Pseudopseudohypoparathyroidism

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Pseudopseudohypoparathyroidism
Specialty Rheumatology, medical genetics, endocrinology   OOjs UI icon edit-ltr-progressive.svg
Usual onset Before birth
DurationLifetime
Differential diagnosis Pseudohypoparathyroidism, hypoparathyroidism, Albright's hereditary osteodystrophy
Treatment Treatments to reduce symptoms, genetic counseling

Pseudopseudohypoparathyroidism (PPHP) is an inherited disorder, [1] named for its similarity to pseudohypoparathyroidism in presentation. It is more properly Albright hereditary osteodystrophy, although without resistance of parathyroid hormone (PTH), as frequently seen in that affliction. The term is used to describe a condition where the individual has the phenotypic appearance of pseudohypoparathyroidism type 1a, but has (unexpected for the phenotype) normal labs, including calcium and PTH. [2]

Contents

It can be considered a variant of Albright hereditary osteodystrophy (pseudohypoparathyroidism type 1A), [3] as they present with the same constellation of signs and symptoms, including short stature, brachydactyly, subcutaneous calcification, and obesity.

Presentation

Pseudopseudohypoparathyroidism can be best understood by comparing it to other conditions:

ConditionAppearance PTH levels Calcitriol Calcium Phosphates Imprinting
Hypoparathyroidism NormalLowLowLowHighNot applicable
Pseudohypoparathyroidism Type 1A Skeletal defects HighLowLowHighGene defect from mother (GNAS1)
Type 1BNormalHighLowLowHighGene defect from mother (GNAS1 and STX16)
Type 2NormalHighLowLowHigh ?
Pseudopseudohypoparathyroidism Skeletal defects NormalNormalNormal [4] NormalGene defect from father

Hormone resistance is not present in pseudopseudohypoparathyroidism. [5] Short stature may be present. Obesity is less common in pseudopseudohypoparathyroidism than in pseudohypoparathyroidism. [6] Osteoma cutis may be present. [7]

Genetics

Protein GNAS Protein GNAS PDB 1azs.png
Protein GNAS

A male with pseudohypoparathyroidism has a 50% chance of passing on the defective GNAS gene to his children, although in an imprinted, inactive form. Any of his children receiving this gene will have pseudopseudohypoparathyroidism. Any of his daughters that have pseudopseudohypoparathyroidism may in turn pass along pseudohypoparathyroidism 1A to her children, as the imprinting pattern on the inherited paternal gene will be changed to the maternal pattern in the mother's ovum during meiosis. The gene will be reactivated in any children who inherit it.[ citation needed ]

Pseudopseudohypoparathyroidism and pseudohypoparathyroidism both involve the same GNAS gene, [8] but pseudopseudohypoparathyroidism has normal calcium homeostasis because of the normal maternal allele in the kidney. [9]

Pathophysiology

The GNAS1 gene involved in both pseudohypoparathyroidism type 1a and pseudopseudohypoparathyroidism is greatly affected by imprinting. When a father who has pseudohypoparathyroidism undergoes spermatogenesis, imprinting of the GNAS1 gene inactivates both copies of his genes: one will be functional, and the other will be defective. Tissues in the body will re-activate different copies of the GNAS1 gene selectively; the kidneys will selectively activate the (functional) maternal copy while keeping the (defective) paternally-derived gene imprinted and inactive, even in normal individuals. Since the maternally-derived GNAS1 gene is functional, renal handling of calcium and phosphate is normal, and homeostasis is maintained in pseudopseudohypoparathyroidism. However, the rest of the tissues will instead selectively display the defective gene, resulting in haploinsufficiency of the GNAS1 product in most tissues, and giving the phenotype of pseudohypoparathyroidism type 1a. As a result, there is also a normal response of urinary cAMP to PTH, and normal serum PTH.[ citation needed ]

Diagnosis

The diagnosis is based on the presence of the Albright hereditary osteodystrophy pseudotype but without the PTH resistance. Blood tests including calcium, phosphate, and PTH will exclude other forms of pseudohypoparathyroidism. X-rays may reveal a short fourth metacarpal. Genetic testing can confirm the diagnosis by showing GNAS gene mutation. [1]

Treatment

Treatments focuses on symptoms, with genetic counseling recommended. [10]

History

It was characterized in 1952 by Fuller Albright as "pseudo-pseudohypoparathyroidism" (with hyphen). [11] [12]

See also

Related Research Articles

<span class="mw-page-title-main">Parathyroid gland</span> Endocrine gland

Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes parathyroid hormone in response to low blood calcium, which plays a key role in regulating the amount of calcium in the blood and within the bones.

<span class="mw-page-title-main">Parathyroid hormone</span> Mammalian protein found in humans

Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney, and intestine.

<span class="mw-page-title-main">Calcium metabolism</span> Movement and regulation of calcium ions in and out of the body

Calcium metabolism is the movement and regulation of calcium ions (Ca2+) in (via the gut) and out (via the gut and kidneys) of the body, and between body compartments: the blood plasma, the extracellular and intracellular fluids, and bone. Bone acts as a calcium storage center for deposits and withdrawals as needed by the blood via continual bone remodeling.

