Mutations in the Gs alpha gene causing hormone resistance

Targeted silencing of GNAS in a human model of osteoprogenitor cells results in the deregulation of the osteogenic differentiation program

Introduction

The dysregulation of cell fate toward osteoprecursor cells associated with most GNAS-based disorders may lead to episodic de novo extraskeletal or ectopic bone formation in subcutaneous tissues. The bony lesion distribution suggests the involvement of abnormal differentiation of mesenchymal stem cells (MSCs) and/or more committed precursor cells. Data from transgenic mice support the concept that GNAS is a crucial factor in regulating lineage switching between osteoblasts (OBs) and adipocyte fates. The mosaic nature of heterotopic bone lesions suggests that GNAS genetic defects provide a sensitized background for ectopic osteodifferentiation, but the underlying molecular mechanism remains largely unknown.

Methods

The effect of GNAS silencing in the presence and/or absence of osteoblastic stimuli was evaluated in the human L88/5 MSC line during osteodifferentiation. A comparison of the data obtained with data coming from a bony lesion from a GNAS-mutated patient was also provided.

Results

Our study adds some dowels to the current fragmented notions about the role of GNAS during osteoblastic differentiation, such as the premature transition of immature OBs into osteocytes and the characterization of the differences in the deposed bone matrix.

Conclusion

We demonstrated that our cell model partially replicates the in vivo behavior results, resulting in an applicable human model to elucidate the pathophysiology of ectopic bone formation in GNAS-based disorders.

Tertiary hyperparathyroidism in patients with pseudohypoparathyroidism type 1a

Pseudohypoparathyroidism type 1a (PHP1a) is a genetic disorder caused by heterozygous loss-of-function mutations on the maternal allele of the GNAS gene. Patients with PHP1a predominantly exhibit parathyroid hormone (PTH) resistance and physical features of Albright's hereditary osteodystrophy. We report two unrelated cases with PHP1a who developed tertiary hyperparathyroidism (HPT). Molecular analyses of the GNAS gene identified a previously known heterozygous 4-bp deletion (c. 565_568delGACT) in exon 7 in case 1 and a novel heterozygous missense mutation (p.Lys233Glu) in exon 9 in case 2. Both patients developed tertiary HPT associated with hyperfunctioning parathyroid glands during long-term treatment of hypocalcemia. Case 1 had severe osteoporosis and underwent parathyroidectomy. Case 2 was asymptomatic with no evidence of bone diseases associated with tertiary HPT. PHP1a patients are at risk of developing tertiary HPT and should be treated with sufficient doses of calcium and vitamin D to achieve serum PTH levels within the mid - normal to double the upper limit of the normal range, regardless of serum calcium levels.

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Pseudohypoparathyroidism type 1a induces tertiary hyperparathyroidism.

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Tertiary hyperparathyroidism can be complicated by hungry bone syndrome.

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Serum PTH levels should be within doubled the upper limit of normal.

Early Diagnosis of Pseudohypoparathyroidism before the Development of Hypocalcemia in a Young Infant

Pseudohypoparathyroidism (PHP) is a rare, heterogeneous disorder characterized by end-organ resistance to parathyroid hormone (PTH). PTH resistance causes elevated PTH levels, hypocalcemia, and hyperphosphatemia. Since hypocalcemia causes life-threatening events, early diagnosis is crucial. However, the diagnosis of PHP is elusive during infancy because PHP is usually diagnosed with hypocalcemia-induced symptoms, which develop later in childhood when calcium requirements increase. A 1-month-old girl was referred to our clinic for elevated thyroid-stimulating hormone (TSH) levels on newborn screening. When measured 1 month after levothyroxine treatment, her TSH level normalized. At 4-months-old, multiple hard nodules were noted on her trunk. A punch skin biopsy revealed osteoma cutis associated with Albright’s hereditary osteodystrophy, a major characteristic of PHP. We performed targeted sanger sequencing of the GNAS gene and detected a heterozygous variant c.150dupA (p.Ser51Ilefs*3) in both the proband and her mother, causing frameshift and premature termination mutations. The patient was diagnosed with PHP Ia when she had normal calcium, phosphorous, and PTH levels. We report the early diagnosis of PHP Ia without hypocalcemia. It emphasizes the importance of meticulous physical examination in patients with congenital hypothyroidism.

New insights into thyroid dysfunction in patients with inactivating parathyroid hormone/parathyroid hormone-related protein signalling disorder (the hormonal and ultrasound aspects): One-centre preliminary results

OBJECTIVE

This study aimed to present the spectrum of thyroid dysfunction, including hormonal and ultrasound aspects, in a cohort of paediatric and adult patients diagnosed with inactivating parathyroid hormone (PTH)/PTH-related protein signalling disorders 2 and 3 (iPPSD).

METHODS

The medical records of 31 patients from 14 families diagnosed with iPPSD between 1980 and 2021 in a single tertiary unit were retrospectively analysed. Biochemical, hormonal, molecular, and ultrasonographic parameters were assessed.

RESULTS

In total, 28 patients from 13 families were diagnosed with iPPSD2 (previously pseudohypoparathyroidism [PHP], PHP1A, and pseudo-PHP) at a mean age of 12.2 years (ranging from infancy to 48 years), and three patients from one family were diagnosed with iPPSD3 (PHP1B). Thyroid dysfunction was diagnosed in 21 of the 28 (75%) patients with iPPSD2. Neonatal screening detected congenital hypothyroidism (CH) in 4 of the 20 (20%) newborns. The spectrum of thyroid dysfunction included: CH, 3/21 (14.2%); CH and autoimmune thyroiditis with nodular goitre, 1/21 (4.8%); subclinical hypothyroidism, 10/21 (47.6%); subclinical hypothyroidism and nodular goitre, 1/21 (4.8%); primary hypothyroidism, 4/21 (19%); and autoimmune thyroiditis (Hashimoto and Graves' disease), 2/21 (9.6%). Thyroid function was normal in 7 of the 28 (25%) patients with iPPSD2 and in all patients with iPPSD3. Ultrasound evaluation of the thyroid gland revealed markedly inhomogeneous echogenicity and structure in all patients with thyroid dysfunction. Goitre was found in three patients.

CONCLUSION

The spectrum of thyroid dysfunction in iPPSD ranges from CH to autoimmune thyroiditis and nodular goitre. Ultrasonography of the thyroid gland may reveal an abnormal thyroid parenchyma.

Bone turnover markers are associated with the PTH levels in different subtypes of pseudohypoparathyroidism type 1 patients

OBJECTIVE

Bone responsiveness to parathyroid hormone (PTH) in different subtypes of pseudohypoparathyroidism type 1 (PHP1) remains controversial. We aimed to investigate this phenomenon using bone turnover markers (BTMs) in a large cohort of PHP1 patients.

DESIGN

Retrospective study.

PATIENTS

Sixty-three PHP1 patients diagnosed by molecular analysis were used as subjects, and 48 sex- and age-matched patients with nonsurgical hypoparathyroidism (NS-HP) were used for comparison.

MEASUREMENTS

Bone turnover markers, alkaline phosphatase (ALP), C-terminal telopeptide of type I collagen (β-CTX) and related parameters in PHP1 were compared among different subtypes and with NS-HP.

