PRE-Radio-iodine Treatment

A. Diagnosis of Feline Hyperthyroidism:                                                                             
                                                                                                                                      
  1. Good Resources:

     a. “Canine and Feline Endocrinology and Reproduction,” Feldman and Nelson, 3rd Ed.,
     pp. 152-218 and pp. 143-151.

     b. “Kirk’s Current Veterinary Therapy” XII, Small Animal Practice, Bonagura, Ed.,
     pp. 372-377.

     c. “VCNA, Small Animal Practice,” May 1994, Ferguson, Ed., pp. 582-584 & 600-603.

     d. “VCNA, Small Animal Practice,” September 2001, Behrend & Kemppainen, Eds.,
     pp. 977-978.

     e. “Textbook of Veterinary Internal Medicine,” Ettinger & Feldman, Eds., 4th Ed.,
     pp. 1466-1483.

     f. “Textbook of Veterinary Internal Medicine,” Ettinger & Feldman, Eds., 5th Ed.,
     pp. 1400-1415.

     g. “Choosing the best tests to diagnose Feline hyperthyroidism,” David S. Bruyette,
     DVM, DACVIM, “Veterinary Medicine”, November 2004, pp. 956-962. 


  2. Other Guidelines:

     a. The most reliable thyroid test results come from true veterinary labs. Ask the “human” lab where
     they derived their cat normal values?

     b. Ignore Feline T-3 results.

     c. If you desire a free T-4 value, then insist that the test be done via Equilibrium Dialysis (ED).

     d. Never try to interpret a free T-4 value without having a concurrent Total T-4 value.

     e. Antech laboratories has an excellent protocol for “borderline” cases: If the Total T-4 is in the “high
     normal” range; and, if the concurrent Free T-4 (by E.D.) is above normal, then this supports a diagnosis
     of Feline hyperthyroidism.


3. Concurrent Disease Considerations:

    As most Feline hyperthyroid patients are “Senior Citizens”, the possibility of
    concurrent non-thyroid disease is very real. Therefore it is prudent to gather a thorough data base in
    order to rule in/rule out other entities. However, please recall that our Feline friends do not respond well
    to stress, especially to physical restraint (accordingly, an ounce of gas may be much safer than a pound
    of “brutothane”).


     And, what to do about concurrent renal disease? Some of the best minds in
     internal medicine will tell you to treat the hyperthyroidism medically in order to avoid
     unmasking the renal disease. Several of us in veterinary nuclear medicine feel that it
     may be better to do the opposite: cure the hyperthyroidism with radio-iodine; then, if
     the creatinine jumps up due to the “normalized” blood pressure in the face of renal
     disease, titrate back with Levothyroxine sodium supplementation at low doses [ie.,
     clinically, it feels like I can more easily and safely regulate “hypothyroidism” with
     supplements as opposed to a chronic fight with a thyroid tumor via a harsh drug such as
     Tapazole aka methimazole]. (While Feldman and Nelson’s text does not advocate this
     approach, they do list some convenient doses on page 148 of the 3rd edition of their
     text).


B.  Discuss the Treatment Options with your Client

     1. Radio-Iodine; or, 2. Surgery; or, 3. Tapazole (aka methimazole)

……If you and your client feel that Radio-Iodine is best for your patient, then continue with this Checklist….



C. 

     1. If the cat has never been on Tapazole: then simply fax us a copy of your lab data and ask
     your client to telephone us to set up a treatment appointment for their cat.

     or,

     2. If the cat has been on Tapazole for two months or less, then:

     a. fax us a copy of your lab data; and,
     b. ask your client to call us to set up a treatment appointment for their cat; and,
     c. coordinate with your client to cease the Tapazole two to four weeks prior to our
     radio-iodine treatment.

     or,


     3. If the cat has been on Tapazole for over two months; and if the client now wants radio-iodine
     treatment, then:


     STOP () the Tapazole for two weeks and then measure the total T-4 and
     concurrent free T-4 (ED):

     if the results still support hyperthyroidism, then:

     fax us the lab data and schedule the treatment appointment.

     However, if the T-4 is low normal {or high normal T-4 plus a normal free T-4 (ED)}, then keep the cat off 
     of Tapazole for another 2-4 weeks, then retest. If the patient’s condition will allow it, repeat this protocol 
     until the “T-4” numbers again support hyperthyroidism; then fax us the lab data and schedule the radio-
     iodine treatment appointment.

     Note: You can skip the “two week wait” before trying to schedule the radio-iodine
     treatment if you have run a thyroid panel while the cat is on Tapazole and
     found that the numbers are above normal.

     The reason for this gray area is the following:

     “In spite of the literature, some cats that have been on Tapazole “chronically”
     (as yet an undefined period of time, but more likely in cats that have been
     on Tapazole for perhaps over six months) seem to have thyroid glands that
     are so suppressed that they do not respond well to radio-iodine until the
     gland is allowed to “resume” production.”

      And, yes there will be cats that need to stay right on Tapazole (at some level) until the day of radio- iodine treatment.  Please consult directly with Dr. Carlin on this important issue.

D.  In addition to this “checklist”, please read the other detailed instructions contained
     in our “Dear Doctor” letter.
 

     Thank you!

Post-Radio-iodine Treatment (after Release from our Radiation Safety Ward):

A.  Emergency Veterinary Care during the 14 Day Home Quarantine?

What does my Local Veterinarian Need to Know if my Cat needs Emergency Veterinary Care during the 14 Day Home Quarantine?

B.  Post-Iodine/Post Quarantine, Laboratory Tests, Checklist   for  Veterinarians

FROM:_____________________________________  (your Hospital name)

FAX To:  (501) 327-4240

Attn:  Dr. Stan Carlin, Feline Radio-Iodine Center, Conway, Arkansas

Reference:      Cat’s name_____________________,  Owner____________________________

Dear Doctor Carlin:

Referenced cat was treated with Radio-Iodine at your Clinic on or about_______________ (date).

As the post-treatment blood test results become available, we are hereby FAXing them to you for your review.     Thank you.

                                              (actual date of tests)      Total T4           Creatinine         Other tests (if any)

(A) 3 weeks post-Treatment:   (______________)    ________         ________       __________________________

(B) 3 months post-Treatment:  (______________)    ________         ________       __________________________

(C) 9 months post-Treatment:  (______________)    ________         ________       __________________________

(D) 18 months post-Treatment: (______________)   ________         ________       __________________________

Note:  We understand that if we measure Free T4, we will do so by equilibrium dialysis (ED); and, we will always run a concurrent Total T4.

Sincerely,

_________________________  (name of Doctor or Tech.)

P.S.  If you have any questions you may telephone our Hospital at:_________________________.

[This form drafted by the Feline Radio-Iodine Center, Conway, Arkansas; ph: 501-328-3344]

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