Neonatal hyperparathyroidism and pamidronate therapy in an extremely premature infant

Invited Mini Review Metabolic Bone Disease of Prematurity: Overview and Practice Recommendations

Metabolic bone disease of prematurity (MBDP) is defined by undermineralization of the preterm infant skeleton arising from inadequate prenatal and postnatal calcium (Ca) and phosphate (PO4) accretion. Severe MBDP can be associated with rickets and fractures. Despite advances in neonatal nutrition, MBDP remains prevalent in premature infants due to inadequate mineral accretion ex utero. There also remain significant knowledge gaps regarding best practices for monitoring and treatment of MBDP among neonatologists and pediatric endocrinologists. Preventing and treating MBDP can prevent serious consequences including rickets or pathologic fractures. Postnatal monitoring to facilitate early recognition of MBDP is best done by first-tier laboratory screening by measuring serum Ca, phosphorus, and alkaline phosphatase to identify infants at risk. If these laboratories are abnormal, further studies including assessing parathyroid hormone and/or tubular resorption of PO4 can help differentiate between Ca and PO4 deficiency as primary etiologies to guide appropriate treatment with mineral supplements. Additional research into optimal mineral supplementation for the prevention and treatment of MBDP is needed to improve long-term bone health outcomes and provide a fuller evidence base for future treatment guidelines. Metabolic bone disease of prematurity (MBDP) is defined by undermineralization of the preterm infant skeleton arising from inadequate prenatal and postnatal calcium (Ca) and phosphate (PO4) accretion. Severe MBDP can be associated with rickets and fractures. Despite advances in neonatal nutrition, MBDP remains prevalent in premature infants due to inadequate mineral accretion ex utero. There also remain significant knowledge gaps regarding best practices for monitoring and treatment of MBDP among neonatologists and pediatric endocrinologists. Preventing and treating MBDP can prevent serious consequences including rickets or pathologic fractures. Postnatal monitoring to facilitate early recognition of MBDP is best done by first-tier laboratory screening by measuring serum Ca, phosphorus, and alkaline phosphatase to identify infants at risk. If these laboratories are abnormal, further studies including assessing parathyroid hormone and/or tubular resorption of PO4 can help differentiate between Ca and PO4 deficiency as primary etiologies to guide appropriate treatment with mineral supplements. Additional research into optimal mineral supplementation for the prevention and treatment of MBDP is needed to improve long-term bone health outcomes and provide a fuller evidence base for future treatment guidelines.

Surgical management of neonatal severe hyperparathyroidism

BACKGROUND

Neonatal severe hyperparathyroidism (NSHPT) is a rare disease that can be lethal. Most patients require parathyroidectomy.

OBJECTIVE

Report experience in managing this severe disease.

DESIGN

Retrospective chart review of case series.

SETTING

Tertiary health care center.

PATIENTS AND METHODS

We reviewed data on patients managed for NSHPT from June 2001 to January 2023. Demographic, clinical, and follow-up data were collected, and descriptive data were generated.

MAIN OUTCOME MEASURES

Pre- and postoperative levels of parathyroid hormone (PTH) and serum calcium, and effect of autotransplantation.

SAMPLE SIZE

19.

RESULTS

The 13 males and 6 females had a a mean age of 46 days at referral. The mean preoperative parathyroid hormone (PTH) and serum calcium levels were 996 ng/L and 4.54 mmol/L, respectively. Twelve patients underwent ultrasonography preoperatively. Of these, six had prominent glands, while no glands were seen in the other six. A Sestamibi scan was done for 15 patients, of which nine showed negative results and six showed positive results, with three glands observed in the neck and three in the sublingual area. Nineteen patients underwent renal ultrasonography, with nine showing nephrocalcinosis. The mean age at surgery was 5.2 months. Total parathyroidectomy (four glands) was performed in 17 patients, and 15 underwent concurrent auto-transplantation. One patient had three glands removed, in addition to auto-transplantation. Another underwent single gland excision as a redo-surgery after previous surgery elsewhere. The mean postoperative follow-up duration was 6 years. The mean postoperative PTH and calcium levels were 25 ng/L and 1.64 mmol/L, respectively. Ultimately, all the patients were required to initiate calcium and vitamin D supplements, except for two patients who had undergone auto-transplantation. Molecular genetic screening of the calcium-sensing receptor gene reported likely pathogenic/pathogenic mutations in 16 of 19 patients (13 were homozygous, two were heterozygous, one was negative, and data was unavailable for the remaining three patients).

CONCLUSIONS

Surgical treatment of NSHPT is effective. Preoperative radiological localization studies did not impact the treatment plan. Auto-transplantation proved ineffective in maintaining independence from medical supplements.

LIMITATIONS

The retrospective nature of the study may imply inaccuracybut since the data are gathered from electronic medical records, we believe it is highly accurate. The small sample size limits generalizability.

Disorders of the Calcium Sensing Signaling Pathway: From Familial Hypocalciuric Hypercalcemia (FHH) to Life Threatening Conditions in Infancy

Familial hypocalciuric hypercalcemia (FHH) is a mostly benign condition of elevated calcium and PTH levels based on a hyposensitive calcium sensing receptor (CaSR) in FHH 1 or its downstream regulatory pathway in FHH2 and FHH3. In children, adolescents and young adults with FHH the main challenge is to distinguish the condition from primary hyperparathyroidism and thereby to avoid unnecessary treatments including parathyroidectomy. However, inheritance of FHH may result in neonatal hyperparathyroidism (NHPT) or neonatal severe hyperparathyroidism (NSHPT), conditions with high morbidity, and in the latter even high mortality. This review focuses on the genetic and pathophysiological framework that leads to the severe neonatal form, gives recommendations for counselling and summarizes treatment options.