RESULTS

Among all the PHP1 patients (15 PHP1A, 14 familial 1B and 34 sporadic 1B), 23.8% had elevated baseline BTM levels. No significant difference was found in the β-CTX levels among different subtypes. The β-CTX level was positively correlated with the PTH level for all PHP1, PHP1B and PHP1A patients (B = 0.001, 0.001 and 0.004, respectively; all p < .05). The BTM levels of PHP1 patients were significantly higher than those of NS-HP patients (β-CTX: 0.56 ng/ml vs. 0.20 ng/ml, p = .001; ALP: 105 U/L vs. 72 U/L, p = .001). The serum β-CTX levels in different PHP1 subtypes were all significantly higher than those in NS-HP patients in adults. Among the 22 followed up patients, changes in BTMs were associated with changes in PTH (β-CTX: r = .507, p = .023; ALP: r = .475, p = .034).

CONCLUSIONS

Bone tissues respond to PTH in different PHP1 subtypes, and it is reasonable to monitor and normalize PTH and BTMs in addition to the serum and urinary calcium levels in the follow-up of PHP1 patients.

Optimizing Fertility in Primary Ovarian Insufficiency: Case Report and Literature Review

Primary ovarian insufficiency (POI) is a clinical spectrum of ovarian dysfunction. Overt POI presents with oligo/amenorrhea and hypergonadotropic hypogonadism before age 40 years. Overt POI involves chronic health problems to include increased morbidity and mortality related to estradiol deficiency and the associated osteoporosis and cardiovascular disease as well as psychological and psychiatric disorders related to the loss of reproductive hormones and infertility. Presently, with standard clinical testing, a mechanism for Overt POI can only be identified in about 10% of cases. Now discovery of new mechanisms permits an etiology to be identified in a research setting in 25-30% of overt cases. The most common genetic cause of Overt POI is premutation in FMR1. The associated infertility is life altering. Oocyte donation is effective, although many women prefer to conceive with their own ova. Surprisingly, the majority who have Overt POI still have detectable ovarian follicles (70%). The major mechanism of follicle dysfunction in Overt POI has been histologically defined by a prospective NIH study: inappropriate follicle luteinization due to the tonically elevated serum LH levels. A trial of physiologic hormone replacement therapy, clinically proven to suppress the elevated LH levels in these women, may improve follicle function and increase the chance of ovulation. Here, we report the case of a woman with Overt POI diagnosed at age 35 years. To attempt pregnancy, she elected a trial of intrauterine insemination (IUI) in conjunction with follicle monitoring and physiologic hormone replacement therapy. She conceived on the eighth cycle of treatment and delivered a healthy baby. Our report calls for a concerted effort to define the best methods by which to optimize fertility for women who have POI.

Hypoparathyroidism in Pregnancy and Lactation: Current Approach to Diagnosis and Management

Background: Hypoparathyroidism is an uncommon endocrine disorder. During pregnancy, multiple changes occur in the calcium-regulating hormones, which may affect the requirements of calcium and active vitamin D during pregnancy in patients with hypoparathyroidism. Close monitoring of serum calcium during pregnancy and lactation is ideal in order to optimize maternal and fetal outcomes. In this review, we describe calcium homeostasis during pregnancy in euparathyroid individuals and also review the diagnosis and management of hypoparathyroidism during pregnancy and lactation. Methods: We searched the MEDLINE, CINAHL, EMBASE, and Google scholar databases from 1 January 1990 to 31 December 2020. Case reports, case series, book chapters, and clinical guidelines were included in this review. Conclusions: During pregnancy, rises in 1,25-dihydroxyvitamin D (1,25-(OH)2-D3) and PTH-related peptide result in suppression of PTH and enhanced calcium absorption from the bowel. In individuals with hypoparathyroidism, the requirements for calcium and active vitamin D may decrease. Close monitoring of serum calcium is advised in women with hypoparathyroidism with adjustment of the doses of calcium and active vitamin D to ensure that serum calcium is maintained in the low-normal to mid-normal reference range. Hyper- and hypocalcemia should be avoided in order to reduce the maternal and fetal complications of hypoparathyroidism during pregnancy and lactation. Standard of care therapy consisting of elemental calcium, active vitamin D, and vitamin D is safe during pregnancy.

Symptomatic spinal cord compression: an uncommon symptom in pseudohypoparathyroidism

We describe symptomatic spinal cord compression associated with pseudohypoparathyroidism (PHP) in a young female patient and reviewed similar cases previously reported in the literature. The characteristics of these cases were analyzed from etiology, clinical subtypes, symptoms, treatment, and prognosis. Neurological examination revealed functional upper extremities with bilateral lower extremity paraplegia. Laboratory tests showed hypocalcemia, hyperphosphatemia, and elevated parathyroid hormone; high-throughput sequencing showed a heterozygous GNAS mutation in exon 12, specifically c.1006C > T (p.R336W). Imaging findings showed multilevel spinal stenosis with significant spinal cord compression at the T2-T3 level. Seventeen cases with similar characteristics were reviewed. We found that the primary clinical manifestation of these patients was bilateral lower extremity spastic paraplegia. Multilevel spinal cord compression was commonly observed, especially at the lower cervical and upper thoracic spinal cord. Most of the patients had poor surgical treatment outcome and prognosis. Clinicians should be aware of paraplegia due to spinal cord compression as a rare neurological complication in patients with PHP. Early diagnosis and treatment of PHP is one basis for preventing severe spinal cord-related complications.

Pseudohypoparathyroidism Type 1A with Normocalcaemia, due to the Novel C.389A&gt;G Variant of Exon 5 of the Guanine Nucleotide-Binding Protein, α-Stimulating Gene

Pseudohypoparathyroidism type 1A (PHP1A) is a rare disease caused by molecular defects in the maternally-inherited allele of the guanine nucleotide-binding protein, α-stimulating (GNAS) gene. The GNAS gene encodes the stimulatory G-protein α-subunit that regulates production of the second messenger cyclic adenosine monophosphate. Heterozygous inactivating mutations in these specific loci are responsible for a spectrum of phenotypic characteristics of the disease, including clinical features of the Albright’s hereditary osteodystrophy, due to resistance to parathyroid hormone (PTH). We report a case of PHP1A and explore the underlying novel point mutation of the GNAS gene that leads to an atypical PHP1A phenotype. A male patient with a round face, short stature, and brachydactyly accompanied by normocalcaemia and mild PTH resistance consulted at our center. The GNAS encoding region from the patient and both of his parents were amplified and sequenced directly in a sample of peripheral blood leukocytes. A novel c.389A>G point mutation in exon 5 of the GNAS gene, resulting in a p.Tyr130Cys peptidic chain change of the Gsα protein, detected in the proband, in heterozygous state. Sequencing of the GNAS gene from his parents did not reveal the c.389A>G mutation, confirming a de novo proband genotype. The maternal origin of the affected GNAS allele, along with mild PTH resistance, confirmed the PHP1A diagnosis. PHP1A, caused by inactivating GNAS mutations, presents a range of complex clinical phenotypes. The novel c.389A>G GNAS mutation presented in this case expands the spectrum of known PHP1A molecular defects and describes the associated phenotype.

Identification of a novel mutation in pseudohypoparathyroidism type Ia in a Chinese family: A case report

INTRODUCTION

Pseudohypoparathyroidism (PHP) indicates a group of rare disorders characterized by end-organ resistance to various hormones, primarily parathyroid hormone (PTH). One of its most common type is PHP-Ia, which is caused by maternally inherited inactivating mutations in GNAS. In this report, we present a Chinese girl with typical features of PHP-Ia and a novel mutation of the GNAS gene.

