Urinary calcium levels reflects intake, rates of intestinal calcium absorption, bone resorption, and renal loss. Hypercalcemia of any cause raises urinary calcium excretion, and its measurement adds little to the differential diagnosis of hypercalcemia. Fasting calcium excretion is useful when assessing the contribution of abnormal renal tubular handling of calcium to disorders of calcium homeostasis.
Normal range:
Twenty-four " “hour urine: 100 " “300 mg/day
Random urine:
Males: 12 " “244 mg/g creatinine
Females: 9 " “328 mg/g creatinine
Use
Evaluation of patients with disorders of bone disease, calcium metabolism, and renal stones
Follow-up of patients on calcium therapy for osteopenia
Best test of calcium excretion in the investigation of possible familial benign hypocalciuric hypercalcemia
Interpretation
Increased In
Primary hyperparathyroidism
Humoral hypercalcemia of malignancy
Vitamin D excess
Sarcoidosis
Fanconi syndrome
Osteolytic bone metastases
Myeloma
Osteoporosis
Distal renal tubular acidosis
Idiopathic hypercalciuria
Thyrotoxicosis
Paget disease
Malignant neoplasm of breast or bladder
Decreased In
Familial hypocalciuric hypercalcemia
Hypoparathyroidism
Pseudohypoparathyroidism
Rickets and osteomalacia
Hypothyroidism
Celiac sprue
Steatorrhea
Limitations
Calcium and protein intake and phosphorus excretion alter urinary calcium excretion.
Decreases late in normal pregnancy.
About one third of hyperparathyroid patients have normal urine output.