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CACRU
89604
important role in blood clotting and bone mineralization. Hypocalcemia is due to the absence or impaired
function of the parathyroid glands or impaired vitamin-D synthesis. Chronic renal failure is also
frequently associated with hypocalcemia due to decreased vitamin-D synthesis as well as
hyperphosphatemia and skeletal resistance to the action of parathyroid hormone (PTH). A characteristic
symptom of hypocalcemia is latent or manifest tetany and osteeomalacia. Hypercalcemia is brought about
by increased mobilization of calcium from the skeletal system or increased intestinal absorption. The
majority of cases are due to primary hyperparathyroidism (pHPT) or bone metastasis of carcinoma of the
breast, prostate, thyroid gland, or lung. Patients who have pHPT and bone disease, renal stones or
nephrocalcinosis, or other signs or symptoms are candidates for surgical removal of the parathyroid
gland(s). Severe hypercalcemia may result in cardiac arrhythmia. Total calcium levels also may reflect
protein levels.
Useful For: Diagnosis and monitoring of a wide range of disorders including disorders of protein and
vitamin D, and diseases of bone, kidney, parathyroid gland, or gastrointestinal tract.
Interpretation: Hypocalcemia- Long-term therapy must be tailored to the specific disease causing the
hypocalcemia. The therapeutic endpoint is to achieve a serum calcium level of 8.0-8.5 mg/dL to prevent
tetany. For symptomatic hypocalcemia, calcium may be administered intravenously. Hypercalcemia- The
level at which hypercalcemic symptoms occur varies from patient to patient. Symptoms are common
when serum calcium levels are >11.5 mg/dL, although patients may be asymptomatic at this level. Levels
>12.0 mg/dL are considered a critical value in the Mayo Health System. Severe hypercalcemia (>15.0
mg/dL) is a medical emergency.
Reference Values:
Males
0-11 months: not established
1-14 years: 9.6-10.6 mg/dL
15-16 years: 9.5-10.5 mg/dL
17-18 years: 9.5-10.4 mg/dL
19-21 years: 9.3-10.3 mg/dL
> or =22 years: 8.9-10.1 mg/dL
Females
0-11 months: not established
1-11 years: 9.6-10.6 mg/dL
12-14 years: 9.5-10.4 mg/dL
15-18 years: 9.1-10.3 mg/dL
> or =19 years: 8.9-10.1 mg/dL
Clinical References: 1. Tietz Textbook of Clinical Chemistry, Edited by CA Burtis, CR Ashwood.
WB Saunders Company, Philadelphia, 1999 2. Baldwin TE, Chernow B: Hypocalcemia in the ICU. J Crit
Illness 1987;2:9-16
Calcium/Creatinine Ratio, Random, Urine
Clinical Information: 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 exists in 3 states in the body; bound to protein, bound to
small anions, and in the free (ionized) state. The concentration of serum calcium in the ionized state is
regulated by parathyroid hormone (PTH) and 1,25 dihydroxy vitamin D. Circulating calcium is excreted
by glomerular filtration and reabsorbed in the proximal tubules. Calcium reabsorption in the proximal
tubule is affected by tubular sodium concentration, whereas PTH induces calcium uptake in the distal
tubule and the collecting duct. Excess is excreted in the urine and the feces. Because PTH increases renal
tubular reabsorption of calcium, one would expect patients with hyperparathyroidism to be hypocalciuric.
However, highly urinary calcium/creatinine ratios were found in most hyperparathyroid patients, and less
frequently in patients with hypercalcemia due to other causes. Calcium/creatinine ratio of random urine
specimens may be used to detect hypercalciuria in patients suspected of having metabolic bone disease or
other abnormalities of calcium metabolism.
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