PATIENT CONCERNS

A 9-year-old Chinese girl presented with recurrent epileptic seizure.

DIAGNOSIS

Biochemical and imaging findings were consistent with PHP-Ia, including typical Albright hereditary osteodystrophy phenotype (short stature, round face, brachydactyly, and mild mental retardation), PTH resistance (hypocalcemia, hyperphosphatemia, elevated serum PTH, and multiple intracranial calcification) and thyroid stimulating hormone resistance (elevated serum thyroid stimulating hormone).

INTERVENTIONS

The patient was given 1α-hydroxylated vitamin D (calcitriol, 0.5 ug/d), calcium carbonate and vitamin D3 tablets (1.5 g/d, including 600 mg calcium and 125 IU vitamin D3). DNA analysis of the GNAS gene was performed for the whole family.

OUTCOMES

Investigation of the GNAS gene revealed a novel mutation c.313delG (p.Glu105Lysfs*7) in the patient, as well as her mother. So the diagnosis of PHP-Ia was confirmed.

CONCLUSION

The study further expands the spectrum of known GNAS mutations associated with PHP and lay emphasis on the genetic analysis of GNAS gene for identifying genetic abnormalities as well as making diagnosis and differentiation of various subtypes of PHP.

Syndromic Disorders Caused by Disturbed Human Imprinting

Imprinting disorders are a group of congenital diseases caused by dysregulation of genomic imprinting, affecting prenatal and postnatal growth, neurocognitive development, metabolism and cancer predisposition. Aberrant expression of imprinted genes can be achieved through different mechanisms, classified into epigenetic - if not involving DNA sequence change - or genetic in the case of altered genomic sequence. Despite the underlying mechanism, the phenotype depends on the parental allele affected and opposite phenotypes may result depending on the involvement of the maternal or the paternal chromosome. Imprinting disorders are largely underdiagnosed because of the broad range of clinical signs, the overlap of presentation among different disorders, the presence of mild phenotypes, the mitigation of the phenotype with age and the limited availability of molecular techniques employed for diagnosis. This review briefly illustrates the currently known human imprinting disorders, highlighting endocrinological aspects of pediatric interest.

A patient with extensive cerebral calcification due to pseudohypoparathyroidism: a case report

BACKGROUND

Pseudohypoparathyroidism(PHP) is a heterogeneous group of disorders due to impaired activation of c AMP dependant pathways following binding of parathyroid hormone (PTH) to its receptor. In PHP end organ resistance to PTH results in hypocalcaemia, hyperphosphataemia and high PTH levels.

CASE PRESENTATION

A 59 year old male presented with a history of progressive impairment of speech and unsteadiness of gait for 1 week and acute onset altered behavior for 1 day and one episode of generalized seizure. His muscle power was grade four according to MRC (medical research council) scale in all limbs and Chovstek's and Trousseau's signs were positive. Urgent non contrast computed tomography scan of the brain revealed extensive bilateral cerebral and cerebellar calcifications. A markedly low ionized calcium level of 0.5 mmol/l, an elevated phosphate level of 9.5 mg/dl (reference range: 2.7-4.5 mg/dl) and an elevated intact PTH of 76.3 pg/l were noted. His renal functions were normal. His hypocalcemia was accentuated by the presence of hypomagnesaemia. His 25 hydroxy vitamin D level was only marginally low which could not account for severe hypocalcaemia. A diagnosis of pseudohypoparathyroidism without phenotypic defects, was made due to hypocalcaemia and increased parathyroid hormone levels with cerebral calcifications. The patient was treated initially with parenteral calcium which was later converted to oral calcium supplements. His coexisting Vitamin D deficiency was corrected with 1αcholecalciferol escalating doses. His hypomagnesaemia was corrected with magnesium sulphate parenteral infusions initially and later with oral preparations. With treatment there was a significant clinical and biochemical response.

CONCLUSION

Pseudohypoparathyroidism can present for the first time in elderly resulting in extensive cerebral calcifications. Identification and early correction of the deficit will result in both symptomatic and biochemical response.

A typical 22q11.2 deletion syndrome and pseudohypoparathyroidism: A CARE compliant case report

RATIONALE

It is rare to find 22q11.2 deletion syndrome with pseudohypoparathyroidism in children. Furthermore, the phenotypic spectrum of this disorder varies widely.

PATIENT CONCERNS

A patient was diagnosed with pseudohypoparathyroidism at age 14 years because of convulsions, hypocalcemia, hyperphosphatemia, normal parathyroid hormone levels, and basal ganglia calcifications. Thereafter, the child presented with symptoms of nephrotic syndrome; subsequently, he was diagnosed with nephrotic syndrome at the local hospital.

DIAGNOSIS

At our hospital, multiplex ligation-dependent probe amplification confirmed that the patient had 22q11.2 deletion syndrome.

INTERVENTIONS

The patient continued to be treated with calcium supplements.

OUTCOMES

Seizure activity and proteinuria ceased.

LESSONS

Signs of this syndrome include delayed speech development due to velofacial dysfunction, recurrent croup attacks during early childhood due to latent hypocalcemia, and mild dysmorphic features. The findings of this patient indicated that 22q11.2 deletion syndrome may include a wide spectrum of clinical findings and that this diagnosis needs to be considered for all patients presenting with hypocalcemia, regardless of age.

Neonatal transient pseudohypoparathyroidism: could it be included among inactivating parathyroid hormone (PTH)/PTH-related protein signalling disorders?

We report a case of transient pseudohypoparathyroidism in a full-term newborn that presented at 20 hours of life with hypocalcemic seizures, hyperphosphatemia and raised parathormone levels. The diagnosis of pseudohypoparathyroidism was made according to biochemical investigations. The infant was treated with calcium supplementation and vitamin D analog therapy, and he remained stable and symptom-free with normal serum biochemistries during follow-up. We suggest that transient pseudohypoparathyroidism of the newborn (ntPHP) might be included among inactivating parathyroid hormone (PTH)/PTH-related protein signaling disorders as defined by the classification schema recently proposed by the European Pseudohypoparathyroidism Network. To the best of our knowledge, this is the first report in which the new classification has been applied to a case of ntPHP.

Resistance to GHRH but Not to PTH in a 15-Year-Old Boy With Pseudohypoparathyroidism 1A

Pseudohypoparathyroidism 1A (PHP1A) consists of signs of Albright hereditary osteodystrophy (AHO) and multiple, variable hormonal resistances. Elevated PTH levels are the biochemical hallmark of the disease. Short stature in PHP1A may be caused by a form of accelerated chondrocyte differentiation leading to premature growth plate closure, possibly in combination with GH deficiency in some patients. Treatment of short stature with recombinant growth hormone (rhGH) in pediatric patients may improve final height if started during childhood. The 10 11/12-year-old boy with clinical signs of AHO presented for evaluation of short stature [height standard deviation score (SDS) −2.72]. Clinically his mother was affected by AHO as well. A heterozygous mutation c.505G>A (p.E169K) in exon 6 of the GNAS gene confirmed a diagnosis of PHP1A in the boy. However, hormonal assessment was unremarkable except for low serum IGF-1 (SDS −2.67). On follow-up, GH deficiency due to GHRH resistance was suspected and confirmed by clonidine and arginine stimulation tests. Treatment with rhGH (0.035 mg/kg) for 2 years resulted in catch-up growth (height SDS −1.52). At age 15 years the PTH levels and bone age of the patient remain within the normal range. In patients with PHP1A, short stature is caused by the effects of G_s-α deficiency on the growth plate. However, resistance to GHRH and the resulting GH deficiency might also contribute. Recombinant GH treatment increases growth in these patients. Diagnostic workup for GH deficiency as a factor contributing to short stature is recommended even in the absence of other hormonal resistances.

