Tuesday, September 13, 2011

The Best Diet to Feed Hyperthyroid Cats

Hyperthyroidism is the most common endocrine disorder of cats, and is one of the most common medical problems seen in small animal practice. Surprisingly, despite the fact that nutritional factors and cat food likely has a role in the etiopathogenesis of this disease (1), there are only limited published recommendations about what to feed these cats.

The question, “What’s the best diet to feed my hyperthyroid cat?” is an extremely common one that I get from concerned cat owners. I’m certain that many of you get the same question.

With the recent introduction of the Hill’s y/d diet (2), the iodine deficient diet which, according to the company website “restores thyroid health,” I thought that my opinion of what diets should be fed to cats with hyperthyroidism might be of interest.

In this post, I’m not going to talk specifically about y/d or any other diet, but which types of food and nutrients hyperthyroid cats need in general. I’ll specifically address the pros and cons of y/d in my upcoming blog posts.

The Many Metabolic Problems Facing the Hyperthyroid Cat

When secreted in excess, thyroid hormones have profound metabolic effects on the whole body, and dysfunction of multiple organ systems (CNS, cardiac, gastrointestinal, hepatic, and renal) is common in hyperthyroid cats (3-5).

Weight Loss and Muscle Wasting
Weight loss, despite a normal to increased appetite, is the classic and most common signs seen in cats with hyperthyroidism (3-5). These cats lose weight because their hyperthyroidism accelerates their metabolic rate and body’s energy expenditure; they are burning up their food calories faster than they can consume their daily meals.

It’s important to realize that hyperthyroidism is a catabolic state. The progressive weight loss and muscle wasting that is so characteristic of feline disease is caused by increased protein catabolism leading to a negative nitrogen balance (6,7).

When hyperthyroid cats first lose weight, the case can usually be first noticed as a loss of muscle mass in the cat’s lumbar paravertebral area. Despite this loss of muscle mass, most mildly hyperthyroid cats retain their “belly” during the initial stages of their thyroid disease and may even have a higher than ideal body condition score.

With time, severe muscle wasting, emaciation, cachexia, and death from starvation can occur if the cat’s hyperthyroidism is left untreated (3-5). In hyperthyroidism, the cat’s body consumes its own muscle tissue to get the protein it needs to sustain its carnivorous life.

Even with treatment of hyperthyroidism, recovery of muscle mass and function may be prolonged, lasting several weeks to months. This is especially true if these cats are not provided with enough protein in their diet to rebuild and maintain their lost muscle mass.

Hyperglycemia, Glucose Intolerance, Insulin Resistance, and Overt Diabetes
Hyperthyroid cats commonly develop profound changes in glucose and insulin metabolism. Mild to moderate hyperglycemia is common in hyperthyroid cats, which is generally attributed to a “stress” reaction (3,5).

However, the actual metabolic changes are actually much more complicated: hyperthyroidism frequently causes moderate to severe “endogenous” insulin resistance, as demonstrated by high resting serum insulin concentrations and an exaggerated insulin response during an IV glucose tolerance test (8,9). This insulin resistance is associated with a decreased glucose clearance (impaired glucose tolerance), which is indicative of a prediabetic state (See Figures below).

Serum insulin concentrations in response to intravenous glucose tolerance test in 11 healthy cats, 15 cats with untreated hyperthyroidism, and 6 hyperthyroid cats after treatment (9). Notice the exaggerated insulin secretion in the untreated hyperthyroidism cats, which becomes even worse after treatment. Such high insulin concentrations is diagnostic for "endogenous" insulin resistance.
Occasionally, an untreated hyperthyroid cat will develop overt diabetes mellitus. Many of these diabetic cats will develop moderate resistance to the injected insulin, with poor diabetic control.

Surprisingly, the insulin resistance and prediabetic state so common in hyperthyroid cats does not always improve and may even worsen despite successful treatment of hyperthyroidism (9): see Figure above. This indicates that hyperthyroid cats may have long-lasting alterations of glucose tolerance and insulin secretion that cannot always be reversed by treatment. In accord with that, some of these hyperthyroid cats (not diabetic at time of diagnosis) will go on to develop overt diabetes mellitus in the months to years after treatment of hyperthyroidism.

Sarcopenia of Aging
In addition to loss of muscle mass from the catabolic effects of thyroid hormone excess, cats also tend to loss muscle mass they age, independent of their thyroid status. This phenomenon, referred to as sarcopenia of aging, is also common in elderly human beings (10-12). The term age-related sarcopenia is derived from Greek (meaning "poverty of flesh") and is characterized by a degenerative loss of skeletal muscle mass and strength, as well as increased muscle fatigability.

In adult cats, maintenance energy requirements decrease by about 3% per year up until the age of 11 years, and then actually start to increase again (13). This contributes to a tendency of senior cats to lose muscle mass if their energy needs are not met. Lean body mass of aging cats drops dramatically after 12 years of age, and by age 15, cats may have a mean lean tissue mass that is a third less than cats aged 7 years or less (13, 14). Body fat also tends to progressively decrease in cats after the age of 12 years; this combination of reduced lean mass and body fat contributes to weight loss experienced by many elderly cats.

The ability to digest protein is also compromised in many geriatric cats. After the age of 14 years, one-fifth of geriatric cats have reduced ability to digest protein (13-15). Reduced protein digestibility in geriatric cats seems to occur in parallel with reduction of lean tissue and it might predispose them to negative nitrogen balance. (16).

