Pseudohypoparathyroidism

Condition associated primarily with resistance to the parathyroid hormone

Aetiology

  • Genetic defect - dysfunction of Gs alpha subunit (GNAS 1 gene)

Pathophysiology

  • End organ resistance to PTH due to mutation of the Gs⍺-protein, which is coupled to the PTH receptor

Clinical presentation

  • Bone abnormalities (McCune Albright)
  • Obesity
  • Subcutaneous calcification
  • Learning disability
  • Brachdactyly (shortened 4th metacarpal)

Investigations

  • Bloods - calcium will be low but PTH concentrations are elevated due to PTH resistance

Pseudo-pseudohypoparathyroidism

  • Describes the phenotypic defects of pseudohypoparathyroidism (Albright's herditary osteodystrophy) but without any abnormalities in calcium metabolism
  • Individuals with this condition may share the same gene defect as those with pseudohypoparathyroidism and be members of the same families