A sporadic case of pseudohypoparathyroidism type 1 and idiopathic primary adrenal insufficiency associated with a novel mutation in the GNAS1 gene

OBJECTIVE

We report an atypical association of primary adrenal insufficiency and pseudohypoparathyroidism (PHP) and a novel GNAS1 gene mutation in a Caucasian female who initially presented with adrenal crisis.

METHODS

A case report and literature review.

RESULTS

A 37-year-old female presented with shock at 11 years of age, and investigations revealed primary adrenal insufficiency and pseudohypoparathyroidism (PHP). She had typical features of Albright hereditary osteodystrophy (AHO) and evidence of thyroid-stimulating hormone (TSH), growth-hormone-releasing hormone (GHRH), and gonadotrophin resistance fitting with the diagnosis of PHP type 1a/1c. She did not have a family history of any autoimmune disease or PHP. Her mother was phenotypically normal. Genomic DNA sequencing of those GNAS exons and adjacent intronic regions that encode the stimulatory guanine nucleotide-binding protein Gsα revealed a novel heterozygous mutation in exon 11, c.857-858delCT.

CONCLUSION

The association of primary adrenal insufficiency and PHP has not been reported in literature and may prove an area for further research. The novel mutation in this case adds to the spectrum of mutations associated with these disorders.

Genetic regulation of linear growth

Linear growth occurs at the growth plate. Therefore, genetic defects that interfere with the normal function of the growth plate can cause linear growth disorders. Many genetic causes of growth disorders have already been identified in humans. However, recent genome-wide approaches have broadened our knowledge of the mechanisms of linear growth, not only providing novel monogenic causes of growth disorders but also revealing single nucleotide polymorphisms in genes that affect height in the general population. The genes identified as causative of linear growth disorders are heterogeneous, playing a role in various growth-regulating mechanisms including those involving the extracellular matrix, intracellular signaling, paracrine signaling, endocrine signaling, and epigenetic regulation. Understanding the underlying genetic defects in linear growth is important for clinicians and researchers in order to provide proper diagnoses, management, and genetic counseling, as well as to develop better treatment approaches for children with growth disorders.

Hypercalcitoninaemia in pseudohypo-parathyroidism type 1A and type 1B

Pseudohypoparathyroidism (PHP) is a heterogeneous group of rare endocrine disorders characterised by normal renal function and renal resistance to the action of the parathyroid hormone. Type 1A (PHP1A), which is the most common variant, also include developmental and skeletal defects named as Albright hereditary osteodystrophy (AHO). We present two cases, a 54- and a 33-year-old male diagnosed with PHP who were referred to us for persistently high levels of serum calcitonin. AHO and multinodular goitre were present in the 54-year-old male, while the second patient was free of skeletal deformities and his thyroid gland was of normal size and without nodular appearance. We performed GNAS molecular analysis (methylation status and copy number analysis by MS-MLPA) in genomic DNA samples for both patients. The analysis revealed a novel missense variant c.131T>G p.(Leu44Pro) affecting GNAS exon 1, in the patient with the clinical diagnosis of PHP1A. This amino acid change appears to be in accordance with the clinical diagnosis of the patient. The genomic DNA analysis of the second patient revealed the presence of the recurrent 3-kb deletion affecting the imprinting control region localised in the STX16 region associated with the loss of methylation (LOM) at the GNAS A/B differentially methylated region and consistent with the diagnosis of an autosomal dominant form of PHP type 1B (PHP1B). In conclusion, hypercalcitoninaemia may be encountered in PHP1A and PHP1B even in the absence of thyroid pathology. Learning points: We describe a novel missense variant c.131T>G p.(Leu44Pro) affecting GNAS exon 1 as the cause of PHP1A. Hypercalcitoninaemia in PHP1A is considered an associated resistance to calcitonin, as suggested by the generalised impairment of Gsα-mediated hormone signalling. GNAS methylation defects, as in type PHP1B, without thyroid pathology can also present with hypercalcitoninaemia.

Parathyroid hormone resistance syndromes - Inactivating PTH/PTHrP signaling disorders (iPPSDs)

Metabolic disorders caused by impairments of the Gsα/cAMP/PKA pathway affecting the signaling of PTH/PTHrP lead to features caused by non-responsiveness of target organs, in turn leading to manifestations similar to the deficiency of the hormone itself. Pseudohypoparathyroidism (PHP) and related disorders derive from a defect of the α subunit of the stimulatory G protein (Gsα) or of downstream effectors of the same pathway, such as the PKA regulatory subunit 1A and the phosphodiesterase type 4D. The increasing knowledge on these diseases made the actual classification of PHP outdated as it does not include related conditions such as acrodysostosis (ACRDYS) or progressive osseous heteroplasia (POH), so that a new nomenclature and classification has been recently proposed grouping these disorders under the term "inactivating PTH/PTHrP signaling disorder" (iPPSD). This review will focus on the pathophysiology, clinical and molecular aspects of these rare, heterogeneous but closely related diseases.

Pseudohypoparathyroidism type 1B in a patient conceived by in vitro fertilization: another imprinting disorder reported with assisted reproductive technology

Pseudohypoparathyroidism type 1B (PHP1B) is characterized by renal tubular resistance to parathyroid hormone (PTH) leading to hyperphosphatemia, hypocalcemia, elevated PTH, and hyperparathyroid bone changes. PHP1B is an imprinting disorder that results from loss of methylation at the maternal GNAS gene, which suppresses transcription of the alpha subunit of the stimulatory G protein of the PTH receptor. Emerging evidence supports an association between assisted reproductive technologies (ART) and imprinting disorders; however, there is currently little evidence linking PHP1B and ART. We present a twin boy conceived by ART to parents with no history of subfertility who presented at age 12 with bilateral slipped capital femoral epiphysis and bilateral genu valgum deformity. Clinical and laboratory investigation revealed markedly elevated PTH, low ionized calcium, elevated phosphorus, TSH resistance, and skeletal evidence of hyperparathyroidism, leading to the diagnosis of PHP1B. A partial loss of methylation at the GNAS exon A/B locus was observed. The patient's dizygotic twin sibling was asymptomatic and had normal laboratory evaluation. This is the second reported case of a child with PHP1B conceived by ART, further supporting the possibility that ART may lead to an increased risk for imprinting defects.

Multiple hormone resistance and alterations of G-protein-coupled receptors signaling

Metabolic disorders deriving from the non-responsiveness of target organs to hormones, which manifest clinically similar to the deficiency of a given hormone itself, derive from molecular alterations affecting specific hormone receptors. Pseudohypoparathyroidism (PHP) and related disorders exemplify an unusual form of hormone resistance as the underlying molecular defect is a partial deficiency of the α subunit of the stimulatory G protein (Gsα), a key regulator of cAMP signaling pathway, or, as more recently described, of downstream effector proteins of the same pathway, such as PKA regulatory subunit 1A (R1A) and phosphodyestarase type 4D (PDE4D). In this group of diseases, resistance to hormones such as PTH, TSH, gonadotropins and GHRH may be variably present, so that the clinical and molecular overlap among these different but related disorders represents a challenge for endocrinologists as to differential diagnosis and genetic counseling. This review will describe the presenting features of multiple resistance in PHP and related disorders, focusing on both our current understanding and future challenges.

