Diet and Endocrine Diseases
Dogs and cats develop many endocrine diseases. Dietary management is unimportant for some but for others is very important.
Thyroid Gland Diseases1,2
Hyperthyroidism has become an important disease of older cats. There is evidence that feline hyperthyroidism results from feeding commercial pet foods. Caused by a tumor or nodule of hyperactive tissue in the thyroid gland it is a new disease (appearing after 1970). Hyperthyroidism appeared with the feeding of canned cat foods. The disease does not occur in developed countries where owners do not feed canned cat food. With the feeding of canned cat foods the problem is appearing there. It is unknown how canned cat foods cause this thyroid abnormality.
If hyperthyroidism was an unimportant disease the feeding of cat canned pet foods could continue. The disease is serious, however. Besides losing weight and having a continuous problem with diarrhea, affected cats' personalities change so that many animals do not remain enjoyable pets. Treatment of the problem is costly and can be life-threatening. Cost of treatment is usually high and is not always successful; some cases are fatal. Medical management importantly includes diets to restore weight losses. Feeding an owner-prepared diet is recommended to prevent hyperthyroidism.
Hypothyroidism usually result in weight gain. Hypothyroidism results from thyroid gland atrophy or inflammation. Management is to administer thyroxine. Dietary management often includes reducing food intake to correct obesity.
Adrenal Gland Diseases1,2
Hyperadrenocorticism or Cushing's disease results in excess cortisol production. Treatment is to medically or surgically reduce cortisol release. Affected animals are also at risk for developing diabetes in part because they develop resistance to insulin. Dietary management can be important when it is also necessary to treat diabetes mellitus. Adrenal gland destruction results in cortisol deficiency or Addison's disease. Treatment is to replace cortisol. Dietary management is not necessary. Increasing salt intake can be done but is not necessary when proper amounts of hormone are given.
Parathyroid Gland Diseases1,2
Hyperparathyroidism releasing increased parathormone can be primary or secondary. Primary is usually caused by a parathyroid tumor. One secondary cause is feeding diets containing low calcium and normal phosphorus. Feeding all meat diets without a calcium supplement causes this secondary or nutritional hyperparathyroidism. Thirty to forty years ago commercial all-meat pet foods were not supplemented with calcium and the problem was common. Since then all commercial diets have enough calcium to prevent hyperparathyroidism. The diets in this website contain NRC recommended amounts of calcium. There are some exceptions, however. Diets to prevent calcium oxalate calculi contain lower calcium. Parathyroid hormone deficiency is uncommon. Causes include parathyroid gland destruction or atrophy and surgery to remove parathyroid tumors that leaves little or no normal tissue. The spontaneous causes can be treated with vitamin D and calcium. Normal blood calcium shows treatment to be successful.
Diabetes mellitus causes hyperglycemia by insulin deficiency and glucagon excess. Insulin is produced only in pancreatic islet cells. Glucagon is produced by pancreatic and small intestinal hormone-producing cells. Increased blood glucose or amino acids stimulates insulin release which inhibits lipolysis in adipose tissue and protein catabolism in muscle. Insulin also inhibits conversion of fat and protein to glucose. Insulin promotes storage of fat, protein and carbohydrate. Inadequate insulin results in hyperglycemia because gluconeogenesis is uninhibited and cells need insulin to take up glucose. Energy deficiency exists causing fat to be mobilized from adipose stores. Circulating fat is removed by the liver and converted to ketone bodies for use as an alternate source of energy. The large amount of fat released cannot be metabolized completely and the liver must store some. Eventually fat accumulations result in hepatic lipidosis.
Diabetes mellitus is managed by insulin and diets to correct metabolic abnormalities. Islet cells normally release insulin at rates responding to subtle blood glucose changes. Insulin given by injection once or twice daily cannot compare with the changing minute to minute release from a normal pancreas. Thus, diabetic patients are never well-regulated, even though they may respond to treatment well and appear normal. The well-regulated diabetic patient will have hepatic lipidosis despite treatment.
Diabetics can be regulated dietarily but diets cannot replace insulin which is almost always required. Insulin needs depend on diabetes type. With insulin dependent diabetes mellitus little or no insulin is produced because islets cells have been destroyed by autoimmune antibodies, drugs, toxins or inflammation. Another group produces insulin but not enough to meet normal or increased needs. In some cases insulin may be antagonized by female reproductive hormones or excess cortisone.
Diagnosis of Diabetes Mellitus1,2
Persistent hyperglycemia identifies diabetes mellitus. Glycosuria suggests diabetes mellitus. Glycosuria is also found in animals with no diabetes mellitus. Sometimes diabetes mellitus must be proven by measuring blood insulin or glucose after giving glucose.
Dietary management of diabetes mellitus is important for animals with complete insulin dependency and with partial insulin dependency. With complete dependency the proper diet must be fed when blood insulin peaks. With partial dependency insulin requirements can be lower with proper dietary management. Insulin is available in short-acting and intermediate-acting forms. Regular insulin is short-acting and used primarily for hospitalized patients. Intermediate-acting forms are Isophane, Lente (NPH) and mixtures of NPH and regular insulins. Time of feeding after insulin injection is critical. A decision is also necessary on feeding once a day or more often. Anorectic or unfed diabetic animals should receive some insulin to reduce fat catabolism. Blood testing during insulin therapy and feeding gives information on how to best manage the frequency of insulin administrations and feeding.
