Testing for Increased Appetite
Is increased appetite always a sign of illness?
No. Increased appetite is completely normal in pets that have high energy requirements, such as growing puppies and kittens, pets that exercise strenuously such as hunting dogs, and pregnant or nursing females. Also, pets eating a poor quality diet may eat more to meet their energy requirements.
When is increased appetite not normal?
a) Increased appetite is not normal when a pet loses weight in spite of eating more, or when a puppy or kitten fails to grow in spite of eating more. This can occur with diseases such as:
- hyperthyroidism (overactive thyroid gland) in middle aged to older cats
- diabetes mellitus ('sugar diabetes')
- intestinal parasitism – 'worms', especially in puppies and kittens
- exocrine pancreatic insufficiency – a condition in which food cannot be properly digested and nutrients are not absorbed.
b) Increased appetite is a sign of illness when it is accompanied by other signs such as:
- seizures – caused by insulinoma (a type of pancreatic cancer)
- hair loss, abdominal enlargement, and increased thirst and urination, due to hyperadrenocorticism (overactive adrenal gland) called Cushing’s disease.
c) Increased appetite is also seen with some medications, especially drugs containing corticosteroid.
How is the cause of my pet’s increased appetite determined?
The search for answers starts with a complete history and physical examination. A pet’s 'history' is the information you give the veterinarian about your pet’s illness. This would include details about the quality and quantity of food your pet is eating, how long you have noticed the increased appetite, any medications you are giving your pet, and whether you have noticed any changes in your pet’s energy levels, water drinking, urination, and bowel habits.
Physical examination involves looking at all parts of the body, and typically includes listening to the heart and lungs with a stethoscope, and 'palpating' the abdomen (gently squeezing or prodding the abdomen with the fingertips to identify abnormalities inside the body). Physical examination may find that a puppy or kitten has a pot-bellied abdomen, suggesting intestinal parasites (‘worms’); abdominal palpation might detect pregnancy or the presence of an abdominal tumor, and so on.
History and physical examination are very important, but further testing will likely be needed and your veterinarian may recommend doing screening tests. These are a series of simple tests that provide information about the overall health of your pet and may provide further clues about the underlying problem.
What screening tests are recommended?
In a pet with increased appetite, the basic screening tests would include: CBC (complete blood count), serum biochemistry profile, urinalysis, and stool tests for parasites; in mature cats, a serum thyroxine (Total T4) would also likely be recommended.
What can these screening tests tell us?
a) Complete Blood Count. This is a simple blood test that provides information about the different cell types in blood. These include red blood cells, which carry oxygen to the tissues, white blood cells, which fight infection and respond to inflammation, and platelets, which help the blood to clot. The CBC provides details about the number, size, and shape of the various cells types, and identifies the presence of abnormal cells in circulation. See handout "Complete Blood Count" for further information.
In a pet with increased appetite, changes seen on a CBC could include:
- anemia (decreases in the numbers of red blood cells and amount of hemoglobin) – could be seen with parasitism or other diseases
- increased numbers of white blood cells – sometimes seen in animals with diabetes or Cushing’s disease
- increased numbers of neutrophils (a type of white blood cell) – could be a sign of Cushing’s disease or underlying infection associated with diabetes.
- increased numbers of eosinophils (a type of white blood cell) – is often a sign of parasites.
b) Serum biochemistry profile. This is the chemical analysis of serum, which is the pale yellow liquid part of blood that remains after the cells and clotting factors have been removed. There are many substances in serum, including proteins, enzymes, fats, sugars, hormones, electrolytes, etc. Measuring the levels of the these substances in the blood provides information about the health of the body’s organs and tissues, as well as the metabolic state of the animal. Changes and abnormalities found in the biochemistry profile can help to diagnose a variety of diseases and disorders. See handout "Serum Biochemistry" for further information.
In a pet with increased appetite, the serum biochemistry profile might show:
- mildly increased levels of the liver-related enzymes. These changes are associated with Cushing's disease, diabetes mellitus, hyperthyroidism (cat), and the use of corticosteroid-containing medications.
- high glucose (blood sugar) – is a sign of diabetes mellitus, especially in the dog.
- very low glucose – could indicate the presence of an insulinoma.
c) Urinalysis is a simple test that analyzes the physical and chemical composition of urine. It measures how well the kidneys are working, identifies inflammation and infection in the urinary system, and helps to detect diabetes and other metabolic disturbances. Urinalysis is important for the proper interpretation of the serum biochemistry profile and should be done at the same time as blood testing. See handout "Urinalysis" for further information.
"A urinalysis is important for the proper interpretation of the serum biochemistry profile."
In a pet with increased appetite, a urinalysis might show:
- increased numbers of red blood cells or white blood cells - suggests urinary tract infection, possibly secondary to diabetes mellitus or Cushing's disease.
- large amounts of glucose - usually indicates diabetes mellitus
- decreased specific gravity (watery pale urine) - is often seen in cats with hyperthyroidism
d) Parasite tests. The simplest screening test for intestinal parasites is called a fecal flotation, in which a small amount of fresh stool is examined microscopically for the presence of parasite eggs (see handout "Fecal Flotation" for further information). A simple version of the fecal flotation can be done in the veterinary clinic, or a sample can be sent to the laboratory for a slightly better test that uses a concentration technique. There are other tests that can be done to detect intestinal parasites and your veterinarian may recommend an alternative test.
e) Serum thyroxine (total T4). This test is used to diagnosis hyperthyroidism in cats (see handout "Hyperthyroidism in Cats" for further information). Hyperthyroidism is caused by an overactive thyroid gland and is a common disorder in middle-aged to older cats. The gland produces excessive amounts of thyroid hormones, which substantially increases the body’s metabolic rate and leads to weight loss and increased appetite. Most cases can be diagnosed with a single blood test that measures the level of total thyroxine (T4) in the blood stream. Affected cats typically have markedly elevated levels of T4 in their blood.
What additional tests might be recommended for a pet with increased appetite?
There are several additional tests that might be recommended depending on the results of a pet’s history, physical examination and screening tests.
Examples of more advanced tests could include:
- ACTH stimulation test or a dexamethasone suppression test – to test for Cushing’s disease
- serum fructosamine – to confirm a diagnosis of diabetes mellitus, especially in cats
- blood insulin:glucose ratio. The simultaneous measurement of blood insulin and blood glucose levels may help to confirm the presence of an insulinoma.
- serum trypsin-like immunoreactivity test (TLI), B12 and folate – if the digestive activity of the pancreas is seems to be decreased.
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