Although moderation of calorie intake might be suitable for some mature cats, it does not appear to match the needs of most geriatric cats. In contrast, it seems more logical to use highly digestible, energy-dense food for geriatric cats in order to prevent or slow their decline in body weight and lean body tissue (13,16,17).

Reducing protein intake in geriatric cats, at a time when lean tissue has been lost, is contraindicated. Geriatric cats seem to have nutritional requirements closer to kittens than to mature adult cat.

Diet Recommendations for Hyperthyroid Cats

High Dietary Protein
As discussed in my last post about what to feed normal cats, obligate carnivores, such as the cat, are unique in their need for large amounts of dietary protein (specifically, dispensable nitrogen) that separates them from omnivores and herbivore species (18-20). This absolute requirement for dietary protein intake in cats is critically important when formulating a diet for hyperthyroid cats, in which protein catabolism and muscle wasting is universally present.

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.

This recommendation for higher amounts of dietary protein does not change once euthyroidism has been restored. The dogma that all older cats should be fed reduced energy “senior” diets must be questioned based on what is now known about the increasing energy requirements and nutritional needs of older cats (12,13).

In most geriatric cats, logic dictates the use highly digestible, energy-dense food mitigate the decline in body weight and lean body tissue and to avoid protein:calorie malnutrition (12,16,17). Protein reduction for this geriatric life stage, at a time when lean tissue is being lost, is contraindicated. Geriatric cats seem to have nutritional requirements closer to kittens than to mature adult cats.

Low Dietary Carbohydrates
Since most of these cats also have subclinical diabetes —as evidenced by their mild hyperglycemia, glucose intolerance, and insulin resistance— feeding a low carbohydrate diet (<10% of total calories) also is strongly recommended (21).

Feeding a low carbohydrate diet will improve insulin sensitivity, reduce the need for exogenous insulin, and help stabilize glucose metabolism in these cats (21-23). This may prevent the development of overt diabetes and control long-term obesity in these cats after successful control of the hyperthyroidism.

Feeding Your Hyperthyroid Cat: The Bottom Line

Like normal and diabetic cats, I believe that it makes sense to feed most hyperthyroid cats a diet composition close to what they would be getting in the wild. That would be a diet composed of approximately 50-60% protein, 5-10% carbohydrates, and 30-50% fat.

Because older cats also loss lean muscle mass in association with the “sarcopenia of aging,” this diet composition needs to be continued even after one treats the cat’s hyperthyroidism and restores euthyroidism.

Check out this website (http://binkyspage.tripod.com/foodfaq.html), which gives you a breakdown of the composition of the various prescription and over-the-counter diets. It turns out that many of the over-the-counter diets have a better composition of protein and carbohydrates than you might have thought — even better than many of the more expensive prescription diets. Very few of my hyperthyroid cat patients require a prescription diet to fulfill their nutritional needs.

As I discussed in my last post, the composition of almost all dry food cat diets are much too high in carbohydrates and most are too low in protein content. That is why I believe it's best to limit the amount of dry food that is fed to cats, or even better, not feed dry food at all.

Cats with advanced renal disease (IRIS Stage 3 or 4) may need lower amounts of dietary protein to lessen uremic episodes (24). However, at least in early to mid-stage renal disease, lowering of the serum phosphate concentration is much more important in management than dietary protein restriction, and this can be easily accomplished with phosphate binders without lowering the protein content of the diet (25,26). It may seem impossible, but no studies have conclusively demonstrated that severe restriction protein alone will prevent further deterioration of kidney function in cats (27).

The major problem that I have with some of the prescription kidney diets is that they restrict protein to the point that some cats – especially those with concurrent hyperthyroidism - will continue to catabolize their own muscle mass despite adequate control of the thyroid condition.

Once we have selected a few diets with the required composition breakdown of carbohydrates, protein, and fat, we next have to look at the ingredient list. Not all of the proteins in cat foods are equal in quality. Remember that quality meat is the best ingredient in a food and that meat by-products are a close second. Some vegetable and grains are fine, but they may supply a less bioavailable form of protein for cats and should not be the primary source of dietary protein.

Remember that when deprived of protein, carnivores will continue to break down muscle tissue to create the energy they need (18-20). By feeding only high-quality protein diets, we will help restore the cat’s muscle mass and improve strength and agility.

Let's use some common sense and not perpetuate the muscle wasting in these older cats by feeding diets that are too low in poor-quality protein.

