Calcium (Ca+) test

       Approximately 98% of all calcium is stored in bones and teeth. Calcium

that is present in the bloodstream circulates in the ionized, or free state, and

in a protein-bound form with albumin. It is the ionized form of calcium that

is used in bodily processes such as muscular contraction, cardiac functioning,

hormone secretion, cell division, and the transmission of nerve impulses.

Ionized calcium is essential for blood coagulation .

Normal Range

Total plasma calcium

9.0-10.5 mg/dl

Free calcium

3.9-4.6 mg/dl

    Variations from Normal. Hypercalcemia, increased plasma calcium, is associated

with many diseases but is most clinically significant in its association

with cancer. The most common cause of increased calcium in the

blood is metastatic bone disease . Cancers of the lung, breast, thyroid, kidney,

and testes are likely to metastasize to bone. Hodgkin's disease, multiple

myeloma, and leukemia may also cause hypercalcemia . Other disorders

or conditions associated with increased calcium levels are hyperparathyroidism,

Paget's disease of bone, prolonged immobilization, and Addison's

disease.

       Since much of the plasma calcium is bound to albumin, decreased

plasma calcium levels, hypocalcemia, can be related to a lowered plasma albumin

level. Once this possibility has been eliminated, hypocalcemia can be

indicative of hypoparathyroidism and renal failure . Vitamin D deficiencies

and malabsorption associated with sprue, celiac disease, and pancreatic

dysfunctions contribute to decreased plasma calcium levels. Since calcium is

essential for clotting, any condition that decreases the amount of ionized calcium

can subsequently lead to coagulation and hemostasis problems.

Interfering Circumstances. Certain dietary considerations can interfere

with accurate plasma calcium test results . Vitamin D intoxication or excessive

milk ingestion, defined as three quarts of milk per day, can cause an increase

in plasma calcium.

      Prescription and over-the-counter drugs such as heparin, magnesium

salts, oral contraceptives, aspirin, and corticosteroids and excessive use of

laxatives may cause a decrease in plasma calcium. Drugs that influence an

increase of plasma calcium include lithium, vitamin D, thiazide diuretics,

thyroid hormone, and hydralazine, an antihypertensive medication.