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Name
Diabetes Mellitus, Feline
Short Description
Feline diabetes mellitus
Affected Animals: Most diabetic cats are older than 10 years of age
when they are diagnosed. However, diabetes mellitus can be diagnosed
at any age. Male cats are diagnosed more frequently than females,
and all breeds can be affected. Obesity and the use of medications
including steroids and progesterone derivatives are risk factors for
the development of diabetes in cats.
Overview: Often suspected because of the presence of the
classic signs of increased thirst, more frequent urination, and a
greater appetite, diabetes mellitus is one of the most common
endocrine diseases in cats. There are two types of diabetes mellitus
in cats. The more common form, type I, or insulin dependent diabetes
mellitus, is characterized by a lack of adequate insulin secretion
by the pancreas and usually requires insulin injections for
treatment.
Type II diabetes mellitus is characterized by resistance to the
normal activity of insulin in body tissues, or abnormalities in
insulin secretion by the pancreas. Its development may be influenced
by the presence of complicating factors such as obesity, concurrent
disease, or medications that interfere with insulin's activity. Type
II diabetics may not require insulin for treatment initially, but
will often eventually develop the need for insulin seen in type I
diabetics.
In addition, transient diabetes mellitus can occur in cats. Unlike
permanently diabetic cats, transient diabetics may require treatment
only for a brief period of time. Transient diabetes can also be seen
in overweight cats, cats with additional diseases, or cats on
medications that interfere with insulin activity. Some transient
diabetics eventually require treatment for permanent diabetes.
Diabetic cats frequently have concurrent diseases at the time of
diagnosis, or develop other conditions during treatment that are
common in older cats. These conditions can influence the ability to
control diabetes and its degree of regulation. Since most cats are
older than 10 years of age at the time of diagnosis, the majority of
diabetic cats do not live an extended period of time. Many cats
diagnosed with diabetes mellitus at a younger age that are able to
be controlled with relative ease can live an extended period of time
with a good quality of life
Clinical Signs: The classic signs of diabetes mellitus in cats
are the same as those in all diabetic animals: polydipsia, polyuria,
polyphagia, and weight loss.
Symptoms: The most common symptoms of diabetes are
increased thirst, increased urination, and weight loss, despite an
increase in appetite. Owners may notice that they have to change the
litter box more frequently because it is wet all the time. Some cats
will begin to void large amounts of urine in places other than the
litter box. This may mistakenly be perceived as a behavioral problem
in some cats.
Description:
One of the hormones secreted by the pancreas is
insulin. Diabetes mellitus results from a relative or absolute
deficiency of the secretion of insulin from the pancreas. This
deficiency causes decreased tissue use of substances including
glucose, amino acids, and fatty acids. As glucose accumulates in the
blood, it reaches concentrations that are so high that it cannot be
eliminated from the urine. Then glucose loss in the urine, a
condition called glucosuria, develops. Once this occurs, the amount
of urine produced increases, and the cat begins to drink more to
avoid dehydration. Since the tissues of diabetic cats are not able
to use glucose properly, weight loss will ensue. Because the cells
in the portion of the brain that mediate hunger are also sensitive
to insulin, the cat may develop an excessive appetite; without
insulin, glucose cannot enter these cells, and perceived hunger
persists. These facts account for the classic clinical signs of
diabetes: increased urination, increased thirst, weight loss, and
increased appetite.
Type I diabetes mellitus is a condition in which destruction or loss
of insulin-secreting cells in the pancreas results in a complete
lack of insulin. This can occur either very quickly, or gradually
over time. This condition, called insulin-dependent diabetes
mellitus or IDDM, usually requires treatment with insulin and
accounts for approximately 60 percent of cats with diabetes
mellitus. IDDM may occur because of protein deposition in the
pancreas with degeneration of insulin-producing cells, or as the
result of chronic pancreatitis. Other changes may be involved in the
development of IDDM, including immune system-mediated inflammation
in the pancreas.
With Type II diabetes mellitus -- also know as non-insulin-dependent
diabetes mellitus or NIDDM -- there is resistance to the action of
insulin on body tissues, as well as abnormalities in insulin
secretion from the pancreas. Type II diabetics may not require
insulin. Type II diabetes is more common in cats than in dogs.
Obesity, hereditary factors, and abnormal protein deposition may be
important factors in its occurrence. For cats, there are currently
no reliable tests to distinguish whether Type I or Type II diabetes
is present. Some cats appear to change from one type to the other
over time, and the revert back again.
