Radioactive Iodine Treatment of Hyperthyroid Cats
I-131 Treatment for Hyperthyroidism in Cats
- Approximate cost
(total bill which includes examination fee, I-131, some limited diagnostic
evaluation if needed, and hospitalization): $950-$1200; a cardiology
evaluation if needed could add $300 to this estimate.
- Length of
time in hospital: 6 to 8 days. The
campus Radiation Safety Office, not the clinician, authorizes release of the
- Route of I-131
administration: single subcutaneous injection
- Side effects: none
expected, though, as with other treatments for hyperthyroidism, decreases in
renal function (please see below) may be observed following I-131 therapy;
hypothyroidism is uncommonly observed.
- Tapazole®: We would
like to have Tapazole® discontinued 2 weeks prior to treatment with I-131.
tests including a minimum of BUN, Creatinine, urine specific gravity and TT4
during a euthyroid state (or nearly normal T4 ) induced by methimazole
treatment, should be available in an otherwise healthy cat. If a cat is showing
signs of illness a CBC, Chemistry panel, UA, and possible further diagnostics
may be required prior to injection. Bloodwork can be sent with the client, or
drawn at WSU. Bloodwork may be repeated at WSU at the discretion of the
We often ask
for Faxes (509-335-3330) of recent laboratory results- especially the CBC,
chemistries and urinalysis- so that any concerns we have may be addressed
prior to the trip to Pullman.
Hyperthyroidism and chronic renal failure
Cats with both hyperthyroidism and chronic renal failure may have an
increase in kidney waste products (azotemia) after treatment for
For the recently diagnosed hyperthyroid cat, the option of trial therapy
with Tapazole® should be considered so that the effect of treatment on renal
function can be evaluated. It is generally felt that if serum BUN and creatinine concentrations remain unchanged with normalization of T4 after
Tapazole® treatment, then definitive therapy with surgery or I-131 is
unlikely to be associated with worsening of renal function post-treatment.
Development of azotemia following implementation of Tapazole® treatment is
not a contraindication to I-131 treatment, but does create management
concerns that may impact the decision to treat with I-131.
Discharge from the hospital
Length of time in hospital: 6-8 days average (shortest has been 5 days,
longest 14 days; the campus Radiation Safety Office, not the clinician,
authorizes release of the cats). Discharge instructions will include
guidelines on special handling of urine and feces, and maintaining the cat
at a safe distance from small children, or pregnant women for two weeks post
release.For further information or to arrange referral, please contact the Referral
Medicine Technician, Roland Munson at 509-335-0711.