An Open-Label Extension Study of Parathyroid Hormone Rhpth(1-84) in Adults with Hypoparathyroidism

Objective: Hypoparathyroidism is characterized by inadequate parathyroid hormone (PTH), resulting in hypocalcemia, hyperphosphatemia, and bone abnormalities. Adults with hypoparathyroidism treated with recombinant human PTH, rhPTH(1-84), in the 24-week, phase III REPLACE study maintained serum calcium despite reductions in oral calcium and active vitamin D. This study assessed the long-term efficacy and safety of rhPTH(1-84) for hypoparathyroidism.Methods: This was a 24-week, open-label, flexible-dose extension study of REPLACE (REPEAT) conducted in 3 outpatient centers in Hungary. Patients who previously completed or enrolled in REPLACE received 50 μg/day rhPTH(1-84), escalated to 75 and then to 100 μg/day, if needed, to reduce active vitamin D and oral calcium. The primary endpoint was ≥50% reduction in oral calcium (or ≤500 mg/day) and active vitamin D (or calcitriol ≤0.25 μg/day or alfacalcidol ≤0.50 μg/day) with normocalcemia.Results: Twenty-four patients (n = 16 previously treated with rhPTH[1-84]; n = 8 rhPTH[1-84]-naïve) were enrolled and completed the study. At Week 24, 75% of patients (95% confidence interval [CI], 53.3–90.2%) achieved the study endpoint; 58% eliminated oral calcium and active vitamin D. Urinary calcium, serum phosphate, and calcium × phosphate (Ca × P) product decreased by Week 24. Mean serum bone turnover markers increased with rhPTH(1-84). Treatment-emergent adverse events (TEAEs) were reported by 92% of patients. No serious adverse events (AEs) occurred.Conclusion: This study used a simplified treatment algorithm intended to better mimic typical clinical practice and demonstrated the extended efficacy and safety of rhPTH(1-84) in patients with hypoparathyroidism and confirmed the REPLACE findings. Sustained rhPTH(1-84) efficacy up to 48 weeks was observed despite treatment interruption between studies.Abbreviations:AE = adverse eventBMD = bone mineral densityBSAP = bone-specific alkaline phosphataseBTM = bone turnover markerCa × P product = calcium × phosphate productCTX = cross-linked C-telopeptide of type 1 collagenOCN = osteocalcin25(OH)D = 25-hydroxyvitamin DP1NP = aminoterminal propeptide of type 1 collagenPTH = parathyroid hormonerhPTH(1-84) = recombinant human parathyroid hormoneTEAE = treatment-emergent adverse eventULN = upper limit of normal     

Decreased Calcitriol Requirement During Pregnancy and Lactation With A Window of Increased Requirement Immediately Post Partum

ObjectiveTo describe the changes in calcium and cal- citriol requirements during pregnancy and lactation in a pa- tient with hypoparathyroidism due to autosomal dominant hypocalcemia.MethodsWe summarize the clinical presentation and treatment of the patient and review the pertinent literature.ResultsCalcitriol requirements disappeared during pregnancy in a 34-yearold woman with autosomal dominant hypoparathyroidism secondary to an activating mutation in the calciumsensing receptor gene. Within hours after delivery, her serum calcium concentration dropped to 4.7 mg/dL (albumin, 3.2 g/dL), and she required intravenous calcium and reinstitution of calcitriol. When lactation began a few days later, her calcitriol requirement again disappeared. As has occasionally been described in the literature, this patient with hypoparathyroidism required no calcitriol during late pregnancy and lactation to maintain a normal serum calcium level.ConclusionsTo our knowledge, this is the first reported case documenting a period of time between pregnancy and lactation when calcitriol requirements reappeared, likely due to a parathyroid hormone-related protein “window” between delivery, when placental production of parathyroid hormone-related protein stops, and lactation, when mammary gland production begins. (Endocr Pract. 2010:16:459-462)     