References:
  1. Peterson ME, Ward CR. Etiopathologic findings of hyperthyroidism in cats. Veterinary Clinics of North America Small Animal Practice 2007;37:633-645.
  2. http://www.hillspet.com/products/pd-feline-yd-dry.html
  3. Peterson ME, Kintzer PP, Cavanagh PG, Fox PR, Ferguson DC, Johnson GF, Becker DV. Feline hyperthyroidism: pretreatment clinical and laboratory evaluation of 131 cases. Journal of the American Veterinary Medical Association 1981;183:103-110.
  4. Joseph RJ, Peterson ME. Review and comparison of neuromuscular and central nervous system manifestations of hyperthyroidism in cats and humans. Progress in Veterinary Neurology 1992;3:114-119.
  5. Baral R, Peterson ME: Thyroid Diseases, In: Little, S. (ed), The Cat: Clinical Medicine and Management. Philadelphia, Elsevier Saunders, in press.
  6. Morrison WL, Gibson JN, Jung RT, Rennie MJ. Skeletal muscle and whole body protein turnover in thyroid disease. European Journal of Clinical Investigation 1988;18:62–68.
  7. Riis AL, Jørgensen JO, Gjedde S, Nørrelund H, Jurik AG, Nair KS, Ivarsen P, Weeke J, Møller N. Whole body and forearm substrate metabolism in hyperthyroidism: evidence of increased basal muscle protein breakdown. American Journal of Physiology: Endocrinology and Metabolism 2005; 288:E1067-1073.
  8. Hoenig M, Ferguson DC. Impairment of glucose tolerance in hyperthyroid cats. Journal of Endocrinology 1989;121:249-251.
  9. Hoenig M, Peterson ME, Ferguson DC. Glucose tolerance and insulin secretion in spontaneously hyperthyroid cats. Research in Veterinary Science 1992;53:338-341.
  10. Short KR, Nair KS. Mechanisms of sarcopenia of aging. Journal of Endocrinological Investigation 1999;22(5 Suppl):95-105. 
  11. Fujita S, Volpi E. Nutrition and sarcopenia of ageing. Nutrition Research Reviews 2004;17:69-76. 
  12. Wolfe RR. Sarcopenia of aging: Implications of the age-related loss of lean body mass. Proceedings of the Nestlé Purina Companion Animal Nutrition Summit: Focus on Gerontology. St. Louis, MO. 2010, pp. 12-17.
  13. Little S: Evaluation of the senior cat with weight loss, In: Little, S. (ed), The Cat: Clinical Medicine and Management. Philadelphia, Elsevier Saunders, in press.
  14. Perez-Camargo G: Cat nutrition: What is new in the old? Compendium for Continuing Education for the Practicing Veterinarian 2004;26 (Suppl 2A):5-10.
  15. Patil AR, Cupp C, Pérez-Camargo G. Incidence of impaired nutrient digestibility in aging cats. Nestlé Purina Nutrition Forum Proceedings. 2003;26,2(A):72.
  16. Wakshlag JJ. Dietary protein consumption in the healthy aging companion animal. Proceedings of the Nestlé Purina Companion Animal Nutrition Summit: Focus on Gerontology. St. Louis, MO. 2010, pp. 32-39. 
  17. Sparkes AH. Feeding old cats— An update on new nutritional therapies. Topics in Companion Animal Medicine 2011;26:37-42. 
  18. MacDonald ML, Rogers QR, Morris JG. Nutrition of the domestic cat, a mammalian carnivore. Annual Review of Nutrition 1984;4:521-562.
  19. Zoran DL. The carnivore connection to nutrition in cats. Journal of the American Veterinary Medical Association 2002;221:1559-1567.
  20. Zoran DL, Buffington CA. Effects of nutrition choices and lifestyle changes on the well-being of cats, a carnivore that has moved indoors. Journal of the American Veterinary Medical Association 2011;239:596-606.
  21. Rucinsky R, Cook A, Haley S, Nelson R, Zoran DL, Poundstone M. AAHA diabetes management guidelines for dogs and cats. Journal of the American Animal Hospital Association 2010;46:215-224.
  22. Frank G, Anderson W, Pazak H, Hodgkins E, Ballam J, Laflamme D. Use of a high-protein diet in the management of feline diabetes mellitus. Veterinary Therapeutics 2001;2:238-246.
  23. Rand JS, Fleeman LM, Farrow HA, Appleton DJ, Lederer R. Canine and feline diabetes mellitus: nature or nurture? The Journal of 2004;134(8 Suppl):2072S-2080S.
  24. Plotnick A. Feline chronic renal failure: Long-term medical management. Compendium for Continuing Education for the Practicing Veterinarian 2007;29:342-324, 346-350.
  25. Kidder AC, Chew D. Treatment options for hyperphosphatemia in feline CKD: what's out there? Journal of Feline Medicine and 2009;11:913-924.
  26. Schmidt B, Spiecker-Hauser U, Murphy M. Efficacy and safety of Lantharenol on phosphorus metabolism in cats with chronic kidney disease. American College of Veterinary Internal Medicine Forum, 2008.
  27. Ross SJ, Osborne CA, Kirk CA, Lowry SR, Koehler LA, Polzin DJ. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. Journal of the Veterinary Medical Association 2006;229:949-957.

47 comments:

Lake Oswego Veterinary said...

Thank you very much for this very well researched document. Our feline pet owners will surely be grateful:-)

renwoman said...

Having lost 3 senior cats to hyperthyroidism in one year, I now have one, Doodles, a 16 year old female, that was slipping away from the symptoms I knew all to well. I researched quality high protein foods and came up with a mix of EVO Turkey and Chicken (50% protein) and Blue Wilderness (40% protein) Supplemented by at least one serving of canned chicken a day. The trick is many small servings during the day, all the way to bedtime, and plenty of fresh water in several rooms she frequents during the day and night. I've been able to stabilize her weight, her coat is beautiful and there is no vomiting or diarrhea, but a looser stool than my healthy younger cat. I choose not to medicate her because the medication upset my other 3 cats systems so dramatically. It has been a year since I started the high protein, high quality diet, fed in small portions at will. At this point, the quality of life for Doodles remains good.