Genetics of primary ovarian insufficiency

Primary ovarian insufficiency (POI) is characterized by a loss of ovarian function before the age of 40 and account for one major cause of female infertility. POI relevance is continuously growing because of the increasing number of women desiring conception beyond 30 years of age, when POI prevalence is >1%. POI is highly heterogeneous and can present with ovarian dysgenesis and primary amenorrhea, or with secondary amenorrhea, and it can be associated with other congenital or acquired abnormalities. In most cases POI remains classified as idiopathic. However, the age of menopause is an inheritable trait and POI has a strong genetic component. This is confirmed by the existence of several candidate genes, experimental and natural models. The variable expressivity of POI defect may indicate that, this disease may frequently be considered as a multifactorial or oligogenic defect. The most common genetic contributors to POI are the X chromosome-linked defects. Here, we review the principal X-linked and autosomal genes involved in syndromic and non-syndromic forms of POI with the expectation that this list will soon be upgraded, thus allowing the possibility to predict the risk of an early age at menopause in families with POI.

Genetic and epigenetic alterations in the GNAS locus and clinical consequences in Pseudohypoparathyroidism: Italian common healthcare pathways adoption

BACKGROUND

Genetic and epigenetic alterations in the GNAS locus are responsible for the Gsα protein dysfunctions causing Pseudohypoparathyroidism (PHP) type Ia/c and Ib, respectively. For these heterogeneous diseases characterized by multiple hormone resistances and Albright's Hereditary Osteodystrophy (AHO) the current classification results inadequate because of the clinical overlap between molecular subtypes and a standard clinical approach is still missing. In the present paper several members of the Study Group Endocrine diseases due to altered function of Gsα protein of the Italian Society of Pediatric Endocrinology and Diabetology (ISPED) have reviewed and updated the clinical-molecular data of the largest case series of (epi)/genetically characterized AHO/PHP patients; they then produced a common healthcare pathway for patients with these disorders.

METHODS

The molecular analysis of the GNAS gene and locus identified the causal alteration in 74 subjects (46 genetic and 28 epigenetic mutations). The clinical data at the diagnosis and their evolution during up to 15 years follow-up were collected using two different cards.

RESULTS

In patients with genetic mutations the growth impairment worsen during the time, while obesity prevalence decreases; subcutaneous ossifications seem specific for this group. Brachydactyly has been detected in half of the subjects with epigenetic alterations, in which the disease overts later in life, often with symptomatic hypocalcaemia, and also early TSH and GHRH resistances have been recorded.

CONCLUSIONS

A dedicated healthcare pathway addressing all these aspects in a systematic way would improve the clinical management, allowing an earlier recognition of some PHP features, the optimization of their medical treatment and a better clinical-oriented molecular analysis. Furthermore, standardized follow-up data would provide new insight into less known aspects.

The Association of Pseudohypoparathyroidism Type Ia with Chiari Malformation Type I: A Coincidence or a Common Link?

A 19-month-old boy was referred for progressive weight gain. His past medical history included congenital hypothyroidism and developmental delay. Physical examination revealed characteristics of Albright Hereditary Osteodystrophy, macrocephaly, and calcinosis cutis. He had hypocalcemia, hyperphosphatemia, and elevated Parathyroid Hormone levels. Genetic testing revealed a known mutation of GNAS gene, confirming the diagnosis of Pseudohypoparathyroidism Type Ia (PHP-Ia) (c.34C>T (p.G1n12X)). He had a normal brain MRI at three months, but developmental delay prompted a repeat MRI that revealed Chiari Malformation Type I (CM-I) with hydrocephalus requiring neurosurgical intervention. This was followed by improvement in attaining developmental milestones. Recently, he was diagnosed with growth hormone deficiency. This case suggests the potential association of CM-I with PHP-Ia. Larger studies are needed to assess whether CM-I with hydrocephalus are common associations with PHP-Ia and to define potential genetic links between these conditions. We propose a low threshold in performing brain MRI on PHP-1a patients, especially those with persistent developmental delay to rule out CM-I. Early intervention may improve neurodevelopmental outcomes and prevent neurosurgical emergencies.

Macrosomia, obesity, and macrocephaly as first clinical presentation of PHP1b caused by STX16 deletion

Pseudohypoparathyroidism (PHP) is a genetic disorder with resistance to parathyroid hormone (PTH) as most important feature. Main subtypes of the disease are pseudohypoparathyroidism 1b (PHP1b) and pseudohypoparathyroidism 1a (PHP1a). PHP1b is characterized by PTH resistance of the renal cortex due to reduced activity of the stimulatory G protein α subunit (Gsα) of the PTH receptor. In addition to resistance to PTH, PHP1a patients also lack sensitivity for other hormones that signal their actions through G protein-coupled receptors and display physical features of Albright hereditary osteodystrophy (AHO), which is not classically seen in PHP1b patients. PHP1a is caused by heterozygous loss-of-function mutations in maternally inherited GNAS exons 1-13, which encode Gsα. PHP1b is often caused by deletion of the STX16 gene, which is thought to have an important role in controlling the methylation and thus imprinting at part of the GNAS locus. Here we present a patient with PHP1b caused by the previously described recurrent 3-kb STX16 deletion. The patient's first symptoms were macrosomia, early onset obesity, and macrocephaly. Since this is an atypical but previously described rare presentation of PHP1b, we reemphasize STX16 deletions and PHP1b as a rare cause for early onset obesity and macrosomia. © 2016 Wiley Periodicals, Inc.

DNA methylation analysis in constitutional disorders: Clinical implications of the epigenome

Genomic, chromosomal, and gene-specific changes in the DNA sequence underpin both phenotypic variations in populations as well as disease associations, and the application of genomic technologies for the identification of constitutional (inherited) or somatic (acquired) alterations in DNA sequence forms a cornerstone of clinical and molecular genetics. In addition to the disruption of primary DNA sequence, the modulation of DNA function by epigenetic phenomena, in particular by DNA methylation, has long been known to play a role in the regulation of gene expression and consequent pathogenesis. However, these epigenetic factors have been identified only in a handful of pediatric conditions, including imprinting disorders. Technological advances in the past decade that have revolutionized clinical genomics are now rapidly being applied to the emerging discipline of clinical epigenomics. Here, we present an overview of epigenetic mechanisms with a focus on DNA modifications, including the molecular mechanisms of DNA methylation and subtypes of DNA modifications, and we describe the classic and emerging genomic technologies that are being applied to this study. This review focuses primarily on constitutional epigenomic conditions associated with a spectrum of developmental and intellectual disabilities. Epigenomic disorders are discussed in the context of global genomic disorders, imprinting disorders, and single gene disorders. We include a section focused on integration of genetic and epigenetic mechanisms together with their effect on clinical phenotypes. Finally, we summarize emerging epigenomic technologies and their impact on diagnostic aspects of constitutional genetic and epigenetic disorders.

Rare diseases in clinical endocrinology: a taxonomic classification system

PURPOSE

Rare endocrine-metabolic diseases (REMD) represent an important area in the field of medicine and pharmacology. The rare diseases of interest to endocrinologists involve all fields of endocrinology, including rare diseases of the pituitary, thyroid and adrenal glands, paraganglia, ovary and testis, disorders of bone and mineral metabolism, energy and lipid metabolism, water metabolism, and syndromes with possible involvement of multiple endocrine glands, and neuroendocrine tumors. Taking advantage of the constitution of a study group on REMD within the Italian Society of Endocrinology, consisting of basic and clinical scientists, a document on the taxonomy of REMD has been produced.

