Parathyroid

Hypoparathyroidism

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Hypoparathyroidism

  • See Also
  1. Hypocalcemia
  2. Parathyroid Hormone
  3. Hyperparathyroidism
  4. Calcium Metabolism
  • Epidemiology
  1. Rare
  • Pathophysiology
  1. Low Parathyroid Hormone (PTH) levels
    1. Inadequate PTH Secretion OR
    2. Activating mutation of CASR gene
  2. Low PTH results in Hypocalcemia
    1. Renal Calcium loss (Hypercalciuria)
    2. Decreased Osteoclast activity
    3. Decreased 1,25 - Dihydroxyvitamin D synthesis
  • Causes
  1. Hereditary
    1. Idiopathic Hypoparathyroidism
    2. DiGeorge Syndrome
    3. Pseudohypoparathyroidism (rare)
      1. Tissue-resistance to PTH
      2. Hypoparathyroidism despite increased PTH levels
  2. Acquired
    1. Anterior neck surgery (75% of Hypoparathyroidism cases)
      1. Thyroidectomy with operative Parathyroid removal (most common cause)
      2. Post-surgical monitoring includes Serum Calcium and PTH levels
    2. Radiation (rare)
    3. Hemochromatosis
  3. Autoimmune Syndrome
    1. Multiple endocrine deficiency syndrome
    2. Adrenal, Ovarian and Parathyroid failure
    3. Mucocutaneous Candidiasis
    4. Alopecia
    5. Vitiligo
    6. Pernicious Anemia
  • Symptoms and signs
  1. See Hypocalcemia
  • Labs
  1. See Hypocalcemia
  2. Intact Parathyroid Hormone (PTH) Low or Normal
  3. Corrected Serum Calcium or Ionized Calcium Low
  4. Serum Magnesium Normal
  • Differential Diagnosis
  1. See Hypocalcemia
  • Evaluation
  1. See Hypocalcemia for protocol
  1. See Calcium Replacement
  2. General
    1. Adjust Calcium dosing to Serum Calcium
    2. Check for Hypomagnesemia and replace if low
    3. Avoid Hypercalciuria (risk of Nephrolithiasis)
      1. Hypercalciuria can be evaluated with 24 hour Urine Calcium and Urine Creatinine
      2. Thiazide Diuretics may be used to reduce Hypercalciuria
  3. Preparations
    1. Calcium supplement 1.5 to 3 g/day (25 to 50 mg/kg/day) of elemental Calcium in divided doses
      1. Calcium Citrate (21% elemental Calcium) 950 mg two tablets orally three times daily
    2. Calcitriol (Vitamin D Analogue) 0.5 mcg/day
  • References
  1. Al-Azem (2012) Best Pract Res Clin Endocrinol Metab 26(4):517-22 [PubMed]
  2. Michels (2013) Am Fam Physician 88(4): 249-57 [PubMed]
  3. Sell (2022) Am Fam Physician 105(3): 289-98 [PubMed]