Table of Contents

Calcium Metabolism
Dietary Metabolism
Skeletal Metabolism
Renal Metabolism
Differential Diagnosis
Clinical Presentation
Lab Values
Normal Ranges
Acute Treatment
Chronic Treatment

Calcium metabolism

Dietary metabolism

  • Calcium is absorbed in the gut under the influence of activated vitamin D.
    • PTH (parathyroid hormone) increases the renal secretion of activated vitamin D.
    • Activated vitamin D binds to VDR (vitamin D receptor) in the gut to increase calcium absorption

Skeletal metabolism

  • 99% of total body calcium is stored as a calcium-phosphate complex in the bone
  • PTH increases osteosclastic activity, resulting in bone resorption and release of calcium into the circulation
  • Calcitonin decreases osteoclastic activity
    • Calcitonin is produced by parafollicular cells in the thyroid (also known as C cells).
    • Calcitonin may be elevated in medullary thyroid cancer (which originates from C cells)

Renal Metabolism

  • PTH increases calcium reabsorption and decreases phosphate reabsorption in the renal rubules
    • This increases the calcium to phosphate ratio in the blood


  • Renal failure (reduced synthesis of vitamin D and impaired calcium reabsorption)
  • Vitamin D deficiency (reduced intestinal absorption of calcium)
  • Hypoparathyroidsm (reduced osteoclastic activity, increased renal excretion of calcium, increased renal reabsorption of phosphate)
  • Hyperphosphatemia (calcium binds to phosphate in the blood and becomes an insoluble, inactive complex)



  • Peri-oral numbness
  • Paresthesia in finger tips
  • Spasms/tetany
  • Confusion/decreased LOC


  • Chvostek’s sign: tapping over the facial nerve results in facial spasm
  • Trousseau’s sign: inflate a blood pressure cuff over the biceps (at a pressure greater than the systolic BP) for 3 minutes. Carpal spasm (flexion) during this test is a sign of hypocalcemia.
  • ECG changes: prolonged QT interval, arrythmias

Lab values

Normal ranges

  • Ionized calcium: 1.1–1.3 mmol/L
  • Phosphate: 0.81–1.47 mmol/L
  • PTH: 1.2–5.7 pmol/L


Acute treatment

  • IV calcium bolus over 10–15 minutes
    • Rapid infusion can lead to arrythmias
  • Close monitoring (telemetry recommended)
  • Serial bloodwork (serum calcium and albumin or ionized calcium)

Chronic treatment

  • Oral calcium and vitamin D supplementation
    • Elemental calcium: 1.5–2 g divided TID
    • Vitamin D
      • Example: calcitriol (Rocaltrol): initial dosing 0.25 mcg/day


  1. Goldenberg, D., Goldstein, BJ. Handbook of Otolaryngology Head and Neck Surgery. Section 5.4.12: Calcium Disorders.
  2. Lexicomp. Calcitriol: Drug Information.
  3. Peacock M. Calcium metabolism in health and disease. Clin J Am Soc Nephrol. 2010 Jan;5 Suppl 1:S23–30.

Section Author

Scott Kohlert
Medical Student (MS-4)
University of Ottawa

Section Editor

This section has not yet been peer reviewed.