Chemotherapy-Induced Hypocalcemia

ObjectiveTo present a unique case of transient, asymptomatic chemotherapy-induced hypocalcemia not attributable to hypomagnesemia or tumor lysis syndrome and review causes of hypocalcemia related to cancer with and without use of chemotherapy.MethodsWe present a case detailing the clinical and laboratory findings of a patient who had severe hypocalcemia during chemotherapy and discuss causes of hypocalcemia with an extensive literature review of chemotherapeutic agents associated with this biochemical abnormality.ResultsIn a 90-year-old man, hypocalcemia developed during 2 courses of chemotherapy for Hodgkin lymphoma, with partial recovery between courses and normal serum calcium 10 months after completion of treatment. Magnesium, vitamin D, and parathyroid hormone levels were low normal. There was no evidence of tumor lysis syndrome. Of the various agents administered, vinca alkaloids seemed the most likely cause. Serial testing suggested that the underlying mechanism may have been acquired, reversible hypoparathyroidism. No other similar case was found in the published literature.ConclusionThe severe hypocalcemia in our patient could not be attributed to hypomagnesemia or tumor lysis syndrome, and it was clearly associated with the timing of his chemotherapeutic regimen. Possibilities include direct parathyroid hormone suppression or alteration of calcium sensing by the chemotherapeutic drugs. Serum calcium surveillance before and during chemotherapeutic management of cancer patients may reveal more instances and provide insight into the exact mechanism of this lesser known yet striking complication. (Endocr Pract. 2010;16:284-290)     

Clinical heterogeneity of pseudohypoparathyroidism: from hyper- to hypocalcemia

Pseudohypoparathyroidism (PHP) is a rare inherited syndrome characterized by parathyroid hormone (PTH) resistance and is frequently associated with Albright's hereditary osteodystrophy and resistance to other cAMP-mediated hormones. The usual neonatal presentation is mild primary hypothyroidism secondary to resistance to thyroid-stimulating hormone; hypocalcemia usually develops after age 3-5 years. This work describes the diversity in the clinical expression and course of PHP, with emphasis on calcium levels by age and treatment, in 8 children under long-term follow-up at our pediatric tertiary center. The calcium levels at presentation ranged from transient neonatal hypocalcemia to infantile hypercalcemia to childhood/adolescence hypocalcemia. Interestingly, relative hypocalciuria at diagnosis and during therapy, in the presence of renal PTH resistance, was the rule. These findings indicate that transient neonatal hypocalcemia associated with other clinical features or a family history of PHP may be a flag for clinicians to screen for PTH resistance later in life. In addition, PTH resistance may be missed by surveying calcium levels only; thus the PTH levels have to be checked as well. In addition, the recommendation for patients with hypoparathyroidism that strict low-normal calcium levels be maintained during therapy in order to prevent hypercalciuria is probably not applicable in PHP.     

Proton Pump Inhibitor-Induced Hypocalcemic Seizure in A Patient with Hypoparathyroidism

ObjectiveTo report a case of proton pump inhibitor-induced hypocalcemic seizure in a patient with hypoparathyroidism.MethodsWe describe the clinical history, physical examination findings, and laboratory values of the patient and briefly review the relevant literature.ResultsA 48-year-old woman with a history of postsurgical hypoparathyroidism who was taking calcium carbonate, 1500 mg 3 times daily, and cholecalciferol, 1200 IU daily, presented with a generalized seizure in the setting of hypocalcemia 12 days after initiating therapy with the proton pump inhibitor lansoprazole. Physical examination revealed a positive Chvostek sign. Electrocardiogram was notable for a prolonged QT_c interval of 576 milliseconds. Laboratory data were notable for the following values: total serum calcium, 5.3 mg/dL; ionized calcium, 2.51 mg/dL; and intact parathyroid hormone, 5.8 pg/mL. The patient’s condition responded to therapy with intravenous calcium gluconate, oral calcium carbonate, and calcitriol. As an outpatient she remained asymptomatic off lansoprazole, treated with calcium carbonate and calcitriol.ConclusionsCaution should be exercised in prescribing proton pump inhibitors to patients with a history of hypoparathyroidism treated with calcium carbonate supplementation because severe hypocalcemia is a potential adverse effect. (Endocr Pract. 2011;17:104-107)     

Delayed-Onset Hypoparathyroidism in an Adolescent with Chromosome 22Q11 Deletion Syndrome