Cinacalcet as a First-Line Treatment in Neonatal Severe Hyperparathyroidism Secondary to Calcium Sensing Receptor (CaSR) Mutation

INTRODUCTION

Neonatal severe hyperparathyroidism (NSHPT) is a rare cause of neonatal hypercalcemia caused by a loss of function mutation in the calcium-sensing receptor (CaSR). Hypercalcemia in NSHPT can be life-threatening. Maintenance of serum calcium within a safe range is the primary goal of treatment through hydration, forced diuresis, and bisphosphonate treatment, nevertheless most cases require parathyroidectomy. We report a case with NSHPT diagnosed on the first day of life (DoL) and successfully treated with cinacalcet as the first-line treatment from the 2nd DoL up to the age of 18 months.

CASE REPORT

A full-term baby evaluated for weight loss at postnatal 14th hour and found to have hypercalcemia (14.4 mg/dL, reference range [RR]: 8.0-11.3). Despite hydration and diuresis, hypercalcemia persisted. Further evaluation revealed a parathyroid hormone (PTH) level of 1,493 pg/mL (RR: 15-65) and urine Ca/Cr of 0.09 mg/mg (RR: 0.03-0.81). Cinacalcet treatment was initiated on the 2nd DoL with the diagnosis of NSHPT due to hypocalciuric hypercalcemia and elevated PTH level. Ca levels decreased to normal levels on the 7th DoL. She was discharged from hospital at postnatal day 15 on cinacalcet treatment and still continued at 18 months of age. Sequencing of CaSR revealed a novel homozygous c.1836G>A (p.G613E) mutation in the patient, for which the parents and sister were heterozygous.

CONCLUSION

This case represents the youngest age at cinacalcet initiation and the longest duration without parathyroidectomy in a homozygous NSHPT and demonstrates that cinacalcet is an effective first-line treatment in patients who are responsive to this treatment modality and allows avoiding/delay in surgical intervention in NSHPT.

Rare diseases caused by abnormal calcium sensing and signalling

The calcium-sensing receptor (CaSR) provides the major mechanism for the detection of extracellular calcium concentration in several cell types, via the induction of G-protein-coupled signalling. Accordingly, CaSR plays a pivotal role in calcium homeostasis, and the CaSR gene defects are related to diseases characterized by serum calcium level changes. Activating mutations of the CaSR gene cause enhanced sensitivity to extracellular calcium concentration resulting in autosomal dominant hypocalcemia or Bartter-syndrome type V. Inactivating CaSR gene mutations lead to resistance to extracellular calcium. In these cases, familial hypocalciuric hypercalcaemia (FHH1) or neonatal severe hyperparathyroidism (NSHPT) can develop. FHH2 and FHH3 are associated with mutations of genes of partner proteins of calcium signal transduction. The common polymorphisms of the CaSR gene have been reported not to affect the calcium homeostasis itself; however, they may be associated with the increased risk of malignancies.

Case Report: Severe Neonatal Course in Paternally Derived Familial Hypocalciuric Hypercalcemia

Familial hypocalciuric hypercalcemia (FHH, [OMIM #145980]) is recognized as a benign endocrine condition affecting PTH and calcium levels due to heterozygous inactivating mutations in the calcium sensing receptor (CaSR). The condition is often un- or misdiagnosed but may have a prevalence as high as 74 in 100.000. Here, the neonatal courses of two brothers with paternally inherited FHH (CaSR c.554G>A; p.(Arg185Gln)) are described. The older brother was born preterm at 25 weeks gestation with hypercalcemia and hyperparathyroidism. The younger brother, born full-term, had severe hyperparathyroidism, muscular hypotonia, thrombocytopenia, failure to thrive and multiple metaphyseal fractures. Treatment with cinacalcet was initiated, which resulted in subsequent reduction of PTH levels and prompt clinical improvement. While it is known that homozygous mutations in CaSR may lead to life-threatening forms of neonatal severe hyperparathyroidism (NSHPT), few reports have described a severe clinical course in neonates with FHH due to heterozygous mutations. However, based on the pathophysiological framework, in de novo or paternally transmitted FHH the differing calcium needs of mother and fetus can be expected to induce fetal hyperparathyroidism and may result in severe perinatal complications as described in this report. In summary, FHH is a mostly benign condition, but transient neonatal hyperparathyroidism may occur in affected neonates if the mutation is paternally inherited. If severe, the condition can be treated successfully with cinacalcet. Patients with FHH should be informed about the risk of neonatal disease manifestation in order to monitor pregnancies and neonates.

Neonatal Severe Hyperparathyroidism: Novel Insights From Calcium, PTH, and the CASR Gene

CONTEXT

Neonatal severe hyperparathyroidism (NSHPT) is rare and potentially lethal. It is usually from homozygous or heterozygous germline-inactivating CASR variant(s). NSHPT shows a puzzling range of serum calcium and parathyroid hormone (PTH) levels. Optimal therapy is unclear.

EVIDENCE ACQUISITION

We categorized genotype/phenotype pairings related to CASRs. For the 2 pairings in NSHPT, each of 57 cases of neonatal severe hyperparathyroidism required calcium, PTH, upper normal PTH, and dosage of a germline pathogenic CASR variant.

