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Radioiodine Treatment for a Hyperthyroid Cat. Treatment for hyperthyroidism in a cat with I-131.


Bica was experiencing weight loss. This was also muscle loss. She seemed healthy, was eating well, but losing muscle mass.


A full blood work panel indicated that she had an overactive thyroid. Hyperthyroidism is common in aging cats.
Blood work from1/21/2017
Total Protein 7.2 5.2-8.8 g/dL
Albumin 3.0 2.5-3.9 g/dL
Globulin 4.2 2.3-5.3 g/dL
A/G Ratio 0.7 0.35-1.5
AST (SGOT) 56 10-100 IU/L
ALT (SGPT) 185 10-100 IU/L HIGH
Alk Phosphatase 70 6-102 IU/L
GGTP 4 1-10 IU/L
Total Bilirubin 0.1 0.1-0.4 mg/dL
Urea Nitrogen 19 14-36 mg/dL
Creatinine 0.9 0.6-2.4 mg/dL
BUN/Creatinine Ratio 21 4-33
Phosphorus 3.9 2.4-8.2 mg/dL
Glucose 131 64-170 mg/dL
Calcium 8.9 8.2-10.8 mg/dL
Magnesium 2.1 1.5-2.5 mEq/L
Sodium 154 145-158 mEq/L
Potassium 3.9 3.4-5.6 mEq/L
Na/K Ratio 39 32-41
Chloride 116 104-128 mEq/L
Cholesterol 201 75-220 mg/dL
Triglycerides 59 25-160 mg/dL
Amylase 739 100-1200 IU/L
PrecisionPSL 12 8-26 U/L Acute pancreatitis is unlikely. Chronic pancreatitis is not excluded by a normal PrecisionPSL.
CPK 63 56-529 IU/L
Comment Hemolysis 1+ No significant interference.
Complete Blood Count
WBC 3.2 3.5-16.0 103/mL LOW
RBC 12.8 5.92-9.93 106/mL HIGH
Hemoglobin 17.2 9.3-15.9 g/dL HIGH
Hematocrit 58 29-48 % HIGH
MCV 45 37-61 fL
MCH 13.5 11-21 pg
MCHC 30 30-38 g/dL
Platelet Count 167 200-500 103/mL LOW Platelet count reflects the minimum number due to platelet clumping.
Platelet EST Adequate
Differential Absolute %
Neutrophils 2112 66 2500-8500 /mL LOW
Lymphocytes 800 25 1200-8000 /mL LOW
Monocytes 128 4 0-600 /mL
Eosinophils 160 5 0-1000 /mL
Basophils 0 0 0-150 /mL
Absolute Neutrophils 2112 2500-8500 /mL LOW
Absolute Lymphocytes 800 1200-8000 /mL LOW
Absolute Monocytes 128 0-600 /mL
Absolute Eosinophils 160 0-1000 /mL
Absolute Basophils 0 0-150 /mL
Total T4
T4 4.5 0.8-4.0 mg/dL HIGH


Dr. Conway treats the hyperthyroid differently than other radiation treatment organizations e.g. radiocat. She does an additional thyroid scan the day of the treatment to confirm the size and other details (of the tumor) to “tailor the dose” for your cat. With Bica being so tiny (5.5 lbs) I think that’s an important difference. The thyroid scan takes two minutes and if you cat is “too wiggly” they can give a mild sedative. (Bica’s middle name is “wiggly” so it’s no surprise she needed a bit of chemical calming.)
The cost seems to be the same between the various radiation treatment places. It’s around $2k but can go up to $2500 or more depending on what’s needed. We paid ~$1,962.00. The initial consult is included in that price but it’s important to note that lab work is not. You know from Bica’s tests that there are many that accompany this process. The tests needed at the initial consult cost $227 and then just before the treatment (after 10 days without medicine) you have to get a thyroid level test but not the whole list that was done before. Also, there are tests involved at the 30 day, three month and six month post procedure milestones. I don’t know how that relates to the cost of the periodic testing needed even if your cat is on the medicine treatment so it may not be as much of an added cost as it seems. The biggest consideration is the cost breakeven point for the I-131 procedure versus medication treatment is two years, i.e. after two years on the medicine regime, you’ve spent the same amount as you would have for the radiation! Also research shows average life expectancy post I-131 is five years whereas it’s two years post diagnosis with the medication (Dr. Conway repeated what you already told me, that the benign tumor sometimes turns malignant after years on the medicine but with I-131 it ceases to be a factor.) Bottom line for cost: $2,000k procedure includes initial consult, +$225 initial lab work and probably $225(?) each time at the 1 month, 3 month and 6 month checkups so it’s probably $3k total all in.

