Feline Hyperthyroidism Flashcards
What clinical signs are associated with feline hyperthyroidism?
- aggressiveness
- reduced tolerance to stress
- increased appetite
- weight loss
- vomiting
- hyperactivity
- PU/PD
- diarrhoea/increased faecal volume
Clinical exam
* muscle wasting
* thin body condition
* tachycardia >240bpm
* cardiac murmur
* hypertension
How can you diagnose feline hyperthyroidism?
- Haematology – not very rewarding… but comorbidities?
- Biochemistry – secondary hepatopathy (ALT, ALP); kidney parameters
- Urinalysis – SG (remember hyperT increases GFR!)
Specific tests:
* Total T4 (increased in 90-95% of hyperT cats, day to day fluctuations, suppresses by non-thyroidal disease, immunoassays may underestimate the level,
* free T4 (unbound, can diffuse into the cell, more sensitive (increases chances of false positives), not affected by non-thyroidal illness,
* T3 (active form of thyroid hormone, derived from T4 in extrathyroidal tissues)
* TSH (canine) – non-thyroidal illness affects it.
* Scintigraphy
Take home message
* NO GOLD STANDARD TEST, interpretation along clinical signs required
* Total T4 best initial test = appropriate clinical signs plus high TT4 = hyperthyroidism
* High TT4 with a few signs only = retest
* Normal TT4 and supportive clinical signs = doesn’t rule out hyperthyroidism-you need another test!
* Free T4 and TSH are secondary tests and should not be used alone to diagnose hyperthyroidism
What are the treatment options for feline hyperthyroidism?
- do nothing
- radioactive iodine
- surgery
- anti-thyroid medication
- dietary management