EVIDENCE SYNTHESIS

Homozygous and heterozygous NSHPT are 2 among a spectrum of 9 genotype/phenotype pairings relating to CASRs and NSHPT. For the 2 NSHPT pairings, expressions differ in CASR allelic dosage, CASR variant severity, and sufficiency of maternofetal calcium fluxes. Homozygous dosage of CASR variants was generally more aggressive than heterozygous. Among heterozygotes, high-grade CASR variants in vitro were more pathogenic in vivo than low-grade variants. Fetal calcium insufficiency as from maternal hypoparathyroidism caused fetal secondary hyperparathyroidism, which persisted and was reversible in neonates. Among NSHPT pairings, calcium and PTH were higher in CASR homozygotes than in heterozygotes. Extreme hypercalcemia (above 4.5 mM; normal 2.2-2.6 mM) is a robust biomarker, occurring only in homozygotes (83% of that pairing). It could occur during the first week.

CONCLUSIONS

In NSHPT pairings, the homozygotes for pathogenic CASR variants show higher calcium and PTH levels than heterozygotes. Calcium levels above 4.5 mM among NSHPT are frequent and unique only to most homozygotes. This cutoff supports early and robust diagnosis of CASR dosage. Thereby, it promotes definitive total parathyroidectomy in most homozygotes.

Novel homozygous inactivating mutation of the calcium-sensing receptor gene in neonatal severe hyperparathyroidism responding to cinacalcet therapy: A case report and literature review

RATIONALE

Calcium-sensing receptor (CaSR) mutations can cause life-threatening neonatal severe hyperparathyroidism (NSHPT). The medical management of NSHPT is often challenging and complex. Here, we present a case of NSHPT caused by a novel homozygous CaSR mutation.

PATIENT CONCERNS

A Chinese female infant presented with poor feeding, constipation, severe hypotonia, and periodic bradycardia. Biochemistry tests revealed markedly elevated serum levels of Ca and parathyroid hormone (PTH).

DIAGNOSES

Genetic sequencing revealed a previously undescribed CaSR mutation in exon 3 (c.242T>A; p.I81K). A diagnosis of NSHPT secondary to homozygously inherited familial hypocalciuric hypercalcemia syndrome was established.

INTERVENTIONS

Cinacalcet was administered after the common treatments (low-calcium intake, hydration, and furosemide), calcitonin, and pamidronate therapy all failed.

OUTCOMES

Serum Ca decreased and stabilized with cinacalcet therapy. During a 10-month follow-up, total calcium was maintained within the high-normal range and PTH was normalized.

LESSONS

A trial of cinacalcet therapy might be undertaken in cases of NSHPT while definitive results of the genetic analysis are awaited.

Heterozygous inactivating CaSR mutations causing neonatal hyperparathyroidism: function, inheritance and phenotype

BACKGROUND

Homozygous inactivating mutations of the calcium-sensing receptor (CaSR) lead to neonatal severe hyperparathyroidism (NSHPT), whereas heterozygous inactivating mutations result in familial hypocalciuric hypercalcemia (FHH). It is unknown why in some cases heterozygous CaSR mutations cause neonatal hyperparathyroidism (NHPT) clinically similar to NSHPT but with only moderately elevated serum calcium.

METHODS

A literature survey was conducted to identify patients with heterozygous CaSR mutations and NHPT. The common NHPT CaSR mutants R185Q and R227L were compared with 15 mutants causing only FHH in the heterozygous state. We studied in vitro calcium signaling including the functional consequences of co-expression of mutant and wild-type (wt) CaSR, patients' phenotype, age of disease manifestation and mode of inheritance.

RESULTS

All inactivating CaSR mutants impaired calcium signaling of wt-CaSR regardless of the patients' clinical phenotype. The absolute intracellular calcium signaling response to physiologic extracellular calcium concentrations in vitro showed a high correlation with patients' serum calcium concentrations in vivo, which is similar in NHPT and FHH patients with the same genotype. Pedigrees of FHH families revealed that paternal inheritance per se does not necessarily lead to NHPT but may only cause FHH.

CONCLUSIONS

There is a significant correlation between in vitro functional impairment of the CaSR at physiologic calcium concentrations and the severity of alterations in calcium homeostasis in patients. Whether a particular genotype leads to NHPT or FHH appears to depend on additional predisposing genetic or environmental factors. An individual therapeutic approach appears to be warranted for NHPT patients.

Treatment experience and long-term follow-up data in two severe neonatal hyperparathyroidism cases

The calcium sensing receptor (CASR) is expressed most abundantly in the parathyroid glands and the kidney. CASR regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. Inactivating mutations in the CASR gene may result in disorders of calcium homeostasis manifesting as familial benign hypocalciuric hypercalcemia (FBHH) and neonatal severe hyperparathyroidsm (NSHPT). Two cases were referred with severe hypercalcemia in the neonatal period. Laboratory evaluation revealed severe hypercalcemia and elevated PTH. The parents also had mild hypercalcemia. The serum calcium level did not normalize with conventional hypercalcemia treatment and there was also no response to cinacalcet in case 1. Total parathyroidectomy was performed when the patient was 70 days old. Genetic analysis revealed a novel homozygous p.Arg544* mutation in the CASR gene. Case 2 underwent total parathyroidectomy and autoimplantation when she was 97 days old, but the parathyroid gland implanted into the forearm was removed 27 days later because the hypercalcemia continued. Genetic evaluation revealed a novel homozygous p.Pro682Leu mutation with normal anthropometric measurements. The neurological development is consistent with age in both cases while case 2 has mild mental retardation. No bone deformity or fracture is present in either case and normocalcemia is ensured with calcitriol in both cases.

