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Feline Hyperthyroidism is affecting more cats every year







 Author, Stacey Kalinnikova, BVetTech for Professional Pet Sitting Etc.

It is important to stay informed of the medical conditions that may affect your cat as they age.  Feline hyperthyroidism is a very common endocrine (hormonal) disorder in older cats.  As long as it is diagnosed early, treatment can be highly effective.


What is hyperthyroidism?


The easiest way to understand any medical condition is to break down its definition.

Hyper – overactive.

Thyroid – a hormonal gland in the body that regulates the rate of metabolism (the chemical reactions that cause all the cells and organs to function).


The thyroid hormones (known as thyroxine) are increased due to an enlarged thyroid gland.  98% of the time the enlargement itself is benign (non-harmful), it is the excess secretion of hormones that cause the problems.


How will it affect my cat?


As a result of the excess thyroxine in the blood stream, the entire body and its organ systems will experience over-stimulation.  Physical changes that you will see on your cat progress gradually.


Common clinical signs or ‘symptoms’ include:

  • Weight loss and an increase in appetite.
  • Increased thirst.
  • Hyperactivity and a rapid heart rate.
  • Unkempt hair coat due to lack of grooming or a thin coat from over grooming.
  • Behavioural changes – your cat may become cranky and irritable.
  • Occasionally they will have diarrhoea and vomiting.


These symptoms in your cat may also be indicative of other diseases so it is important to get a definitive diagnosis.


How is it diagnosed?


The first thing your veterinarian will do is feel the thyroid glands for enlargement.  This is not always obvious however, so a blood test is used to confirm the diagnosis of hyperthyroidism.


The blood test that is performed is known as a ‘T4’ test to measure the concentration of thyroid hormones in the blood.   Elevated T4 levels indicate hyperthyroidism.  The early stages of the disease are the hardest to diagnose as T4 levels can be mild and fluctuate within normal range.


Once it has been diagnosed, other blood parameters are usually checked to rule out coexisting problems.


Is it painful?


Many of us would gladly welcome an increase in metabolism, but eating a lot and not gaining weight is not all it’s cracked up to be.  While the excess thyroxine is not painful in itself, the side effects do cause discomfort.


Cats with hyperthyroidism are often hungry and thirsty all the time, their hyperactivity can cause insomnia and the lack of sleep can contribute to mood swings.  Although there won’t be a specific ‘sore spot’, your cat will feel very ill overall.  They will often lack energy and become irritable.  Hyperthyroidism is not a comfortable condition for your cat to live with.


What if it is left untreated?


Left untreated, hyperthyroidism can cause a range of secondary problems due to the role the thyroid hormones play in regulating the metabolism in all organs.


The biggest risk of hyperthyroidism if left untreated is heart failure.  This is due to the increased heart rate as well as stronger contractions of the heart muscles leading to thickening of heart walls.  Another risk is an increase in blood pressure.  High blood pressure can affect organs including the eyes, kidneys, brain, and heart.


Medications may be needed to treat these ancillary conditions in addition to the hyperthyroidism.


What are the treatment options?


There are currently three main treatment options for hyperthyroidism:


Lifelong medication

Anti-thyroid medications such as methimazole and carbimazole reduce the production and release of thyroxine from the glands.  The right dose of medication is highly effective, but is not a cure so will be required daily for the duration of your cats lifetime.


Surgical removal

Surgically removal of the thyroid glands provides a longterm solution to the disease.  Unfortunately there can be anaesthetic risks in older cats undergoing surgery especially if they have underlying heart and kidney problems.


Radioactive iodine treatment

Radioactive iodine is given by injection and becomes concentrated in the thyroid gland.  It irradiates and kills the over-functioning tissue.  Your cat is required to stay in the veterinary hospital until the radiation secreted in their urine and faeces falls to an acceptable level.


You may also hear about chemical ablation of the thyroid gland or dietary management.  These are both relatively new treatment options that are not commonly used.


What is the prognosis?


If hyperthyroidism is diagnosed early and treated effectively, then a complete reversal of clinical symptoms can be seen.  Heart function will usually return to normal and treatment can add many years onto your cats life.


Hyperthyroidism is not something to panic about but it is important to be aware of so that you are comfortable to seek veterinary advice once changes are noticed in your cat.  Ensuring your cat receives proper medical care will keep them happy and healthy for years to come.


A great colleague and owner of Love and Kisses Pet Sitting, wrote a great article you may also be interested in – How To Tell If Your Cat Is Sick, check it out!


If you liked this article, check out our other articles – Complete List Of Our Article and Videos



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