Disorders of calcium metabolism occur when the body has too little or too much calcium. The serum level of calcium is closely regulated within a fairly limited range in the human body. In a healthy physiology, extracellular calcium levels are maintained within a tight range through the actions of parathyroid hormone, vitamin D and the calcium sensing receptor. Disorders in calcium metabolism can lead to hypocalcemia, decreased plasma levels of calcium or hypercalcemia, elevated plasma calcium levels.

<span class="mw-page-title-main">Parathyroid hormone-related protein</span> Mammalian protein

Parathyroid hormone-related protein (PTHrP) is a proteinaceous hormone and a member of the parathyroid hormone family secreted by mesenchymal stem cells. It is occasionally secreted by cancer cells. However, it also has normal functions in bone, teeth, vascular tissues and other tissues.

<span class="mw-page-title-main">Parathyroid chief cell</span>

Parathyroid chief cells are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells. It is perceived that oxyphil cells may be derived from chief cells at puberty, as they are not present at birth like chief cells.

Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany, and several other symptoms. It is a very rare disease. The condition can be inherited, but it is also encountered after thyroid or parathyroid gland surgery, and it can be caused by immune system-related damage as well as a number of rarer causes. The diagnosis is made with blood tests, and other investigations such as genetic testing depending on the results. The primary treatment of hypoparathyroidism is calcium and vitamin D supplementation. Calcium replacement or vitamin D can ameliorate the symptoms but can increase the risk of kidney stones and chronic kidney disease. Additionally, medications such as recombinant human parathyroid hormone or teriparatide may be given by injection to replace the missing hormone.

<span class="mw-page-title-main">Hyperparathyroidism</span> Increase in parathyroid hormone levels in the blood

Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands or as response to external stimuli. Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood calcium excreted from the bones and flowing into the blood stream in response to increased production of parathyroid hormone. In healthy people, when blood calcium levels are high, parathyroid hormone levels should be low. With long-standing hyperparathyroidism, the most common symptom is kidney stones. Other symptoms may include bone pain, weakness, depression, confusion, and increased urination. Both primary and secondary may result in osteoporosis.

<span class="mw-page-title-main">Primary hyperparathyroidism</span> Medical condition

Primary hyperparathyroidism is a medical condition where the parathyroid gland produce excess amounts of parathyroid hormone (PTH). The symptoms of the condition relate to the resulting elevated serum calcium (hypercalcemia), which can cause digestive symptoms, kidney stones, psychiatric abnormalities, and bone disease.

<span class="mw-page-title-main">Osteitis fibrosa cystica</span> Medical condition

Osteitis fibrosa cystica is a skeletal disorder resulting in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue, and the formation of cyst-like brown tumors in and around the bone. Osteitis fibrosis cystica (OFC), also known as osteitis fibrosa, osteodystrophia fibrosa, and von Recklinghausen's disease of bone, is caused by hyperparathyroidism, which is a surplus of parathyroid hormone from over-active parathyroid glands. This surplus stimulates the activity of osteoclasts, cells that break down bone, in a process known as osteoclastic bone resorption. The hyperparathyroidism can be triggered by a parathyroid adenoma, hereditary factors, parathyroid carcinoma, or renal osteodystrophy. Osteoclastic bone resorption releases minerals, including calcium, from the bone into the bloodstream, causing both elevated blood calcium levels, and the structural changes which weaken the bone. The symptoms of the disease are the consequences of both the general softening of the bones and the excess calcium in the blood, and include bone fractures, kidney stones, nausea, moth-eaten appearance in the bones, appetite loss, and weight loss.

<span class="mw-page-title-main">Albright's hereditary osteodystrophy</span> Form of osteodystrophy and a rare human disease

Albright's hereditary osteodystrophy is a form of osteodystrophy, and is classified as the phenotype of pseudohypoparathyroidism type 1A; this is a condition in which the body does not respond to parathyroid hormone.

Pseudohypoparathyroidism is a rare autosomal dominant genetic condition associated primarily with resistance to the parathyroid hormone. Those with the condition 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. Pseudohypoparathyroidism is a very rare disorder, with estimated prevalence between 0.3 and 1.1 cases per 100,000 population depending on geographic location.

<span class="mw-page-title-main">GNAS complex locus</span> Gene locus

GNAS complex locus is a gene locus in humans. Its main product is the heterotrimeric G-protein alpha subunit Gs-α, a key component of G protein-coupled receptor-regulated adenylyl cyclase signal transduction pathways. GNAS stands for Guanine Nucleotide binding protein, Alpha Stimulating activity polypeptide.

There are two known parathyroid hormone receptors in mammals termed PTH1R and PTH2R. These receptors bind parathyroid hormone and are members of the GPCR family of transmembrane proteins.

<span class="mw-page-title-main">Jansen's metaphyseal chondrodysplasia</span> Rare genetic disorder involving dwarfism and endocrine symptoms

Jansen's metaphyseal chondrodysplasia (JMC) is a disease that results from ligand-independent activation of the type 1 (PTH1R) of the parathyroid hormone receptor, due to one of three reported mutations.