GENETICS IN ENDOCRINOLOGY: Gain and loss of function mutations of the calcium-sensing receptor and associated proteins: current treatment concepts

The calcium-sensing receptor (CASR) is the main calcium sensor in the maintenance of calcium metabolism. Mutations of the CASR, the G protein alpha 11 (GNA11) and the adaptor-related protein complex 2 sigma 1 subunit (AP2S1) genes can shift the set point for calcium sensing causing hyper- or hypo-calcemic disorders. Therapeutic concepts for these rare diseases range from general therapies of hyper- and hypo-calcemic conditions to more pathophysiology oriented approaches such as parathyroid hormone (PTH) substitution and allosteric CASR modulators. Cinacalcet is a calcimimetic that enhances receptor function and has gained approval for the treatment of hyperparathyroidism. Calcilytics in turn attenuate CASR activity and are currently under investigation for the treatment of various diseases. We conducted a literature search for reports about treatment of patients harboring inactivating or activating CASR, GNA11 or AP2S1 mutants and about in vitro effects of allosteric CASR modulators on mutated CASR. The therapeutic concepts for patients with familial hypocalciuric hypercalcemia (FHH), neonatal hyperparathyroidism (NHPT), neonatal severe hyperparathyroidism (NSHPT) and autosomal dominant hypocalcemia (ADH) are reviewed. FHH is usually benign, but symptomatic patients benefit from cinacalcet. In NSHPT patients pamidronate effectively lowers serum calcium, but most patients require parathyroidectomy. In some patients cinacalcet can obviate the need for surgery, particularly in heterozygous NHPT. Symptomatic ADH patients respond to vitamin D and calcium supplementation but this may increase calciuria and renal complications. PTH treatment can reduce relative hypercalciuria. None of the currently available therapies for ADH, however, prevent tissue calcifications and complications, which may become possible with calcilytics that correct the underlying pathophysiologic defect.

The extracellular calcium-sensing receptor regulates human fetal lung development via CFTR

Optimal fetal lung growth requires anion-driven fluid secretion into the lumen of the developing organ. The fetus is hypercalcemic compared to the mother and here we show that in the developing human lung this hypercalcaemia acts on the extracellular calcium-sensing receptor, CaSR, to promote fluid-driven lung expansion through activation of the cystic fibrosis transmembrane conductance regulator, CFTR. Several chloride channels including TMEM16, bestrophin, CFTR, CLCN2 and CLCA1, are also expressed in the developing human fetal lung at gestational stages when CaSR expression is maximal. Measurements of Cl⁻-driven fluid secretion in organ explant cultures show that pharmacological CaSR activation by calcimimetics stimulates lung fluid secretion through CFTR, an effect which in humans, but not mice, was also mimicked by fetal hypercalcemic conditions, demonstrating that the physiological relevance of such a mechanism appears to be species-specific. Calcimimetics promote CFTR opening by activating adenylate cyclase and we show that Ca²⁺-stimulated type I adenylate cyclase is expressed in the developing human lung. Together, these observations suggest that physiological fetal hypercalcemia, acting on the CaSR, promotes human fetal lung development via cAMP-dependent opening of CFTR. Disturbances in this process would be expected to permanently impact lung structure and might predispose to certain postnatal respiratory diseases.

Neonatal severe hyperparathyroidism caused by homozygous mutation in CASR: A rare cause of life-threatening hypercalcemia

Neonatal severe hyperparathyroidism (NSHPT) is a rare, life-threatening condition that presents with severe hypercalcemia, hyperparathyroidism, and osteopenia in the newborn period. Treatment of NSHPT traditionally includes hydration and bisphosphonates; however newer calcimimetic agents, such as cinacalcet, are now being utilized to prevent or delay parathyroidectomy which is technically difficult in the newborn. Medical treatment success is related to calcium sensing receptor (CaSR) genotype. We report a 4-day-old infant who presented with hyperbilirubinemia, poor feeding, weight loss, severe hypotonia and was ultimately diagnosed with NSHPT. The patient's total serum calcium level of 36.8 mg/dL (reference range: 8.5-10.4 mg/dL) is, to our knowledge, the highest ever documented in this setting. Exome data previously obtained on the infant's parents was re-analyzed demonstrating bi-parental heterozygosity for a mutation of the CASR gene: c.206G > A, and Sanger sequencing data confirmed the patient was a homozygote for the same mutation. Though a patient with the same CaSR gene mutation described here has responded to cinacalcet, our patient did not respond and required parathyroidectomy. Though this case has previously been published as a surgical case report, a full report of the medical management and underlying genetic etiology is warranted; this case underscores the importance of disclosing bi-parental heterozygosity for a gene causing severe neonatal disease particularly when treatment is available and illustrates the need for further in vitro studies of this CaSR mutation.

