Causes
Diabetes in cats occurs due to either insulin deficiency or insulin resistance
as it does in dogs, however the underlying causes are different. Immune
mediated destruction of beta cells is rare in cats. Chronic pancreatitis
and amyloid deposition are important. Insulin resistance may be triggered
by obesity, progestagens, glucocorticoids, HAC, acromegaly, hyperthyroidism,
infection and concurrent disease. Both insulin deficiency and resistance
may occur in one patient.
Two thirds of diabetic cats require insulin. About one third of diabetic
cats experience resolution of their diabetes within the first few months
of therapy and are termed 'transient diabetics'. Remission occurs if the
underlying causes are removed eg obesity, steroid therapy and may last weeks
to years.
Signalment and clinical signs
Diabetes can affect any breed or gender of cat, male neutered are most commonly
affected. One of the main clinical signs is PUPD, which occurs due to glucosuria
that draws water into the urine. Polyphagia with concurrent weight loss
is also important due to the inability to utilise sugars as a result of
the lack of insulin. Cats occasionally present with a plantigrade stance.
Cataracts are rare.
Diagnostic tests
Cats can develop stress hyperglycaemia. Blood glucose can rise up to 20nmol/L
from stress alone, this will then cause glucosuria, which can persist for
several days. Therefore making a diagnosis of diabetes on the basis of hyperglycaemia
and glucosuria can lead to over diagnosis. Measurement of serum fructosamine
usually confirms the diagnosis. Fructosamine is formed when albumin and
glucose react together irreversibly and gives an idea of average blood glucose
over the preceding 1-2 weeks. Reduced total protein and hyperthyroidism
can cause a decrease in the result. Chronic stress can cause a small increase
but not usually into the same range as diabetes.
Treatment
The details of this are covered in fact sheet no 5.1.Stabilising the healthy
diabetic cat. The main difference between cats and dogs is that although
most cats require insulin therapy some can be treated successfully with
diet alone or a combination of diet and oral hypoglycaemic drugs. However,
resolution of diabetes may be less likely if normoglycaemia is not established
rapidly eg cats on oral hypoglycaemic drugs. There are 3 main aspects to
therapy:
Diet: either high protein low carbohydrate diets or high fibre
'weight reducing' diets can be used. Most cats can be stabilised without
the need for a precise feeding regime, if they prefer to nibble ad lib this
can usually continue.
Insulin: PZI can be given once or twice daily. Lente
must always be used twice daily in cats.
Oral hypoglycaemics - should only be considered in non-ketotic clinically
well cats. They should not be used in thin cases. Glipizide is the most
commonly used tablet.
Monitoring
In cats that experience stress hyperglycaemia blood glucose measurements
are not helpful. These cats can be stabilised by monitoring a mixture of
clinical signs, body weight and serum fructosamine.
In those that do not have the stress problem clinical signs, fructosamine,
blood glucose nadirs and intermittent blood glucose curves can be used. |