So your cat has been diagnosed with Hyperthyroidism-What now?
Hyperthryroidism is the most common endocrine disorder seen in cats. It has become more prevalent since the late 70’s. The underlying cause is not really known. Most cases are due to benign adenomatous hyperplasia of one or more commonly both thyroid glands. Less commonly (<5%)it is due to thyroid carcinoma. The thyroid glands are situated in the neck region and sit alongside the trachea (windpipe). Thyroid hormones produced by these glands are widely used in metabolism around the body.
Your cat may be exhibiting one or more of the following signs:-
- Weight loss
- Increased appetite
- Change in behaviour-more temperamental/fractious/hyperactive
- Increased heart rate/heart murmur
- Increased thirst/increased urination
- Intermittent vomiting/diarrhoea
- Less commonly skin changes are seen with hair loss and unkempt coat.
Blood screening will usually show an increase in circulating thyroid hormone (T4) concentrations. Sometimes early in the disease this will be normal and we will suggest a repeat blood test. Other changes in the blood profile may support the diagnosis-often there is an elevation of liver enzyme levels (these will generally return to normal with successful management of the hyperT4).
There are a number of options for managing this disorder and the treatment chosen will be done with consideration to each individual case.
Carbimazole is a drug administered 2-3 times daily and it is concentrated in the thyroid gland where it inhibits thyroid hormone production. It is an effective from of treatment however it can have some side effects and may not be suitable for cats that are difficult to medicate. It is available in a transdermal form that can be applied to the cat’s ear and is absorbed through the skin for those cats that are difficult to tablet. In about 20 % of cats side effects will be seen and can include-vomiting, lethargy, off food or less commonly (<5 %) can be more serious side effects such as problems with the white blood cells, bleeding tendencies, itchy face, anaemia, muscle weakness or liver problems .Regular monitoring is advised via blood tests particularly in the early stages.
Radioactive Iodine Treatment
This is considered the safest, simplest and most effective therapy. It is readily available in the Frankston area. The radioactive iodine is administered orally (or by injection) and your cat will need to stay hospitalized usually for one week and once your cat returns home there must be minimal handing for a further two weeks. Although the initial financial outlay may seem large, in the long term it is often more economical than medical management. A small percentage of cats may require repeat radioactive treatment.
This is an option but is generally not done at our clinic as we have radioactive iodine treatment readily available. If both thyroid glands are affected it is best to remove one at a time to reduce the complications post surgery. If your cat has ectopic (situated outside the normal area) hyperplastic thyroid tissue then surgery may not be successful.
COMPLICATIONS OF UNDERLYING CHRONIC KIDNEY DISEASE.
Some cats will have underlying kidney disease that is being masked by hyperthyroidism. For this reason it can be preferable to treat your cat medically for a few weeks prior to undergoing radioactive iodine therapy. Underlying kidney problems may then be revealed. Some cases treated with radioactive iodine may go on to develop kidney disease-these cases can be difficult to predict.
Hyperthyroidism if left untreated will eventually cause irreversible damage to vital organs such as the heart and kidneys. Treatment of this disease is recommended in most cases. The attending vet will discuss options with the owner and because each case is different the most appropriate treatment plan will be chosen in consultation with the owner.