Patricia's T4 level

detmut said:

there was an article in the June 2012 issue of Catnip newsletter about a possible therapeutic diet for hyperthyroidism. it's still early and the diet is from the evil Hill's (y/d). it has a much lower concentration of iodine in it.

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"Poorly controlled hyperthyroidism on the y/d diet
First of all, the serum T4 concentration in this hyperthyroid cat only decreased into the high-normal range. If you had measured a free T4 concentration in this cat when fed the y/d, I can guarantee that the free T4 value would have been quite high. No matter what treatment is given, it’s important to lower the total T4 concentration into the mid-normal range to ensure that the cat’s free T4 is also normalized and whole-body euthyroidism is restored (3,5,6).

So persistent and poorly controlled hyperthyroidism certainly contributed to the worsening of this cat’s weight loss and muscle wasting, despite the increased appetite in this cat. Remember hyperthyroidism accelerates the metabolic rate and body’s energy expenditure (7,8); these cats are burning up their food calories faster than they can consume their daily meals (5,6,9). In some cats, as in your patient, the body consumes its own muscle tissue to get the protein it needs to sustain its carnivorous life.

Decreased caloric intake on the y/d diet
In addition to the poorly controlled hyperthyroidism, it also appears that your cat was eating significantly fewer calories when fed the y/d. If we compare the caloric content of Purina DM to Hill’s y/d, we find that ½ cup of DM provides almost 300 kcal whereas ½ cup of y/d provides only 259 kcal (2,10). This 40 kcal per day might not seem like much, but that’s a 15% decrease in the amount of daily calories ingested!

Another important point in this cat is the fact that she did not find the y/d particularly palatable, and therefore did not eat more of the y/d food to compensate for the lower-caloric food. Remember, a few cats may actually like the y/d, but almost all of the cats I have seen on the diet would much rather eat another type of food if given the choice (11).

Decreased protein intake on y/d diet
In addition to caloric density, Hill’s y/d is also much lower in protein compared to the Purina DM (36% vs 58% on a dry matter basis) (2,10).

Remember that protein is the primary macronutrient responsible for maintenance of muscle mass. Restoring and preserving any remaining muscle tissue in cats treated for hyperthyroidism depends upon the cat consuming a diet with sufficient amounts of high-quality protein.

The lower protein intake of Hill’s y/d, together with the lower caloric intake, both contributed to the muscle breakdown and rapid loss of muscle mass in this cat when fed the diet. If this cat had been able to increase the daily amounts of y/d ingested, this may have lessened or prevented the loss of muscle mass that developed in the cat (12,13).

Higher carbohydrate intake on y/d diet
It is well accepted by most practicing veterinarians who specialize in feline medicine that a low-carbohydrate diet is a mainstay in the treatment of diabetes mellitus, especially if remission of the diabetic state is the goal. Feeding a low-carbohydrate diet will improve insulin sensitivity, reduce or eliminate the need for exogenous insulin, and help stabilize glucose metabolism in these cats (14-16).

If remission is achieved, it is very important to continue the low carb diet. In this cat, remission of diabetes was maintained for years by feeding Purina DM diet, which is relatively low in carbohydrates (i.e., 15% on a dry matter basis). Most feline veterinarians like to feed even lower levels of carbs (< 10%) to cats with active diabetes (14,15). To achieve these low carbohydrate levels, we must feed a canned food —none of the available dry cat foods contain <10% carbohydrates. If the diabetic cat goes into remission, we recommend maintaining a restricted carbohydrate diet for life to help prevent relapse of the diabetic state.

In contrast, Hill’s dry y/d diet is relatively high in carbs (i.e., 29% on a dry matter basis), much higher than the 15% found in Purina dry DM diet (2,10). This increased carbohydrate load likely contributed to this cat’s hyperglycemia and probably would have led to recurrence of overt diabetes mellitus if the y/d diet had been continued."

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EmilyMayWilcha said:

I would never even think about buying any Hill's products again. If Patricia does get into the HT range, I will do the same thing for her I did for Emily because nothing works better than I-131.

However, it is good to know a diet change can help for those kitties who don't live close to a qualified HT treatment hospital or can't afford it.

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detmut said:

Yes, the place down the street from me charges $1700 for radioactive iodine therapy (I-131): http://svsvets.com/hyperthyroidtxDVM.html

I imagine that the homemade raw feeders could create a low-iodine diet.

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