ObjectiveTo describe the first case of established chromosome 22q11 deletion syndrome with late onset presentation of hypocalcemia secondary to hypoparathyroidism.MethodsWe present the history, clinical and laboratory investigations, and management of a 17-yearold adolescent boy who presented with 3 separate seizures secondary to hypocalcemia. This patient had an established diagnosis of chromosome 22q11 deletion syndrome at the time of the seizure presentations, but had previously normal calcium levels.ResultsHypocalcemia was noted during each seizure, with corrected calcium levels ranging from 6.64 to 7.76 mg/dL (reference range, 8.52 to 10.52 mg/dL). The hypocalcemia was secondary to hypoparathyroidism, with parathyroid hormone levels < 2.75 pg/mL (reference range, 22.9 to 68.75 pg/mL). He was treated with calcitriol, 0.5 μg daily, and calcium carbonate, 2,400 mg daily, leading to normalization of serum calcium and resolution of seizures.ConclusionChromosome 22q11 deletion syndrome is a relatively common genetic disorder with a wide variety of phenotypic manifestations including cardiac abnormalities, abnormal facies, thymic dysfunction, cleft palate, and hypocalcemia. This case shows that medical practitioners should be aware that hypocalcemia can present after an established diagnosis, which has implications for the management of this disorder. (Endocr Pract. 2011;17: e123-e125)     

The Ca2+-sensing receptor gene (PCAR1) mutation T151M in isolated autosomal dominant hypoparathyroidism

Isolated autosomal dominant hypoparathyroidism is a heterogeneous disorder characterized by parathyroid hormone (PTH) deficiency, hypocalcemia and hyperphosphatemia. The candidate gene approach was used to study a large Norwegian family. The loci for the PTH gene, PTH receptor gene and RET protooncogene were excluded using dinucleotide markers and restriction fragment length polymorphism analysis. Complete cosegregation of this trait was found with the chromosomal region 3q13, using the short tandem repeat markers D3S1267, D3S1269, D3S1303, D3S1518, and RHO. This region contains the candidate locus for the Ca²⁺-sensing receptor (PCAR1). By single-strand conformation polymorphism (SSCP) analysis of all PCAR1 exons followed by automated sequencing, we identified a C to T transition in exon 2 (cDNA position 452) on the mutant allele in the family. The mutation predicts a substitution of Thr to Met in amino acid position 151 (T151M). A StyI restriction site created by the nucleotide substitution was used to confirm the mutation on all alleles, as well as to exclude it among 100 normal alleles (blood donors). SSCP analysis also identified a novel polymorphism of PCAR1 intron 4 (1609–88t→c) on normal alleles.The T151M mutation is located in the extracellular N-terminal domain of PCAR1, which belongs to the superfamily of G protein-coupled receptors. We suggest that this is a gain-of-function mutation that increases the sensitivity of the receptor to [Ca²⁺], thereby decreasing the calcium set point. Received: 29 September 1995 / Revised: 19 January 1996     

Suppressibility of Parathyroid Hormone in Primary Hyperparathyroidism

ObjectiveTo describe an unusual case of pathologically confirmed primary hyperparathyroidism in a patient presenting with severe hypercalcemia and an undetectable parathyroid hormone (PTH) level.MethodsWe present a detailed case report and outline the serial laboratory findings. In addition, the possible causes of low serum PTH levels in the setting of primary hyperparathyroidism are discussed.ResultsA 16-year-old female patient presented with severe epigastric pain, found to be attributable to acute pancreatitis. At hospital admission, her serum calcium concentration was high (14.0 mg/dL); the patient also had a normal serum phosphorus level of 3.6 mg/dL and an undetectable PTH level (< 0.2 pmol/L). An evaluation for non-PTH-mediated causes of hypercalcemia revealed a partially suppressed thyroid-stimulating hormone concentration and a below normal 1,25-dihydroxyvitamin D level, consistent with her suppressed PTH. One week after the patient was dismissed from the hospital, repeated laboratory studies showed a serum calcium value of 11.1 mg/dL, a serum phosphorus level of 2.8 mg/dL, and an elevated PTH concentration of 11.0 pmol/L, consistent with primary hyperparathyroidism. A repeated 1,25-dihy-droxyvitamin D measurement was elevated. A parathyroid scan showed a parathyroid adenoma in the left lower neck area, and she subsequently underwent successful surgical resection of a pathologically confirmed parathyroid adenoma.ConclusionThis case demonstrates that the serum PTH level can be suppressed in patients with primary hyperparathyroidism. Moreover, it emphasizes the need for careful evaluation of the clinical context in which the PTH measurement is determined. Consideration should be given to repeating measurement of PTH and serum calcium levels when the initial laboratory evaluation of hypercalcemia is unclear because dynamic changes in calcium metabolism may occur in the presence of secondary contributing factors. (Endocr Pract. 2007;13:785-789)     

