Hypercalcemia

Diagnosis

Indications for Testing

• Fatigue, muscle weakness, recurrent nephrolithiasis, bone pain, constipation, changes in mental status
• Elevated calcium on laboratory testing

Laboratory Testing

• Initial testing: comprehensive metabolic panel (CMP)
  • Abnormalities in other lab results may provide clues to underlying pathology
  • Chronic kidney disease with metabolic bone disease results in abnormalities of calcium, phosphorus, PTH, and bone turnover
• Calcium
  • Calculate corrected calcium
    • Corrected calcium = serum calcium + [0.8 x (normal albumin - serum albumin)]
    • Normal albumin is usually 4-4.5 g/dL, depending on testing lab
  • Consider ionized calcium if albumin is low
  • Total serum calcium
    • In asymptomatic patient with concentration >10.3 but <11.0 mg/dL, repeat with albumin measurement or ionized calcium
    • In symptomatic patient and/or patient with concentration >11.0 mg/dL: order PTH
• PTH (intact)
  • Elevated or normal: indicates primary hyperparathyroidism; order urine calcium, 24-hour collection
    • High urine calcium (≥100 pg/mL): primary hyperparathyroidism
    • Low urine calcium (<100 pg/mL): familial benign hypercalcemia
  • Low: order PTH-related peptide (PTHrP)
    • High PTHrP: consider cancer
    • Low or normal PTHrP: order vitamin D, 1,25-dihydroxy [1,25-(OH)₂-D]
      • High 1,25-(OH)₂-D: consider lymphoma or granulomatous disease
      • Low or normal 1,25-(OH)₂-D: consider vitamin D excess, cancer, milk-alkali syndrome, or hyperthyroidism
• Other testing
  • Thyroid-stimulating hormone (TSH): rarely, hyperthyroidism can cause hypercalcemia