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Most
diabetic cats require lifelong oral or injectable
medication. For a few lucky cats (and owners), however,
diabetes resolves. How does this happen?
Introduction
“Mooch” Kahn was looking okay in the exam room. Two
days earlier, the 14 year old diabetic cat had been to
an after-hours emergency clinic where he was diagnosed
with an acute episode of hypoglycemia (low blood
sugar). Mooch’s owner, Ann Kahn, had given him his
usual evening dose of insulin. Two hours later, Mooch
wasn’t acting right. “He was stumbling around the
apartment, twitching a little and acting weird and
spacey”, she recalls, “and being a diabetic, I didn’t
want to take any chances. I took him to an emergency
clinic”.
Mooch’s story
Mooch had been diagnosed as diabetic elsewhere, and was
prescribed 4 units of insulin, to be given twice daily.
When I initially saw him, his clinical signs of diabetes
were still prominent – he was drinking a lot, urinating
a lot, eating a lot, and losing weight. His blood sugar
was high, and his fructosamine levels – a measure of how
well controlled his diabetes has been over the previous
two weeks – indicated that his diabetes was poorly
controlled. I increased his insulin dose to 5 units
twice daily, and prescribed a special diet designed to
get him down to his ideal weight. I had him come back in
two weeks for reassessment. There was some improvement
in his clinical signs and blood sugar levels, but it
still wasn’t perfect. One more dosage adjustment, to 6
units twice daily, should do the trick.
Two
weeks later, Mooch’s signs had resolved, and his
fructosamine levels were ideal. We had found Mooch’s
proper insulin dose – 6 units twice daily – and had his
diabetes nicely regulated. Four weeks after that,
however, came the setback: Mooch’s emergency visit for
“insulin shock” – hypoglycemia due to insulin overdose.
Indeed, Mooch’s blood sugar at the emergency clinic was
dangerously low. Fortunately, it responded quickly to
treatment, and Mooch’s lightheaded behavior and
uncoordinated gait promptly resolved.
Readjusting Mooch’s medication
As
noted above, Mooch was fine on examination. I advised
the owner not to give Mooch any insulin for the next two
days, and then start the insulin again, but at a lower
dose – 4 units twice daily. We’d be rechecking him a
few days later. Ms. Kahn followed my instructions,
however, four days later, after his evening insulin
dose, Mooch started acting odd and began walking
unusually. Suspicious of another hypoglycemic episode,
Ms. Kahn administered corn syrup to Mooch, and the
clinical signs resolved promptly. Again on examination,
Mooch was fine – bright, alert, happy. A blood sugar
measurement in the exam room told a different story,
though. Although he was acting fine, Mooch’s blood
sugar was dangerously low - low enough to warrant an
intravenous injection of glucose. Five minutes
afterward, the blood sugar was reassessed, and it was
normal. “Stop all insulin for two days”, I told Ms.
Kahn, “and then start again at 2 units twice daily”.
This was a 66% dose reduction from his formerly ideal
dose.
Problem solved?
Over
the next two weeks, frequent phone conversations with
Ms. Kahn revealed that Mooch was back to his old self,
eating and drinking normally, acting like a kitten
again. When I examined him, he had gained a few ounces
and was happy as can be. Imagine my surprise when a
blood sugar measurement in the exam room revealed very
low blood sugar levels.
I
advised Ms. Kahn to discontinue all insulin. It’s been
several weeks that he’s been off insulin, and Mooch
remains happy and healthy, with no signs of diabetes and
a normal blood sugar.
Although the vast majority of diabetic cats require
lifelong therapy, Mooch is one of a small population of
diabetic cats whose diabetes somehow “resolves” a few
weeks after the diagnosis. Some of these cats become
diabetic again later on in life and require insulin for
the remainder of their lives, while others continue to
live normally, without insulin. In order to understand
this unusual phenomenon, let’s review the basics of
diabetes.
Diabetes 101
Diabetes is one of the most common endocrine (glandular)
disorders in cats. While the exact cause of diabetes in
not known, obesity, genetic predisposition, pancreatic
disease, hormonal imbalances, and certain medications
have all been incriminated. Diabetes occurs when the
pancreas fails to produce adequate amounts of insulin, a
hormone necessary for controlling blood glucose (sugar)
levels. When food is digested, sugar enters the
bloodstream. The body uses this sugar for energy,
growth, and repair. Insulin is necessary for the sugar
in the bloodstream to enter into tissue cells where it
is needed – in muscles, for example. Without enough
insulin, sugar accumulates in the bloodstream where it
eventually gets filtered out into the urine. Large
quantities of water accompany the sugar that is lost
through the kidneys. Consequently, diabetics produce a
large volume of urine. To avoid getting dehydrated,
cats compensate for this fluid loss by drinking
excessively. Because the sugar cannot get into their
cells without insulin, they switch to using fat and
protein as an energy source, and diabetic cats usually
lose weight as a result. Overweight cats are more
likely to be afflicted with diabetes.
Diabetes is usually easy to diagnose. Most cats are
presented to the veterinarian with the classic signs of
diabetes: excessive urination, excessive thirst, very
good appetite, and weight loss. High levels of sugar in
the blood and the presence of sugar in the urine allow
for a straightforward diagnosis. Occasionally, the
clinical signs can be misleading, and the blood and
urine tests can be equivocal, making the diagnosis
somewhat tricky. In these instances, some additional
tests may be necessary before arriving at a definitive
diagnosis
Treatment of diabetes involves medication and special
diets. The majority of feline diabetics receive insulin
injections, however, some may be managed using oral
glucose-lowering drugs. Although some cat owners are
distraught at the thought of administering injections
and prefer to give pills, in most cases, insulin
injections are the best choice and are actually much
easier to administer than pills. Cats that initially
respond to oral medication often become refractory to
these drugs and eventually require insulin injections to
keep their diabetes under control.
