Causes of Diabetes in Cats
By Jennifer Coates, DVM
Diabetes in cats is a growing problem. In fact, the prevalence of feline diabetes has increased 18.1 percent since 2006, according to Banfield Pet Hospital’s State of Pet Health 2016 report. To reverse that trend, pet parents need to know the causes of diabetes and what can be done to prevent and treat the condition in cats. Read on to learn more.
Symptoms of Diabetes in Cats
Increased thirst and urination, weakness, and weight loss despite a normal or even ravenous appetite are the first symptoms of diabetes that pet parents typically notice. Your cat may also have infections that fail to respond normally to antibiotic treatment. As the disease progresses, diabetic cats may become weak, walk with bent hind legs, and develop cataracts. Ketoacidosis—a potentially fatal condition characterized by electrolyte disturbances, extreme dehydration, vomiting, diarrhea, and respiratory difficulties—is possible if diabetes goes untreated.
Of course, other diseases can cause similar symptoms in cats. Therefore, a veterinarian will need to perform a physical examination, take a complete health history, and run blood work and a urinalysis before she can diagnose diabetes.
Diet, Exercise, and Obesity
Type 2 diabetes is the most common form of diabetes in cats, which is good news since, in many cases, it is preventable. The disease typically develops because of a combination of lifestyle factors, including lack of exercise, a high-carbohydrate/low-protein diet, and obesity.
Early in the course of Type 2 diabetes, cats still produce what should be adequate amounts of insulin, but the body has lost the ability to respond normally to it. If at this point a cat is treated with extra insulin, eats a high-protein/low-carbohydrate food, and loses weight, it is possible for her diabetes to go into a remission that can last for years. If treatment is delayed, however, cats with Type 2 diabetes often need life-long insulin treatment.
Autoimmune Destruction of Insulin-Producing Cells
In some cases, a cat’s own immune system can attack and destroy the pancreatic cells that produce insulin. This is the typical cause of Type 1 diabetes, which is more common in dogs than it is in cats. Treatment for Type 1 diabetes involves life-long insulin replacement therapy and dietary management with a low-carbohydrate/high-protein food to smooth out the fluctuations in a cat’s blood sugar levels and reduce her insulin needs.
Severe cases of pancreatic inflammation (pancreatitis) can destroy so much tissue that the organ is unable to produce enough insulin to maintain a cat’s blood sugar levels. Unfortunately, the symptoms of pancreatitis in cats (poor appetite and lethargy) are vague and non-specific and diagnosing the condition can be difficult and often requires specialized testing. Cats who have fully recovered from pancreatitis but have persistent diabetes as a result will likely require life-long treatment with insulin.
Glucocorticoid medications (e.g. prednisolone, prednisone, dexamethasone, and methylprednisolone) can be used to treat many different feline diseases, including allergies, inflammatory bowel disease, and asthma. While the short-term use of these drugs is quite safe, cats who receive them over long periods of time, especially at high doses, are at risk for developing diabetes. To reduce this risk, glucocorticoids should be given at the lowest dose needed to control a cat’s symptoms.
Cats who become diabetic after receiving glucocorticoids should be slowly be weaned off of these medications, treated with insulin, and eat a low-carbohydrate/high-protein diet. As long as no permanent damage to insulin-secreting pancreatic cells has been done, the need for insulin therapy is usually temporary.
When a cat has Cushing’s disease (hyperadrenocorticism), his adrenal glands over-produce cortisol, a hormone that has wide effects throughout the body, including making it less able to respond to insulin. Too much cortisol can lead to diabetes.
Feline Cushing’s disease is quite rare. Typically, these cats are first diagnosed as having diabetes, and later the diagnosis of Cushing’s disease is made because their blood sugar levels don’t drop as expected with insulin therapy. If the cause of the Cushing’s disease can be addressed (e.g. surgical removal of an adrenal tumor), the cat’s diabetes may also be “cured.” However, most cats develop the disease as a result of a tumor within the pituitary gland that can’t easily be removed and continue to need insulin injections in addition to medications to manage the symptoms of Cushing’s.
Cats develop acromegaly because a tumor within their pituitary glands overproduces growth hormone. Excess growth hormone causes these cats to be larger than normal, with a big head, big paws, and enlarged internal organs. They also typically develop diabetes because of the anti-insulin effects of growth hormone. Treatment for acromegaly in cats is very difficult. Cases can be managed for a period of time with high doses of insulin, but eventually most cats with acromegaly-induced diabetes are euthanized.