Calcium, Urine

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Subject: Calcium, Urine

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Definition

  • 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.

 
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