Type
1 and 2 vs. IDDM and NIDDM
In
humans, we classify the diabetes as Type 1 or Type 2.
Type 1 diabetes is characterized by genetic
susceptibility to diabetes as well as destruction of the
beta cells, the pancreatic cells responsible for
producing insulin. Type 1 diabetics cannot produce
enough insulin to keep their blood sugar regulated, and
are dependent on insulin treatment for control of the
disease. People with Type 1 diabetes are therefore
classified as having insulin-dependent diabetes
mellitus (“IDDM”). Humans with Type 2 diabetes, on
the other hand, usually have a combination of insulin
resistance and beta cell dysfunction. Their beta cells
produce insulin, but usually in inadequate amounts, and
their bodies don’t recognize or react to the insulin in
the proper way. In humans with Type 2 diabetes, control
of the diabetic state is usually possible through diet,
exercise, and oral drugs. In other words, most humans
with Type 2 diabetes can be controlled without the need
for insulin and are said to have
non-insulin-dependent diabetes mellitus (“NIDDM”).
If beta cell dysfunction and insulin resistance become
severe, however, insulin may eventually be necessary.
As such, humans with Type 2 diabetes can have IDDM or
NIDDM.
In
cats, it is very difficult to figure out whether a cat
has Type 1 diabetes vs. Type 2. It is perhaps more
accurate to classify feline diabetes as IDDM or NIDDM,
based on their need for insulin to control the diabetes,
rather than Type 1 or Type 2. At the time diabetes is
diagnosed, about 70% of cats have IDDM, while NIDDM
accounts for the remaining 30%.
Transient diabetes
A
small percentage of diabetic cats are revealed to be
“transiently” diabetic, usually within a few weeks after
the disorder is diagnosed and treatment has begun. In
these cats, the high blood sugar, presence of sugar in
the urine, and clinical signs resolve, and insulin
treatment can be discontinued. How does this happen?
In
normal cats, when the pancreas detects elevated levels
of sugar in the blood stream, it responds by secreting
insulin. Blood sugar levels will then drop, gradually
returning to normal. Some cats, however, may have a
hidden problem with their pancreas – a decreased number
of beta cells, and an impaired ability to secrete
insulin. They may appear clinically normal, but they’re
actually on the “brink” of being diabetic. If they’re
then given drugs that impair insulin function, or if
they become overweight or obese, the cats become
intolerant of carbohydrates and develop high blood
sugar. In some of these cats, though, the high levels
of blood sugar causes something called “glucose-induced
desensitization”, a temporary, reversible state in which
beta cell function becomes even further suppressed, and
these cats become insulin-dependent diabetics. In this
population of cats, if you lower the blood sugar by
giving insulin and correct or control concurrent
disorders, beta cell function may be restored, and they
begin to release insulin again, and the cat returns to
their subclinical state, i.e. they’re go back to being
“on the brink” again. Most likely, Mooch’s pancreas was
experiencing glucose-induced desensitization at the time
his diabetes was diagnosed, and initiating insulin
therapy and controlling his weight caused the
desensitization to resolve allowing the pancreas to
start releasing insulin again. Unfortunately for Mooch,
his own insulin, combined with the insulin he was
receiving by injection, was a bit too much, and he
became hypoglycemic.
Mooch
is currently off all insulin, and his pancreas seems to
be able to secrete enough insulin to keep things under
control.
End
of story?
In a
study, published in 1999, of ten cats with transient
diabetes, seven cats did not experience a recurrence of
their diabetes. Three of the cats, however, had a
recurrence of their diabetes, one six months later, one
14 months later, and one 3.4 years later. In the study,
it was not possible to predict which of the transient
diabetics were at higher risk of a relapse. Certainly,
cats whose diabetes seems to have resolved should be
considered to be susceptible to a recurrence of their
clinical diabetes, and it would be important to avoid
the circumstances that could promote a return to the
diabetic state. That would include avoiding any
medications known to antagonize the effectiveness of
insulin, such as glucocorticoids and progestins,
maintaining ideal body weight, and minimizing concurrent
illnesses.
Sidebar: Dr. Mary Anna Labato answers some common
questions about feline diabetes
Q:
How common is diabetes in cats?
A:
Feline diabetes is a common hormonal disorder, affecting
about 1 in 400 cats.
Q:
Is diabetes more likely to strike at a certain age, or a
certain gender, or certain breeds?
A:
Although it can strike cats at any age, diabetes is more
commonly seen in middle aged cats. Males are more often
affected than females. There is no apparent breed
predisposition, although some people report that Burmese
cats may be slightly more susceptible than other breeds.
Q:
What are the most common signs that a cat might be
diabetic?
A:
The four classic signs of diabetes are increased thirst,
increased urine output, ravenous appetite, and weight
loss. For many cat owners, the first thing they notice
is that they’re having to change the cat litter more
frequently, or that the size of the kitty litter clumps
have gotten larger. Decreased grooming, an unkempt coat,
and weakness in the rear limbs can also be seen.
Q:
How is diabetes treated?
A:
Although some cats may respond to oral medications that
lower blood sugar, most cats require insulin injections
to keep their diabetes under control
Q:
What is the best diet to feed a diabetic cat?
A:
For years, a high-fiber diet was recommended. Recently,
it has been shown that a high-protein-low-carbohydrate
diet may be even more suitable for feline diabetics.
Updated
4/25/06 |
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