Familial hypocalciuric hypercalcemia with a de novo heterozygous mutation of calcium-sensing receptor

A de novo heterozygous inactivating mutation of calcium-sensing receptor (CASR) gene typically causes neonatal hyperparathyroidism (NHPT) with moderate hypercalcemia and hyperparathyroid bone disease. We present a case of asymptomatic hypocalciuric hypercalcemia with a de novo heterozygous mutation in CASR, S591C, which is primarily reported to be responsible for NHPT. A 54-year-old female was referred for investigation of asymptomatic hypercalcemia that was initially found in the 1980s but without a history of bone disease during the perinatal period. She had moderate hypercalcemia (12.4 mg/dl) and relative hypocalciuria (fractional extraction of calcium 1.07%) but normal intact parathyroid hormone and serum 1,25-dihydroxyvitamin D3. Pedigree analysis revealed that she carried a de novo heterozygous mutation of S591C, which she transmitted to an affected child with moderate hypercalcemia but not to other children, who had normal serum calcium levels. A de novo heterozygous CASR mutation that is responsible for NHPT may also present in individuals with asymptomatic hypocalciuric hypercalcemia. Caution is required when predicting course and outcome in a pedigree with CASR mutation, as well as incidental hypercalcemia, because of its variable phenotypes.

LEARNING POINTS

The phenotype and severity of CASR mutations are thought to be dependent on genotypes.We report an asymptomatic case of the de novo heterozygous S591C mutation in CASR, which has previously been reported as a responsible mutation of NHPT with bone diseases.Variable phenotypes of CASR raise a cautionary note about predicting outcome by genotyping in a pedigree with CASR mutation.

Unusual case of neonatal hypercalcemia

We present a rare case of neonatal hyperparathyroidism secondary to a homozygous calcium sensing receptor (CASR) mutation, diagnosed by the genetics team. The CASR mutation is a homozygous inactivating mutation at the calcium sensing receptor. Inactivation of the receptor leads to hypercalcemia and activation leads to hypocalcemia. Heterozygous mutations can cause mild forms of asymptomatic hypercalcemia that often run in families. The homozygous mutation causes a rare form of neonatal severe hyperparathyroidism.

Surgical treatment of children with hyperparathyroidism: single centre experience

BACKGROUND

Hyperparathyroidism (HPT) in children is rare and surgical management is supported only by limited evidence.

METHODS

Retrospective case series of all children under the age of 16 years who underwent parathyroidectomy (PTx) between 1978 and 2012.

RESULTS

We identified 29 children who had surgery for HPT. Six were neonates with neonatal severe hyperparathyroidism (NSHPT) and 23 older children (age range 7-16 years) with sporadic (16) or familial (7) HPT and 93% were symptomatic. Accuracy of ultrasound and MIbi in localising solitary parathyroid adenomas was 96%, but less helpful in hyperplasia and neonates. Children with NSHPT underwent 5 curative total and 1 subtotal PTx (no reoperations). Children with familial HPT underwent 3 total and 4 subtotal PTx. One child with subtotal PTx required a reoperation. Children with sporadic HPT underwent subtotal PTx prior to 1980 (2), exploration and removal of enlarged glands 1980-2002 (5) and minimally invasive PTx since 2002 (9) and all cured by the first operation.

CONCLUSIONS

Our study documents that HPT in children is predominantly symptomatic on presentation and genetically determined in 46% of cases. Imaging is accurate in localising parathyroid adenomas, but not hyperplasias. Total PTx for familial HPT was curative and minimally invasive PTx is the operation of choice for older children with sporadic HPT.

Intraoperative parathyroid hormone monitoring in neonatal severe primary hyperparathyroidism

Neonatal severe primary hyperparathyroidism presents in the first days of life with severe life-threatening hypercalcemia. It is associated with an inactivating homozygous mutation of the calcium sensing receptor gene. Total parathyroidectomy is the treatment of choice, so the surgeon must identify all the parathyroid tissue, including supernumerary and ectopic glands. We present the case of an infant who underwent total parathyroidectomy at age 4 months in which intraoperative parathyroid hormone monitoring provided immediate confirmation of surgical cure.

Intraoperative parathyroid hormone monitoring corroborates the success of parathyroidectomy in children

OBJECTIVE

To assess the efficacy of intraoperative parathyroid hormone (PTH) monitoring in evaluating the outcome of parathyroidectomy in pediatric patients.

METHODS

Intraoperative PTH monitoring during parathyroidectomy was performed in five children (3M, 2F); three had parathyroid adenomas (single gland disease) and two had primary hyperplasia. One patient had undergone two previous surgical interventions to remove the parathyroid glands, but the PTH levels had remained high with persistence of symptoms. Immunoradiometric analysis was used for PTH measurements. Preoperative PTH values were obtained to monitor the baseline levels. Serum samples were collected 20 minutes after removal of the adenoma/parathyroid gland(s) and PTH levels were compared with preoperative values. Specimens were also confirmed by frozen sectional examination.

RESULTS

Mean age of the patients was 11 years (range: 3 months-16 years). Mean preoperative PTH values were 633.3±579 pg/mL (range: 143-1300 pg/mL). Intraoperative values decreased to 18.7±5.5 pg/mL (range: 8-27 pg/mL) following removal of the gland(s). Normal calcium levels were achieved with adequate management following surgery. One patient (with multiple surgeries and found to have an ectopic parathyroid gland) had hungry bone syndrome after the operation and was treated successfully. There were no major complications. All patients maintained normal calcium/phosphorus levels in the follow-up period, ranging from 2 to 5 years.