Secondary diabetes also can occur in cats, usually as a result of
diseases or medications that influence insulin activity.
Medications, including some long-acting steroids and some
progesterone derivatives, are the most common drugs implicated in
the development of secondary diabetes in cats. Another confusing
fact about diabetes mellitus in cats is that the need for insulin in
an individual cat may come and go over time. Some of these
transiently diabetic cats eventually require life-long treatment,
but others seem to overcome this state and ultimately require no
further treatment.
Diagnosis: The diagnosis of diabetes mellitus is usually
first suspected because of the presence of typical clinical signs.
Since similar signs can be seen in other conditions, further
evaluation is needed to confirm a diagnosis of diabetes mellitus and
to rule out other disorders that can cause similar symptoms. On
physical examination, diabetic cats may be either thin or
overweight, but many will appear to have normal body condition.
Weakness, depression, and dehydration may also be noted.
The diagnosis is based on the observation of
these clinical signs as well as documentation of persistently
elevated blood glucose concentrations and elevated urine glucose
levels. Because stress can cause significant elevations of blood
glucose levels in cats, and in rare circumstances, glucose can be
seen in the urine of stressed cats, the measurement of a substance
called fructosamine may help distinguish stress-induced changes in
blood and urine sugar levels from true diabetes mellitus. In
stressed cats, serum fructosamine concentrations are usually normal,
but they are elevated in diabetic cats. Ketones are another
substance that can appear in the urine of diabetic cats, but they
are generally not seen due to stress.
There are many other parameters that need to be assessed in a
suspected or confirmed diabetic cat once persistent blood and urine
sugar levels are noted and stress is ruled out as a factor. A
complete blood count is used to look for changes in the red blood
cell, white blood cell, and platelet counts. A biochemistry profile
may detect evidence of concurrent liver or kidney disease and
electrolyte abnormalities. A thyroid hormone level should be checked
to rule out hyperthyroidism, as this disease can cause the exact
same signs as diabetes mellitus, and can also complicate management
of diabetes in a cat that also has hyperthyroidism. However,
sometimes hyperthyroidism cannot be ruled out by a single normal
reading, as this hormone level can be falsely lowered in the
presence of uncontrolled diabetes mellitus. Complete urinalysis and
urine cultures are necessary to rule out a complication called
ketoacidosis and to rule out urinary tract infection. Chest x-rays
and abdominal ultrasound may also be recommended, depending on the
cat's overall condition.
Prognosis: The outlook for diabetic cats depends on a number
of factors. The owner's commitment to treatment is a key point, as
treatment is seldom easy and is usually life-long. Cats that develop
diabetes mellitus along with other diseases may also have a worse
prognosis. One study that looked at the length of survival following
the diagnosis of diabetes mellitus in cats found that the cats in
the group examined live an average of two years after diagnosis.
Proper home care, regular veterinary evaluation, and most
importantly excellent client-veterinary communication are vital to
the successful treatment of diabetes mellitus in cats.
Transmission or Cause: There is no one specific, established cause for
diabetes in cats. In many Type I diabetic cats, the deposition of an
abnormal protein called amyloid is present in the pancreas, and this
protein deposition may interfere with the normal insulin secretion
by the pancreas. The cause of this protein deposition is unknown.
Many diabetic cats will also show chronic inflammatory changes
consistent with pancreatitis. This inflammation can ultimately
effect insulin secretion from the pancreas, but its cause has not
been determined. Obesity, the presence of infection or other
concurrent illnesses, and treatment with drugs known to be
associated with insulin resistance, such as some steroids and
progesterone derivatives, are also factors that may be involved in
the development of diabetes in some cats. Other possible causes
include genetic predisposition and immune system mediated
destruction of insulin secreting cells in the pancreas. The exact
role of many of these factors remains to be elucidated.
Treatment: It is vital that careful thought be given to the decision
to proceed with treatment. The management of diabetes mellitus
requires very close observation and daily medication. In some
situations, the owner's lifestyle may not allow for careful
treatment. However, if the classic signs of diabetes mellitus are
present, and the owners are willing to proceed, then treatment
usually is recommended. The goals of treatment are to lessen the signs
due to diabetes mellitus and to avoid complications of the disease.
It is important to prevent the serum glucose concentration from
dropping below the normal range, as serious consequences can occur
when hypoglycemia, or a low concentration of serum glucose
concentration, develops. Owners should watch for signs of
hypoglycemia, which can vary from subtle behavioral changes, to
wobbliness and weakness, to severe generalized seizure activity.