ES said...

Thank you for this article. I get so disgusted at vets who preach low protein Rx diets for kidney issues (full of by-products and fillers and chemicals) at the expense of the rest of the body.

Our "Belle" (18 or 19 years old) was diagnosed with both CKD and hyperthyroidism almost 3 years ago. It's tough trying to juggle both, as it's her thyroid that's keeping her kidneys going. She's on a relatively low dose of Tapezol but I have to very gradually increase it now and then, to keep her from being too hyper, but not so much that it sends her kidneys over the edge.

Recent blood work showed her CKD hasn't worsened. I feed her high-quality, no-grain raw (with some veggies) and canned, with a little organic squash baby food topping now and then, plus salmon oil and extra vitamin B, C and E and some other supplements for her heart. I always add extra water to her food to make sure she's getting enough water (SQ fluids are difficult with her so, she gets them very infrequently), and she eats probably 5-7 times a day.
Unfortunately now there is more muscle wasting in her legs so I will feed her even more often.

NATURALLOGIC said...

Hi Dr. Mark! Thanks for your time & information. I'm looking for anew wet food for my hyper-t kitty and am hard pressed to find one with the 50% or more protein you mentioned. Just to be sure I know what you mean, am I looking for the crude protein percentage listed on the can, or the overall content. For example, EVO lists the crude protein at 9.0%, but the product description says 95% chicken & turkey. Thanks for your help!

Dr. Mark E. Peterson said...

Best place to go is Dr. Lisa Pierson's website (catinfo.org). On the homepage, there is a chart that breaks down canned foods into the % calories based on the amount of protein, carbs, and fats.

Go to http://www.catinfo.org, look at the sidebar on the right, open the Protein/Fat/Carbs chart, and look at the first column. Pick a food with the % calories as protein close to or greater than 50%.

Hope this helps in your selection.

Kate Monro said...

My vet persuaded me to stop my cats medication (which we had a lot of problems getting the correct dosage with) and change to Hill's Y/D. All well and good but my cat has lost a lot of weight in the last 4 months. He had 4 teeth out today which we hope is the cause of the weight loss. My problem is this: bad teeth or not, I still don't believe that the Y/D is giving my cat enough nutrition and want to feed him additional cooked chicken/turkey or liver as well as the Y/D to get some weight back on him. My vet is dead set against this idea and says I must stick to the Y/D as its iodine free. But I've researched on the internet and poultry is apparently iodine free so what shall I do? This issue is particularly pertinent now as post op, the Y/D soft food is much too rich for my cat and he keeps throwing it up. I really need to get some decent food into him and fast! What shall I do?

Dr. Mark E. Peterson said...

Unfortunately, as long as you are using the Hill's y/d to control your cat's high T4 value, you cannot give any other food. The only way to give low-iodine chicken or turkey woud be to feed those birds an iodine deficient diet so that their body would be low in iodine. And that's not going to be possible unless you raised the birds yourself!

It is very possible, and even likely, that part of your cat's weight loss is due to protein deficiency. Hyperthyroid cats need protein and y/d doesn't contain high amounts of protein, even for a "normal" cat. I'd consider another treatment for the hyperthyroidism so you can get your cat on a proper diet.

horphan said...

I've just been told my 18-yr old NM DSH tabby (Bud) has hyperthyroidism. Vet gave me Tapazole 5mg and said Hills y/d. I said no to the y/d. Bud has been in diabetic remission for 5 years and I do not want to give him food that may bring the diabetes back. He's been on a strict, canned food diet, which began with Fancy Feast, it was great for a couple yrs until he started vomiting every night, so we switched to two flavors of Friskies Pate, and he has been fine all this time. over the past couple weeks he has been losing weight and muscle mass, won't eat, and vomits during the night. It's like no vomit I've ever seen (always dark green, thick, and smells like his poop, even worse). The vet initially told me he had kidney disease and gave him an appetite stimulant, and did blood work. She called me three days later and said it wasn't kidney disease, but hyperthyroidism. His T4 was 5.1. I'm older and live alone, and pilling is nearly impossible. Though Bud is weak, he clamps his mouth shut like a bear trap, I can't even get my finger in his mouth to gently pry it open. I've tried hiding the pills in his food, pill pockets, a pilling gun, crushing and sprinkling in his food...it's like he can smell it and will not eat any of it. He refuses to eat his canned food now and I have been baking chicken for him - which he does eat, but very little at a time - he eats MAYBE 2 oz of food per day. He just vomited again but this time it was actual vomit, not the horrid green stuff. At this rate I know he's not going to last much longer. I want to be proactive with this like I was with his diabetes and get him healthy again. Prior to this, he weighed 15 lbs. Now he is at 10.5.
I've looked at Dr. Lisa's food list and am now more confused. I don't know which would be best for him. Can you point me in the right direction, or tell me which food to buy? Sorry, I'm pretty distressed at this point. Any advice you can give is so much appreciated.
Thank you so much!

Dr. Mark E. Peterson said...

Sorry to hear that Bud isn't doing well. I agree with your decision not to start y/d as the initial treatment for hyperthyroidism. Feeding a higher carb diet certainly could result in a relapse of his diabetes. Plus, this will not help restore his lost muscle mass, since y/d is too low in protein.

