Tag Archives: hyperthyroidism

High blood pressure

 Hypertension is the medical term for high blood pressure, a silent killer of older cats.

 What causes hypertension in cats?

Hypertension is usually secondary to another disease. Kidney disease is the most common cause of hypertension but cats with adrenal gland tumours or treated for hyperthyroidism also develop high blood pressure at times. Sometimes no underlying cause is found.

Most cats with hypertension are older than 9 years of age.

What are the effects of hypertension?

Hypertension damages all body organs but we notice it most in:

  • the eyes. The small vessels in the retina break under pressure. The bleeding detaches the retina and the cat becomes blind.
  • the brain. Ruptured blood vessels cause ‘strokes’, fits, twitches or unusual behaviour
  • the kidneys. Increased blood pressure damages the delicate filtration system of the kidney.
  • the heart. The heart has to work harder to push the blood out into the body and the heart muscle thickens and becomes less efficient. Sometimes the heart goes out of rhythm or we hear a murmur with the stethoscope. Affected cats may show signs of heart failure such as breathlessness, lethargy, weakness or fainting.

How do we detect hypertension?

We measure the blood pressure of all cats over 9 years old as part of the regular seniors’ examination. We also check the blood pressure of all cats with kidney disease or hyperthyroidism, or with any signs of eye, brain or heart disease.

Most cats tolerate the cat sized cuffs we put on their arms. Some don’t like the feel of the gel or the sound of the amplifier we use to hear the pulse. We try to put them at ease so that we get an accurate reading.

How do we treat hypertension?

A daily dose of amlopidine as a fragment of tablet (Norvasc), or as chicken, fish, cheese or beef flavoured drops to put on the food, brings the blood pressure down rapidly.

After a week on amlopidine we recheck the blood pressure to see if it has come down to normal. If all goes well we recheck it every 3 months.

Sometimes other medications like benazepril (Fortekor or Vetace) are added in, particularly if we detect kidney disease.

Kitty Dementia

Dementia, also known as feline cognitive dysfunction, is an age-related disorder of brain function causing multiple behaviour changes.

In cats the behaviour changes include:

  • Yowling excessively and inappropriately
  • Urinating or defecating outside the litter box and around the house
  • Disorientation and aimless wandering
  • Restlessness
  • Changes in interaction with people or other pets such as aggression, irritability and clinginess
  • Erratic sleeping behaviour: waking, pacing or yowling at night, sleeping less at night and more during the day
  • Decreased grooming

Some diseases mimic cognitive dysfunction. These include hyperthyroidism, brain tumours, viral diseases, high blood pressure, chronic pain, arthritis, diabetes, and urinary tract infections. Many of these diseases exacerbate the behaviour changes of cognitive dysfunction, too, so we must check for and/or treat them before we confirm a diagnosis of cognitive dysfunction.

Some commonly used drugs such as prednisolone and valium also reduce brain function. Alternatives that reduce decline are often available.

Therapies

1. Diet: Anti-oxidants delay and treat dementia. Antioxidants include Vitamin E, Vitamin C, Alpha-lipoic acid, L-carnitine and beta-carotene. Fruits and vegetables contain many of these.

Omega 3 fatty acids as found in fish oil or food supplements such as Nutricoat also help.

2. Physical therapy and environmental enrichment: Stimulate brain function and delay the onset of dementia with environmental enrichment and games. Try scattering or hiding food or catnip around the house, provide toys that require batting or rolling to release food, give opportunities for climbing, perching and exploring, trail ribbon or feathers along. Petting, brushing and massage stimulate the nerves and brains of old cats, too.

3. Your vet may prescribe medications to reduce inflammation, enhance memory or improve brain function.

Hyperthyroidism

Hyperthyroidism is a common disorder of older cats.  An overactive thyroid gland produces and secretes too much thyroid hormone putting pressure on all body organs. Any sex or breed of cat can be affected.

The signs of hyperthyroidism include:

  • Weight loss
  • Increased appetite
  • Hyperactivity and restlessness
  • Increased heart rate, associated with irregularities in rhythm, murmurs and high blood pressure
  • Increased frequency of defecation with occasional accidents inside
  • Increased thirst and urination
  • Occasional vomiting
  • Panting
  • Matted, greasy and unkempt coat
  • Enlarged thyroid glands on the neck

If we suspect that your cat has hyperthyroidism we send blood for measurement of the thyroid hormone, T4. We also check for secondary liver, heart or kidney problems.

We usually treat hyperthyroidism with tablets or drops and recommend radioactive iodine therapy once your cat’s system has settled down.

  1. 1. Anti-thyroid drug therapy

Anti-thyroid drugs interfere with the production and secretion of thyroid hormone. They control rather than cure the condition.

Carbimazole (brand name Neo Mercazole) tablets are given twice daily. We see mild and often transient side effects in a few cats on this medication. These include poor appetite, vomiting and lethargy. More serious side effects including a fall in the white blood cell count, clotting problems, or liver disorders occasionally result. If we find any serious side effects after 2 weeks of medication we switch to another treatment.

Many owners prefer methimazole as a gel applied to the inside of the ear or made up into a palatable liquid.

Hyperthyroidism often covers up kidney troubles in cats.  If your cat seems to be drinking or urinating a lot more on medication then alert us as soon as possible.

  1. 2. Radioactive iodine therapy

If kidney problems are not uncovered by anti-thyroid therapy then we suggest radioactive iodine, a more permanent cure for hyperthyroidism. Radioactive iodine only destroys the affected thyroid tissue and leaves adjacent normal tissue, including the parathyroid glands, untouched.

We refer you to a special facility at Canberra Veterinary Hospital for radioactive iodine therapy. Treated cats are kept in hospital for a week after the treatment until they are no longer a radiation risk to people.

Radioactive iodine treatment is curative and has no serious side-effects. Depending on the age of the cat at diagnosis the cost of treatment is similar to long term anti-thyroid drugs or surgery.

It is the only effective treatment for thyroid adenocarcinoma, the cancer that causes 1 to 2% of feline hyperthyroid cases.

  1. 3. Surgical thyroidectomy

Removal of the thyroid glands provides an immediate cure but has some nasty potential side effects so we don’t often recommend it.