the condition, but it only works if it is the cat’s sole food, which is challenging in multi-cat homes. Your veterinarian will advise whether a dietary approach suits your cat or whether another treatment is better.
Has your older cat been losing weight while eating well? Book a senior check with the team at PoCo West Animal Hospital to have their thyroid assessed.