Diabetes mellitus, or sugar
diabetes, is a commonly diagnosed disease in cats and ultimately affects all
the organs. It develops in about 1 in 400 cats. It is due to inadequate
production of insulin by the beta cells in the pancreas or inadequate response
of the cells to insulin. Insulin is secreted directly into the circulation. It
acts upon cell membranes, enabling glucose to enter the cells, where it is metabolized for
energy. Without insulin, the body can’t utilize glucose. This results in
elevated blood sugar levels (hyperglycemia). In diabetic cats, excess glucose
is eliminated by the kidneys, producing frequent urination. There is a need to
compensate for the increased urination by drinking unusual amounts of
Pancreatitis, hyperthyroidism, medications such as
megestrol acetate (Megace), and some corticosteroids, all have the potential to
cause or mimic diabetes in a cat. Obesity is a predisposing factor for all cats, and
Burmese cats may have a genetic predisposition. Male cats have twice the risk
of females. At greatest risk are neutered male cats over 10 years of age
and over 15 pounds in weight.
Problems that affect a cat’s lower urinary system often prevent the bladder from emptying correctly or may even cause fatal blockage of the urethra, the tube connecting the bladder to the outside of the body. Very often the culprit is Feline Lower Urinary Tract Disease (FLUTD). Once called Feline Urologic Syndrome (FUS), FLUTD is not merely one problem, but a collection of clinical symptoms that may have more than one possible cause. Symptoms of FLUTD include frequent or painful urination, bloody...
Glycosuria is sugar in the urine. When a urine glucose test is
positive, suspect diabetes. Some cats will show high glucose levels in urine
and blood due to stress, however, so a repeat test may be needed to verify the
results. Defects in the kidney tubule function, such as with antifreeze poisoning, may also cause high glucose levels in the
blood and urine.
Ketones (the end-product of rapid or excessive fatty-acid
breakdown) are formed in the blood of diabetics because of the inability to
metabolize glucose. High levels lead to a condition called ketoacidosis. It is
characterized by acetone on the breath (a sweet odor like nail polish remover);
rapid, labored breathing; and, eventually, diabetic coma.
In the early stages of diabetes, a cat will try to compensate
for the inability to metabolize blood glucose by eating more food. Later, with
the effects of malnourishment, there is a drop in appetite. Accordingly, the
signs of early diabetes are frequent urination, drinking lots of water, a large
appetite, and unexplained weight loss. The laboratory findings are glucose and
possibly ketones in the urine and a high blood glucose level.
In more advanced cases, there is loss of appetite, vomiting, weakness, acetone breath, dehydration, labored breathing, lethargy, and, finally,
coma. Unlike dogs, diabetic cats rarely
develop cataracts. A muscle weakness, usually shown by an unusual stance in the
rear with the cat walking down on her hocks instead of up on her toes, is often
seen if glucose regulation is poor.
Three types of diabetes are seen in cats. Type I diabetic cats
are insulin dependent and need to receive daily insulin injections because the
beta cells of their pancreases are not making enough insulin. In cats with type
II diabetes, the cat’s pancreas may make enough insulin but the cat’s body does
not use it properly. This is the most common type of feline diabetes. Some of
these cats will require insulin as well, but others may get by on oral drugs to
control blood glucose and dietary changes. About 70 percent of all diabetic
cats will require at least some insulin.
The third type is known as transient diabetes. These are type II cats who
present as diabetics and require insulin initially, but over time, their system
re-regulates so they can go off insulin-especially with a change to a
high-protein, low-carbohydrate diet.