Calcium (Urine)

General Information

Urine calcium can be used to assess parathyroid disease and familial hypocalciuric hypercalcemia (FHH). Although not predictive of stone formation, urine calcium is frequently elevated in patients with lithiasis. The primary clinical value of urine calcium measurement is to aid in the differential diagnoses of patients and direct optimal treatment options for patients with abnormal serum calcium

Hypocalciuria is often mistakenly due to incomplete collection (a random sample thought to be an aliquot from a 24-hour specimen). Some drugs can decrease urine calcium, including thiazide diuretics, benzothiadiazide diuretics (like chlorthalidone), and estrogen. Decreased urine calcium is also seen in hypoparathyroidism, pseudohypoparathyroidism (a lack of response to PTH rather than decreased secretion of PTH), rickets, hypothyroidism, steatorrhea, and nephrosis. Another cause of low urine calcium is familial hypocalciuric hypercalcemia (FHH), also known as familial benign hypercalcemia.

Any disease causing increases in serum calcium can lead to increases in urine calcium. In addition to hyperparathyroidism, other diseases include multiple myeloma (or any osteolytic neoplasm), osteoporosis, vitamin D overdose, renal tubular acidosis, hyperthyroidism, Paget's disease, and sarcoidosis. Drugs containing calcium (such as some antacids) and calcium supplements can lead to direct increases in urine calcium. The diuretic spironolactone can also cause increases in urine calcium since it is given as a calcium salt and appears to decrease tubule reabsorption of calcium. Androgens such as nandrolone and treatment with growth hormone can also cause increases in urine calcium.

Patient Preparation

None

Notes

Random or 24 hour collection may be assayed.