Feline
Hyperthyroidism
Feline
Hyperthyroidism: Hyperthyroidism
(also called thyrotoxicosis) is one of the most common diseases
of the middle-aged and older cat. It is a multi-system disorder
caused by an increase in the amount of thyroid hormones (T3 and
T4) produced by an enlarged thyroid gland. It was first documented
in cats almost 30 years ago but the cause of the disease has been
elusive. Although the enlargement in the thyroid gland is caused
by a tumour, called an adenoma, it is non-cancerous.
The
most common clinical signs of hyperthyroidism in cats include weight
loss, increased appetite (although some patients have decreased
appetite), vomiting, increased thirst and urination, hyperactivity,
and diarrhea. The high levels of thyroid hormones can cause the
development of heart disease, and these patients may have a heart
murmur, difficulty breathing, high heart rate and arrhythmias. Once
hyperthyroidism has been confirmed, there are several treatment
options. They include treatment with radioactive iodine, surgical
removal of the gland, and treatment with antithyroid medications.
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