The thyroid is a small endocrine gland located beside the trachea. It produces thyroid hormones using iodine from food and releases these hormones into the bloodstream.
Thyroid hormones play vital roles, including:
Promoting metabolism
Regulating body temperature
Activating the heart and digestive system
Brain development and growth
These hormones are essential for maintaining a healthy life.
Thyroid hormone levels in the blood are regulated by thyroid-stimulating hormone (TSH) sent from the brain. When this regulatory mechanism fails, leading to excessive thyroid hormone activity, it causes various symptoms known as hyperthyroidism.
In cats, hyperthyroidism is one of the most common endocrine disorders, particularly in senior cats aged eight years and older.
Causes of Hyperthyroidism
1. Thyroid Tumors and Hyperplasia
Both benign and malignant conditions can cause hyperthyroidism by leading to excessive production of thyroid hormones. In cases of hyperplasia (an increase in the number or size of thyroid cells), more thyroid hormones are secreted than usual, resulting in hyperthyroidism symptoms.
Most cases involve benign tumors (thyroid adenomas) or hyperplasia, which are the primary causes of hyperthyroidism in cats. Generally, only one side of the thyroid swells, but both sides can swell in some cases.
2. Environmental Factors
Excessive intake of iodine and isoflavones from commercial cat food and exposure to environmental chemicals may contribute to thyroid hyperplasia.
3. Other Factors
Although not yet clearly identified, genetic predisposition, immune system factors, and increased longevity are thought to play roles.
Symptoms of Hyperthyroidism
Symptoms of hyperthyroidism in cats include:
Weight loss (despite eating well)
Loss of appetite
Increased activity and appetite in an older cat
Frequent loud meowing
Hair loss
Increased water intake and urination
Diarrhea and vomiting
Lethargy
Feeling of heat in the body (elevated body temperature)
Among these, symptoms such as “losing weight despite eating,” “frequently vocalizing loudly,” and “hair loss” are often seen as age-related and may be easily overlooked by pet owners.
Additionally, there may be concurrent conditions such as arrhythmia, cardiomyopathy, or kidney disease.
Diagnosis of Hyperthyroidism
Abnormalities in the thyroid can be detected through physical examination, including signs such as weight loss, hair loss, and palpation revealing an enlarged thyroid.
Even if there are abnormalities in the thyroid, routine blood tests (CBC) may not show abnormalities unless there are other concurrent conditions.
In biochemical tests, an increase in alkaline phosphatase (ALP, ALKP) liver enzyme, AST, and BUN can be observed. Additionally, an increase in thyroid hormones (T4 or FT4) is also confirmed.
T4 (thyroxine) levels can be low due to various diseases, so diagnosing hyperthyroidism involves measuring FT4 (free thyroxine), which is less affected by other conditions, alongside T4.
Other diagnostic methods include X-ray and ultrasound examinations, where an enlarged heart can be observed.
Treatment of Hyperthyroidism
① Medication
Anti-thyroid drugs (e.g., methimazole, propylthiouracil) are used to suppress the synthesis of thyroid hormones and alleviate symptoms. Possible side effects include loss of appetite and vomiting, with severe side effects such as a decrease in granulocytes, a type of white blood cell, and a decrease in platelets, which are important for clotting. Treatment usually starts with a low dose, with regular blood tests and symptom monitoring to adjust the dosage.
② Surgical Operation
Surgery involves the removal of the thyroid gland. If both sides are removed, it will result in a complete lack of thyroid hormone production, necessitating lifelong supplementation with thyroid hormone (e.g., levothyroxine). However, since the thyroid is attached to small endocrine glands called parathyroid glands, which secrete parathyroid hormone to regulate blood calcium levels, there is a risk of damaging or removing these glands during surgery. In such cases, low blood calcium levels will be confirmed in blood tests, requiring concurrent treatment for hypoparathyroidism with hyperthyroidism.
③ Therapeutic Diet
A therapeutic diet restricting iodine is used to reduce the intake of raw materials for thyroid hormones. Hills’ y/d is one such diet.
Supporting Hyperthyroidism with Immune Power
We often receive consultations from owners of cats with hyperthyroidism. Many reports indicate a feeling of heat in the body, so we recommend Cordy without organic germanium.
If there is no sensation of heat in the body, it is safe to start with a small amount of Cordy containing organic germanium and adjust the dosage according to the condition.
Maintaining immune strength can help balance the body, and we have received reports that medication dosage could be reduced in some cases.
Support your cat’s health by managing their immune system.