METHODS AND RESULTS

This document has been designed to include mainly REMD manifesting or persisting into adulthood. The taxonomy of REMD of the adult comprises a total of 166 main disorders, 338 including all variants and subtypes, described into 11 tables.

CONCLUSIONS

This report provides a complete taxonomy to classify REMD of the adult. In the future, the creation of registries of rare endocrine diseases to collect data on cohorts of patients and the development of common and standardized diagnostic and therapeutic pathways for each rare endocrine disease is advisable. This will help planning and performing intervention studies in larger groups of patients to prove the efficacy, effectiveness, and safety of a specific treatment.

GNAS mutations in Pseudohypoparathyroidism type 1a and related disorders

Pseudohypoparathyroidism type 1a (PHP1a) is characterized by hypocalcaemia and hyperphosphatemia due to parathyroid hormone resistance, in association with the features of Albright's hereditary osteodystrophy (AHO). PHP1a is caused by maternally inherited inactivating mutations of Gs-alpha, which is encoded by a complex imprinted locus termed GNAS. Paternally inherited mutations can lead either to pseudopseudohypoparathyroidism (PPHP) characterized by AHO alone, or to progressive osseous heteroplasia (POH), characterized by severe heterotopic ossification. The clinical aspects and molecular genetics of PHP1a and its related disorders are reviewed together with the 343 kindreds with Gs-alpha germline mutations reported so far in the literature. These 343 (176 different) mutations are scattered throughout the 13 exons that encode Gs-alpha and consist of 44.9% frameshift, 28.0% missense, 14.0% nonsense, and 9.0% splice-site mutations, 3.2% in-frame deletions or insertions, and 0.9% whole or partial gene deletions. Frameshift and other highly disruptive mutations were more frequent in the reported 37 POH kindreds than in PHP1a/PPHP kindreds (97.3% vs. 68.7%, P < 0.0001). This mutation update and respective genotype-phenotype data may be of use for diagnostic and research purposes and contribute to a better understanding of these complex disorders.

Different pattern of epigenetic changes of the GNAS gene locus in patients with pseudohypoparathyroidism type Ic confirm the heterogeneity of underlying pathomechanisms in this subgroup of pseudohypoparathyroidism and the demand for a new classification of GNAS-related disorders

CONTEXT

Disorders characterized by PTH resistance are grouped within the term pseudohypoparathyroidism type I (PHPI). Most subtypes of this disease are caused by genetic or epigenetic changes of the GNAS locus leading to deficiency of the α-subunit of stimulatory G proteins (Gsα). Because the in vitro measured Gsα protein activity is normal in pseudohypoparathyroidism Ic (PHPIc), it had previously been postulated that this subtype is caused by impairment of distinct components of the G protein-signaling pathway. However, recently, pathogenic GNAS mutations in a subset of PHPIc patients were found.

OBJECTIVE

To clarify the underlying pathogenic mechanism of GNAS exon 1-13 mutation-negative PHPIc cases by investigating the differentially methylated regions of GNAS for epigenetic abnormalities.

PATIENTS AND METHODS

The methylation pattern of GNAS exons A/B, AS, XL, and NESP from blood-derived leukocytes of 26 PHPIc patients was assessed by pyrosequencing of bisulfite-converted DNA.

RESULTS

Six patients presented with three different patterns of epigenetic changes. One patient had an exclusive loss of methylation of exon A/B associated with a STX16 deletion; four patients had an additional loss of methylation in XL and AS and a gain of methylation in NESP; and one patient presented with partial GNAS methylation changes concerning all differentially methylated regions.

CONCLUSIONS

Our results confirm that PHPIc is a heterogeneous entity caused in part by impaired Gsα function, not only due to mutations, but also due to abnormal imprinting of GNAS. However, in the majority of cases of PHPIc, the underlying etiopathogenesis remains elusive.

European guidance for the molecular diagnosis of pseudohypoparathyroidism not caused by point genetic variants at GNAS: an EQA study

Pseudohypoparathyroidism is a rare endocrine disorder that can be caused by genetic (mainly maternally inherited inactivating point mutations, although intragenic and gross deletions have rarely been reported) or epigenetic alterations at GNAS locus. Clinical and molecular characterization of this disease is not that easy because of phenotypic, biochemical and molecular overlapping features between both subtypes of the disease. The European Consortium for the study of PHP (EuroPHP) designed the present work with the intention of generating the standards of diagnostic clinical molecular (epi)genetic testing in PHP patients. With this aim, DNA samples of eight independent PHP patients carrying GNAS genetic and/or epigenetic defects (three patients with GNAS deletions, two with 20q uniparental disomy and three with a methylation defect of unknown origin) without GNAS point mutations were anonymized and sent to the five participant laboratories for their routine genetic analysis (methylation-specific (MS)-MLPA, pyrosequencing and EpiTYPER) and interpretations. All laboratories were able to detect methylation defects and, after the data analysis, the Consortium compared the results to define technical advantages and disadvantages of different techniques. To conclude, we propose as first-level investigation in PHP patients copy number and methylation analysis by MS-MLPA. Then, in patients with partial methylation defect, the result should be confirmed by single CpG bisulphite-based methods (ie pyrosequencing), whereas in case of a complete methylation defect without detectable deletion, microsatellites or SNP genotyping should be performed to exclude uniparental disomy 20.

A patient with features of albright hereditory osteodystrophy and unusual neuropsychiatric findings without coding Gsalpha mutations

BACKGROUND

Pseudohypoparathyroidism(PHP) is a heterogeneous group of rare metabolic disorders characterized by hypocalcemia and hyperphosphatemia resulting from PTH resistance. Different forms of PHP have been reported based on biochemical and clinical manifestation and genetic findings. Most of these forms are caused by defects in GNAS, an imprinted gene locus with multiple subunits. We reported a 12- year- old girl with unusual clinical manifestations of Pseudopseudohypoparathyroidism(PPHP).

METHODS

After clinical and biochemical evaluations, the patients' genomic DNA was isolated from peripheral blood leukocytes using salting out method. The whole coding sequences of GNAS gene including 13 exons were amplified by PCR. Quantitative PCR reactions were performed too.

FINDINGS

We described a 12- year- old girl with Albright Hereditory osteodystrophy (AHO) phenotype, poor school performance, some abnormal movements, TSH resistance with normal serum calcium and phosphorus levels and normal Gsα bioactivity with no mutation in GNAS exons. Unusual neuropsychiatric findings in this patient were compatible with Asperger syndrome.

CONCLUSIONS

According to our findings this patient could not be categorized in any of PHP subgroups. Identifying of such individuals may be useful to discover different genetic patterns in pseudohypoparathyroidism and pseudopseudohypoparathyroidism. It is important to identify patients in whom PHP is caused by novel GNAS mutations, as careful investigations of these findings will likely further our knowledge of this complex and this unique disorder. In addition this case presented with unusual neuropsychiatric findings which has not been reported up to now.

