Hyperthyroidism Flashcards
Hematology findings in case of feline hyperthyroidism
-Erythrocytosis (because of too much EPO)
-Might also see lymphopenia, eosinopenia
Most important biochemistry findings in feline hyperthyroidism?
-Increased ALT
-Also increased ALP, AST, GGT + some other stuff
Why does hyperthyroidism cause increased EPO poruduction and erythrocytosis?
Hyperthyroidism can cause cardiomegaly and pleural effusions + oedema of lungs which cause oxygen deficiency –> activation of EPO
What might you see in thoracic radiography in case of feline hyperthyroidism?
Cardiomegaly
Pleural effusions
Oedema in lungs
Three things you might check from urine
Urinary glucose
UPC (Urine Protein Creatinine ratio)
SDMA (symmetric dimethylarginine)
What are the thyroid function tests in felines?
Total T4 - very specific in cats, often the only test needed
Scintigraphy
What is the most common cause of feline hyperthyroidism?
Functional thyroid adenoma (adenomatous hyperplasia)
Most common signs of hyperthyroidism
-Weight loss
-Increased appetite
-Hyperexcitability
-Polydipsia
-Polyuria
-Palpable enlargement of thyroid gland
-GI signs are also common
-Cardiovascular signs like tachycardia, systolic murmurs, dyspnea…
In rare cases, hyperthyroid cats might be apathetic (anorexia, lethargy, depression)
What should you remember with cats that have non-thyroidal illnesses?
Many illnesses will lower the TT4-values. This means that a cat that has a significant non-thyroidal illness, shows clinical symptoms of hyperthyroidism, but has normal levels of TT4, could still have hyperthyroidism that is masked by the other disease.
If situation is unclear, you should do more tests e.g. measure simultaneous free T4 + TSH or repeat TT4.
What are four treatments for feline hyperthyroidism?
- Radioiodine
- Thyroidectomy
- Chronic antithyroid medication
- Lifelong iodine-deficient diet
What is considered to be the best treatment for hyperthyroidism?
Radioactive iodine. It’s a simple, effective, and safe treatment. Radioactive iodine is concentrated within the thyroid tumor, where it selectively destroys hyperfunctioning thyroid tissue.
What can be a side-effect of treating cats with thyroidectomy
Iatrogenic hypothyroidism and hypoparathyroidism
In case of hypoparathyroidism, you need to also treat with calcitriol and calcium
What are some drugs used in treatment of hyperthyroidism?
Methimazole - blocks thyroid hormone synthesis
Carbimazole - will convert into methimazole after administration
Propylthiouracin - not recommended because of side effects
For symptomatic treatment of hyperthyroidism, you might give b-blockers
