Goaltending the Food Bowl

Answers: Goaltending the Food Bowl

I have two cats with hyperthyroidism. They are both taking methimazole, one at 5 mg and the other at 7 mg. The 7 mg cat had been on 5 mg but the vet increased it recently when her T4 came back elevated.
I have been feeding them a raw diet for about 4 months now. I am feeding her 4 to 6 times a day and she's still goaltending the food bowl like never before. The recipe I'm using is Pitcairn's for kidney issues, as recommended by my vet, which keeps the phosphorus low by providing protein through eggs. Is it possible she's just not getting enough calories?
The recipe I used is:
2/3 pound ground chicken, turkey or lean heart
4 cups cooked white enriched rice
4 eggs
2 tablespoon cold pressed safflower, soy or corn oil
1500 mg calcium
1/8 teaspoon salt
5000 IU vitamin A
Taurine and other cat vitamins
50 mg B complex
2500 mg vitamin C as 1/2 teaspoon sodium ascorbate
As I understand it, the concern you have is that the cat on the 7 mg dose of methimazole is still goaltending the food bowl. What an accurate description of the overeating behavior we call polyphagia! And you clearly are already aware that polyphagia is a symptom of untreated or undertreated hyperthyroidism.
There are several issues here that could be in play.
The first question in my mind is whether you are dosing twice a day. The effective half-life of methimazole in the cat is about 11 1/2 hours, so if you do once-a-day dosing, you are really only controlling the disorder for half of the 24 hour cycle. This leaves your cat uncontrolled and craving food for the other half of the day. Worse, all of the negative effects of the elevated metabolism are also continuing for those 12 hours, and the damage to every other organ in the body continues to accrue, albeit at half the rate. Once-a-day dosing for methimazole is simply not appropriate medical therapy. Unfortunately, it is still prescribed that way all too frequently for the convenience of the owner, without adequate explanation of the consequences. So, if you are dosing once a day, you should ask your vet if he or she feels it would be okay to give half of the dose twice a day. Control the problem around the clock and your goaltending may go away.
Next, you mentioned the dose increase to 7 mg was done recently when the T4 came back elevated. It is good procedure to recheck the T4 two to three weeks after such a dose elevation to make sure that you have gotten your kitty back into the desired range. I always do this and it surprises me how often a refractory hyperthyroidism needs more methimazole than I expected. If you have not done a recheck, you should ask your vet about it. You might find your kitty is still undertreated.
Then there is the question of the renal issues you mentioned. Handling this with appropriate nutrition requires defining the stage of the chronic renal disease.¹ Even then there is great controversy about when protein intake should be limited. Cutting-edge nutritionists are now advocating maintaining normal protein intake until Stage 4, the final stage. The vast majority of cats we manage are in Stage 2, and most stay there for many years. This is the time to begin limiting phosphorus intake, as you are already aware.
Managing hyperthyroidism and renal insufficiency together is a complex problem since the two are interactive. Hyperthyroidism induces an increase in water intake and therefore urine output. This self-flushing will drive down the renal blood test values and can make you think kidney function is better than it is. Correcting or controlling the hyperthyroidism will usually not worsen the kidney function, but it will decrease the self-flushing and make the test results look worse. They really aren't worse, they are just more accurate. In rare cases, treating the hyperthyroidism can have an actual negative effect on the kidney function, so this should be monitored regularly.
In my mind, the deeper question your diet raises – the question that may tie all this together – has to do with the rice.
There are a rapidly growing number of us who believe that grain in a cat's diet, any grain at all, may cause a sequence of inflammatory events beginning in the gut and cascading outward to affect every single organ in the body. If true, it may well be that many of the chronic inflammatory diseases of the cat which we did not recognize until the last 20 to 40 years – hyperthyroidism was defined as recently as 1978 – may have been recognized in that time frame not because we got good enough to see them, but because they didn't exist until pet food companies began making cat foods with substantial amounts of grain.
Chronic renal disease is an inflammatory disorder. Inflammatory bowel disease, pancreatitis and hepatitis, often seen as a triad, are inflammatory in nature. What is less obvious is that cancers, which are much more likely to occur in areas that have experienced chronic inflammation, are also influenced by inflammation. Hyperthyroidism is often caused by a cancer, usually a benign thyroid adenoma, which makes the gland hyper-productive. Wouldn't it be interesting and ironic if the grain in the prescribed diet, by causing the beginning of the inflammatory cascade in the gut, was actually making the hyperthyroidism worse at the same time that you are using medication to try to control it?
Should this be the case, and you were to change the diet, you would not see an overnight improvement. Inflammation does not disappear immediately, or we wouldn't scratch our mosquito bites for days on end. You have to give it time. Typically, I find that removing grain from the diet in these situations produces a visible change in about two to four weeks, although I've seen plenty of cats respond faster than that.
So one very simple thing you might try, if your vet feels it appropriate and if your kitty is not in Stage 4 renal insufficiency, is to cut the rice out completely and increase the meat and eggs. You'd also have to avoid any grain or carbohydrate replacement for the rice, so no potato, pea, barley, wheat, corn or soy.
Cats evolved to eat prey, and mice are not made of rice and corn. I can't imagine why we ever thought we could force such a radical change in their diet without grave consequences. And I believe we are seeing these consequences now.
Additional thoughts: the polyphagia could be a third disease issue. In older cats, this is often more the rule than the exception. Your cat may need a full workup to look for this.
Radioactive iodine therapy does more than control the disease, it effectively cures it. You don't have to give medications with significant possible side effects and you don't have the continued accrued disease damage you still get for two half-hour periods a day with the best of pill control. There are risks and costs associated with it, but they should be discussed with your vet and balanced with the costs and risks of the course you are currently pursuing. 
In summary: talk to your vet. If you are not dosing twice a day, bring it up for discussion. Consider rechecking that T4 if you have not done so since the dose change. Consider a full workup to look for other causes of polyphagia. And definitely discuss changing the diet by removing the grain entirely if the stage of the renal disorder permits.
Note: Feline Nutrition provides feline health and nutrition information as a public service. Diagnosis and treatment of specific conditions should always be in consultation with your own veterinarian. Feline Nutrition disclaims all warranties and liability related to the veterinary advice and information provided on this site.
Fern Crist, DVM is a graduate of the University of Georgia and has a feline only practice in Fairfax, Virginia.
  1. Chronic renal disease in cats is generally divided into four stages, each indicating the approximate level of kidney function that has been lost. There are usually no symptoms of renal disease in Stage 1, which denotes function loss of less than 66%. Stage 2 denotes 66 to 75% loss of function, Stage 3 denotes 75 to 90% loss and Stage 4 denotes over 90% loss.

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