CONCLUSION

An ectopic parathyroid gland or another undetected adenoma can be overlooked during surgery. Owing to the short life of the hormone, intraoperative PTH monitoring to determine PTH clearance proved to be a feasible marker for adequacy and safety of surgery and "cure".

Novel homozygous inactivating mutation of the calcium-sensing receptor gene (CASR) in neonatal severe hyperparathyroidism-lack of effect of cinacalcet

BACKGROUND

NSHPT is a life-threatening disorder caused by homozygous inactivating calcium-sensing receptor (CASR) mutations. In some cases, the CaSR allosteric activator, cinacalcet, may reduce serum PTH and calcium levels, but surgery is the treatment of choice.

OBJECTIVE

To describe a case of NSHPT unresponsive to cinacalcet.

PATIENT AND RESULTS

A 23-day-old girl was admitted with hypercalcemia, hypotonia, bell-shaped chest and respiratory distress. The parents were first-degree cousins once removed. Serum Ca was 4.75 mmol/l (N: 2.10-2.62), P: 0.83 mmol/l (1.55-2.64), PTH: 1096 pg/ml (9-52) and urinary Ca/Cr ratio: 0.5mg/mg. First, calcitonin was given (10 IU/kg × 4/day), and then 2 days later, pamidronate (0.5mg/kg) for 2 days. Doses of cinacalcet were given daily from day 28 of life starting at 30 mg/m2 and increasing to 90 mg/m2 on day 43. On day 33, 6 days after pamidronate, serum Ca levels had fallen to 2.5 mmol/l but, thereafter, rose to 5 mmol/l despite the cinacalcet. Total parathyroidectomy was performed at day 45. Hungry bone disease after surgery required daily Ca replacement and calcitriol for 18 days. At 3 months, the girl was mildly hypercalcemic, with no supplementation, and at 6 months, she developed hypocalcemia and has since been maintained on Ca and calcitriol. By CASR mutation analysis, the infant was homozygous and both parents heterozygous for a deletion-frameshift mutation.

CONCLUSION

The predicted nonfunctional CaSR is consistent with lack of response to cinacalcet, but total parathyroidectomy was successful. An empiric trial of the drug and/or prompt mutation testing should help minimize the period of unnecessary pharmacotherapy.

Is calcium signaling relevant for long bone growth?

BACKGROUND

Neonatal severe hyperparathyroidism (NSHPT) is a rare autosomal recessive disorder of calcium homeostasis, more often induced by homozygous inactivating mutations of the calcium-sensing receptor gene. This rare syndrome can be lethal if total parathyroidectomy is not performed within the first weeks of life.

CLINICAL REPORT

We report the clinical case of a male patient, son of consanguineous hypercalcemic parents, with clinical and biochemical features of NSHPT, followed until the age of 21 years. The patient underwent total parathyroidectomy, and then, due to the low compliance to calcium and calcitriol supplementation, an attempt was made with recombinant human parathyroid hormone [rhPTH (1-84)]. The patient did not reach the predicted height with an increased ratio of the upper and lower segments.

CONCLUSIONS

While this case is unique for the length of follow-up, the continuous and detailed description of NSHPT after total parathyroidectomy in its adult phenotype, and the treatment of hypoparathyroidism with rhPTH (1-84). Following this first description of a statural defect due to shortening of long bones in NSHPT, future investigations will attempt to uncover the role of calcium signaling in growth plate cartilage in humans.

The extracellular calcium-sensing receptor, CaSR, in fetal development

In fetal mammals, serum levels of both total and ionized calcium significantly exceed those in the adult. This relative fetal hypercalcemia is crucial for skeletal development and is maintained irrespectively of maternal serum calcium levels. Elegant studies by Kovacs and Kronenberg have previously addressed the role of the CaSR in creating and maintaining this relative fetal hypercalcemia, through the regulation of parathyroid hormone-related peptide secretion. More recently we have shown that the CaSR is widely distributed throughout the developing fetus, where the receptor plays major, unexpected roles in ensuring growth and maturation of several organs. In this article, we present evidence for a role of the CaSR in the control of skeletal development, and how fetal hypercalcemia, acting through the CaSR, regulates lung development.

Neonatal hypercalcemia due to a homozygous mutation in the calcium-sensing receptor: failure of cinacalcet

A neonate affected by a novel inactivating mutation in the calcium-sensing receptor (CASR) gene is presented. This mutation is homozygously inherited and has not been previously described. A deletion in exon 5 (c.1392_1404del13) of the gene causes a loss of function of the receptor, which results in neonatal severe hyperparathyroidism and an ensuing extreme hypercalcemia. In a case of homozygosis of the CASR gene, the use of cinacalcet is the second reported calcimimetic treatment attempt and the first treatment attempt prior to surgery. However, because of the type of mutation, parathyroid surgery was necessary at 4 months of age after therapeutic failure. Because there are multiple mutations that affect the CASR gene in different ways, treatment with cinacalcet as an alternative to surgery may be valuable in homozygous cases that are caused by different mutations than the reported case.

A novel CaSR mutation presenting as a severe case of neonatal familial hypocalciuric hypercalcemia

BACKGROUND

Familial Hypocalciuric Hypercalcemia (FHH) is a generally benign disorder caused by heterozygous inactivating mutations in the Calcium-Sensing Receptor (CaSR) gene resulting in altered calcium metabolism.