My main concern with Bud is the fact that he isn't eating well and is vomiting. Although his hyperthyroidism is not very severe, hyperthyroid cats should have a good appetite. Vomiting, when it does occur, generally occurs shortly after eating because they eat too much too fast. In an 18-year old cat, we always have to worry about other problems, concurrent to the hyperthyroidism.

Any older cat that isn't eating very well is likely to develop muscle wasting, not matter what the diet. Even if you are feeding a high protein diet, they still have to ingest enough of it to get the protein they need. In addition, other diseases can lead to enhanced muscle breakdown (cachexia of illness).

Was he eating better and not vomiting before the methimazole? From you email, it sound like he was not. If you haven't done so, an abdominal ultrasound would be my next step in diagnosis to help exclude other problems.

If nothing else is found and you decide to continue the methimazole, you might want to talk to your veterinarian about using transdermal methimazole instead of the pills. Cats tolerate that form better - just apply some gel to their ear pinnae twice a day.

jv1987 said...

Thank God I found this website. My 17 yr old cat has hyperthyroid and I do not want to put her on any meds and risk her not feeling well. I will try a high protein diet! Fingers crossed...

macia pressa said...

Hi Dr. Mark! I am a veterinary from Portugal and I am struggling with a case I've been following for a year. I have a 15 year old DSH cat with HT, controled with metibasol, but he has diarrhea that doesn't respond to any medication or food... I tried hipoalergenic food (royal canin, hill's (z/d,y/d)), intestinal food, tried antibiotics (metronidazol, neomicine), did fenbendazol,probiotics, pancreatic enzimes and even a little steroids! Every test is ok, except for the echography that shows a "reactive intestine". I'm running out of ideas... Can you help me? Thank you! Filipa Cordeiro

Dr. Mark E. Peterson said...

Most hyperthyroid cats with severe diarrhea have primary G.I. disease rather than thyroid-related diarrhea. This is especially true in this cat, where you have controlled the hyperthyroidism with San antithyroid drug.

I don't have any answers - you probably need a small intestinal biopsy to rule out lymphoma vs severe inflammatory bowl disease. If you haven't done so, you should also measure the serum cobalamin, folate, and PLI levels to to help in your workup.

These are very difficult cases to diagnose and manage. Good luck!

Ana said...

You know, in response to some posts below, I recently had the same issue with our vet pushing the Science Diet Y/D on us DESPITE all of my cat's thyroid and kidney levels normalizing in ONE MONTH'S time on a purely raw food / veggie / homemade chicken soup diet. This is in addition to her medication... half a Methimazole in the morning and half at night and 100CCs of fluids every night. Her holistic vet also put her on one Azodyl a day which is amazing. It literally sucks out the toxins from her bloods without her kidneys having to process them. Also homeopathic drops for her immune system and a supplement for enteric support. We are, after all, supposed to treat not just the disease, but our cat's entire body, as these illnesses can affect more than one organ.

Back to the Science Diet issue... please don't be swayed if your gut tells you it's not right for your cat. I found a Wallstreet journal article that explains why so many vets recommend Science Diet, and it involves incentives and Hills paying for a lot of vets' education, and after some additional research, I found out that most vets are not educated in pet nutrition! So they are going to recommend the one thing they know and have been brainwashed to recommend, Science Diet. I have stopped taking her there, as I believe it is very unprofessional to recommend ONE thing without researching other options. On my own, I found that the Veterinary School at UC Davis has a Nutrition Department that can formulate a special diet for your pet based on his / her health condition(s). I found this extremely helpful.

The fact is, it IS a delicate balance to have a cat with hyperthyroidism AND kidney disease, and most vets will recommend a low protein diet for kidney disease, but this has not proven to improve kidney values. The study was based off of a study done on rats, which have VERY different needs than cats (AND humans for that matter...but that's a different topic).

Hope this helps!

Zuba said...

Hi Dr Peterson
I wrote on your blog earlier today about my 16 y/o female cat who was diagnosed last fall with hyperthyroidism. I've been doing more reading and see that it's not only phosphorous levels in supplementing the Hills y/d diet I need to be concerned about but also iodine levels that will counteract the Hills diet. What do they say about a little knowledge? I'm not sure how long it will take now for her thyroid levels to go up as she's still only eating the Hills diet b/c Ive been adding a little tuna in oil to it. I'm not sure what the outcome will be but I guess the bottom line is that I couldn't watch her starve herself to death. The most recent check in with the Vet (before I started supplementing the Hills diet with tuna) was that her thyroid level and electrolytes were good but that her kidney (urea) level was quite high in the 20s I think. Her weight was down to a little over 5 lbs. I am grateful that she has lived this long (you see she's a Siamese with lots of personality and attitude and she thinks she's human) and I'm just hoping that when she dies that she has a good death and maybe that will mean euthanasia, I'm not sure. I'd appreciate it If you have any recommendations or suggestions. Thanks so much!

Dr. Mark E. Peterson said...

You are right-- if a cat isn't eating a prescription diet, such as y/d, what good does it do if the cat is going to starve to death! I assume that you have already tried methimazole or carbimazole and those drugs failed.

You could add L-carnitine (open a 250-mg capsule and mix into her food). That drug is available at any health food store. It may block some of the actions of excessive thyroid hormone and make your cat feel a bit better once the levels start to go up again.

Zuba said...