<span class="mw-page-title-main">Parathyroid hormone 1 receptor</span> Protein-coding gene in the species Homo sapiens

Parathyroid hormone/parathyroid hormone-related peptide receptor, also known as parathyroid hormone 1 receptor (PTH1R), is a protein that in humans is encoded by the PTH1R gene. PTH1R functions as a receptor for parathyroid hormone (PTH) and for parathyroid hormone-related protein (PTHrP), also called parathyroid hormone-like hormone (PTHLH).

<span class="mw-page-title-main">Parathyroid hormone 2 receptor</span> Protein-coding gene in the species Homo sapiens

Parathyroid hormone 2 receptor is a protein that in humans is encoded by the PTH2R gene.

Familial hypocalciuric hypercalcemia (FHH) is an inherited condition that can cause hypercalcemia, a serum calcium level typically above 10.2 mg/dL; although uncommon. It is also known as familial benign hypocalciuric hypercalcemia (FBHH) where there is usually a family history of hypercalcemia which is mild, a urine calcium to creatinine ratio <0.01, and urine calcium <200 mg/day.

<span class="mw-page-title-main">Osteoma cutis</span> Medical condition

Osteoma cutis is a cutaneous condition characterized by the presence of bone within the skin in the absence of a preexisting or associated lesion. Osteoma cutis often manifests as solid, varying-sized, skin-colored subcutaneous nodules.

Archibald's sign refers to a feature in the hand characterized by a shortening of the fourth or/and fifth metacarpals when the fist is clenched.

References

  1. 1 2 "Pseudopseudohypoparathyroidism | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Retrieved 2017-01-31.
  2. ↑ Tafaj, O.; Jüppner, H. (April 2017). "Pseudohypoparathyroidism: one gene, several syndromes". Journal of Endocrinological Investigation . 40 (4): 347–356. doi:10.1007/s40618-016-0588-4. ISSN   1720-8386. PMID   27995443. S2CID   20811779.
  3. ↑ Solomon SS, Kerlan RM, King LE, Jones GM, Hashimoto K (January 1975). "Pseudopseudohypoparathyroidism with fibrous dysplasia". Arch Dermatol. 111 (1): 90–3. doi:10.1001/archderm.111.1.90. PMID   1119829.
  4. ↑ Shahid Hussain; Sharif Aaron Latif; Adrian Hall (1 July 2010). Rapid Review of Radiology. Manson Publishing. pp. 262–. ISBN   978-1-84076-120-7 . Retrieved 30 October 2010.
  5. ↑ Mouallem M, Shaharabany M, Weintrob N, et al. (February 2008). "Cognitive impairment is prevalent in pseudohypoparathyroidism type Ia, but not in pseudopseudohypoparathyroidism: possible cerebral imprinting of Gsalpha". Clin. Endocrinol. 68 (2): 233–9. doi:10.1111/j.1365-2265.2007.03025.x. PMID   17803690. S2CID   23654317.
  6. ↑ Long DN, McGuire S, Levine MA, Weinstein LS, Germain-Lee EL (March 2007). "Body mass index differences in pseudohypoparathyroidism type 1a versus pseudopseudohypoparathyroidism may implicate paternal imprinting of Galpha(s) in the development of human obesity". J. Clin. Endocrinol. Metab. 92 (3): 1073–9. doi: 10.1210/jc.2006-1497 . PMID   17164301.
  7. ↑ Jeong KH, Lew BL, Sim WY (May 2009). "Osteoma cutis as the presenting feature of albright hereditary osteodystrophy associated with pseudopseudohypoparathyroidism". Ann Dermatol. 21 (2): 154–8. doi:10.5021/ad.2009.21.2.154. PMC   2861203 . PMID   20523775. Archived from the original on 2012-03-15. Retrieved 2010-10-30.
  8. ↑ Lebrun M, Richard N, Abeguilé G, et al. (June 2010). "Progressive osseous heteroplasia: a model for the imprinting effects of GNAS inactivating mutations in humans". J. Clin. Endocrinol. Metab. 95 (6): 3028–38. doi: 10.1210/jc.2009-1451 . PMID   20427508.
  9. ↑ David Terris; Christine G. Gourin (15 November 2008). Thyroid and Parathyroid Diseases: Medical and Surgical Management. Thieme. pp. 193–. ISBN   978-1-58890-518-5 . Retrieved 30 October 2010.
  10. ↑ Simpson, Catherine (21 March 2015). "Pseudopseudohypothyroidism" (PDF). The Lancet. 385 (9973): 1123. doi:10.1016/s0140-6736(14)61640-8. PMID   25484027. S2CID   208793989.
  11. ↑ Philip R. Beales; I. Sadaf Farooqi; Stephen O'Rahilly (12 September 2008). The genetics of obesity syndromes. Oxford University Press US. pp. 91–. ISBN   978-0-19-530016-1 . Retrieved 30 October 2010.
  12. ↑ ALBRIGHT F, FORBES AP, HENNEMAN PH (1952). "Pseudo-pseudohypoparathyroidism". Trans. Assoc. Am. Physicians. 65: 337–50. PMID   13005676.
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