Hypercalcemia Diagnosis

Confirm hypercalcemia

• Measure total serum Ca & ionized Ca at least twice

Obtain detailed history, physical exam, review prior routine chemistry results

• Inquire about:
  • Past kidney stones
  • Fractures
  • Weight loss
  • Bone pain
  • Fatigue
  • Vitamin & mineral ingestion
  • Lithium or thiazide diuretic use

Measure Serum Parathyroid Hormone (PTH)

• Immunoassays specific for intact molecules using double antibody is preferred (intact parathyroid hormone)
• Diagnosis: Elevated or inappropriately normal serum parathyroid w/ hypercalcemia usually indicates primary hyperparathyroidism
  • Exceptions: Familial hypocalciuric hypercalcemia (FHH), autonomous parathyroid secretion & rarely ectopic malignant neoplasm

• Diagnosis: Low-undetectable serum parathyroid hormone suggests parathyroid-independent hypercalcemia
  • Evaluate patient for malignancy (many times, malignancy will already be known)
  • If malignancy is not present, search for unusual causes of hypercalcemia

Measure 24-hr urinary calcium & creatinine (Cr) excretion

• In patients w/ familial hypocalciuric hypercalcemia, the urinary Ca excretion is low
• Calculation of the Ca/Cr clearance ratio is believed to be preferable in diagnosing familial hypocalciuric hypercalcemia
  • The ratio is calculated from the results of 24-hour urine collection & simultaneously measured total serum Ca & Cr concentrations using the below formula: Ca/Cr clearance ratio = [24-hr urine CA x serum Cr] / [Serum CA x 24-hr urine Cr]
  • A ratio of <0.01 usually indicates familial hypocalciuric hypercalcemia, while a ratio of >0.02 is present in patients w/ hyperparathyroidism