Hii Dr. Peterson
I just wanted to check in and say thank you so much for your recommendation to try L-Carnitine, 250 mg. back two months ago. My cat is doing so much better, it's quite hard to believe. She started eating a can daily of Y/D. To entice her to eat this (and believe me she needed enticement) I've added the juice plus water from Clover Leaf, white tuna, vegetable broth and oil and mix the L-carnitine powder in and so she doesn't actually get any of the tuna itself. She continues to take Azodyl daily (I break open the capsule and mix it in a little cream early in the AM. She's better than any alarm clock at 6am.To respond to your question re: Methamazole; yes, she has had the topical ear ointment that controlled the thyroid values however I had to change to Y/D as I rely on others to come in and look after her from time to time and she was not very compliant with them. She has a bit of vomit about once weekly and other than that she definitely has her 'mojo' back:). I'm not sure what her values are at this point in time and right now there doesn't appear to be any reason to take her back to the Vet however I will take her in for a check up in the near future......
Again, thank you so much!!

crogers said...

Hi, I just came across your site and find this conversation very useful. I have a 16.5 year old cat who was just diagnosed with hyperthyroidism. The vet didn't say anything about changing her diet, but did prescribe Methimazole liver and tuna flavored chews, 2x a day, which Marbles gobbled up happily. Until today. (She threw up twice last night, and I think she's connected her nausea to the chews.) My question: it appears from these threads that with a high protein diet, we can restore her thyroid condition to normal. Is this true?

crogers said...

Hi, I just came across your site and find this conversation very useful. I have a 16.5 year old cat who was just diagnosed with hyperthyroidism. The vet didn't say anything about changing her diet, but did prescribe Methimazole liver and tuna flavored chews, 2x a day, which Marbles gobbled up happily. Until today. (She threw up twice last night, and I think she's connected her nausea to the chews.) My question: it appears from these threads that with a high protein diet, we can restore her thyroid condition to normal. Is this true?

Dr. Mark E. Peterson said...

No, it's not true that a high-protein diet will cure hyperthyroidism. But it is important to help restore and preserve lost muscle mass, which is very common in hyperthyroid cats.

The hyperthyroidism should still be controlled with methimazole. Or it can be cured either with surgical removal of the thyroid tumor or by administering radioiodine to destroy the thyroid tumor.

Dr. Mark E. Peterson said...

In addition to the higher protein, lower carbohydrate diet that I discuss above, I like to feed a varied diet. No all companies use BPA in the canned lining but it's difficult to find. In general, the small can sizes seem to be the best bet for canned foods.

I agree that fish foods should be limited but I don't believe it's necessary to totally eliminate them.

If you must feed a dry diet, you could try Purina DM, a diet higher in protein and relatively low in carbohydrates. It's marketed as a food for diabetic cats but I feed a small amount to my cats as a treat and they love it!

crogers said...

Hi, thanks for the clarification regarding the high protein diet.

luvmycat said...

Interesting to read all the different ways to treat hyperthyroidism. My 18 year old cat has it. My vet has put her on the Y/D diet. It did help. She still has an appetite and the yd has kept her from vomiting. She has lost so much weight. She loves turkey and chicken. Why do you say that you cannot feed anything along with the yd diet?

Dr. Mark E. Peterson said...

All natural foods contain iodine. Hill's y/d diet is the only diet that can be fed that is iodine deficient and that will not allow the thyroid to make normal amoutns of thyroid hormone.

Colleen said...

My cat has been on Hill's y/d for the past year and it has been successful. The past few days he has turned picky. He has eaten small amounts of the canned food but that is it. I can tell he is hungry cause he goes crazy when I eat.

What can I do? Is there any other food I can try?

Dr. Mark E. Peterson said...

If you start to feed any other diet, the hyperthyroid state will relapse. This is the problem with the Hill's y/d diet.

Talk to your veterinarian about what to do next, but you need to make sure that something serious isn't developing.

mookie said...

Hi
A week ago I was told my cat has "Thyroid problems" And was given 30 10mg Vidalta tablets and to come back in 6 weeks and they'll test to see if my cat is "fixed". He's nearly 14 years old and has had arthritis for at least a year. He weighs about 5 or 6 kg, so he's a big cat. The vet was busy when I picked up my cat so I was left to google what all this meant. After googling I just found horror stories! I don't know if the meds I've been given will harm my cat, what to look for etc. Some people just did what the vet said no matter how their cats were reacting. And I only have 30 tablets, that is not 6 weeks worth, I've read that they go back to hyperthyroid within 24 hours. I give him metacam every day and have j/d Feline mobility biscuits mixed with whiskers biscuits available at all times.
I'm pretty much confused about what I should feed him, taking into account the arthritis. I've been feeding him 85mg Dine cat food (fish) as this seems to hide the pills the best. I pretty much have no idea what kind of food, man made or natural to feed him for all of this or even what the condition means overall. I don't want to go to the vet as I'm wary of them just prescribing things, but armed with hopefully unbiased knowledge, I will be able to navigate them much easier. Plus he never gets my cats gender right (he's a dude). Can you possibly give me any hopefully clear information about the food and that to help? To be honest I'm not even sure how to look for the correct percentage of whatever food and even how much of said food I should give him. Thanks!

Dr. Mark E. Peterson said...

If you go to www.catinfo.org, you can learn a great deal about how cats should be fed.

