Glucose

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Indications for performing this test:  Glucose is included on a standard serum chemistry profile.  Glucose is an important indicator of several body systems. 

The Test:  In testing serum glucose it is important not to leave the clotted blood too long before centrifuging.  In vitro glycolysis by the blood cells can cause decreased serum glucose levels at a rate of 10% per hour at room temperature.

Interpretation of serum glucose levels:  There are many disease processes that may affect the body's glucose levels.  Indeed, hyperglycemia and hypoglycemia are very common laboratory findings.  It is therefore important to remember to look at the "big picture" when evaluating abnormal glucose levels.  The clinical presentation will be of enormous importance in interpreting the results.  Included below is a systemic approach to glucose metabolism and clinical abnormalities.  These are just examples of possible causes and it should not be considered an inclusive list.

    Endocrine

    Normal glucose levels are carefully regulated in the healthy animal by various endocrine systems.  The most important of these are:  insulin, glucagon, corticosteroids, and growth hormone.  Alterations in these hormones produce predictable shifts in serum glucose.  The following table lists some common endocrine disorders causing hyper- and hypoglycemia.
   

Hyperglycemia

  • Diabetes Mellitus

  • Hyperadrenocorticism

  • Hyperglucagonemia

  • Hyperpituitariasm

  • Hyperthyroidism

Hypoglycemia

  • Hypoadrenocorticism

  • Hypopituitarism

  • Hypothyroidism

  • Hyperinsulinemia

  • Production of insulin-like hormones

    Hepatobiliary

    The liver is an important site of glucose metabolism, gluconeogenesis and glycogen storage.  In progressive hepatobiliary disease, serum glucose levels may drop dramatically.  This is an end stage change and reflects a poor prognosis.  A portosystemic shunt may also present with mildly decreased serum glucose levels.   

 Hepatic Cirrhosis:  An animal with this disease is no longer able to retrieve or store glycogen normally.

 

Gastrointestinal

    The diet has a direct and profound effect on the serum glucose levels.  We can expect post-prandial rises in serum glucose to last a couple of hours.  Other gastrointestinal diseases may also alter the serum glucose concentration. 

Hyperglycemia

  • Pancreatitis

  • Exocrine Pancreatic Insufficiency

  • Acute Severe Colic

Glucose levels rise post-prandially.

 Hypoglycemia

  • Exocrine Pancreatic Neoplasia

  • Prolonged Starvation

  • Malabsorption

    Neuromuscular


A cat getting some exercise.

     The neuromuscular system is one of the primary consumers of blood glucose.  In an animal that is experiencing rigorous exercise, there may be transient periods of hypoglycemia following workouts.  In cattle, neurologic diseases may cause hyperglycemia.

 

    Reproductive

    The reproductive status of an animal can significantly effect serum glucose levels, especially in the female animal.

Hyperglycemia

  • Diestrus (dog)

  • Bovine Milk Fever

  • Stress/endogenous corticosteroids associated with pregnancy

Hypoglycemia

  • Ketosis (cattle)

  • Pregnancy Toxemia (sheep)

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