08 Apr Hyperthyroidism in Cats: What Every Cat Owner Needs to Know
If you have a cat over the age of 8, this might surprise you.
Up to 10% of senior cats develop hyperthyroidism, yet many cases go undiagnosed because the early signs can look like “just getting older” (Peterson 2013).
The reassuring part is this: diagnosis is usually as simple as a quick blood test.
At Southern Cross Vet, we see this condition regularly across Sydney, from Redfern and Surry Hills to Bellevue Hill and Bondi. The earlier we detect it, the better the outcome for your cat.
If you are even slightly concerned about your cat’s behaviour or weight, you can book a senior health check here: https://scvet.com.au/book or call 1300 DOC SAM (1300 362 726).
What Is Hyperthyroidism in Cats?
Hyperthyroidism in cats is a common hormonal condition where the thyroid glands produce too much thyroid hormone.
These hormones control metabolism. When levels are too high, your cat’s body essentially goes into overdrive.
This condition is one of the most common feline endocrine disorders we see in older cats.
In most cases, hyperthyroidism is caused by a benign thyroid adenoma, which is a non-cancerous enlargement of the thyroid gland (Carney et al. 2016).
Causes and Risk Factors
The number one risk factor is simple: Age.
Hyperthyroidism is primarily a condition of senior cats, usually over 8 years old.
Other contributing factors may include:
- benign thyroid adenomas
- environmental influences
- diet and iodine exposure
- genetics in some cases
If your cat is getting older, screening becomes increasingly important. This is why we often recommend bringing your senior cats in to the clinic at least once, if not twice a year for Senior Health Checks.
Recognising the Symptoms of Hyperthyroidism in Cats
The tricky part about cat hyperthyroidism symptoms is that they can look subtle at first.
Here are the most common signs we see in the clinic:
Classic symptoms
- Weight loss in older cats, despite eating more
- Increased appetite in cats
- Increased thirst and urination
- Hyperactivity or restlessness
- Vomiting or diarrhoea
Physical changes
- Unkempt or greasy coat
- Muscle loss
- Fast heart rate
- A palpable thyroid nodule in the neck
Behavioural signs owners often mention
When owners observe the symptoms of hyperthyroidism and physical changes mentioned above, they are often left with queries such as:
- “He’s eating like crazy but getting thinner”
- “She’s more vocal and restless at night”
- “He seems anxious or unsettled”
- “She drinks water constantly now”
These are age-old signs of hyperthyroidism in cats, and they are often missed early on.
Why So Many Cases Go Undiagnosed
One of the biggest challenges with hyperthyroidism in senior cats is that early symptoms can be mistaken for normal ageing.
Owners often observe the signs discussed earlier and think, “My cat is just getting older” or “She’s just been a little skinny always.” Since these symptoms are so easy to overlook, getting a veterinary professional to assess their health periodically becomes of paramount importance.
Because of this, many cats are not diagnosed until the condition has progressed.
Early detection is key, which is why we strongly recommend senior cat wellness exams in Sydney.
Diagnosis: The Simple Blood Test That Changes Everything
Diagnosing hyperthyroidism in cats is usually straightforward.
What we do at Southern Cross Vet
1. Physical examination
We check for weight loss, heart rate changes and feel for thyroid enlargement.
2. Blood test for hyperthyroidism in cats
A simple blood test measures T4 levels, which indicate thyroid function.
3. Additional tests if needed
These may include kidney function tests or blood pressure checks.
The blood test is quick, safe and minimally stressful for your cat.
In many cases, this simple thyroid test for cats provides a clear diagnosis.
If your cat hasn’t had a recent check, you can book an appointment today or call 1300 DOC SAM (1300 362 726).
Treatment Options for Hyperthyroid Cats
There is no one-size-fits-all approach. The best hyperthyroidism in cats treatment depends on your cat’s age, health and lifestyle.
