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Pseudohypoparathyroidism [PHP]

= resistance to PTH due to dysfxal G Protein [due to imprinting defects in GNAS1: OMIM#139320], resulting in lo Ca, hi PO4, hi PTH (appropriate);
  • T1a: phenotype of Albright hereditary osteodystrophy [AHO] [OMIM#103580]
    • brachydactyly: short 4th,5th metacarpals, subcut calcifications, other skeletal anomalies
    • short stature, obesity, round facies
    • sometimes mental retardation
    • usu. AD
      • NB: do not confuse with: [McCune-]Albright syndrome: [OMIM#174800] activating GNAS1 mutation: polyostotic fibrous dysplasia: skeletal abnmlties, endocrine abnmlties: usu precocious puberty in females [occas males], also: hyperthyroidism, gigantism, Cushing's
  • T1b: nml phenotype
  • T2: nml phenotype, but differing urinary excretion of cAMP in response to exogenous PTH
  • Pseudopseudohypoparathyroidism [PPHP]: T1a phenotype but nml biochem