The Facts on Hyperthyroidism

What is hyperthyroidism?

A disorder where the thyroid gland, which controls metabolism, is overactive in the production of its hormones. Too much of these hormones result in the animal burning off their energy stores which affects the general wellbeing of the cat. Diagnosis is made by a simple routine blood test.

All cats at risk

The risk of developing hyperthyroidism increases with age and is therefore common in older cats. The underlying reason why the thyroid becomes uncontrolled remains unclear. Both males and females are just as susceptible to the disease. Siamese breeds are less likely to develop the disorder.

Watch for clinical signs

As the overactive thyroid gland increases the demand for energy, the cat becomes ravenous for food even though they lose weight. Other side effects occur too, as shown below, and have a knock-on effect on other organs.

Possible clinical signs of hyperthyroidism:

  • Weight loss despite increased eating
  • More vocal, irritable or hyperactive
  • Increased drinking and urinating
  • Vomiting and/or diarrhoea
  • Increased heart rate
  • Unkempt coat

Treatment tailored to the individual

There is no universal treatment that works for all, so each cat is managed on an individual case-by-case basis, taking into account their age, severity of the disorder, and the presence of other concurrent illnesses such as kidney or heart disease.

Range of medication options

Long-term medication tries to reduce the productivity of the thyroid and reduce the hormones down to a more manageable state. The first line of treatment is usually tablets which are readily available and easy to implement. Other medicine alternatives include transdermal gels smeared on the ear, or a heavily iodine-restricted diet

Consistent medication for life

For the animal to respond well to treatment, medication should be given every day at set times as prescribed because a lapse can result in the return of the disorder in just 2 days. This obviously requires the compliance of the cat if being tableted on a long-term basis! Hiding tablets in treats (e.g.  Webbox) can also mask the taste. Giving just treats twice daily to a healthy cat can help introduce them to being tableted in the future if the need arises and increases success rates.

Long term monitoring

As each cat responds differently, repeat bloods are required to make sure they are receiving the right dose of medication. Blood pressure checks may be taken as 10-15% of affected cats can have high blood pressure. Hyperthyroid cats are also prone to urinary tract infections so urine checks may be needed

Possible cure?

Surgical removal of an affected thyroid gland can be performed to try and cure the disorder but the cat needs to be clinically stable before the procedure. Radiotherapy at selected centres (e.g. Bishopton and The Pride Veterinary Centres) is successful in curing hyperthyroid patients in up to 95% of cases.

Treating concurrent disorders

Renal disease may be masked by hyperthyroidism and only become apparent once the thyroid is controlled. Also, heart disease, such as hypertrophic-cardiomyopathy (HCM) can occur as increased metabolism puts pressure on the heart to beat faster. Both conditions need to be balanced with the thyroid treatment to get a better outcome.

Love your cat

Making sure you take time to stroke and play with your cat before and after medicating will prevent the cat from resisting the attention. Stroking the ears and face stops the animal from associating the negative effects from holding to medicate. Routine positive reinforcement also improves the cat/human bond and reduces the possibility of stress-induced disorders in cats in the long term.