Common illnesses in cats: thyroid disease
Hyperthyroidism, a disease of the thyroid gland, is a common illness in cats and mainly affects middle-aged and older cats.
Also known as thyrotoxicosis, hyperthyroidism is caused by increased production of thyroid hormones. Hyperthyroidism in cats is usually caused by a benign tumour on the thyroid gland. This tumour results in overproduction of the thyroid hormone thyroxine. One of its main functions is to regulate the animal's metabolism. Some rare cases of hyperthyroid disease are caused by malignant tumours known as thyroid adenocarcinomas. Certain environmental factors are also thought to play a role in the disease.
Older cats (aged 12-13) are at higher risk of developing hyperthyroidism. No particular breed is known to be at greater risk, although Siamese, Burmese, Persian, Abyssinian and British Shorthair cats appear to have a slightly lower incidence of hyperthyroidism compared with other breeds, but there are no precise statistics.
Thyroid hormones affect almost every organ in the body. Around 20% of cats with hyperthyroidism become hypertensive (develop high blood pressure). In some of these cats, blood pressure can rise so high that it causes bleeding or retinal detachment, leading to sudden blindness. Permanent blindness can result if the retinal detachment isn't treated immediately.
Thyrotoxic cardiomyopathy can develop, because the heart enlarges and thickens to meet the increased metabolic demands. In some cases, the cat will develop a heart murmur linked to the cardiomyopathy. Both the cardiomyopathy and the hypertension are potentially reversible with appropriate treatment of the underlying disease. Thyroid disease often causes secondary problems.
Symptoms of hyperthyroidism in cats
Cats with hyperthyroidism often show a range of signs, which may start out mild but worsen over time. The most common symptoms include:
• Weight loss
• Increased appetite
• Increased thirst and urination
• Vomiting
• Diarrhoea
• Hyperactivity
• A coat that looks unkempt, matted or greasy
Diagnosis
To reach a diagnosis, blood tests are carried out and T4 levels are measured (the thyroid hormone, or as most owners know it, the thyroid hormone). Most cats with hyperthyroidism have elevated T4 thyroid hormone levels in their blood, but a small percentage of cats with hyperthyroidism have T4 levels within the normal range. If your cat doesn't have elevated T4 levels, but your vet still suspects hyperthyroidism, further tests may be recommended.
Treatment
The treatment a cat receives for hyperthyroidism will depend on specific circumstances, including the patient's overall health, the owner's ability and willingness to treat them regularly, and financial considerations.
Preventive blood tests can catch early signs of hyperthyroidism and other health problems before they become serious. Until the end of June, take advantage of a 35% discount on preventive blood tests, to give your cat the best chance at a long, healthy life. Book an appointment at Veterinary Clinic Lozenets with the code CAT and get 35% off the price. The offer is valid until 30/06/2024.
