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Tan RSG, Lee CHL, Dimke H, Todd Alexander R. The role of calcium-sensing receptor signaling in regulating transepithelial calcium transport. Exp Biol Med (Maywood) 2021; 246:2407-2419. [PMID: 33926258 DOI: 10.1177/15353702211010415] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The calcium-sensing receptor (CaSR) plays a critical role in sensing extracellular calcium (Ca2+) and signaling to maintain Ca2+ homeostasis. In the parathyroid, the CaSR regulates secretion of parathyroid hormone, which functions to increase extracellular Ca2+ levels. The CaSR is also located in other organs imperative to Ca2+ homeostasis including the kidney and intestine, where it modulates Ca2+ reabsorption and absorption, respectively. In this review, we describe CaSR expression and its function in transepithelial Ca2+ transport in the kidney and intestine. Activation of the CaSR leads to G protein dependent and independent signaling cascades. The known CaSR signal transduction pathways involved in modulating paracellular and transcellular epithelial Ca2+ transport are discussed. Mutations in the CaSR cause a range of diseases that manifest in altered serum Ca2+ levels. Gain-of-function mutations in the CaSR result in autosomal dominant hypocalcemia type 1, while loss-of-function mutations cause familial hypocalciuric hypercalcemia. Additionally, the putative serine protease, FAM111A, is discussed as a potential regulator of the CaSR because mutations in FAM111A cause Kenny Caffey syndrome type 2, gracile bone dysplasia, and osteocraniostenosis, diseases that are characterized by hypocalcemia, hypoparathyroidism, and bony abnormalities, i.e. share phenotypic features of autosomal dominant hypocalcemia. Recent work has helped to elucidate the effect of CaSR signaling cascades on downstream proteins involved in Ca2+ transport across renal and intestinal epithelia; however, much remains to be discovered.
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Affiliation(s)
- Rebecca Siu Ga Tan
- Department of Physiology, University of Alberta, Edmonton T6G 1C9, Canada.,Membrane Protein Disease Research Group, University of Alberta, Edmonton T6G 1C9, Canada
| | | | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense 5000, Denmark.,Department of Nephrology, Odense University Hospital, Odense 5000, Denmark
| | - R Todd Alexander
- Department of Physiology, University of Alberta, Edmonton T6G 1C9, Canada.,Membrane Protein Disease Research Group, University of Alberta, Edmonton T6G 1C9, Canada.,Department of Pediatrics, University of Alberta, Edmonton T6G 1C9, Canada
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Veldeman L, Robbrecht S, Breckpot J, Weynand B, Decallonne B. A Case of a Heterozygous Inactivating CASR Variant with Adult-Onset Symptomatic Hypercalcemia Requiring Extensive Surgery. Calcif Tissue Int 2020; 107:104-108. [PMID: 32306059 DOI: 10.1007/s00223-020-00693-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 04/08/2020] [Indexed: 11/29/2022]
Abstract
We describe the case of an adult female patient with symptomatic familial hypocalciuric hypercalcemia requiring a step-wise therapeutic approach and the eventual need for a total parathyroidectomy and thyroidectomy to cure symptoms. Genetic analysis demonstrated a heterozygous R227L inactivating CASR gene variant, previously only described in neonatal severe hyperparathyroidism. Post-operative histology showed diffuse hyperplasia of all four parathyroid glands along with the presence of intrathyroidal parathyroid tissue. With regard to clinical management this case suggests that familial hypocalciuric hypercalcemia should be classified as an atypical form of primary hyperparathyroidism rather than a distinct entity.
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Affiliation(s)
- Laurens Veldeman
- Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
- Department of Endocrinology, AZ St.-Blasius Dendermonde, Dendermonde, Belgium.
| | - Saskia Robbrecht
- Department of Endocrinology, AZ St.-Blasius Dendermonde, Dendermonde, Belgium
| | - Jeroen Breckpot
- Center for Human Genetics, University Hospitals Leuven, Leuven, Belgium
| | - Birgit Weynand
- Department of Pathology, University Hospitals Leuven, Leuven, Belgium
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Savas-Erdeve S, Sagsak E, Keskin M, Magdelaine C, Lienhardt-Roussie A, Kurnaz E, Cetinkaya S, Aycan Z. Treatment experience and long-term follow-up data in two severe neonatal hyperparathyroidism cases. J Pediatr Endocrinol Metab 2016; 29:1103-10. [PMID: 27390877 DOI: 10.1515/jpem-2015-0261] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 05/26/2016] [Indexed: 12/20/2022]
Abstract
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.
