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Pseudohypoparathyroidism

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Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology |

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Pseudohypoparathyroidism
Classification and external resources
ICD-10 E201
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 actually appropriately high (due to the hypocalcemia). Its pathogenesis has been linked to dysfunctional G Proteins (in particular, Gs alpha subunit).

TypesEdit

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 conditionsEdit

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


Causes, incidence, and risk factorsEdit

The parathyroid glands help control calcium use and removal by the body. They do this by producing parathyroid hormone, or PTH. PTH helps control calcium, phosphorus, and vitamin D levels within the blood and bone.

Persons with pseudohypoparathyroidism produce the right amount of PTH, but the body is "resistant" to its effect. This causes low blood calcium levels and high blood phosphate levels.

Pseudohypoparathyroidism is caused by abnormal genes. All forms of pseudohypoparathyroidism are very rare.

Type Ia is inherited in an autosomal dominant manner. That means only one parent needs to pass you the defective gene in order for you to develop the condition. The condition causes short stature, round face, and short hand bones, and is also called Albright's hereditary osteodystrophy.

Type Ib involves resistance to PTH only in the kidneys. Type Ib is less understood than type Ia. Type II is very similar to type I in its clinical features, but the events that take place in the kidneys are different.

Type II pseudohypoparathyroidism also involves low blood calcium and high blood phosphate levels, but persons with this form do not develop the physical characteristics seen in those with Type Ia.

All forms of pseudohypoparathyroidism are very rare.

SymptomsEdit

Symptoms are related to low levels of calcium and include:

  • Cataracts

  • Dental problems

  • Numbness

  • Seizures

  • Tetany (a collection of symptoms including muscle twitches and hand and foot spasms)

Persons with Albright's hereditary osteodystrophy may have the following symptoms:

  • Calcium deposits under the skin

  • Dimples that can replace knuckles on affected fingers

  • Round face and short neck

  • Short hand bones, especially the bone below the 4th finger

  • Short stature

Signs and testsEdit

Blood tests will be done to check calcium, phosphorus, and PTH levels. Urine tests may also be done.

Other tests may involve:

TreatmentEdit

Calcium and vitamin D supplements are prescribed to maintain proper calcium levels. If blood phosphate levels remain high, a low-phosphorus diet or medicines called phosphate binders (such as calcium carbonate or calcium acetate) may be necessary.

Expectations (prognosis)Edit

Low blood calcium in pseudohypoparathyroidism is usually milder than in other forms of hypoparathyroidism.

ComplicationsEdit

Patients with type Ia pseudohypoparathyroidism have an increased rate of other endocrine abnormalities (such as hypothyroidism and hypogonadism).

Complications of hypocalcemia associated with pseudohypoparathyroidism may include seizures and other endocrine problems, leading to lowered sexual drive and lowered sexual development, lowered energy levels, and increased weight.

Calling your health care providerEdit

Call your health care provider if you or your child have any symptoms of hypocalcemia or other features of pseudohypoparathyroidism.


See alsoEdit

ReferencesEdit

  1. Bastepe M (2008). The GNAS locus and pseudohypoparathyroidism. Adv. Exp. Med. Biol. 626: 27–40.
  2. 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.
  4. 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.
  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.
  7. OMIM 203330
  8. Aldred MA (May 2006). Genetics of pseudohypoparathyroidism types Ia and Ic. J. Pediatr. Endocrinol. Metab. 19 (Suppl 2): 635–40.

ReferencesEdit

  1. Wysolmerski JJ, Insogna KL. The parathyroid glands, hypercalcemia, and hypocalcemia. In: Kronenberg HM, Schlomo M, Polansky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, Mo: WB Saunders; 2008:chap 266.
  2. Bringhurst FR, Demay MB, Kronenberg HM. Disorders of mineral metabolism. In: Kronenberg HM, Schlomo M, Polansky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 11th ed. St. Louis, Mo: WB Saunders; 2008:chap 27.


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