Causes
Diabetes mellitus is not a single disease or condition with a solitary cause
or treatment. It is the state of persistent uncontrolled hyperglycaemia
and may be the result of many contributory factors. Factors that promote
relative hyperglycaemia include anything that causes failure of adequate
insulin secretion and/or peripheral insulin antagonism. Common causes of
insulin secretory failure in dogs include immune mediated B-cell destruction
and chronic pancreatitis, whereas insulin antagonism is often the result
of obesity, or an increased progestagen, glucocorticoid or growth hormone
influence (both naturally occurring and therapeutic). Depending on the cause/s,
the Diabetes may be temporary/reversible (e.g. DM caused by increased
circulating endogenous progestogen during metoestrus) or persistent
(e.g. end stage chronic pancreatitis). It is important to understand
the variable causes of DM as this can influence both the treatment and long
term prognosis.
Signalment and Clinical Signs
Diabetes affects both males and females of any age but is most common in
middle aged and elderly dogs. Typical breeds include rottweilers, small
terrier breeds, poodles and crossbreed terriers. The main clinical signs
of Diabetes mellitus are polydipsia, polyuria, polyphagia, weight loss,
scurfy coat, signs related to cataract development, exercise intolerance
and recurrent infection esp. chronic cystitis.
Diagnostic Tests
Diabetes mellitus is confirmed by demonstrating persistent hyperglycaemia.
Isolated episodes of hyperglycaemia do not confirm DM almost irrespective
of their magnitude. Fructosamine is the product of glycated proteins and
its rate of production is directly related to circulating glucose concentration.
Circulating fructosamine concentration reflects the "average"
blood glucose over the preceding 2-3 weeks. Increased blood fructosamine
values are confirmatory of DM.
Treatment
Treatment of DM in dogs usually consists of treatment of the underlying
causes/s, lifestyle management changes and exogenous insulin therapy. Almost
all dogs with Diabetes mellitus require insulin treatment. Most dogs are
stabilised on one or twice daily lente or ultralente preparations. Depending
on the underlying cause/s of the Diabetic state, insulin therapy may be
needed for only a few weeks or months or more commonly may be required for
the rest of the animal's life. If a known contributor to the condition is
known then it may be practical to treat and reduce/remove this influence
(e.g. withdrawal of exogenous steroid therapy, treatment of hyperadrenocorticism)
which may reduce or remove the requirement for exogenous insulin therapy.
Appropriate therapy in the early stages can potentially avoid development
of permanent DM, depending on the underlying cause. A crucial and often
underestimated aspect of treating DM cases is adherence to lifestyle management
changes, especially ensuring consistency of feeding and exercise patterns.
This is also important during the initial stabilisation procedure (see
Axiom Fact sheet 4.1).
Therapeutic Monitoring
Long term therapeutic monitoring consists of clinical evaluation and biochemical
monitoring. Regular circulating fructosamine is useful, typically every
6 weeks once initial stabilisation has been achieved and specifically timed
glucose concentrations can be useful. The timing of blood sampling in relation
to insulin administration is critical and for worthwhile interpretation
samples should usually be collected 5-6 hours post insulin (see Axiom
Fact sheet 4.1). |