Idiopathic Hypoparathyroidism Presenting with Severe Hypocalcemia and Asymptomatic Basal Ganglia Calcification Followed by acute Intracerebral Bleed

ObjectiveTo report a case of idiopathic hypoparathyroidism presenting with severe hypocalcemia and intracerebral calcifications that resulted in a spontaneous intracerebral bleed.MethodsWe present the clinical, laboratory, and radiologic findings in a woman with idiopathic hypoparathyroidism who developed spontaneous intracerebral bleed in the setting of chronic intracerebral calcifications.ResultsA 37-year-old woman presented with vague symptoms of hypocalcemia. Clinical evaluation revealed brisk deep tendon Reflexes and positive Chvostek’s and Trousseau’s signs. The serum calcium level was 3.7 mg/ dL (reference range, 8.0 to 10.6 mg/dL) and the phosphorus level was 8.2 mg/dL (reference range, 2.3 to 5.0 mg/dL). Serum intact parathyroid hormone was undetectable. Computed tomography of the head showed extensive bilateral symmetrical calcification of basal ganglia and dentate nucleus in the cerebellum and centrum semiovale. Fluid and electrolytes were replaced appropriately, and calcium and calcitriol were prescribed. While in the hospital, the patient developed an acute intracerebral bleed confirmed by computed tomography. The patient recovered without neurologic sequelae and was discharged from the hospital on calcium supplementation and calcitriol. Repeated computed tomography of the head 3 years later demonstrated complete resolution of the bleed.ConclusionThis case suggests that patients with severe hypoparathyroidism and intracerebral calcification may be at risk for spontaneous intracerebral bleed and should be monitored accordingly. (Endocr Pract. 2007; 13:487-492     

Excessive Signal Transduction of Gain-of-Function Variants of the Calcium-Sensing Receptor (CaSR) Are Associated with Increased ER to Cytosol Calcium Gradient

In humans, gain-of-function mutations of the calcium-sensing receptor (CASR) gene are the cause of autosomal dominant hypocalcemia or type 5 Bartter syndrome characterized by an abnormality of calcium metabolism with low parathyroid hormone levels and excessive renal calcium excretion. Functional characterization of CaSR activating variants has been so far limited at demonstrating an increased sensitivity to external calcium leading to lower Ca-EC50. Here we combine high resolution fluorescence based techniques and provide evidence that for the efficiency of calcium signaling system, cells expressing gain-of-function variants of CaSR monitor cytosolic and ER calcium levels increasing the expression of the Sarco-Endoplasmic Reticulum Calcium-ATPase (SERCA) and reducing expression of Plasma Membrane Calcium-ATPase (PMCA). Wild-type CaSR (hCaSR-wt) and its gain-of-function (hCaSR-R990G; hCaSR-N124K) variants were transiently transfected in HEK-293 cells. Basal intracellular calcium concentration was significantly lower in cells expressing hCaSR-wt and its gain of function variants compared to mock. In line, FRET studies using the D1ER probe, which detects [Ca2+]ER directly, demonstrated significantly higher calcium accumulation in cells expressing the gain of function CaSR variants compared to hCaSR-wt. Consistently, cells expressing activating CaSR variants showed a significant increase in SERCA activity and expression and a reduced PMCA expression. This combined parallel regulation in protein expression increases the ER to cytosol calcium gradient explaining the higher sensitivity of CaSR gain-of-function variants to external calcium. This control principle provides a general explanation of how cells reliably connect (and exacerbate) receptor inputs to cell function.     