OBJECTIVE

We report a case of unusually severe neonatal FHH due to a novel CaSR gene mutation that presented with perinatal fractures and moderate hypercalcemia. CASE OVERVIEW: A female infant was admitted at 2 weeks of age for suspected non-accidental trauma (NAT). Laboratory testing revealed hypercalcemia (3.08 mmol/L), elevated iPTH (20.4 pmol/L) and low urinary calcium clearance (0.0004). Radiographs demonstrated multiple healing metaphyseal and rib fractures and bilateral femoral bowing. The femoral deformity and stage of healing were consistent with prenatal injuries rather than non-accidental trauma (NAT). Treatment was initiated with cholecalciferol, 400 IU/day, and by 6 weeks of age, iPTH levels had decreased into the high-normal range. Follow up radiographs demonstrated marked improvement of bone lesions by 3 months. A CaSR gene mutation study showed heterozygosity for a T>C nucleotide substitution at c.1664 in exon 6, resulting in amino acid change I555T in the extracellular domain consistent with a missense mutation. Her mother does not carry the mutation and the father is unknown. At 18 months of age, the child continues to have relative hyperparathyroidism and moderate hypercalcemia but is otherwise normal.

CONCLUSION

This neonate with intrauterine fractures and demineralization, moderate hypercalcemia and hyperparathyroidism was found to have a novel inactivating missense mutation of the CaSR not detected in her mother. Resolution of bone lesions and reduction of hyperparathyroidism was likely attributable to the natural evolution of the disorder in infancy as well as the mitigating effect of cholecalciferol treatment.

Successful use of bisphosphonate and calcimimetic in neonatal severe primary hyperparathyroidism

Neonatal primary hyperparathyroidism (NPHT) is associated with an inactivating homozygous mutation of the calcium sensing receptor (CaSR). The CaSR is expressed most abundantly in the parathyroid glands and the kidney and regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. NPHT leads to life threatening hypercalcemia, nephrocalcinosis, bone demineralization, and neurologic disabilities. Surgery is the treatment of choice. While waiting for surgery, bisphosphonates offer a good alternative to deal with hypercalcemia. Cinacalcet is a class II calcimimetic that increases CaSR affinity for calcium, leading to parathormone suppression and increased calcium renal excretion. At present, there is little evidence as to whether cinacalcet could improve the function of mutant CaSR in NPHT. We report a case of NPHT, treated successfully with bisphosphonates and cinacalcet after surgery failure. To our knowledge, it is the first time cinacalcet has been used for NPHT.

Neonatal severe hyperparathyroidism: further clinical and molecular delineation

We report a newborn female from a consanguineous Sri Lankan family with clinical and biochemical features of neonatal severe hyperparathyroidism (NSHPT). Mutation screening of the calcium-sensing receptor (CASR) gene in genomic DNA revealed a homozygous truncating mutation (c.679C>T, predicting p.R227X), confirming the clinical diagnosis. Other mutations at the R227 position are reported to cause varying degrees of hypercalcemia and hyperparathyroidism, but this nonsense variant is novel and expected to induce unremitting hyperparathyroidism from birth onward. In our patient with NSHPT, early bisphosphonate therapy was crucial in counteracting the marked hypercalcemia and allowed for safe surgical intervention ("total" parathyroidectomy, "thymectomy and hemithyroidectomy") at 3 months of age.

CONCLUSION

This report highlights the continuing challenges in diagnosis and management of this life-threatening condition.

Neonatal hyperparathyroidism with a heterozygous calcium-sensing receptor (CASR) R185Q mutation: clinical benefit from cinacalcet

Neonatal hyperparathyroidism can be caused by a heterozygous inactivating mutation in the calcium-sensing receptor. Calcimimetics, allosteric activators of the calcium-sensing receptor, may provide an effective means of reducing PTH secretion in such patients. OBJECTIVE/PATIENT: The objective of the study was to identify the molecular defect and to monitor the postnatal course of a 1-wk-old infant with elevated blood ionized calcium, serum PTH, and alkaline phosphatase and low calcium excretion. The parents were normocalcemic.

METHODS

CASR gene mutation analysis was performed on genomic DNA of the proband and her parents. The infant was treated initially with pamidronate and then cinacalcet.

RESULTS

A heterozygous mutation (R185Q, CGA > CAA) in exon 4 of the CASR gene was identified in the proband. The CASR gene of both parents was normal. At 1 wk of age, iv fluids and furosemide were initiated, but hypercalcemia, hyperparathyroidism, and low calcium excretion persisted. At 2 wk of age, a single iv dose of pamidronate resulted in hypocalcemia and further increase in PTH levels, but hypercalcemia recurred within 1 wk. At 3 wk of age, a single oral dose of cinacalcet resulted in decreased PTH levels at 2 h; blood-ionized calcium reached a nadir at 10 h. Three days later daily cinacalcet was initiated, resulting in normalization of ionized calcium. The suppression of serum PTH and reduction in total serum calcium was maintained long term.

CONCLUSIONS

In neonatal hyperparathyroidism secondary to presumed de novo heterozygous CASR mutation, treatment with cinacalcet decreases PTH secretion and serum calcium levels and mitigates the need for parathyroidectomy.

Surgical management of severe neonatal hyperparathyroidism: one center's experience

INTRODUCTION

Neonatal severe hyperparathyroidism (NSHPT) is a rare disease that presents early with severe hypercalcemia. We reviewed our experience with NSHPT management at a tertiary-care institution.

METHODS

A retrospective chart review was conducted for patients managed for NSHPT over the last 10 years. Demographic, clinical, and follow-up data were collected, and descriptive data were generated.

