It is always prudent to be aware of your cat’s habits as any change can indicate a potential problem. One such change is a sudden change in your cat’s appetite (known as polyphagia). Most of us would associate sickness with a loss of appetite, however, an increased appetite can also be a sign of an underlying problem.
What are the causes of increased appetite in cats?
- Acromegaly - Growth hormone excess usually as a result of a pituitary gland tumour.
- Certain medications.
- Cushing's Syndrome - Caused by excessive production of cortisol by the adrenal gland or veterinary induced, which is caused by the administration of corticosteroids.
- Diabetic ketoacidosis (DK) - Caused by uncontrolled diabetes when the body is unable to access glucose for energy so begins to break down fat as an alternate source, during this process, waste products known as "ketones" begin to build up in the body causing the blood to become too acidic.
- Diabetes mellitus - Either caused by insufficient insulin production or a failure of the cells to respond to insulin.
- Exocrine pancreatic insufficiency - Insufficient secretion of pancreatic enzymes required to digest food.
- Hyperthyroidism - Usually caused by a benign tumour of the thyroid glands.
- Inflammatory bowel disease - A group of disorders in which different types of inflammatory cells invade the gastrointestinal tract.
Depending on the cause, there may be other symptoms accompanying the increased appetite. Things to watch for include:
How will the cause be diagnosed?
Your veterinarian will perform a complete physical examination of your cat and obtain a medical history from you. He will ask if you have noticed any other changes to your cat. Increased thirst and urination, change in behaviour etc.
Some tests he may wish to perform may include:
Upon completion of these tests, more thorough tests may be required, some of which may include:
- ACTH stimulation test: This test measures the ability of the adrenal glands to respond to a hormone known as adrenocorticotropic hormone (ACTH) which is made in the pituitary gland, travelling through the bloodstream to the adrenal glands where it stimulates the secretion of other hormones such as hydrocortisone from the cortex. The ACTH stimulation test measures levels of cortisol in the blood before and after an injection of synthetic ACTH.
- Low dose dexamethasone suppression test (also known as ACTH suppression test): This test can help distinguish between adrenal dependent hyperadrenocorticism (ADH) and pituitary-dependent hyperadrenocorticism (PDH). It measures the response of the adrenal glands to ACTH. Dexamethasone is a synthetic steroid (similar to cortisol) which suppresses ACTH. Dexamethasone is administered and blood cortisol levels are measured. Cortisol levels should decrease in response to the administration of dexamethasone.
- Urine Cortisol:Creatinine Ratio (UC:Cr): This tests levels of cortisol in the urine and is measured against levels of creatinine. If the level is normal, hyperadrenocorticism can be ruled out.
- fTLI (feline Trypsin-Like Immunoreactivity) - This test measures the concentrations of trypsin-like proteins in serum.
- TAP (trypsin activation peptide)
- fPLI (feline Pancreatic Lipase Immunoreactivity) - This test measures feline pancreatic lipase (an enzyme secreted by the pancreas which breaks down fat) immunoreactivity in serum.
- T3 suppression test: This involves taking a blood test to check the levels of T3 and T4, 7 oral doses of the thyroid hormone T3 and a blood test after the hormone was given. In a normal cat, the level of T4 will drop, in a cat with hyperthyroidism the T4 levels will stay the same or increase slightly.
How is it treated?
Treatment depends on the underlying cause and may include:
- Acromegaly - There is no cure for acromegaly, treatment is based on addressing the underlying conditions.
- Certain medications - Stopping medications where possible.
- Cushing's Syndrome - Gradual withdrawal of the medication if veterinary induced.
- Diabetic ketoacidosis - Mild cases require may just require home monitoring of glucose levels, more severe cases may require intravenous fluids, administration of short-acting insulin to bring down glucose levels and supportive care where necessary.
- Diabetes mellitus - Dietary changes, switching to a low protein and phosphorous diet, insulin injections if dietary changes are not enough to control the disease.
- Exocrine pancreatic insufficiency - Pancreatic enzyme extract to replace low levels of pancreatic enzymes, high protein and low-fat diet, and in some cases antibiotics will be prescribed.
- Hyperthyroidism - Radioactive iodine therapy to destroy the tumour or surgery to remove it.
- Inflammatory bowel disease - Dietary changes such as a highly digestible, low-fat diet, steroids and antibiotics where necessary.
- Pregnancy - A pregnant cat requires more calories, especially towards the end of her pregnancy and while she is nursing her kittens.