Hypoparathyroidism

Hypoparathyroidism is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Hypoparathyroidism occurs secondary to a deficiency in parathyroid hormone (PTH)
  • Pseudohypoparathyroidism occurs secondary to end-organ unresponsiveness to PTH
  • PTH:
    • Decreases urinary Ca2+ loss
    • Increases urinary PO4 loss
    • Stimulates vitamin D conversion from 25(OH)-D to 1,25(OH)2-D in kidney
    • Liberates Ca2+ and PO4 from bone
  • Hypocalcemia is the major metabolic derangement
  • Calcitonin:
    • Promotes deposition of Ca2+ and PO4 into bone (produced primarily in C cells in thyroid)
  • Magnesium:
    • Cofactor in production of PTH
    • Essential for action of PTH in target tissues
  • Hypoparathyroidism:
    • Primary failure of the parathyroid gland (may have associated Addison disease)
  • Pseudohypoparathyroidism:
    • Tissue unresponsiveness with elevated PTH levels
    • Associated with hypothyroidism and hypogonadism
  • Genetics:
    • Congenital absence
    • DiGeorge syndrome:
      • Hypoparathyroidism
      • Thymic dysplasia
      • Severe immunodeficiency
    • Wilson disease:
      • Destruction of gland owing to copper deposition
    • Autoimmune polyglandular syndrome type I
      • Hypoparathyroidism
      • Adrenal insufficiency
      • Mucocutaneous candidiasis
    • Albright syndrome (hereditary osteodystrophy):
      • Short stature
      • Obesity
      • Round face
      • Short neck
      • Short 4th and 5th metacarpals and metatarsals (type I pseudohypoparathyroidism)

Etiology

  • Failure of parathyroid gland:
    • Autoimmune destruction
    • Surgical interruption of blood supply or gland removal
    • Radiation damage
    • Hypomagnesemia (PTH cofactor)
  • End-organ unresponsiveness to PTH

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