What is Feline Hyperthyroidism?
This is a disease of the thyroid gland found mainly in felines. It does occur in canines but to a much lesser degree.
Probably close to 98 % of the feline patients that have hyperthyroidism, will have a functional tumor in their thyroid gland that may or may not be palpable. It is a rare that the thyroid tumor is malignant.
CLINICAL SIGNS
- Increased appetite
- Increased weight loss
- Increased heart rate
- Poor coat condition
- Panting
- Heat intolerance
- Possible cardiomyopathy
- A BLOOD SERUM analysis in 98 % of the felines may indicate one or more of the following enzymes, to be elevated:
- ENDOCRINE SERUM analysis:
- Thyroxin (T4) hormone. This seems to be the main endocrine diagnostic test that veterinarians use, to determine if a feline has hyperthyroidism.
- Triiodothyronine (T3) Hormone suppression test. This is a test that is usually not performed. It involves giving the patient a T3 hormone supplement and in a normal feline, the T4 hormone levels will decrease. When this T3 hormone supplement is given to a feline with hyperthyroidism, the T4 hormone level still remains elevated.
- Surgical removal of the thyroid gland
- Radioactive iodine therapy
- Medical treatment
- A cortisol imbalance will lead to the production of elevated adrenal estrogen.
- The elevated adrenal estrogen will bind the receptor sites for T3 and T4 hormones.
- When this occurs, the metabolism of the liver and kidney is decreased.
- This in turn allows for the normal production of thyroid hormones to continue, but because of the bound thyroid receptor sites, both the T3 and T4 hormones will increase in amounts because of the decreased metabolism of the liver. The decreased metabolism will not allow for a normal 24 hour breakdown of the T3 and T4 hormones. At the same time, because of the decreased metabolism in the kidneys, normal 24 hour excretion of the T3 and T4 hormones will not occur.
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