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Genetic and Rare Diseases Information Center (GARD)

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Pseudohypoparathyroidism type 1B


Other Names for this Disease

  • PHP1B
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Overview

What is pseudohypoparathyroidism type 1B?

Is genetic testing available for pseudohypoparathyroidism type 1B?

How is pseudohypoparathyroidism type 1B diagnosed?

What is pseudohypoparathyroidism type 1B?

Pseudohypoparathyroidism type 1B (PHP1B) is a genetic disorder that is caused by a lack of response (resistance) to parathyroid hormone (PTH) and other hormones such as thyroid-stimulating hormone (TSH). This condition is very similar to hypoparathyroidism (in which not enough PTH is produced), causing low calcium levels and high phosphate levels in the blood. Resistance to PTH in individuals with type 1B may be limited to the kidneys. The severity of the condition can vary considerably among affected individuals, even within the same family. Most individuals do not have an abnormal physical appearance and usually do not exhibit other endocrine abnormalities. In some cases, PHP1B is inherited in an autosomal dominant manner and is caused by mutations in either the GNAS or STX16 genes. In other cases, it has been shown to be sporadic (not inherited), caused by imprinting defects in the GNAS gene.[1][2][3][4] The goals of treatment are to correct the calcium deficiency and prevent complications.[3]
Last updated: 7/8/2013

Is genetic testing available for pseudohypoparathyroidism type 1B?

Yes. The Genetic Testing Registry (GTR) provides information about the genetic tests for pseudohypoparathyroidism type 1B. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
Last updated: 7/8/2013

How is pseudohypoparathyroidism type 1B diagnosed?

Pseudohypoparathyroidism (PHP) is a complex condition with extreme variability among affected individuals. The diagnosis is difficult and often delayed due to the different ways that onset of signs and symptoms can occur. Although the onset of signs and symptoms may be related to severe hypocalcemia leading to seizures or fainting episodes, the condition may only become evident during major growth spurts, when calcium requirements are higher.[5]

The diagnosis of PHP type 1B is generally based on clinical features (signs and symptoms, and physical exams) and biochemical findings from a blood test for calcium-phosphate metabolism (which includes calcium, phosphate, magnesium and parathyroid hormone (PTH) serum measurements) in order to distinguish PHP from other conditions. PHP type 1B can be distinguished from types 1A and 1C by the absence of Albright's hereditary osteodystrophy (AHO) which occurs in types 1A and 1C, and in most cases, hormonal resistance being limited to PTH. Molecular genetic testing has also become a reliable way to differentiate between the various subtypes of PHP.[5]
Last updated: 7/9/2013

References
  1. Topiwala S. Pseudohypoparathyroidism. MedlinePlus. July 2012; http://www.nlm.nih.gov/medlineplus/ency/article/000364.htm. Accessed 10/17/2012.
  2. Pseudohypoparathyroidism type 1B . Online Mendelian Inheritance of Man (OMIM). June 2010; http://omim.org/entry/603233. Accessed 10/7/2011.
  3. Mini R Abraham. Pseudohypoparathyroidism. Medscape Reference. April 23, 2013; http://emedicine.medscape.com/article/124836-overview. Accessed 7/8/2013.
  4. A. Dixit et al. Pseudohypoparathyroidism type 1b due to paternal uniparental disomy of chromosome 20q. The Journal of clinical endocrinology and metabolism. January 2013; 98(1):E103-E108 .
  5. Valentina Donghi, Stefano Mora, Ilaria Zamproni, Giuseppe Chiumello and Giovanna Weber. Pseudohypoparathyroidism, an often delayed diagnosis: a case series. Cases Journal. 2009; http://www.casesjournal.com/content/2/1/6734. Accessed 7/9/2013.


Other Names for this Disease
  • PHP1B
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.