Diabetic dogs should be fed a diet high in complex carbohydrates (starch and dietary fiber that provide 50 to 55 percent of total energy), containing no simple sugars such as sucrose, restricted in fat (providing less than 20 percent of energy) and moderate in protein (providing 14 to 30 percent of energy). Older wisdom held that a diabetic's diet should be low in carbohydrates. This is no longer proven to be correct. As mentioned above it is almost impossible to regulate diabetics because optimal amounts of insulin are not always available. Dietary complex carbohydrates can improve this regulation.
Cats are not designed to eat a diet containing 50 percent complex carbohydrates. There is also no evidence that any special diet is of benefit in managing a cat with diabetes mellitus. Thus, this website location has no recipes for feeding cats with diabetes. Diabetes mellitus in cats is associated with obese and overweight cats so diets to treat this problem with should use one of the diets for overweight cats in the section on managing obesity.
Carbohydrates-the source of energy
Carbohydrate is the preferred source for energy in dogs. Digestion and absorption of selected carbohydrates can be slow. This prevents absorption of large amounts that worsens hyperglycemia and fewer wide fluctuations are seen in blood glucose. Also high dietary carbohydrate appears to increase sensitivity of cells to insulin and improves their glucose uptake, thereby relieving hyperglycemia.
The digestion of one complex carbohydrate, starch, is usually never complete. With the exception of rice starch many cereal starches are not completely digested. Feeding more poorly digested starches results in slower digestion and absorption so that blood glucose fluctuates less than with feeding readily digested carbohydrates. Sugar results in blood glucose fluctuating the most. Fiber is another form of complex carbohydrate, but it is not digested and enters the colon. Dietary fiber helps control diabetes by promoting weight loss, slowing carbohydrate digestion, slowing glucose absorption and reducing blood glucose fluctuations following a meal.
Dietary fiber is described as soluble or insoluble and fermentable or nonfermentable (see section on dietary nutrients). Soluble fibers take up water and form gels. They show gastric emptying, reduce nutrient absorption, and increase intestinal transit. Insoluble fibers take up little or no water and have a smaller effect on reducing digestion and absorption of a meal. Fibers that can be fermented are broken down by colonic bacteria. Fermentable fiber provides nutrients, short chain fatty acids. Both soluble and insoluble fiber benefit diabetic dogs. Guar gum, one form of soluble fiber, at levels of 8 grams/400 kcalories sprinkled on food reduces hyperglycemia in both normal and diabetic dogs for at least 4 hours after feeding. An insoluble fiber, wheat bran, has a similar but less pronounced effect at levels of 8 grams/400 kcalories of diet. Feeding greater amounts of soluble fiber such guar or pectin causes diarrhea in dogs. Feeding larger amounts of insoluble fiber such as wheat bran has little effect on dogs other than possibly reducing a diet's palatability. Current recommendations are to feed a combination of soluble and insoluble fiber. Of the two the soluble is more important and more effective; less soluble fiber than insoluble fiber is needed to achieve the same desired effect. The combination can reduce blood glucose fluctuations in diabetics eating regular diets and receiving daily injections of insulin. There is no evidence that additional fiber is of any benefit in managing a cat with diabetes mellitus. Cats also do not readily accept a high fiber diet.
High fiber, high carbohydrate and low fat
cups oatmeal or rolled oats, cooked (291 grams)
0.4 cup kidney beans, canned (71 grams)
1 egg, large, chicken, whole, cooked
1 cup vegetables mixed, cooked and drained
1 1/2 calcium carbonate tablets (600 mg calcium)
provides 452 kcalories, 24.5 g protein, 8.9 g fat
supports caloric needs of 12 to 13 pound dog
High fiber, high carbohydrate and low fat
pound (weight before cooking) poultry (152 grams)
2 cups potato, cooked with skin (246 grams)
1 egg yolk, large, chicken, cooked
1/2 cup vegetables mixed, cooked and drained
1 ounce wheat bran 30 grams
2 calcium carbonate tablets (800 mg calcium)
512 kcalories, 45.8 g protein, 10.2 g fat
supports caloric needs of 14 to 15 pound dog
1. Maskell Ian E. and Peter A. Graham. 1994. Endocrine Disorders. In The Waltham Book of Clinical Nutrition of the Dog and Cat. edited by J. M. Wills and K. W. Simpson, 373-393. Oxford: Pergamon Press.
2. Peterson, Mark E. and Thomas K. Graves. Diagnosis and Treatment of Occult Hyperthyroidism in Cats. Endocrinology. 15th Waltham Symposium. edited by Dennis J. Chew and James H. Sokolowske, 7-12 Vernon: Kal Kan Foods.
3. Bauer, John E. and Ian E. Maskell. 1994. Dietary Fibre: Perspectives in Clinical Management. In The Waltham Book of Clinical Nutrition of the Dog and Cat. Edited by J. M. Wills and K. W. Simpson, 87-104. Oxford: Pergamon Press.