Mapping of the calcium-sensing receptor gene (CASR) to human Chromosome 3q13.3-21 by fluorescence in situ hybridization,and localization to rat Chromosome 11 and mouse Chromosome 16

The calcium-sensing receptor (CASR), a member of the G-protein coupled receptor family, is expressed in both parathyroid and kidney, and aids these organs in sensing extracellular calcium levels. Inactivating mutations in the CASR gene have been described in familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT). Activating mutations in the CASR gene have been described in autosomal dominant hypoparathyroidism and familial hypocalcemia. The human CASR gene was mapped to Chromosome (Chr) 3q13.3-21 by fluorescence in situ hybridization (FISH). By somatic cell hybrid analysis, the gene was localized to human Chr 3 (hybridization to other chromosomes was not observed) and rat Chr 11. By interspecific backcross analysis, the Casr gene segregated with D16Mit4 on mouse Chr 16. These findings extend our knowledge of the synteny conservation of human Chr 3, rat Chr 11, and mouse Chr 16.     

Inhibition of PTH Secretion by Interleukin-1β in Bovine Parathyroid Glandsin VitroIs Associated with an Up-Regulation of the Calcium-Sensing Receptor mRNA

The principal regulator of parathyroid hormone (PTH) secretion is ionized calcium, but other factors are also known to modulate PTH secretion, such as vitamin D, estrogen, and recently inorganic phosphate. Interleukin-1 (IL-1) possesses a wide variety of biological activities and is produced by leukocytes as well as by various other cells including cells from endocrine tissues and might play a role as a paracrine factor in the control of PTH secretion. We investigated the effectin vitroof IL-1β on PTH release, PTHmRNA and the mRNA for the extracellular calcium-sensing receptor (CaR) levels in preparations of bovine parathyroid cells. PTH secretion from cultured parathyroid tissue slices was significantly inhibited in a medium containing IL-1β at a concentration of 2000 pg/ml (PTH in % of control: 63.5 ± 5.3), n=10 (p<0.01). The inhibitory effect of IL-1β was not found in preparations of dispersed cells. The inhibitory effect of IL-1β could be counteracted by the IL-1 receptor antagonist (IL-1ra), indicating that the inhibitory effect was mediated through the specific IL-1 receptor on the parathyroid cells. IL-1β (2000 pg/ml) up-regulated CaRmRNA levels to 180% of control, whereas no change in PTHmRNA was found. IL-1ra abolished the upregulating effect of IL-1β on the CaRmRNA. This study demonstrates a direct effectin vitroof IL-1β on PTH secretion from bovine parathyroid glands, an effect which may be mediated at least in part through the specific IL-1 receptor causing an upregulation of the calcium-sensing receptor mRNA. IL-1 might therefore play a role as a auto- and/or paracrine factor in the regulation of the PTH secretion.     

A patient of short stature with idiopathic hypoparathyroidism round face and metacarpal signs

A 16-year old girl of short stature, with round face, mental retardation, and Albright's dimple sign was admitted for evaluation of hypocalcemia. Her serum calcium levels were 6.3-8.0 mg/dl, and phosphorus 6.9-7.8 mg/dl. Although a diagnosis of pseudohypoparathyroidism was initially suggested, her serum iPTH concentration was low (0.1 ng/ml). Furthermore, an injection of synthetic human parathyroid hormone (100 U, hPTH (1-34] was followed by a marked increase in urinary excretion of cyclic AMP and phosphorus. This case suggests that a shortened metacarpal is not a reliable guide in distinguishing between idiopathic hypoparathyroidism and pseudohypoparathyroidism and that a standard Ellsworth-Howard test is a prerequisite to differential diagnosis.     

Hypercalcemia and Acromegaly-Clarifying the Connections: A Case Report and Review of the Literature