Various Notes:
· Every cat has to stay five days due to the regulation on radiation levels. From what I’ve read, there’s a lot of desire to change the regulation for animals because the required levels are unnecessarily high compared to radiation level regs for humans receiving treatments. This leads me to believe that five days is an abundance of caution even though for legal reasons a professional can’t say that.
· They only treat a small number of cats per week (maybe 5?) so your cat is with only a few others, has his/her own cage, and twice daily human interaction for feeding, cage cleaning and a few snuggles and pets.
· During the day, there is always either classical music or bird noises playing. (I love this!)
· It’s actually an unbelievably easy event for the cat. They show up, they get the two minute scan, they get an injection et voila….done….they hang out for a week (but in the case of Bica I’m sure she was unhappy her servants (us) weren’t there to spoilm her. There’s no anesthesia, there’s no side effects. They don’t feel any different after the treatment. Dr. Conway has successfully treated cats up to 20 years old (amazing eh?) with many with more problems than the hyperthyroidism.
· Dr. Conway says the biggest risk is: getting the dose a little low or high so the cat needs a second treatment or becomes hypothyroid. Both are rare, but can happen.

For us the issues came after the treatment and were largely unique to Bica. She stopped eating, which happens sometimes but an appetite stimulant should take care of that. She was on the stimulant and was drinking but hadn’t started eating again when we picked her up. Everyone at VRA was sure she’d start eating once she got home since she had been drinking all along, licked the food a bit and was her usual bossy, silly self. However, by Sunday she’d lost 20% of her body weight from when we dropped her off a week earlier and she was starting to get lethargic. Honestly I can’t thank you enough for the texts you so generously sent (on a Sunday) to advise us to start feeding her with a syringe. On Monday, she switched to a different appetite stimulant called “Entice” and that made all the difference. Thanks again to both you and Dr. Conway for thinking of that. I wouldn’t have thought a switch of brand/product could be so important. Bica couldn’t come into the office since she was radioactive (they have to stay confined as much as possible away everyone for 10 days after coming home) so getting advice remotely was critical. The only other note is she developed a herpes eye issue as you know, but if that’s related at all it would be from the stress of being in an unfamiliar environment for five days and the weight loss. It wouldn’t be directly connected to anything with the treatment. It could have happened any time she was stressed for one reason or another.

All in all we are VERY happy to have done the treatment. Not worrying about the medicine dosage changing and whether her running around means she’s being Bica or whether she’s being a little hyper because her thyroid levels are getting out of whack is a wonderful thing.

Hopefully this is helpful! I’m not sure what might turn out to be useful info so I just tried to give enough detail from our experience along with a few notes and thoughts.

Let me know if you have questions or if I can provide anything else.

Above all, THANKS for all you do!!!!


Bica has been seen by us, her primary veterinarian for her 1 and 4 month post radiation blood work panels. She has continued to gain muscle mass and her blood work numbers are all within normal limits.
Her latest blood work can be found in the documents file.
This story was published with Bicas families permission,,, We thank them for sharing her story! Dr Magnifico, at Jarrettsville Veterinary Center in Jarrettsville MD is her primary care provider.

Pet Type: Cat
Pet Breed: Bombay
Pet Date of Birth: 09/18/2005
Treatment Cost (USD): $1962.00
Provider Name: Tiny Conway, DVM
Provider Business Name: Veterinary Referral Associates
500 Perry Parkway
Gaithersburg, Maryland 20877
Files of Receipts, Invoices, Documents, etc.:
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