Diet is an important aspect of treatment, especially since many
diabetic cats are either obese or severely underweight. It is
essential to ensure a regular intake of calories and to prevent the
cat from consuming excessive protein and fat. As a general rule,
semi-moist foods are avoided. Especially for overweight cats, high
fiber diets may be helpful in encouraging weight loss and in
controlling fluctuations in the serum glucose concentrations. It may
be difficult to get a cat to eat a high fiber diet because these
diets are sometimes not particularly palatable; introducing the diet
gradually, however, may encourage acceptance of the new food. If a
cat refuses to eat a high fiber diet, then other diets should be
used. In underweight diabetic cats, high fiber diets are generally
avoided until blood sugar levels are controlled with medication and
a normal weight is achieved. Frequency of feeding is usually
dictated by the cat's normal dietary behavior. Cats that eat all day
long are probably best fed small amounts many times per day, while
cats that eat voraciously but infrequently may do better with meal
feedings.
Since some cats have NIDDM, the use of oral medications to lower
blood glucose concentrations can be considered. This is especially
true if the owners are unwilling to give insulin, if transient
diabetes mellitus is suspected, or if the cat seems excessively
sensitive to small doses of insulin. The most common oral drug used
to treat diabetes mellitus in cats is glipizide. Adverse reactions
can include gastrointestinal upset, hypoglycemia, and liver damage.
Despite some successes, most permanently diabetic cats cannot be
controlled by oral glipizide alone. Other oral medications
prescribed for diabetic cats include vanadium and chromium
picolinate. The primary medication used to treat permanent
diabetes mellitus in cats is insulin. There are many different types
and sources of insulin, but in general, the recombinant human forms
of insulin are used most commonly. Production of these types of
insulin is unlikely to be discontinued because they are the main
types of insulin used to treat human diabetics, although
availability of other insulin types has been limited in recent years
by discontinuation of their production by manufacturers. The Lente
and Ultralente types of recombinant human insulin are used most
commonly in diabetic cats. Although some cats do well with
once-daily injections of ultralente insulin, most cats eventually
require twice-daily administration. Virtually all cats on lente
insulin require twice-daily injections.
At-home monitoring requires careful observation for the signs
associated with diabetes mellitus. Measurement of urine glucose
concentrations and ketones with strips designed for their detection
may aid in treatment decisions, but most veterinarians no longer
rely heavily on such readings for changes in treatment
recommendations. If the signs of increased thirst, urination,
appetite, and weight loss are improving, then the treatment is
probably appropriate. If those signs are persisting or getting
worse, adjustments to the treatment protocol may be needed.
Measurement of serum glucose concentrations over
several hours -- ideally 24 hours -- is probably the best way to
assess diabetic control. Such glucose curves may be done on an
abbreviated basis, as many hospitals are not open overnight.
Nevertheless, the ideal method is to measure the glucose level every
few hours over 24 hours in a hospital where 24-hour care is
available. The measurement substances called fructosamine and
glycosylated hemoglobin have recently become more common in
veterinary medicine. However, it can be difficult to make specific
treatment recommendations based on these readings alone. The
measurement of fructosamine can be very helpful in separating
stress-induced changes in the blood sugar level from true diabetes
mellitus. In cats with well-controlled signs that are extremely
distressed by being in the veterinary hospital, the measurement of a
single fructosamine level on an outpatient basis may be used in lieu
of hospitalization for a full glucose curve. If it is normal,
control may be adequate. If the fructosamine level is elevated, then
a glucose curve will need to be done to determine what adjustments
might be helpful.
As with most illnesses, follow-up recommendations for diabetic cats
depend on how well they are responding to treatment at home. For
clinically stable cats on insulin, blood glucose curves, or serum
fructosamine concentrations where appropriate, should be assessed
every three to four months. Cats with persistent signs of diabetes
mellitus or episodes of hypoglycemia will need much more frequent
follow-up until they are better regulated. It can take months to
establish regulation in some cats, and there are some cats that can
never be adequately regulated with treatment for diabetes mellitus.
Prevention: Since diabetes mellitus in cats frequently is
associated with obesity, prevention of excessive weight gain may
reduce the likelihood of its development. Certain drugs,
particularly high doses of some types of steroids and progesterone
derivatives used to treat behavioral abnormalities and skin
diseases, can lead to the development of transient or permanent
diabetes mellitus in cats. Such medications should be used
cautiously, if at all.