ObjectiveHypercalcemia in patients with acromegaly is rare and usually due to co-existent primary hyperparathyroidism. The etiology of hypercalcemia directly related to acromegaly is debated.MethodsWe present a case report of 1,25(OH)2D3-mediated hypercalcemia in a patient with acromegaly and discuss potential pathophysiological mechanisms contributing to the development of hypercalcemia late in the course of the disease.ResultsA 67-year-old female presented with classical features of acromegaly. A review of her previous photographs suggested a disease duration of approximately 10 years, and her serum calcium (Ca) was normal during this period. A biochemical work up confirmed a combined growth hormone (GH-) and prolactin (PRL-) cosecreting tumor with a GH level of 92.03 ng/mL (normal 0-3.61), an insulin-like growth factor-1 (IGF-1) level of 1,498 ng/ mL (59-225), and a PRL level of 223.3 ng/mL (2-17.4). Magnetic resonance imaging (MRI) of the pituitary showed a 1.9-cm macroadenoma. Her preoperative work up revealed new onset hypercalcemia with a corrected serum Ca level of 10.7 mg/dL (8.5-10.5), an ionized Ca level of 1.37 mmol/L (1.08-1.30), a parathyroid hormone (PTH) level of 13.0 pg/mL (10-60), and a high 1,25(OH)2D3 level of 72.6 pg/mL (15-60). She underwent resection of the pituitary adenoma with normalization of GH and PRL levels, and her IGF-1 level decreased to 304 ng/mL. Her serum Ca (9.3 mg/dL), ionized Ca(1.22) and 1,25(OH)2D3 levels (38.6 pg/mL) normalized after surgery.ConclusionWhile overt hypercalcemia in acromegaly is rare, it tends to occur late in the disease course. The hypercalcemia is mediated by elevated 1,25(OH)2D3 levels rather than PTH. (Endocr Pract. 2014;20:e86-e90)     

Hypoplasia of the bone marrow in rats following removal of the parathyroid glands

Removal of the parathyroid glands caused a marked and permanent lowering of the mitotic activity in rat bone marrow, which was followed by a pronounced decline (ca. 40%) in the size of the marrow's nucleated cell population. These changes occurred only when the hypocalcemia induced by the lack of parathyroid hormone (PTH) was maintained by feeding the animals a calcium deficient diet. Since the overall marrow hypoplasia was almost entirely due to strikingly large reductions (ca. 70%) in the size of the erythroid and lymphoid subpopulations, it is concluded that PTH and calcium are major physiological regulators of the proliferation of erythroid and lymphoid cells.     

A Parathyroid Hormone–Guided Calcium and Calcitriol Supplementation Protocol Reduces Hypocalcemia-Related Readmissions Following Total Thyroidectomy

ObjectiveTo determine the effect of a 4-hour postoperative serum parathyroid hormone (PTH)–guided calcium (Ca) and calcitriol supplementation protocol on the incidence of hypocalcemia and hospital readmissions in patients undergoing total thyroidectomy.MethodsThis was a single-institution, retrospective chart review of patients who underwent total thyroidectomy; 148 and 389 of the patients underwent surgery prior to and after the protocol implementation, respectively. The risk of hypocalcemia was stratified as low (PTH level of >30 pg/mL), medium (15-30 pg/mL), and high (<15 pg/mL), using serum PTH values obtained 4 hours postoperatively. Hypocalcemia was defined as a total serum Ca level of <8 mg/dL. Baseline demographic and operative characteristics and postoperative outcome were recorded for both groups. The Fisher exact test and Wilcoxon rank sum test were used to compare the characteristics of the 2 groups. A multivariate logistic regression model was applied to account for potentially confounding variables.ResultsPostoperative hypocalcemia occurred significantly less frequently in the protocol group compared with that in the preprotocol group (10.3% vs 20.9%, P = .002). The reduction in hypocalcemia in the protocol group was observed in both patients with (16.3% vs 25.6%) and without (8.4% vs 19.3%) cervical lymph node dissection. The protocol group had a significantly lower incidence of hospital readmission events than the preprotocol group (1.0% vs 4.7%, P = .013).ConclusionCompared with a historical cohort, a PTH-guided protocol for Ca and calcitriol supplementation significantly reduces the postoperative hypocalcemia and hospital readmission rates in patients undergoing total thyroidectomy.     