On the homepage of the catinfo.org website, the is a link entitled "Protein/fats/carbs chart" which will give you a breakdown of the dietary composition of many of the OTC (over the counter) catfoods. You can use my information to select a good canned food that will provide higher levels of protein and lower amounts of fat.

mookie said...

I've looked at the chart on catinfo and it lists all the cat foods that they don't sell in my country. The only product in Binky's page that may possibly be sold here is Friskies. I've been feeding him Dine Desire (which isn't on any chart) and whiskers pouches which from binky's chart seem to be bad. I feed my cat J/D Feline Mobility biscuits too, which I told me was a horrible diet. What else am I supposed to feed my arthritic, hyperthyroid cat? The vets told me there isn't really another option other than the biscuits. I can't afford a grinder to make my own cat food and there aren't really places to source rabbits etc, so I'm really at a loss. I can't even find a solid answer on whether it's a good idea to feed him 1 scrambled egg a day. And I'm not supposed to feed him fish? So far I've googled all these things for weeks and still haven't found a concrete answer. I pretty much feel like I'm poisoning my cat every day because I can't figure out what is good and what is bad. I am not asking for specific instructions just maybe some more information about the things I've raised. The labels on my dine do not give me any real information on the percentages of the proteins, etc. Where are the canned mice and birds when you need them?

Dr. Mark E. Peterson said...

If your goal is to increase the protein and lower the carbs, that should not be that difficult. You may have to call the pet food companies to find out what % of the calories make up the protein and carb content. We want the protein to be greater than 35-40% of calories (metabolizable energy or ME) - that's the most important. This is all discussed in detain at www.catinfo.org.

Good luck!

yheasley said...

Our 10 year old cat was recently diagnosed with hyperthyroidism. Do you have any information on some of the natural remedies such as NHV Resthyro or PetWellbeing Thyroid Support Gold? Could these coupled with a high protein diet help maintain healthy thyroid levels?

Dr. Mark E. Peterson said...

The underlying cause of hyperthyroidism in cats is an overactive thyroid tumor. All of the natural remedies act to control signs of the disease, but they are only a temporary measure. The only way to cure the disease is by removal or irradiation of the thyroid tumor,

K said...

My thorough comment disappeared so here goes with a shorty:

My hyperthyroid cat is thriving on the y/d. Though I was reluctant to put her on a sub-standard (IMO) diet of by products and processed junk, she's been on it about one year now. She is doing so well, I can't think of a better option for her. She's BARH, playful, fur has grown back everywhere, no GI symptoms, and all else is well. Even her toenails are normal again.
I would like to do I-131 but the specialist doesn't think kitty is a candidate.

That said, what the heck is it about y/d that works? How is their pork iodine deficient? Do you think they are farming their own pork for this product? Or maybe they have a deal with a farmer to feed an iodine defficient diet for a few weeks (months?) prior to slaughter? I am so confused about how they do this. I could feed an iodine deficient diet to some chickens then feed these to my cats, but I have to know that's really going to work and there's not some other trick hills is pulling. I do notice they include L-cysteine in this diet and not in other prescription diets. I wonder if that's not the part that's suppressing thyroid function. Could it be Hills magic ingredient with it's ability to enhance excretion of trace minerals?

Nisey Wee said...

My kitty is on the meds and responded well at first, but I can tell he is declining. Very thin. We live in alaska and have plenty of fresh wild salmon that I have been giving to him every day in addition to his regular science diet kibble and iams wet food. Is the salmon ok for him? Do I need to up the dose of the meds? His labwork showed high t4 but nothing else that was out of range. He has been on the meds since july and he is getting twice a day, on oral med. due to our remote location, surgery and irradiation are not an option. Just trying to understand this disease. Thanks for your informative site. Can I continue with the fresh salmon?

Dr. Mark E. Peterson said...

You need to recheck with your veterinarian in order to measure the T4 value on the methimazole. It sounds like the dose needs to be adjusted.

Eating too much fish is probably not a good idea. That's not at all natural - cats were meant to eat rodents, birds, and insects - not fish.

luvmykitty said...

Help! My Spotty is 15 1/2 years old. He is a total indoor cat. He was diagnosed with hyperthyroidism about 2 months ago. My vet suggested putting him on the Y/D. Since being on the food I noticed his lethargic, not cleaning himself and makes jumpy twitches. Just had him in to re-run his tests and she called yesterday to say his kidneys are terrible. They were fine 2 months ago! She said she spoke to specialist who told her we should keep him on the y/d. Now she wants to put him on meds for his kidneys. Today, I noticed he is having trouble with constipation. I don't want to pump him full of medication if some other type of diet will help him. He started on the prescription diet food a long time ago because he developed crystals in his bladder from the cheap cat food. I was hoping to have him around for a few more years.

Dr. Mark E. Peterson said...

It's likely that the side effect you have been seeing recently are due to the kidney failure. I can't recommend an easy fix for that - no diet alone will work.

Talk to your veterinarian to ensure that hypertension and urinary tract infection have been excluded, and to decide how to help support his kidney function.

tonikay1209 said...