-
Medication (Methimazole)
- Controls thyroid hormone production
- Usually given daily
- Requires ongoing monitoring
-
Radioiodine Therapy for Cats
Often considered the gold standard treatment.
- Targets abnormal thyroid tissue
- High success rate
- Often curative
-
Prescription Diet
- Special iodine-restricted diets
- Helps manage hormone production
-
Surgery
- Removal of the affected thyroid gland
- Considered in selected cases
Learn more about our surgical care.
We will always guide you through the pros and cons so you can make the best decision for your cat.
The Critical Importance of Early Screening
Early detection of hyperthyroidism in cats can make a significant difference.
Benefits include:
- Preventing heart complications
- Protecting kidney function
- Maintaining healthy weight
- Improving quality of life
- Extending life expectancy
Left untreated, hyperthyroidism can lead to serious complications, including heart disease and high blood pressure.
How Southern Cross Veterinary Clinic Can Help You
At Southern Cross Vet, we focus on early detection, accurate diagnosis and personalised care.
We support cat owners across the Inner West of Sydney, including suburbs Redfern, Surry Hills, St Peters, Erskineville, Pyrmont, Darlinghurst and Marrickville, and through our clinic in Bellevue Hill, serving patients in the Eastern suburbs from Rose Bay and Double Bay to Vaucluse and Bondi Junction.
Our approach includes:
- comprehensive senior cat health checks
- in-house diagnostic testing
- tailored treatment plans
- ongoing monitoring and support
If you are looking for a cat hyperthyroidism Sydney vet, our team is here to help.
Book here: https://scvet.com.au/book or 1300 DOC SAM (1300 362 726).
Going Away? We Can Care for Your Hyperthyroid Cat
Managing hyperthyroidism in cats often requires consistency with medication, diet and monitoring. We know this can be stressful if you are planning to travel or be away from home.
At Southern Cross Vet, we also run Lions Den Cat Boarding Sydney, located on the first floor of our Surry Hills clinic.
Because the boarding facility is operated by the same veterinary team, your cat receives a level of care that goes beyond standard boarding.
This is especially helpful for cats with ongoing medical conditions such as hyperthyroidism.
While staying with us, your cat can benefit from:
- consistent medication administration
- monitoring of appetite and behaviour
- prompt veterinary care if needed
- a calm, cat-only environment
You can learn more here https://lions-den.com.au/
If you are heading away and need trusted care, you can book by calling 1300 DOC SAM (1300 362 726) or (02) 9699 3951.
FAQ: Hyperthyroidism in Cats
What are the symptoms of hyperthyroidism in cats?
Weight loss, increased appetite, hyperactivity, increased thirst, vomiting and poor coat condition.
How common is hyperthyroidism in cats over 8 years old?
Around 10% of cats over 8 are affected.
How is hyperthyroidism diagnosed in cats?
With a simple blood test measuring thyroid hormone levels.
What causes hyperthyroidism in cats?
Most commonly benign thyroid growths.
Can hyperthyroidism in cats be cured?
Yes, particularly with radioiodine therapy.
What is the best treatment for hyperthyroidism in cats?
Depends on the individual case, but radioiodine is often considered gold standard.
Should I screen my senior cat for hyperthyroidism?
Yes, routine screening is strongly recommended.
How long can a cat live with untreated hyperthyroidism?
It can significantly reduce lifespan and lead to complications.
What are the treatment options for hyperthyroid cats in Sydney?
Medication, diet, surgery and radioiodine therapy.
Is a blood test for thyroid levels painful or stressful?
It is quick, minimally invasive and well tolerated.
References
Carney, H. C. et al. 2016, ‘AAFP Guidelines for the Management of Feline Hyperthyroidism’, Journal of Feline Medicine and Surgery.
Peterson, M. E. 2013, ‘Feline Hyperthyroidism: An Update’, Veterinary Clinics of North America.
American Animal Hospital Association 2021, Feline Endocrine Disorders Guidelines.