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If your older cat becomes restless or even aggressive, has excessive hair loss and loses weight, this could be due to the thyroid gland. Hyperthyroidism is the most common hormonal (endocrine) disease in cats and usually affects older cats from the age of 8 years, but younger animals can also become ill.
The thyroid gland is located on the neck below the larynx and in our domestic mammals is divided into two parts to the right and left of the windpipe. The iodine-containing thyroid hormones T3 and T4 that it produces play an important role in energy metabolism and the growth of individual cells and the organism as a whole. They increase heart rate and blood pressure as well as body temperature, sweat production, intestinal motor activity and the excitability of nerve cells. This is why the thyroid gland is often referred to as the body's powerhouse.
If thyroid cells are destroyed and too few hormones are produced as a result, this leads to hypothyroidism. If, on the other hand, too many hormones are released (e.g. due to the influence of a thyroid tumor), this is known as hyperthyroidism.
Note: Cats usually suffer from hyperthyroidism, while dogs are more likely to suffer from hypothyroidism!
What is the cause of hyperthyroidism in cats?
In around 98% of cases, benign growths of thyroid tissue are the cause of hyperthyroidism in cats. This is often so-called "adenomatous - multimodular hyperplasia", in which tiny nodules develop in both lobes of the thyroid gland, causing the thyroid gland as a whole to enlarge. Somewhat less frequently, the growth develops in the form of benign tumors on one side (thyroid adenomas). Only very rarely is a malignant tumor present in cats. Enlargement of the thyroid gland leads to increased production of thyroid hormones.
What triggers these adenomas is not yet fully understood. Nutrition and environmental influences, but also genetic factors, could have an influence. According to studies, feeding commercial cat food is a risk factor for the development of the disease, which is attributed to the high content of thyroid-enlarging substances such as soy isoflavones or phthalates. In addition, environmental factors such as the use of certain cat litters may also be involved in the development of the disease. Flame retardant chemicals such as diphenyl ether in home textiles, carpets and furniture are also suspects. Although the use of diphenyl ether was banned in the EU some time ago, there are certainly still plenty of furnishings that contain the substance. It is also still frequently found in imported goods from outside the EU.
What symptoms do cats with hyperthyroidism show?
The first signs are often not perceived by cat owners as a disease, but rather as a sign of health. The increasingly increased activity of the old cat, combined with an increased appetite, is reminiscent of a young, growing cat. Often the cat is only presented to the vet when it loses body weight with an increased appetite and increased food intake and other signs such as increased thirst (polydipsia) and increased urine output (polyuria) are added. Increased hair loss is also one of the non-specific symptoms and is often dismissed as a change of coat.
Typical symptoms of hyperthyroidism in cats are
- Restlessness
- hyperactivity
- Increased heart rate and high blood pressure
- Significantly increased appetite
- Weight loss up to extreme emaciation
The overproduction of thyroid hormones T3 (= triiodothyronine) and T4 (= thyroxine) and thus their increased release into the blood leads to an increase in metabolism in every single cell of the cat's body. This increases the energy consumption of each cell, which in turn means that the cat with hyperthyroidism has to eat significantly more food in order to provide sufficient energy. As the disease progresses, it becomes increasingly difficult for the cat to meet its energy requirements through food intake. This eventually leads to weight loss. Weight loss despite a good appetite is the most obvious sign of hyperthyroidism.
Other frequently occurring symptoms:
- Great thirst
- Frequent urination
- Coat changes such as hair loss, bald patches and dull, lackluster coat
- vomiting
- Diarrhea
- Aggressiveness
- Excessive or reduced grooming behavior
- Weakness and lethargy
- Damage to the kidneys
- Damage to the eyes
- Damage to the heart
- Even loss of appetite in advanced stages
How does the vet diagnose hyperthyroidism?
In most cases, the vet can feel an enlarged thyroid gland in the cat's neck. A healthy thyroid gland is not normally palpable in cats.
In order to obtain a reliable diagnosis, the vet should carry out a blood test, as almost all cats with hyperthyroidism have a high concentration of the thyroid hormone T4 (thyroxine) in their blood serum. In some cases, the diagnosis is more difficult because the T4 level is only slightly elevated or even within the normal range. If all other symptoms nevertheless indicate hyperthyroidism, either the T4 determination can be repeated after some time or free T4 (fT4) and TSH can be determined in the blood serum.
Due to the frequent presence of concomitant diseases, it is also advisable to have a complete blood count and a serum profile carried out, for example to check liver and kidney function and also the heart. If there is a suspicion that other organs have also been affected, an X-ray may be necessary or an ultrasound may be performed to assess the organs in the abdominal cavity.
What are the treatment options for hyperthyroidism in cats?