Hello, thank you so much for all of this fantastic information! My 15 year old cat has been hyperthyroidism for maybe a year now. Long story short, I learned in January that my husband was not giving the cat his meds like I thought he was so I took over all the feeding and medicating of the pets. I took him off dry taste of the wild kibble and he is on rotating canned tiki, weruva & similar high protein low carb foods. He was supposed to get 1 5mg tapazole a day, but when I took it over, I started at a half, because I hate him being on meds. I also started feeding him a mid day feeding as well. Trying to go for about 80 calories 3 times a day, but he doesn't always eat it all. I feel like recently his face has gotten more sunken in, but I do not notice any other new typical hyperthyroid symptoms. I got him very slowly gaining weight, and is not acting cranky or anything else like he was off his meds. He did have diarrhea when I first started meds again, used fortiflora to encourage him to eat new wet food and it maybe helped with the diarrhea as well. He has lost half of his body weight in the past 2 years. He was down to 9.3 on 1/13 and is up to 10:6 lbs. So the only thing I am concerned with is his sunken in face but I am wondering if I should increase his Tapazole or leave it the way it is for now. I am considering a sure flap cat door to make a feeding box for him, so he can eat more often. http://www.pinterest.com/pin/222013456604841099/ or even a meowspace http://www.pinterest.com/pin/222013456604841064/

Would love your opinion and would even be willing to pay for it!!!!

(We have 3 dogs and 3 cats, so I am policing pet meals all days)

Thank you!!!!
Toni A.

Dr. Mark E. Peterson said...

It sounds like the methimazole dose needs to be increased. I'd recommend at least a serum T4 determination to ensure that that value is within the middle of the reference interval.

Doing a complete thyroid panel (T4, T3, free T4, and TSH) is ideal, especially if we are trying to fine tune to the ideal dosage.

Diet is important but only in conjunction with taking care of the hyperfunctional thyroid tumor that is causing the hyperthyroidism.

tonikay1209 said...

Great, thank you so much!!! He is due back in a few months to have the testing done again!

Jan Kuyper Erland said...

In reading the "newwoman" 2011 post, I luckily hit upon the same solution methodology -- small servings of protein given frequently during the day (poached fish & Whiskas packet cat food alternating) - but I warm the servings with a bit of water and microwave it 15 seconds. My 18 year old male cat is now thriving, and the coat is improving after one month of this treatment.

Rhonda said...

My 13 y/o part-Himalayan/Siamese, Zada, who I rescued when she was only 7 mos. old, was diagnosed with hyperthyroidism just yesterday. She was put on methimazole & loves her Fancy Feast. I've been slowly researching sites to see how I can help her have a great life as 2 of my "fur" babies who had this aliment had in the past. They were diagnosed at a much older age, though. My precious, Zoe (I have no idea why my keyboard will not allow me to place the accent mark over the "e" in her name?? As well as using what I learned in college??), passed away c/in 3 mos. p being Dx with thyroid CANCER at 17.5 yrs!! Dr. Mark, there was one product which read, "this product has been tested by the FDA & approved." Well, I'm a pharmacist. If it had been tested by & approved by the FDA, why is it so easy to obtain?? The meds. I get from my Veterinarian have the Federal warning label on them & if I can get it from the pharmacy, I have to have a written rx from my Vet. Just curious as to whether such herbal products, such as the one I just read, are effective?? I would love an answer, please as I'm not ready to watch her deteriorate quickly!! Thank you very much!!! PS: Still interested in how people are feeding their babies, etc. PPS: She looks more like a Himalayan, but is finicky as her previous predecessors.

Dr. Mark E. Peterson said...

Herbal products may help the cat's symptoms but do not lower the high thyroid levels or do anything about the thyroid tumor that is causing the problem. Take a look at my other posts, which should help you decide on the best treatment for your cat.

Bubba's Mom said...

My 17 yr cat is scheduled for the i131 treatment in 4 weeks but is losing weight despite feeding a raw diet. He cannot tolerate the medication and am wondering if the yd would be a good interim food until the treatment can be performed. I also would like your opinion on Feline's Pride version of iodine free mix that you add your own meat to.

Dr. Mark E. Peterson said...

First of all, why do you have do wait for another month to treat with radioiodine? (We do the treatment at least once every week!)

I would not start y/d because that diet takes at least a month to work and may interfere with the radioiodine treatment. The iodine free mix doesn't help because all meat contains iodine, unless the cattle or chickens are fed no iodine (which is never the case since iodine is an essential nutrient).

Claire4407 said...

I have a 17 year old cat who was diagnosed with hyperthyroidism 5 weeks ago. She was prescribed Felimazole 2 x 2.5mg per day. Into the 5th week she developed a rare side effect of the drug and the vet recommended that I stopped this & try the y/d diet instead. She has only been on this diet for 3 days but is only eating 1 can of 156g in 3 days whereas the recommended intake should be 1/2 to 3/4 tin per day. The vet also gave Vidalta in case she refused the diet food.
My concern is that she is losing weight & is showing new symptoms of hyperthyroidism.
Having read your comments and blog, I would be interested in your view as to wether I should persevere with the diet or start her on the new medication. She is also on Mitrazapine to stimulate her appetite.

Dr. Mark E. Peterson said...

What good is y/d if the cat won't eat it? Obviously, it's not making for a great quality of life for you cat. Isn't that the most important aspect of any treatment?

I'd talk to you vet about another treatment.

Dr. Mark E. Peterson said...

What good is y/d if the cat won't eat it? Obviously, it's not making for a great quality of life for you cat. Isn't that the most important aspect of any treatment?

I'd talk to you vet about another treatment.