RESULTS

Five patients were managed for NSHPT, 3 females and 2 males, with a mean age of 18 days at presentation. The mean preoperative parathyroid hormone and calcium levels were 3607 ng/L and 3.84 mmol/L, respectively. Preoperative parathyroid gland localization tests were all negative. All patients had a total parathyroidectomy and autotransplantation at a mean age of 65 days, with a mean follow-up of 5.5 years. One patient had normal parathyroid hormone and normal calcium levels 9.5 years after surgery without medication. One patient had normal levels without medication for 2 years then needed calcium and vitamin D supplements thereafter (8.5 years postoperatively). Three patients are still on calcium and vitamin D supplementation 5.5 years, 3.5 years, and 8 months, respectively, after surgery.

CONCLUSIONS

Neonatal severe hyperparathyroidism is managed effectively with total parathyroidectomy. Preoperative localization studies are not helpful, and autotransplantation has a modest effect in our experience.

Physiology and pathophysiology of the calcium-sensing receptor in the kidney

The extracellular calcium-sensing receptor (CaSR) plays a major role in the maintenance of a physiological serum ionized calcium (Ca2+) concentration by regulating the circulating levels of parathyroid hormone. It was molecularly identified in 1993 by Brown et al. in the laboratory of Dr. Steven Hebert with an expression cloning strategy. Subsequent studies have demonstrated that the CaSR is highly expressed in the kidney, where it is capable of integrating signals deriving from the tubular fluid and/or the interstitial plasma. Additional studies elucidating inherited and acquired mutations in the CaSR gene, the existence of activating and inactivating autoantibodies, and genetic polymorphisms of the CaSR have greatly enhanced our understanding of the role of the CaSR in mineral ion metabolism. Allosteric modulators of the CaSR are the first drugs in their class to become available for clinical use and have been shown to treat successfully hyperparathyroidism secondary to advanced renal failure. In addition, preclinical and clinical studies suggest the possibility of using such compounds in various forms of hypercalcemic hyperparathyroidism, such as primary and lithium-induced hyperparathyroidism and that occurring after renal transplantation. This review addresses the role of the CaSR in kidney physiology and pathophysiology as well as current and in-the-pipeline treatments utilizing CaSR-based therapeutics.

Pamidronate therapy for hypercalcemia and congenital mesoblastic nephroma: a case report

Hypercalcemia can causes life threatening complications. We report an infant with severe hypercalcemia due to congenital mesoblastic nephroma. Hypercalcemia was corrected before nephrectomy by pamidronate. According to our knowledge this is a rare case with severe neoplasm induced hypercalcemia among neonates who treated by bisphosphonates. The aim of this report is to define new approach to neoplasm induced neonatal hypercalcemia.

Regulation of mouse lung development by the extracellular calcium-sensing receptor, CaR

Postnatal lung function is critically dependent upon optimal embryonic lung development. As the free ionized plasma calcium concentration ([Ca(2+)](o)) of the fetus is higher than that of the adult, the process of lung development occurs in a hypercalcaemic environment. In the adult, [Ca(2+)](o) is monitored by the G-protein coupled, extracellular calcium-sensing receptor (CaR), but neither its ontogeny nor its potential role in lung development are known. Here, we demonstrate that CaR is expressed in the mouse lung epithelium, and that its expression is developmentally regulated, with a peak of expression at embryonic day 12.5 (E12.5) and a subsequent decrease by E18, after which the receptor is absent. Experiments carried out using the lung explant culture model in vitro show that lung branching morphogenesis is sensitive to [Ca(2+)](o), being maximal at physiological adult [Ca(2+)](o) (i.e. 1.0-1.3 mM) and lowest at the higher, fetal (i.e. 1.7 mM) [Ca(2+)](o). Administration of the specific CaR positive allosteric modulator, the calcimimetic R-568, mimics the suppressive effects of high [Ca(2+)](o) on branching morphogenesis while both phospholipase C and PI3 kinase inhibition reverse these effects. CaR activation suppresses cell proliferation while it enhances intracellular calcium signalling, lung distension and fluid secretion. Conditions which are restrictive either to branching or to secretion can be rescued by manipulating [Ca(2+)](o) in the culture medium. In conclusion, fetal Ca(2+)(o), acting through a developmentally regulated CaR, is an important extrinsic factor that modulates the intrinsic lung developmental programme. Our observations support a novel role for the CaR in preventing hyperplastic lung disease in utero.

Surgical treatment of primary hyperparathyroidism in children: report of 10 cases

Primary hyperparathyroidism in children is very rare. It is caused by overproduction of parathormone by a pathologically changed parathyroid gland. We carried out a retrospective study in 10 patients (age 10-17 years) who had surgical treatment between 1996 and 2007. The main signs of primary hyperparathyroidism were urolithiasis, nephrolithiasis, nephrocalcinosis and bone resorption, as well as non-specific signs such as fatigue, torpidness and muscle weakness. Patients were examined using sonography, MIBI-scintigraphy, CT and MRI. Calcium was measured before and after surgery; parathormone was monitored postoperatively. Surgery was curative in nine patients; reoperation was necessary in one patient because an ectopic parathyroid gland was not detected during the primary operation. Other major complications were not observed. Removal of pathologically changed parathyroid glands offers definitive and safe treatment of primary hyperparathyroidism in children. Special care should be taken if an ectopic parathyroid gland is suspected.