hypercalcemia
HYPERCALCEMIA
Hypercalcemia is having serum calcium level of >10.5 mg/dL (>2.5 mmol/L).
Mild hypercalcemia is usually asymptomatic. While, more severe hypercalcemia has a constellation of clinical manifestations commonly described as "bones, abdominal moans, stones & groans."
Etiologies may be parathyroid-dependent or parathyroid independent.
Surgery is the treatment of choice for hypercalcemic patients with classic symptoms or complications of primary hyperparathyroidism.

Diagnosis

Confirm hypercalcemia

  • Measure total serum Ca & ionized Ca at least twice

History

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

Laboratory Tests

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
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