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Pseudohypoparathyroidism
Classification and external resources
ICD-10 E20.1
ICD-9 275.49
DiseasesDB 10835 10851
MedlinePlus 000364
eMedicine med/1940
MeSH D011547

Pseudohypoparathyroidism is a condition associated primarily with resistance to the parathyroid hormone.[1] Patients have a low serum calcium and high phosphate, but the parathyroid hormone level (PTH) is inappropriately high. Its pathogenesis has been linked to dysfunctional G Proteins (in particular, Gs alpha subunit).

Contents

Types

Types include:

Type Description OMIM Gene
Type 1a Has a characteristic phenotypic appearance (Albright's hereditary osteodystrophy), including short fourth and fifth metacarpals and a rounded facies. It is most likely an autosomal dominant disorder.[2] It is also associated with thyroid stimulating hormone resistance.[3] 103580 GNAS1
Type 1b Lacks the physical appearance of type 1a, but is biochemically similar.[4] It is associated with a methylation defect.[5][6] 603233 GNAS1, STX16
Type 2 Also lacks the physical appearance of type 1a.[7]Since the genetic defect in type 2 is further down the signalling pathway than in type 1, there is a normal cAMP response to PTH stimulation despite the inherent abnormality in calcium regulation. 203330  ?

While biochemically similar, type 1 and 2 disease may be distinguished by the differing urinary excretion of cyclic AMP in response to exogenous PTH.

Some sources also refer to a "type 1c".[8]

Related conditions

The term pseudopseudohypoparathyroidism is used to describe a condition where the individual has the phenotypic appearance of pseudohypoparathyroidism type 1a, but is biochemically normal.

Presentation

Patients may present with features of hypocalcaemia including; carpo-pedal spasm, tetany, muscle cramps and seizures. Type 1a Pseudohypoparathyroidism is clinically manifest by blunting of fourth and fifth metacarpals (The common mnemonic "knuckle knuckle dimple dimple" refers to the blunting of the fourth and fifth metacarpal bones), short stature, obesity, developmental delay.

Biochemical Findings

References

  1. ^ Bastepe M (2008). "The GNAS locus and pseudohypoparathyroidism". Adv. Exp. Med. Biol. 626: 27–40. PMID 18372789.  
  2. ^ Online 'Mendelian Inheritance in Man' (OMIM) 103580
  3. ^ de Nanclares GP, Fernández-Rebollo E, Santin I, et al. (June 2007). "Epigenetic defects of GNAS in patients with pseudohypoparathyroidism and mild features of Albright's hereditary osteodystrophy". J. Clin. Endocrinol. Metab. 92 (6): 2370–3. doi:10.1210/jc.2006-2287. PMID 17405843. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=17405843.  
  4. ^ Online 'Mendelian Inheritance in Man' (OMIM) 603233
  5. ^ Laspa E, Bastepe M, Jüppner H, Tsatsoulis A (December 2004). "Phenotypic and molecular genetic aspects of pseudohypoparathyroidism type Ib in a Greek kindred: evidence for enhanced uric acid excretion due to parathyroid hormone resistance". J. Clin. Endocrinol. Metab. 89 (12): 5942–7. doi:10.1210/jc.2004-0249. PMID 15579741. http://jcem.endojournals.org/cgi/pmidlookup?view=long&pmid=15579741.  
  6. ^ Fröhlich LF, Bastepe M, Ozturk D, Abu-Zahra H, Jüppner H (June 2007). "Lack of Gnas epigenetic changes and pseudohypoparathyroidism type Ib in mice with targeted disruption of syntaxin-16". Endocrinology 148 (6): 2925–35. doi:10.1210/en.2006-1298. PMID 17317779. http://endo.endojournals.org/cgi/pmidlookup?view=long&pmid=17317779.  
  7. ^ Online 'Mendelian Inheritance in Man' (OMIM) 203330
  8. ^ Aldred MA (May 2006). "Genetics of pseudohypoparathyroidism types Ia and Ic". J. Pediatr. Endocrinol. Metab. 19 Suppl 2: 635–40. PMID 16789628.  

See also

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