Common Endocrine Diseases in Cats

In our last blog, we talked about the most common endocrine diseases of dogs.  In case you missed that one, an endocrine disease is caused by an imbalance in hormone levels – usually due to the body producing too much or too little of a specific hormone. In this blog, we will give you an overview of two most common endocrine diseases that we see in cats.

Hyperthyroidism
Hyperthyroidism (or overactive thyroid) is one of the most common feline endocrine diseases that we see. The overactivity is caused by a tumour in the thyroid gland – usually benign – that pumps excessive amounts of thyroid hormone into the bloodstream.  

Thyroid hormone is responsible for regulating metabolic rate. Too much circulating thyroid hormone will result in an increase in your cat’s metabolism, which can result in:

  • Excessive drinking
  • Weight loss
  • Increased appetite
  • Restlessness
  • Increased vocalising
  • Intermittent vomiting or diarrhoea. 

Upon examination, we often find an increased heart rate and can sometimes palpate, increased levels of thyroid hormone (T4) in the blood and an enlarged thyroid gland under your cat’s neck. Hyperthyroidism usually affects older cats – the average age at diagnosis is around 13 years. If left untreated, hyperthyroidism will cause continued weight loss and muscle wastage and can lead to the development of heart disease and high blood pressure.

There are four main treatment options for hyperthyroid cats:

Medical Management – Methimazole is the most common medication used to manage the condition. This medication blocks the production of thyroid hormone – it’s inexpensive compared to other treatment options and has a low incidence of side effects. Cats need to be medicated twice daily, which can be a problem for our more cantankerous kitties! Ongoing blood work is required to ensure the dosage is correct, and treatment will likely be lifelong.

Surgical – Surgical treatment involves removing the abnormal thyroid tissue under anaesthetic. If successful, the treatment is permanent and your cat will no longer require any medical management. There is however a chance of recurrence if abnormal thyroid tissue is left behind. The cost of surgery can be a prohibitive factor, and so is the increased anaesthetic risk in geriatric cats. As the parathyroid glands are very close to the thyroid glands, there can be complications post-operatively – however, this is unlikely. 

Dietary Therapy – Thyroid hormone is made with iodine. Therefore, cats with excessive amounts of thyroid hormone will be using a lot of iodine. Feeding a diet that is very low in iodine will prevent the excessive thyroid hormone being manufactured. Cats fed this low iodine diet exclusively should have normal T4 levels in around 8 weeks. The hardest part about using this method to treat hyperthyroidism is that the cats must eat this diet exclusively – zero treats or other foods are permitted! This means dietary therapy is not an option for any cat with outside access, or cats in multi-cat households.  Due to the relative newness of the low iodine diets, there is not yet any concrete information as to the long-term side effects. 

Radioactive Iodine Treatment – Often considered to be the gold star option, this is the safest and most effective method of treating hyperthyroidism.  The main disadvantage of this line of therapy is that there is no access to this treatment in Western Australia.  All cats must be flown to the eastern states to receive treatment.  This increases the cost of treatment and can be difficult logistically. Cats receiving radioactive iodine need to be fully assessed and scanned before being approved for treatment. They are then given a dose of radioactive iodine which attaches to the thyroid tissue and destroys the thyroid tumour.  All other healthy tissues are unaffected, meaning it is extremely safe and low stress on the cat.  Cats must be boarded and monitored in a licenced facility while the medication is excreted, usually a week in total.  Nearly all cats are cured after one treatment and require no ongoing management for hyperthyroidism.

Diabetes

Diabetes mellitus is caused by a deficiency of the hormone insulin. All the cells of the body require fuel to function, and glucose is an essential fuel. Tissues cannot absorb glucose without insulin, and when there is insufficient insulin in the body, glucose stays in the bloodstream. The tissues then go into starvation mode, resulting in increased appetite and weight loss. Glucose also moves into the urine in high amounts, drawing water with it, which causes excessive urination and thirst. All that sugar in the urine creates a very suitable environment for bacteria to grow, making urinary tract infections common as well. 

If you read our last blog post about endocrine diseases in dogs, you will be aware that diabetic dogs tend to have an insulin dependent diabetes and require insulin injections.

The situation in cats is more complicated. Cats can have a form of diabetes that is similar to a human Type II diabetes, in that they do not require insulin injections. However, most of these cats will require injections of insulin to start with, after which the pancreas can somewhat recover and the cat will go into a type of remission. Some of these cats however will not be easy to regulate due to other health issues, and will remain insulin dependent.   

Some cats will only be mildly diabetic when they are diagnosed, and as such their diabetes can be managed through diet. These cats tend to do better with multiple small meals, so allowing access to food all day is best. Cats have been found to regulate their glucose levels better when fed a high protein and low carbohydrate diet.  Prescription diabetes diets are available.

This information is all fairly general – each case and each cat is different. For the best advice suited to your cat, please reach out on 08 9277 7488 or at ascotvet.com.au!