Quantitative analysis of methylation defects and correlation with clinical characteristics in patients with pseudohypoparathyroidism type I and GNAS epigenetic alterations

CONTEXT

Pseudohypoparathyroidism type I (PHP-I) includes two main subtypes, PHP-Ia and -Ib. About 70% of PHP-Ia patients, who show Albright hereditary osteodystrophy (AHO) associated with resistance toward multiple hormones (PTH/TSH/GHRH/gonadotropins), carry heterozygous mutations in the α-subunit of the stimulatory G protein (Gsα) exons 1-13, encoded by the guanine nucleotide binding-protein α-stimulating activity polypeptide 1 (GNAS), whereas the majority of PHP-Ib patients, who classically display hormone resistance limited to PTH and TSH with no AHO sign, have methylation defects in the imprinted GNAS cluster. Recently methylation defects have been detected also in patients with PHP and different degrees of AHO, indicating a molecular overlap between the two forms.

OBJECTIVES

The objectives of the study were to collect patients with the following characteristics: clinical PHP-I (with or without AHO), no mutation in Gsα coding sequence, but the presence of GNAS methylation alterations and to investigate the existence of correlations between the degree of the epigenetic defect and the severity of the disease.

PATIENTS AND METHODS

We quantified GNAS methylation alterations by both PCR-pyrosequencing and methylation specific-multiplex ligation-dependent probe amplification assay in genomic DNA from 63 patients with PHP-I and correlated these findings with clinical parameters (age at diagnosis; calcium, phosphorus, PTH, TSH levels; presence or absence of each AHO sign).

RESULTS

By both approaches, the degree of the imprinting defect did not correlate with the onset of the disease, the severity of endocrine resistances, or with the presence/absence of specific AHO signs.

CONCLUSIONS

Similar molecular alterations may lead to a broad spectrum of diseases, from isolated PTH resistance to complete PHP-Ia, and the degree of methylation alterations does not reflect or anticipate the severity and the type of different PHP/AHO manifestations.

Spinal cord compression in pseudohypoparathyroidism

BACKGROUND CONTEXT

Spinal cord compression associated with pseudohypoparathyroidism (PHP) is an increasingly reported sequelae of the underlying metabolic syndrome. The association of neurologic dysfunction with PHP is not well appreciated. We believe this to be secondary to a combination of underlying congenital stenosis, manifest by short pedicles secondary to premature physeal closure, and hypertrophic ossification of the vertebral bony and ligamentous complexes.

PURPOSE

The purpose of this case report is to review the case of spinal stenosis in a child with PHP Type Ia. We are aware of only eight published reports of patients with PHP Type Ia and spinal stenosis-there are only two previously known cases of pediatric spinal stenosis secondary to PHP.

STUDY DESIGN/SETTING

This is a case report detailing the symptoms, diagnosis, interventions, complications, and ultimate outcomes of a pediatric patient undergoing spinal decompression and fusion for symptomatic stenosis secondary to PHP Type Ia. Literature search was reviewed regarding the reports of spinal stenosis and PHP, and the results are culminated and discussed.

PATIENT SAMPLE

We report on a 14-year-old obese male with PHP and progressive lower extremity weakness secondary to congenital spinal stenosis. Examination revealed functional upper extremities with spastic paraplegia of bilateral lower extremities. The patient's neurologic function was cautiously monitored, but he deteriorated to a bed-bound state, preoperatively.

METHODS

The patient's chart was reviewed, summarized, and presented. Literature was searched using cross-reference of PHP and the terms "spinal stenosis," "myelopathy", "myelopathic," and "spinal cord compression." All relevant case reports were reviewed, and the results are discussed herein.

RESULTS

The patient underwent decompression and instrumented fusion of T2-T11. He improved significantly with regard to lower extremity function, achieving unassisted ambulation function after extensive rehabilitation. Results from surgical decompression in previously reported cases are mixed, ranging from full recovery to iatrogenic paraplegia.

CONCLUSIONS

The association of neurologic dysfunction with PHP is not well appreciated. It is important to highlight this rare association. Surgical decompression in patients with PHP yields mixed results but may be of greatest efficacy in younger patients who receive early intervention.

Progressive extreme heterotopic calcification

The formation of ectopic calcifications in soft tissues can occur either sporadically or as a genetically determined condition, and is seen only infrequently. We report on a girl in whom widespread, rapidly progressive ectopic calcifications were detected shortly after birth. Calcifications became present around all joints, tendons and ligaments, but did not involve internal organs and skin, and eventually caused almost complete immobility of the child at 2 years. There were no other health problems and cognitive development was normal. We compare the manifestations in the child to the characteristics of known entities causing ectopic calcifications and conclude the child differs to each. Laboratory evaluation failed to identify autoimmune phenomena as well as calcium metabolism or other biochemical abnormalities; molecular studies did not identify occurrence of mutations in disease genes known to be involved in ectopic calcifications. We conclude the manifestations in the child represent an unreported entity of hitherto unknown etiology.

Severe hypercalcemic hyperparathyroidism developing in a patient with hyperaldosteronism and renal resistance to parathyroid hormone

We evaluated an African American woman referred in 1986 at age 33 years because of renal potassium and calcium wasting and chronic hip pain. She presented normotensive, hypokalemic, hypocalcemic, normophosphatemic, and hypercalciuric. Marked hyperparathyroidism was evident. Urinary cyclic adenosine monophosphate (cAMP) excretion did not increase in response to parathyroid hormone (PTH) infusion, indicating renal resistance to PTH. X-rays and bone biopsy revealed severe osteitis fibrosa cystica, confirming skeletal responsiveness to PTH. Renal potassium wasting, suppressed plasma renin activity, and elevated plasma and urinary aldosterone levels accompanied her hypokalemia, suggesting primary hyperaldosteronism. Hypokalemia resolved with spironolactone and, when combined with dietary sodium restriction, urinary calcium excretion fell and hypocalcemia improved, in accord with the known positive association between sodium intake and calcium excretion. Calcitriol and oral calcium supplements did not suppress the chronic hyperparathyroidism nor did they reduce aldosterone levels. Over time, hyperparathyroid bone disease progressed with pathologic fractures and persistent pain. In 2004, PTH levels increased further in association with worsening chronic kidney disease. Eventually hypercalcemia and hypertension developed. Localizing studies in 2005 suggested a left inferior parathyroid tumor. After having consistently declined, the patient finally agreed to neck exploration in January 2009. Four hyperplastic parathyroid glands were removed, followed immediately by severe hypocalcemia, attributed to "hungry bone syndrome" and hypoparathyroidism, which required prolonged hospitalization, calcium infusions, and oral calcitriol. Although her bone pain resolved, hyperaldosteronism persisted.

Current loss-of-function mutations in the thyrotropin receptor gene: when to investigate, clinical effects, and treatment

Thyroid-stimulating hormone receptor (TSHR) loss-of-function (LOF) mutations lead to a wide spectrum of phenotypes, ranging from severe congenital hypothyroidism (CH) to mild euthyroid hyperthyrotropinemia. The degree of TSH resistance depends on the severity of the impairment of the receptor function caused by the mutation and on the number of mutated alleles In this review data about genotype-phenotype correlation and criteria for clinical work-up will be presented and discussed. Complete TSH resistance due to biallelic LOF TSHR mutations must be suspected in all patients with severe not syndromic CH and severe thyroid hypoplasia diagnosed at birth by neonatal screening. Partial forms of TSH resistance show a more heterogeneous hormonal and clinical pattern . In these cases TSH serum levels are above the upper limit of normal range for the age but with a very variable pattern, free thyroxine (T4) concentrations are within the normal range and thyroid size can be normal or hypoplastic at ultrasound scan. An early substitutive treatment with L-T4 must be mandatory in all patients with severe CH due to complete uncompensated TSH resistance diagnosed at birth by neonatal screening. The usefulness of substitutive treatment appears much more controversial inpatients with subclinical hypothyroidism due to partial TSH resistance in whom the increased TSH concentration should be able to compensate the mild functional impairment of the mutant receptor. Together with standard criteria we recommend also an accurate clinical work-up to select patients who are candidates for a LOF TSHR mutation.

