What happens if you discontinue use of methimazole?
cat reverts to hyperthyroid state 24-48hrs after discontinuation
What is another way to use methimazole other than PO?
transdermally in inner-pinna SID (5mg) [WEAR GLOVES]
What are the advantages of surgery to treat hyperthyroidism? (2)
potentially curative, available in private practice
What are the disadvantages of surgery to treat hyperthyroidism? (6)
irreversible, damage to parathyroid blood supply, anesthetic risk, risk of Horner's syndrome, development of disease in contralateral lobe, clinical hypothyroidism (rare)
How does treatment of hyperthyroidism with radioactive iodine work?
functioning cells that take up iodine are killed by beta-particles from radioactive iodine (healthy thyroid tissue is suppressed and therefore, not affected)
What is the ideal treatment for hyperthyroidism, and what is the caveat to it?
radioactive iodine; expense and expertise
When do you see results after radioactive iodine treatment?
serum T4 decreases to normal over days to weeks- 95% are euthyroid within 3 months after one treatment
What special precautions must be followed by owners after radioactive iodine therapy? (6)
[30 days] flushable litter and flush soiled litter down toilet, wash hands after handling cat/cat stuff, cat must be confined to house, no exposure to children or pregnant, cat must wear radioactive ID collar, blood/urine samples handled appropriately
What nutritional changes can be made to manage hyperthyroidism in cats?
iodine-restricted diet (Hill's y/d) exclusively for 3 months--> decreased T4
What are some issues with the Hill's y/d diet? (5)
T4 not low enough, cats must eat ONLY y/d which can be difficult, long-term effects unknown, low protein/high carb (too low protein?), palatability
What are potential complications of feline hyperthyroidism? (3)
increased RBF and GFR--> decreased BUN and Cre, making the kidneys look better than they are; CKD can lower T4 and mask hyperthyroidism; hypertension may not resolve with txt (require Ca2+ channel blocker)
Hyperthyroidism can mask __________, and vice versa.
If you have a cat that you are suspecting hyperthyroidism and kidney disease, how should you treat?
Methimazole challenge test (because you can take it back)
How can you determine if the kidneys are functional enough to go ahead with I131 treatment of hyperthyroidism?
Methimazole challenge- if therapeutic dose of methimazole is achieved with an increase in BUN and Cre, and remain stable for 30 days
What is the prognosis of hyperthyroidism?
very good- average survival is 2 years (remember these cats are already old!)... often die of something else