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Test ID: CAU    
Calcium, 24 Hour, Urine

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Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of abnormal physiologic states causing excess or suppressed excretion of calcium, such as hyperparathyroidism, vitamin D abnormality, diseases that destroy bone, prostate cancer, and drug treatment, such as thiazide therapy

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Calcium is the fifth most common element in the body. It is a fundamental element necessary to form electrical gradients across membranes, an essential cofactor for many enzymes, and the main constituent in bone. Under normal physiologic conditions, the concentration of calcium in serum and in cells is tightly controlled.

 

Calcium is excreted in both urine and feces.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Males: 25-300 mg/specimen*

Females: 20-275 mg/specimen*

Hypercalciuria: >350 mg/specimen

*Values are for persons with average calcium intake (ie, 600-800 mg/day).

Interpretation Provides information to assist in interpretation of the test results

Increased urinary excretion of calcium accompanies hyperparathyroidism, vitamin D intoxication, diseases that destroy bone (such as multiple myeloma), metastasis from prostatic cancer, and following calcium supplementation.

 

Patients with absorptive hypercalciuria (increased gut absorption) will have lowered urine calcium with dietary restriction and, therefore, can be differentiated from patients with hypercalciuria caused by hyperparathyroidism, hyperthyroidism, Paget disease, or "renal leak" type of calciuria as seen in renal tubular acidosis.

 

Thiazide drugs tend to reduce excretion of calcium.

 

For individuals consuming an average daily intake of 600 to 800 mg of calcium per day, the normal daily excretion of calcium is:

-25 to 300 mg for men

-20 to 275 mg for women

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Acidification of the specimen is not required. 

 

Sodium bicarbonate must not be used as a preservative.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

Rockwell GF, Morgan MJ, Braden G, et al: Preliminary observations of urinary calcium and osteopontin excretion in premature infants, term infants and adults. Neonatology 2008;93(4):241-245

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test