Hyperthyroidism is the most common endocrine (hormonal) disorder in cats. It causes many symptoms resulting from the overproduction of thyroid hormone by the thyroid.
What is the thyroid?
The thyroid is a gland formed of two lobes, on either side of the trachea, in the neck. The two types of hormones produced (T3 and T4) are involved in the basic metabolism (system that burns calories as a function of physical activity) and the regulation of body temperature.
Origin
Hyperthyroidism is defined by the secretion of too much thyroid hormone. This runaway causes a hyperfunction of all metabolisms: everything works "too" and too fast. In the great majority of cases (99%) the cause of this hypersecretion is explained by the presence of benign (non-cancerous) nodules on the thyroid glands. These clusters of abnormal cells are adenomas. In 1 to 2% of cases hyperthyroidism is due to a malignant tumor (cancer).
Hyperthyroidism is defined by the secretion of too much thyroid hormone. This runaway causes a hyperfunction of all metabolisms: everything works "too" and too fast. In the great majority of cases (99%) the cause of this hypersecretion is explained by the presence of benign (non-cancerous) nodules on the thyroid glands. These clusters of abnormal cells are adenomas. In 1 to 2% of cases hyperthyroidism is due to a malignant tumor (cancer).
Symptoms
The symptoms are very variable. The most common signs are weight loss (90% of cases), increased food intake in more than half the cases, vomiting, diarrhea, increased water intake, Activity, behavioral changes, nervousness. The coat becomes dull, hair loss is possible. At the end of the disease the cat is generally very slaughtered, prostrate and very lean. The hyperthyroid cat often has an increased heart rate and may have cardiac abnormalities (hypertrophic cardiomyopathy, cardiac muscle disease).
The diagnosis
Normally the thyroid gland in cats is not palpable. In cases of hyperthyroidism, the gland generally becomes large enough to be palpable. A blood test is performed by your veterinarian. A high rate of T4 signs hyperthyroidism. Once the diagnosis has been made, further tests will be proposed by your veterinarian to investigate possible complications of this hyperthyroidism.
The treatment
There are currently three ways to treat hyperthyroidism in cats: medical treatment, treatment with radioactive iodine and surgical removal of the gland.
The most common is medical treatment with an antihyperthyroid (thiamazole) that blocks the synthesis of thyroid hormones. The advantage is that it requires no surgery or hospitalization. The disadvantage is that it does not cure the disease and it must be given for life. Side effects such as lethargy, vomiting, itchiness in the neck and head occur in about 15% of cats. These side effects usually appear within the first 3 months of treatment and can be reduced by starting treatment with low doses, and gradually increasing the dose. Blood tests are performed every 3 to 6 months.
Surgery heals provided all abnormal tissue is removed. An ultrasound or scintigraphy is performed to identify the location of the abnormal tissue. Surgery is not often recommended as it requires great experience from the surgeon. This is a delicate operation because the parathyroid glands and nerves are very close in this region.
The other solution is to irradiate the thyroid gland with radioactive iodine. This solution is definitive in 90% of the cases. Very few veterinary clinics are equipped for this procedure. It is also an expensive procedure and a quarantine of the cat is obligatory (urine and radioactive stools).
After medical stabilization the prognosis is very good. The cat can live many years, healthy
Hypothyroidism is a malfunction of the thyroid that does not produce enough thyroid hormones. It is rare in the cat unless after surgery.
Mechanism of hypothyroidism in cats
Thyroid hormones stimulate all body metabolisms, hypothyroidism is causing a general slowdown: decreased energy production by the cells and thus the overall body temperature, decreased destruction of fat Are stored in the fat cells and cause a general thickening of the skin.
Signs of Hypothyroidism in Cats
A thyroid that works less well will give a set of signs that associates more or less importantly:
- Weight gain.
- Depressive tendency.
- Thickening of the skin.
- Dry and cold skin as a whole.
- Loss of hair that is dry and brittle.
- Constipation.
- Chilliness, drop in temperature.
- Reduced libido.
- Spacing and irregularity of the heat.
- Sometimes slow heartbeat.
Causes of Hypothyroidism in Cats
Surgery suites for thyroid ablation for thyroiditis or thyroid cancer or radiotherapy for cancer of the neck area.
Absence of thyroid (very rare problem).
Some forms of thyroiditis.
Enzymatic block, ie absence of an enzyme that makes thyroid hormones.
Treatment of Hypothyroidism in Cats
It relies on the administration of thyroid hormones that must be taken for life. This treatment should be followed to avoid overdose.
