Thyroid hormones regulate many body processes and when too much hormone is produced the clinical signs can be quite dramatic, and cats can become seriously ill. Thyroid hormones also help control the body’s metabolic rate and cats with hyperthyroidism tend to burn up energy too rapidly and typically suffer weight loss despite having an increased appetite and increased food intake.
Fortunately, the vast majority of cats that develop hyperthyroidism can be treated very successfully and most cats will make a complete recovery.
In the vast majority of cases hyperthyroidism in cats is caused by a benign (non-cancerous) change.
Hyperthyroidism is usually seen in middle-aged and older cats, rarely being seen in cats less than 7 years of age. Male and female cats are affected equally.
In affected cats, a wide variety of signs usually develop, but these are usually subtle at first, and become more severe over time as the underlying disease gets worse. Also, as it is mostly older cats that are affected, some cats will have other diseases that can complicate and even mask some of the clinical signs.
The ‘classic’ signs of hyperthyroidism are: Weight loss despite a good or increased appetite, increased thirst, increased activity, restlessness or irritability, an increased heart rate and a poor and unkempt hair coat. Affected cats are often unusually ‘vocal’ also.
To confirm a diagnosis, a blood test is needed to measure the level of thyroid hormones in the blood. This can be taken during routine consultation.
Most hyperthyroid cats can be managed with medication which is safe and effective. As an alternative, surgical removal of the affected tissues (thyroidectomy) can produce a permanent cure or there are options for specialist diet management or even Radiotherapy.
If treated, hyperthyroid cats can be fully controlled however uncontrolled hyperthyroidism has important consequences on the heart (causing increased heart rate but also changes in the muscular wall of the heart that will eventually cause heart failure if untreated), kidneys, and blood vessels in the eyes and brain (causing blindness and ‘strokes’).
If your elderly cat shows signs that could be associated with hyperthyroidism, you should contact your Vet for advice.