Calcium (Ca)

 

Indications for performing this test:  This test is part of a standard serum chemistry panel and is a useful tool in the diagnosis of many conditions.

    Calcium is present in the body in three forms.  Approximately 50% of the body's calcium is present as ionized calcium, 40% is protein bound, and 10% is complexed with anions.  These relationships can be altered by the acid-base status of the animal, or the amount of proteins available in the blood to bind calcium.  Alkalosis will cause a decrease in ionized calcium and acidosis will cause an increase in ionized calcium.  Only the ionized calcium is biologically active.  It is used in the formation and remodeling of bone, neuromuscular activity, cellular biochemical processes, and coagulation.  In most instances of hypercalcemia, it is the ionized calcium that is elevated.  Dietary intake will seldom be reflected in serum calcium levels.

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Interpretation of serum calcium levels:

  Hypercalcemia:

  • Primary hyperparathyroidism
  • Hypercalcemia of malignancy  (pseudohyperparathyroidism)
  • Renal failure in dogs, cats and horses
  • Hypervitaminosis D
  • Hypoadrenocorticism
  • Osteolytic bone disease
  • Acidosis
  • Granulomatous disease in dogs and cats
  • Lipemia may also cause an artifactual increase in serum calcium


Hypoalbuminemia:  Remember that approximately 40% of calcium is normally bound to plasma protein. 

This formula will correct for a false hypocalcemia due to hypoalbuminemia.

3.5 - albumin (g/dl) + measured Ca (mg/dl) = corrected calcium

     

  Hypocalcemia:

  • Hypoproteinemia
  • Hypoparathyroidism
  • Milk Fever in ruminants
  • Grass tetany in ruminants
  • Malabsorption
  • Acute Pancreatitis
  • Ethylene Glycol Toxicity
  • Alkalosis

Calcium Oxalate Monohydrate crystals seen in the urine of animals poisoned with Ethylene Glycol.


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