II. Epidemiology
- Rare
III. Pathophysiology
- Low Parathyroid Hormone (PTH) levels
- Inadequate PTH Secretion OR
- Activating mutation of CASR gene
- Low PTH results in Hypocalcemia
- Renal Calcium loss (Hypercalciuria)
- Decreased Osteoclast activity
- Decreased 1,25 - Dihydroxyvitamin D synthesis
IV. Causes
- Hereditary
- Idiopathic Hypoparathyroidism
- DiGeorge Syndrome
- Pseudohypoparathyroidism (rare)
- Tissue-resistance to PTH
- Hypoparathyroidism despite increased PTH levels
- Acquired
- Anterior neck surgery (75% of Hypoparathyroidism cases)
- Thyroidectomy with operative Parathyroid removal (most common cause)
- Post-surgical monitoring includes Serum Calcium and PTH levels
- Radiation (rare)
- Hemochromatosis
- Anterior neck surgery (75% of Hypoparathyroidism cases)
- Autoimmune Syndrome
- Multiple endocrine deficiency syndrome
- Adrenal, Ovarian and Parathyroid failure
- Mucocutaneous Candidiasis
- Alopecia
- Vitiligo
- Pernicious Anemia
V. Symptoms and signs
- See Hypocalcemia
VI. Labs
- See Hypocalcemia
- Intact Parathyroid Hormone (PTH) Low or Normal
- Corrected Serum Calcium or Ionized Calcium Low
- Serum Magnesium Normal
VII. Differential Diagnosis
- See Hypocalcemia
VIII. Evaluation
- See Hypocalcemia for protocol
IX. Management: Calcium Replacement
- See Calcium Replacement
-
General
- Adjust Calcium dosing to Serum Calcium
- Check for Hypomagnesemia and replace if low
- Avoid Hypercalciuria (risk of Nephrolithiasis)
- Hypercalciuria can be evaluated with 24 hour Urine Calcium and Urine Creatinine
- Thiazide Diuretics may be used to reduce Hypercalciuria
- Preparations
- Calcium supplement 1.5 to 3 g/day (25 to 50 mg/kg/day) of elemental Calcium in divided doses
- Calcium Citrate (21% elemental Calcium) 950 mg two tablets orally three times daily
- Calcitriol (Vitamin D Analogue) 0.5 mcg/day
- Calcium supplement 1.5 to 3 g/day (25 to 50 mg/kg/day) of elemental Calcium in divided doses