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hypoparathyroidism

Etiology: 1) inadvertant surgical removal of parathyroid glands during surgical thyroidectomy* 2) parathyroidectomy* for hyperparathyroidism 3) post-irradiation of the neck 4) autoimmune disease - NALP5 autoantibodies 5) congenital disorders, genetic disorders 6) infiltrative diseases a) hemochromatosis b) Wilson's disease c) thalassemia 7) Mg+2 deficiency diminishes PTH release & effect 8) DiGeorge syndrome * removal of all 4 parathyroids or impairment of their blood supply is required for permanent hypoparathyroidism; otherwise hypoparathyroidism & hypocalcemia is transient of duration days to weeks Clinical manifestations: - signs & symptoms of hypocalcemia - mostly paresthesias, muscle cramps - most prominent in patients with rapid drop in serum calcium after surgery - tetany, seizures & prolonged QTc [9] Laboratory: 1) serum calcium & serum magnesium [2] 2) ionized calcium 3) 24 hour urine calcium & calcium/creatinine in urine (assess hypercalciuria) 4) intact parathyroid hormone (fasting) 5) serum phosphate may be elevated (target < 6.5 mg/dL) [2] 5) NALP5 autoantibody in serum (no Loinc) Special laboratory: - electrocardiogram - prolonged QT interval with more severe hypocalcemia - routine renal ultrasound of low yield in asymptomatic patients (5%) [8] - detect asymptomatic nephrolithiasis or nephrocalcinosis Radiology: - bone-mineral density testing - evaluate indication for parathyroidectomy - risk factors similar to general population in asymptomatic patients [8] Management: 1) supplemental calcium a) oral calcium will increase serum calcium within minutes in patients with inadvertant surgical removal of parathyroid glands during surgical thyroidectomy [2,3] b) 1-2 g of elemental calcium PO TID (initially) c) 0.5-1 g PO TID with meals (maintenance) d) goals are to maintain serum Ca+2 in low-normal range, 8.0-8.5 mg/dL & avoid hypercalciuria, urinary calcium to < 300 mg/24 hours [2] - decrease or increase oral calcium to meet these goals e) IV calcium (CaCl) may be indicated in patients with tetany or QT prolongation [2,3] f) serum magnesium must be corrected to 2.0 mg/dL or higher to correct hypercalcemia [2] 2) vitamin D or 1,25-dihydroxyvitamin D3 (calcitriol) a) calcitriol (preferred agent) 1] 0.25 ug PO QD (initially) 2] 0.5-2.0 mg PO QD (maintenance) 3] serum calcium increases over several days [2,3] 4] dose may be increased at 2-4 week intervals b) Vitamin D 1] requires weeks to achieve full effect 2] 50,000 IU (1.25 mg) PO QD (initially) 3] 50,000-100,000 IU PO QD (maintenance) 4] dose may be increased at 4-6 week intervals 3) if hypercalcemia develops, stop vitamin D, then restart at a lower dose 4) calcium acetate (Phoslo) as needed to maintain serum phosphorus < 6.5 mg/dL 5) hydrochlorothiazide 50 mg PO QD to reduce calciuria 6) important NOT to fully normalize serum calcium because of risk of nephrolithiasis (absence of PTH renal effect) [2] 7) teriparatide not FDA-approved for use in hypoparathyroidism - safety & effectiveness not established [2]

Related

hyperparathyroidism lymphedema-hypoparathyroidism syndrome

Specific

autosomal dominant hypoparathyroidism; familial isolated hypoparathyroidism; autosomal dominant hypocalcemia DiGeorge syndrome; velocardiofacial syndrome; pharyngeal pouch syndrome hypoparathyroidism, sensorineural deafness & renal dysplasia (HDR syndrome)

General

chronic endocrine disease hypocalcemia parathyroid disease

Database Correlations

OMIM correlations

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 472, 495-496
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 15, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2009, 2012, 2015, 2018.
  3. Khan MI, Waguespack SG, Hu MI. Medical management of postsurgical hypoparathyroidism. Endocr Pract. 2011 Mar-Apr;17 Suppl 1:18-25 PMID: 21134871
  4. Shoback D Clinical practice. Hypoparathyroidism. N Engl J Med. 2008 Jul 24;359(4):391-403 PMID: 18650515
  5. Al-Azem H, Khan AA. Hypoparathyroidism. Best Pract Res Clin Endocrinol Metab. 2012 Aug;26(4):517-22. Review. PMID: 22863393
  6. Brandi ML, Bilezikian JP, Shoback D et al Management of Hypoparathyroidism: Summary Statement and Guidelines. J Clin Endocrinol Metab. 2016 Jun;101(6):2273-83. Review. PMID: 26943719
  7. Gafni RI, Collins MT Hypoparathyroidism. N Engl J Med 2019; 380:1738-1747. May 2, 2019 PMID: 31042826 https://www.nejm.org/doi/full/10.1056/NEJMcp1800213
  8. Reid LJ, Muthukrishnan B, Patel D, Seckl JR, Gibb FW. Predictors of nephrolithiasis, osteoporosis, and mortality in primary hyperparathyroidism. J Clin Endocrinol Metab 2019 Sep 1; 104:3692-3700 PMID: 30916764 https://academic.oup.com/jcem/article-abstract/104/9/3692/5419224?redirectedFrom=fulltext
  9. NEJM Knowledge+ Endocrinology