Pseudohypoparathyroidism type I‐b with neurological involvement is associated with a homozygous PTH1R mutation

Pseudohypoparathyroidism type 1b (PHP1b) is characterized by hypocalcemia, hyperphosphatemia, increased levels of circulating parathyroid hormone (PTH), and no skeletal or developmental abnormalities. The goal of this study was to perform a full characterization of a familial case of PHP1b with neurological involvement and to identify the genetic cause of disease. The initial laboratory profile of the proband showed severe hypocalcemia, hyperphosphatemia and normal levels of PTH, which was considered to be compatible with primary hypoparathyroidism. With disease progression the patient developed cognitive disturbance, PTH levels were found to be slightly elevated and a picture of PTH resistance syndrome seemed more probable. The diagnosis of PHP1b was established after the study of family members and blunted urinary cAMP results were obtained in a PTH stimulation test. Integration of whole genome genotyping and exome sequencing data supported this diagnosis by revealing a novel homozygous missense mutation in PTH1R (p.Arg186His) completely segregating with the disease. Here, we demonstrate segregation of a novel mutation in PTH1R with a phenotype of PHP1b presenting with neurological symptoms, but no bone defects. This case represents the extreme end of the spectrum of cognitive impairment in PTH dysfunction and defines a possible novel form of PHP1b resulting from the impaired interaction between PTH and PTH1R.     

Identifying Parathyroid Hormone Disorders and their Phenotypes through a Bone Health Screening Panel: It's not Simple Vitamin D Deficiency!

Objectives: To determine the utility of bone health screening panels in identifying disorders of parathyroid gland secretions.Methods: A retrospective analysis of biochemical parameters in a bone health screening panel (BHSP) was conducted. Low and high cutoffs were applied to determine hypofunctioning and hyperfunctioning conditions related to parathyroid hormone. Clinical phenotypes of parathyroid gland abnormalities were determined using a combination of levels of calcium, 25-hydroxyvitamin D, and intact parathyroid hormone (iPTH). A PTH nomogram was applied to calculate the maximum expected PTH for existing levels of 25-hydroxyvitamin D. Medical records of patients were reviewed for clinical validation of biochemical findings.Results: Sixty-eight percent of subjects showed abnormal PTH secretion. Primary hyper- and hypoparathyroidism were detected in 1% (n = 5) and 0.4% (n = 2) of subjects, respectively. Normocalcemic hyperparathyroidism and hypercalcemia with inappropriately high-normal PTH were identified in 8.5% (n = 37) and 2% (n = 10) of subjects, respectively. All subjects with primary and normocalcemic hyperparathyroidism had higher measured PTH than calculated maximum PTH using the PTH nomogram. Secondary hyperparathyroidism and functional hypoparathyroidism were present in 18% (n = 88) and 39% (n = 194) of subjects, respectively. High prevalence of bone pains, renal stones, and low bone mineral density were identified in patients with abnormal PTH secretion.Conclusion: Panel testing is useful in early diagnosis of metabolic bone disorders related to PTH. A BHSP helps identify normocalcemic hyperparathyroidism and hypercalcemia with inappropriately high PTH.Abbreviations:25OHD = 25-hydroxyvitamin DAKUH = Aga Khan University HospitalBHSP = bone health screening paneliPTH = intact parathyroid hormonemaxPTH = maximum parathyroid hormoneMBD = metabolic bone diseaseNCHPT = normocalcemic hyperparathyroidismPHPT = primary hyperparathyroidismPTH = parathyroid hormoneSHPT = secondary hyperparathyroidismVDD = vitamin D deficiency     

Parathyroid hormone gene analysis in autosomal hypoparathyroidism using an intragenic tetranucleotide (AAAT) n polymorphism

We have identified a polymorphic tetranucleotide consisting of (AAAT) _n within the first intron of the parathyroid hormone (PTH) gene, and have used this to investigate the segregation of the PTH gene and idiopathic hypoparathyroidism in 7 affected and 21 unaffected members from three families. An association between the PTH locus and autosomal dominant idiopathic hypoparathyroidism in one family was excluded by observing recombination between the two loci. In the remaining two families with autosomal recessive idiopathic hypoparathyroidism, the PTH locus was not similarly excluded. We had previously demonstrated a donor splice site mutation of the PTH gene in one of these families, and PTH gene abnormalities were therefore sought in the second of these families. DNA sequence analysis of the three exons, together with 4 exon-intron boundaries and the promoter region of the PTH gene revealed no abnormalities, thereby indicating molecular pathology at another locus. Thus, our analysis of idiopathic hypoparathyroidism reveals genetic heterogeneity for this disorder. In addition, our indentification of a microsatellite polymorphism of the PTH gene should help further segregation studies of this locus in families with parathyroid disorders.