Pseudohypoparathyroidism type 1b with hypothyroidism

Pseudohypoparathyroidism due to deficient end organ response to parathyroid hormone (PTH) is characterized by hypocalcemia, hyperphosphatemia and increased serum PTH. We report a case of an 8-year-old girl with pseudohypoparathyroidism without features of Albright's hereditary osteodystrophy. The case is of interest as the child on serial follow-up over a period of 2 years developed hypothyroidism. This is a rare feature seen in pseudohypoparathyroidism type1b.

Clinical review: Pseudohypoparathyroidism: diagnosis and treatment

CONTEXT

The term pseudohypoparathyroidism (PHP) indicates a group of heterogeneous disorders whose common feature is represented by impaired signaling of various hormones (primarily PTH) that activate cAMP-dependent pathways via Gsα protein. The two main subtypes of PHP, PHP type Ia, and Ib (PHP-Ia, PHP-Ib) are caused by molecular alterations within or upstream of the imprinted GNAS gene, which encodes Gsα and other translated and untranslated products.

EVIDENCE ACQUISITION

A PubMed search was used to identify the available studies (main query terms: pseudohypoparathyroidism; Albright hereditary osteodystrophy; GNAS; GNAS1; progressive osseous heteroplasia). The most relevant studies until February 2011 have been included in the review.

EVIDENCE SYNTHESIS AND CONCLUSIONS

Despite the first description of this disorder dates back to 1942, recent findings indicating complex epigenetic alterations beside classical mutations at the GNAS complex gene, pointed out the limitation of the actual classification of the disease, resulting in incorrect genetic counselling and diagnostic procedures, as well as the gap in our actual knowledge of the pathogenesis of these disorders. This review will focus on PHP type I, in particular its diagnosis, classification, treatment, and underlying molecular alterations.

Syndromes of resistance to TSH

The resistance to TSH action is a genetic disease characterized by molecular defects hampering the adequate transmission of TSH stimulatory signal into thyroid cells. In principle the defect may affect every step along the cascade of events following the binding of TSH to its receptor (TSHR) on thyroid cell membranes. The phenotypic expressivity of TSH resistance is highly variable going from severe congenital hypothyroidism (CH) with thyroid hypoplasia to mild hyperthyrotropinemia (hyperTSH) associated with an apparent euthyroid state. More severe forms follow a recessive pattern of inheritance and occur in patients with biallelic mutations both causing a severe loss of TSHR function. Differential diagnosis in these cases includes the exclusions of other causes of isolated thyroid dysgenesis. Mildest forms may instead occur in patients with monoallelic TSHR defects following a dominant mode of inheritance. In these cases we described the dominant negative effect exerted by some mutants on the activity of the receptor encoded by the wild type allele. In these cases, differential diagnosis involves the exclusion of autoimmune thyroid disease or pseudohypoparathyroidism associated with defects at the GNAS locus. This review will focus on the variable clinical expression of this disease.

Functional characterization of GNAS mutations found in patients with pseudohypoparathyroidism type Ic defines a new subgroup of pseudohypoparathyroidism affecting selectively Gsα-receptor interaction

Pseudohypoparathyroidism type Ia (PHPIa) is caused by GNAS mutations leading to deficiency of the α-subunit of stimulatory G proteins (Gsα) that mediate signal transduction of G protein-coupled receptors via cAMP. PHP type Ic (PHPIc) and PHPIa share clinical features of Albright hereditary osteodystrophy (AHO); however, in vitro activity of solubilized Gsα protein is normal in PHPIc but reduced in PHPIa. We screened 32 patients classified as PHPIc for GNAS mutations and identified three mutations (p.E392K, p.E392X, p.L388R) in four unrelated families. These and one novel mutation associated with PHPIa (p.L388P) were introduced into a pcDNA3.1(-) expression vector encoding Gsα wild-type and expressed in a Gsα-null cell line (Gnas(E2-/E2-) ). To investigate receptor-mediated cAMP accumulation, we stimulated the endogenous expressed β(2) -adrenergic receptor, or the coexpressed PTH or TSH receptors, and measured the synthesized cAMP by RIA. The results were compared to receptor-independent cholera toxin-induced cAMP accumulation. Each of the mutants associated with PHPIc significantly reduced or completely disrupted receptor-mediated activation, but displayed normal receptor-independent activation. In contrast, PHPIa associated p.L388P disrupted both receptor-mediated activation and receptor-independent activation. We present a new subgroup of PHP that is caused by Gsα deficiency and selectively affects receptor coupling functions of Gsα.

Diseases associated with genomic imprinting

Genomic imprinting is the phenomenon where the expression of a locus differs between the maternally and paternally inherited alleles. Typically, this manifests as transcriptional silencing of one of the alleles, although many genes are imprinted in a tissue- or isoform-specific manner. Diseases associated with imprinted genes include various cancers, disorders of growth and metabolism, and disorders in neurodevelopment, cognition, and behavior, including certain major psychiatric disorders. In many cases, the disease phenotypes associated with dysfunction at particular imprinted loci can be understood in terms of the evolutionary processes responsible for the origin of imprinting. Imprinted gene expression represents the outcome of an intragenomic evolutionary conflict, where natural selection favors different expression strategies for maternally and paternally inherited alleles. This conflict is reasonably well understood in the context of the early growth effects of imprinted genes, where paternally inherited alleles are selected to place a greater demand on maternal resources than are maternally inherited alleles. Less well understood are the origins of imprinted gene expression in the brain, and their effects on cognition and behavior. This chapter reviews the genetic diseases that are associated with imprinted genes, framed in terms of the evolutionary pressures acting on gene expression at those loci. We begin by reviewing the phenomenon and evolutionary origins of genomic imprinting. We then discuss diseases that are associated with genetic or epigenetic defects at particular imprinted loci, many of which are associated with abnormalities in growth and/or feeding behaviors that can be understood in terms of the asymmetric pressures of natural selection on maternally and paternally inherited alleles. We next described the evidence for imprinted gene effects on adult cognition and behavior, and the possible role of imprinted genes in the etiology of certain major psychiatric disorders. Finally, we conclude with a discussion of how imprinting, and the evolutionary-genetic conflicts that underlie it, may enhance both the frequency and morbidity of certain types of diseases.

Progressive osseous heteroplasia in a 10-year-old male child

We report a sporadic case of progressive osseous heteroplasia (POH) in a 10-year-old male child who developed progressive ossification of the skin and deep connective tissue. The condition needs to be distinguished from other causes of childhood heterotopic ossification, such as fibrodysplasia ossificans progressiva, pseudohypoparathyroidism, and pseudopseudohypoparathyroidism. The cause of POH is an inactivating GNAS1 (guanine nucleotide-binding protein alpha-stimulating activity polypeptide 1) mutation caused only by paternal inheritance of the mutant allele. Most cases are sporadic and only 2 instances of familial transmission have been documented, suggesting an autosomal dominant mode of inheritance with possible somatic mosaicism. The condition is associated with progressive superficial to deep ossification, progressive restriction of range of motion, bleak prognosis, and recurrence if excised.