Diabetes Mellitus

Introduction: Diabetes mellitus is a common disease in cats. There are two types of diabetes mellitus (DM) which affect cats: Type I (insulin-dependent diabetes mellitus or IDDM) and Type II (non insulin-dependent diabetes mellitus or NIDDM). Type I is more common in cats, affecting approximately 60-80% of diabetic cats. NIDDM or Type II affects the remainder of the diabetic cat population. Diabetes is a remarkably complex disease; only a brief summary can be given here.

The literal translation of diabetes mellitus is "sweet urine," due to the presence of glucose (sugar) in the urine. This phenomenon occurs as a result of a series of abnormalities in the bodyís normal metabolism of sugars. These abnormalities begin with the decline in insulin stimulation of the bodyís cells. Insulin is an important hormone produced by the pancreas, an organ near the liver and the stomach. In IDDM or Type I diabetes mellitus in cats, this decline in insulin stimulation usually occurs as a result of a failure on the part of the pancreas to produce enough insulin to meet the bodyís needs. In NIDDM or Type II diabetes mellitus, insulin is still produced in normal quantities, and may even be found to be abnormally high. However, the bodyís cells do not respond to insulin in a normal fashion. In severe cases of Type II diabetes mellitus, the cells may not respond to insulin at all.

Insulin stimulates glucose (sugar) from the bloodstream to enter all the cells of the body to provide energy for each cell to function. Without enough insulin or without a sufficient response to insulin, glucose climbs to abnormally high levels in the bloodstream, yet falls to low levels inside the cells. The body receives a response from the cells that not enough energy sources are arriving, and that the body is basically starving. One of the most common symptoms of diabetes mellitus is an increase in appetite. Meanwhile, the kidneys, the bodyís natural filter system, are overwhelmed by the massive quantities of blood glucose and begin allowing glucose to spill over into the urine. The extra glucose in the urine begins to pull in water from the rest of the body which the kidneys then excrete. This then leads to one of the most common symptoms seen in diabetic cats, the increased need to urinate. Cat owners may find that their petís litter box requires much more frequent changing. By drinking larger quantities of water, the cat then attempts to make up for the water lost in the urine.

As the disease progresses, the animal begins to lose weight and may become very susceptible to infections, especially of the urinary tract. The body, perceiving that it is starving, begins to metabolize other sources of energy, particularly fats. Fats are broken down into fatty acids which accumulate in the body as "ketones." The word ketone is a specialized term for a limited group of fatty acids which tend to accumulate in untreated diabetic animals. A syndrome called "diabetic ketoacidosis" (too much acid accumulation as a result of ketone formation in a diabetic animal) results. An animal in untreated diabetic ketoacidosis can eventually slip into a diabetic coma and die.

Clinical Signs: Most of these signs have been listed in the introduction. The predominant signs are increased thirst, increased need to urinate, increased appetite, and weight loss.

Diagnosis: The diagnosis of diabetes is made with results from blood and urine testing in conjunction with observation of the classical clinical signs. Increased blood glucose, glucose and possibly ketone presence in the urine, and increased levels of acidic products in the blood are the typical results of such testing. To determine whether a cat is suffering Type I or Type II diabetes mellitus, a veterinarian may recommend further laboratory tests or may simply assess the patientís response to certain types of therapy.

Treatment: The key to treating diabetes mellitus in cats usually centers around insulin therapy. All Type I and most Type II diabetic cats respond to insulin, although those cats which suffer Type II may require a higher insulin dose than those with Type I. Insulin must be given daily by injection, and owners of diabetic cats are instructed how to give an injection of insulin (please see discussion on giving injections in the Section B). Other important features of insulin administration include the need to carefully roll the bottle rather than shake it in order to preserve the delicate structure of the insulin in the solution and the need to administer fresh and not expired insulin.

It is becoming more popular to use several drugs other than insulin which help to lower blood glucose levels. These drugs may be used alone in mild to moderate cases; when these drugs are used in conjunction with insulin, they may actually allow lowering of the insulin dose.

Treatment of a diabetic cat may also include IV (intravenous) or SQ (subcutaneous) fluid therapy, hospitalization, antibiotics, and diet changes. Regular checkups and careful monitoring of weight and blood glucose levels are extremely important in the maintenance of a diabetic cat.

One complication seen occasionally in the diabetic cat on insulin therapy is a sudden reversal of blood glucose levels. Without much warning, the cat may become extremely weak, cold, and even suffer seizures due to dangerously low blood sugar levels. A natural reaction may be that the first dose of insulin was given incorrectly and another may be needed. Administration of insulin to a cat with low blood glucose can be fatal! If the above symptoms are noted in a diabetic cat, it is strongly advised to withhold any insulin treatments and contact a veterinarian immediately. Cats with low blood glucose levels may be coaxed to eat, which will help the situation. As a general rule, if weakness is noted in a diabetic cat it is better to try feeding the cat rather than administering insulin. Feeding will not cause dramatic harm, whereas administering extra insulin may be extremely dangerous. Counsel from a veterinarian should be sought in all insulin/glucose complications.