As a rule, hyperthyroidism is easily treatable. However, if the disease remains undetected and is not treated, the cat's condition will worsen.
The most common treatment for hyperthyroidism is the lifelong administration of thyrostatic drugs. These are drugs that interfere with the formation of T4 and T3 by blocking the incorporation of iodine. They therefore only suppress the disease and when the medication is discontinued, previously existing symptoms reappear. Thyrostatic drugs for cats are available in the form of tablets or an ointment that can be applied to the auricles and massaged in. To avoid initial side effects or negative effects on the kidneys, therapy is often started with a low dosage. If the blood and urine values are OK, the dose is gradually increased after two to three weeks.
In certain cases, the thyroid gland can also be surgically removed. Surgical removal of the thyroid gland is advisable, for example, in cats with a malignant thyroid tumor. However, only as long as no metastases have formed. The procedure should be carried out in a specialized veterinary clinic and the cat should be monitored in the clinic for some time afterwards, as various complications can occur. The most common complication is a (usually temporary) life-threatening calcium deficiency, which occurs because the parathyroid glands have also been removed (only in the case of large thyroid tumors) or are still recovering from the procedure. If both thyroid lobes have to be removed, the operation will result in hypothyroidism and the cat will need thyroid hormones in tablet form for the rest of its life.
Another option is radioiodine therapy. Here the cat is administered radioactive iodine. This destroys the thyroid tissue. Disadvantage: the cat must be kept isolated in a special room for a period of time as it "emits radioactive radiation". Excrement must be disposed of as hazardous waste. Only trained and protected personnel are allowed to care for the animals. For cats with metastatic malignant tumors, which are very rare, radioiodine therapy is the only chance of surviving the disease.
What do I have to bear in mind when treating with thyroid hormones?
- If possible, always give the thyroid tablets at the same time of day.
- Either always give the tablet with food or always without, not one way or the other.
- If you forget a tablet, this is not normally a problem. Continue the treatment as normal the next day. However, if a blood test is due, the vet must be informed that a tablet has been missed. The examination date should possibly be postponed.
- Pay attention to whether the cat is completely symptom-free or whether symptoms of hyperthyroidism may reappear after some time. If so, the thyroid levels should be checked again and the dose of medication adjusted if necessary.
- If your cat shows symptoms of hypothyroidism, such as tiredness, loss of appetite, excessive weight gain or hair loss, the dose of medication is probably too high. In this case, show your cat to your vet again.
Rarely, thyroid medication can cause side effects such as loss of appetite or vomiting. They usually only occur briefly at the start of treatment and are harmless. However, if the side effects persist, the dosage may need to be adjusted or the medication discontinued. It is then best to make an appointment with your vet.
Supportive nutrition for hyperthyroidism
Iodine-free food has now been developed that works in theory. In practice, however, it is more difficult as the cat must not be given any other food for the rest of its life. This means that iodine-free food is hardly an option for hyperthyroidism, especially for outdoor cats that catch prey and thus ingest iodine.
When choosing a food, you should make sure that no gullet meat, stick meat or poultry necks are used. These can contain thyroid tissue and make treatment more difficult. You should also look for products with a lower iodine content in their food supplements.
Cats with hyperthyroidism are often picky when it comes to food. Good, healthy food, if possible wet food, contributes a lot to a good quality of life.
Can naturopathic methods support your cat?
Complementary methods such as phytotherapy and homeopathy help to increase your cat's well-being and alleviate symptoms and accompanying signs. They can always be used to supplement and support conventional medicine, but not usually as the sole therapy. For example, AniForte® elm bark can be used to support stomach complaints. The immune system can also be strengthened as an adjunct. AniForte® Premium Colostrum or AniForte® Immun-Aktiv can provide support here.
Complications and prognosis of hyperthyroidism
It is not uncommon for hyperthyroidism to mask chronic renal insufficiency. Cats with hyperthyroidism drink more, which benefits the kidneys. If the cat is now treated, the amount of drinking is also reduced, which makes renal insufficiency visible. The kidneys should therefore also be checked during a follow-up examination, even if they did not show any abnormalities in the initial blood count.
Another complication is blindness. Hyperthyroidism and renal insufficiency can lead to high blood pressure. If the cat suddenly shows wide, open pupils or runs into objects, a vet should be consulted as soon as possible.
The heart can also be affected by hyperthyroidism. In this case, the heart disease must be treated. However, if it was caused by hyperthyroidism, there is hope that the heart will return to normal if the thyroid gland is treated and the heart medication can be discontinued.
Conclusion
The quality of life of your properly medicated cat is very good. Regular blood tests and an adapted diet are necessary and important. You should also keep an eye on your cat's behavior. This way, your cat can lead a largely normal cat life even with hyperthyroidism.
