Hypocalcemia

Aka: Hypocalcemia, Low Serum Calcium, Serum Calcium Decreased

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II. Causes

  1. Most common causes
    1. Hypoalbuminemia
    2. Vitamin D Deficiency
  2. Miscellaneous and Multifactorial causes
    1. Hypoalbuminemia
      1. Use Corrected Serum Calcium for albumin or Ionized Calcium to interpret Calcium level
    2. Gram-Negative Sepsis (Marker for increased Sepsis related mortality)
      1. Zaloga (1987) Ann Intern Med 107(1): 36-41 [PubMed]
  3. Low Parathyroid Hormone (or normal Parathyroid Hormone level)
    1. Hypomagnesemia
    2. Hypoparathyroidism
      1. Urine Calcium to Creatinine Ratio decreased
      2. Serum Phosphorus increased
    3. Calcium-sensing receptor activating mutation
      1. Serum Phosphorus increased
      2. Urine Calcium to Creatinine Ratio increased
  4. High Parathyroid Hormone (secondary Hyperparathyroidism as a reflex response to Hypocalcemia)
    1. Low Serum Phosphate
      1. See Medication-Induced Hypocalcemia
      2. Pancreatitis
      3. Vitamin D Deficiency
        1. Decreased 25-hydroxyvitamin D
    2. High or normal Serum Phosphate
      1. Rhabdomyolysis
      2. Tumor lysis
      3. Acute Renal Failure or Chronic Kidney Disease
        1. Decreased 1,25-dihydroxyvitamin D
        2. See Renal Osteodystrophy
      4. Pseudohypoparathyroidism (genetic PTH resistance)
        1. Associated with adequate PTH levels, but a PTH receptor defect
        2. Associated with a shortened fourth digits on the hands and feet

III. Symptoms

  1. Cardiovascular (Systolic Dysfunction)
    1. Dyspnea
    2. Edema
    3. Palpitations
    4. Syncope
  2. Neurologic
    1. Headache
    2. Muscular Fasciculations, Muscle cramping, Muscle spasms, Muscle stiffness
    3. Seizures
    4. Paresthesias
    5. Circumoral numbness
    6. Nervousness
    7. Weakness
    8. Decreased Vision
    9. Chronic Hypocalcemia may demonstrate Parkinsonism, Dementia
  3. Gastrointestinal
    1. Vomiting
    2. Diarrhea
    3. Dysphagia
    4. Abdominal Pain
  4. Psychiatric
    1. Anxiety
    2. Depressed Mood

IV. Signs

  1. Cardiovascular
    1. Hypotension
    2. Heart Failure
  2. Respiratory
    1. Bronchospasm (Wheezing)
    2. Laryngospasm (Stridor)
  3. Neurologic
    1. Tetany
    2. Carpopedal Spasm (Trousseau's Sign)
    3. Chvostek's Sign
  4. Skin
    1. Hair Loss (due to dry, brittle hair)
    2. Dry, puffy skin
  5. Eyes
    1. Premature Cataracts
    2. Papilledema

V. Diagnostics: Electrocardiogram (EKG)

  1. Prolonged QTc with severe Hypocalcemia (may degenerate into Torsades de Pointes)

VI. Labs

  1. Serum Calcium low
    1. Total Corrected Serum Calcium (for Serum Albumin) or
    2. Ionized Calcium
  2. Serum Electrolytes
    1. Serum Phosphorus
    2. Serum Magnesium
    3. Serum Creatinine
    4. Serum Albumin (used for Corrected Serum Calcium)
  3. Parathyroid Hormone (PTH)
  4. Vitamin D
    1. 25-Hydroxyvitamin D
    2. 1,25-Dihydroxyvitamin D
    3. Urine Calcium to Creatinine Ratio (24 hour Urine Calcium and Urine Creatinine)

VII. Evaluation

  1. Confirm Hypocalcemia
    1. Obtain Corrected Serum Calcium (for Serum Albumin) or Ionized Calcium
    2. Correct Serum Calcium 0.8 mg/dl for every 1 gram Serum Albumin is below normal range
  2. Obtain labs to narrow causes (see labs above)
    1. Parathyroid Hormone
    2. Serum Electrolytes (Serum Phosphate, Serum Magnesium, Serum Creatinine)
    3. Vitamin D (25-Hydroxyvitamin D, 1,25-Dihydroxyvitamin D)
  3. Initial correction of abnormalities (if indicated)
    1. Treat severe, symptomatic Hypocalcemia (See Calcium Replacement)
    2. Correct Serum Magnesium if abnormal
  4. Parathyroid Hormone (PTH) Low or Normal
    1. Serum Magnesium Low
      1. Hypomagnesemia
    2. Serum Magnesium Normal
      1. Hypoparathyroidism
  5. Parathyroid Hormone (PTH) High
    1. Serum Creatinine increased
      1. Evaluate for Chronic Kidney Disease
      2. Manage as Renal Osteodystrophy
    2. Serum Creatinine normal
      1. Serum Phosphorus high
        1. Pseudohypoparathyroidism (genetic PTH resistance)
      2. Serum Phosphorus normal or low
        1. Treat as Vitamin D Deficiency if low 25-Hydroxyvitamin D

VIII. Management

  1. See Calcium Replacement
  2. Consider replacement if Corrected Serum Calcium <10 mg/dl

IX. References

  1. Cooper (2008) BMJ 336(7656): 1298-302 [PubMed]
  2. Michels (2013) Am Fam Physician 88(4): 249-57 [PubMed]
  3. Sell (2022) Am Fam Physician 105(3): 289-98 [PubMed]

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