Managment of Hyperthyroid Cats Flashcards
What are the main treatments for Hyperthyroidism in cats?
Methimazole
Hills y/d (low iodine)
Surgical Thyroidectomy
Radioiodine
What is the most common endocrinopathy of cats?
Hyperthyroidism (10yr and up)
What is hyperthyroidism and what can cause it?
Excess production of T4 and T3
Thyroid adenoma, adenomastur hyperplasia and carcinoma
Benign most of the time
In the absence of thyroid stimulating hormone from the pituitary, the thyroid continues to secrete Thyroid hormone
What are clinical signs of hyperthyroidism?
Weight loss
Increased appetite
Increased thirst and urination
Restlessness
Vomit and diarrhea
Poor coat
Increase activity and vocalization
Thyroid slip
How do you diagnose hyperthyroidism?
90% have elevated T4
FT4 and TSH, Thyrooid scintigraphy
What are the goals of treating a hyperthyroid cat?
Achieve euthryoridism
Avoid hyperthyroid and hypothyroid (both bad)
-Harm kidney function
What happens if you have a hyperthyroid cat that also had CKD?
Address both
- dont want mild hyperthyroid to improve creative concentration
Need to get to euthyroid to see if the kidneys were injured
What do you treat first if the cat is hyperthyroid and has hypertension?
Treat hyperthyroid first unless TOD, usually resolves after treatment
How does methimazole work to treat hyperthyroidism?
Cheap, effective, reversible oral drug or transdermal
-most cats get this
-Long term
-Tumor is still progressing (can turn into carcinoma, large goiter)
Can become resistant - 4yr treatment (big tumor = bigger dose)
Warn owner they may need to switch
When treating with methamizole, what should you do when there is CKD?
Start at lower doses so they dont decompensate
How do you monitor methimazole treatment?
CBC (check blood side effect) /Chem (check liver) T4 (normalizing?) 2-4 weeks
Watch for side effects: GI, hepatotoxicity, facial puritis, BUN, Creatinine, USG, BP
4 weeks to see good control
By running a methimazole trial before radioiodine you can preview what?
Kidney Function
Describe radioiodine as a treatment?
Treatment of choice
Destroys abnormal thyroid tissue
95% efficacy with one treatment
SC 1131 - hospital isolation or at home (5 days) - keep inside and collect poop 2 weeks
-Ensure they dont need daily handling and that you are pretty sure they will not decompensate
-Can lead tohypothyroidism (levothyroxine)
-may still have to pill the cat
What type of diet should a hyperthyroid cat be put on?
Low iodine diet
y/d
Improved signs 4 weeks
Creatine decrease or no change
When can you use diet therapy? when shouldn’t you use diet therapy?
Good - cant tolerate methimazole, concurrent disease, renal insufficncy
Bad - indoor/outdoor, multiple cats, cat need other diet
How does surgical thyroidectomy work?
Less common with iodine
Carcinoma
Risk hypothyroid
Recurrence in bilateral
What is hypothyroidism?
Decreased T3 and T4
Spontaneous
Iatrogenic
Radioactive iodine therapy - resolve 3-6 month
What is the clinical signifigance of being hypothyroid?
More likely azotemic - decreased GFR, decreased survival
What are clinical signs of hypothyroidism?
Weight gain
decreased appetite
lethargy
PU/PD
Dermatologic change
What values are used to diagnose thyroid diseases?
Total T4: decrease (CKD can cause) (effected by non thyroid diseases)
Free T4: Not great stand alone, in reference (effected by non thyroid diseases)
TSH: Spontaneous, iatorgenic, increased, most sensitive, best in combo with T4 (not effected by non thyroid diseases)
What are the 2 forms of hypothyroidism?
Overt: Decreased T4 and Increase TSH
Subclinical: Increased TSH
When should you monitor these animals post treatment?
1m, 3m, 6m, 12m
T4, TSH, Chem or renal, UA
Resolution, detect opposite, and check renal function)
When do you need to treat hypothyroidism after treatment?
Permanent 6m, new or worsening azotemia
What is the treatment for hypothyroidism?
Levothyroxine
Without food (1-3hr before or after a meal)
Recheck T4 and TSH in 1 mon
Should you use Y/d with methimizole?
No, increased risk of hypothyroidism