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Park JY, Kim JH, Kim SW, Chung JH, Min YK, Lee MS, Lee MK, Kim KW. Using growth hormone levels to detect macroadenoma in patients with acromegaly. Endocrinol Metab (Seoul) 2014; 29:450-6. [PMID: 25325263 PMCID: PMC4285038 DOI: 10.3803/enm.2014.29.4.450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/07/2014] [Accepted: 04/16/2014] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND The aim of this study was to assess the clinical differences between acromegalic patients with microadenoma and patients with macroadenoma, and to evaluate the predictive value of growth hormone (GH) levels for early detection of macroadenoma. METHODS We performed a retrospective analysis of 215 patients diagnosed with a GH-secreting pituitary adenoma. The patients were divided into two groups: the microadenoma group and the macroadenoma group, and the clinical parameters were compared between these two groups. The most sensitive and specific GH values for predicting macroadenoma were selected using receiver operating characteristic (ROC) curves. RESULTS Compared with the microadenoma group, the macroadenoma group had a significantly younger age, higher body mass index, higher prevalence of hyperprolactinemia and hypogonadism, and a lower proportion of positive suppression to octreotide. However, there were no significant differences in the gender or in the prevalence of diabetes between the two groups. The tumor diameter was positively correlated with all GH values during the oral glucose tolerance test (OGTT). All GH values were significantly higher in the macroadenoma group than the microadenoma group. Cut-off values for GH levels at 0, 30, 60, 90, and 120 minutes for optimal discrimination between macroadenoma and microadenoma were 5.6, 5.7, 6.3, 6.0, and 5.8 ng/mL, respectively. ROC curve analysis revealed that the GH value at 30 minutes had the highest area under the curve. CONCLUSION The GH level of 5.7 ng/mL or higher at 30 minutes during OGTT could provide sufficient information to detect macroadenoma at the time of diagnosis.
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Affiliation(s)
- Ji Young Park
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jae Hyeon Kim
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Sun Wook Kim
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jae Hoon Chung
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Yong Ki Min
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Myung Shik Lee
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Moon Kyu Lee
- Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kwang Won Kim
- Department of Endocrinology and Metabolism, Gachon University Gil Medical Center, Gachon University of Medicine and Science, Incheon, Korea.
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Kovacs CS. Bone development and mineral homeostasis in the fetus and neonate: roles of the calciotropic and phosphotropic hormones. Physiol Rev 2014; 94:1143-218. [PMID: 25287862 DOI: 10.1152/physrev.00014.2014] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24-48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium.
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Affiliation(s)
- Christopher S Kovacs
- Faculty of Medicine-Endocrinology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
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Kulkarni A, Mohite M, Vijaykumar R, Bansode P, Murade S, Tamhankar PM. Neonatal severe hyperparathyroidism due to compound heterozygous mutation of calcium sensing receptor (CaSR) gene presenting as encephalopathy. Indian J Pediatr 2014; 81:1228-9. [PMID: 24763815 DOI: 10.1007/s12098-014-1442-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 03/27/2014] [Indexed: 11/30/2022]
Abstract
The authors report a 14-d-old neonate who presented with lethargy, polyuria and dehydration and was found to have severe hypercalcemia with hyperparathyroidism. This neonate was treated with saline hydration, diuresis and injection pamidronate. Genetic analysis revealed a compound heterozygous mutation of CaSR.
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Affiliation(s)
- Abhishek Kulkarni
- Department of Pediatrics & Adolescent Endocrinology, Jaslok Hospital & Research Centre, Mumbai, India
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Leach K, Sexton PM, Christopoulos A, Conigrave AD. Engendering biased signalling from the calcium-sensing receptor for the pharmacotherapy of diverse disorders. Br J Pharmacol 2014; 171:1142-55. [PMID: 24111791 DOI: 10.1111/bph.12420] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Revised: 08/22/2013] [Accepted: 08/26/2013] [Indexed: 12/14/2022] Open
Abstract
The human calcium-sensing receptor (CaSR) is widely expressed in the body, where its activity is regulated by multiple orthosteric and endogenous allosteric ligands. Each ligand stabilizes a unique subset of conformational states, which enables the CaSR to couple to distinct intracellular signalling pathways depending on the extracellular milieu in which it is bathed. Differential signalling arising from distinct receptor conformations favoured by each ligand is referred to as biased signalling. The outcome of CaSR activation also depends on the cell type in which it is expressed. Thus, the same ligand may activate diverse pathways in distinct cell types. Given that the CaSR is implicated in numerous physiological and pathophysiological processes, it is an ideal target for biased ligands that could be rationally designed to selectively regulate desired signalling pathways in preferred cell types.
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Affiliation(s)
- K Leach
- Pharmaceutical Sciences, Monash University, Melbourne, Vic., Australia
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Feng J, Xu X, Li B, Brown E, Farris AB, Sun SY, Yang JJ. Prostate cancer metastatic to bone has higher expression of the calcium-sensing receptor (CaSR) than primary prostate cancer. ACTA ACUST UNITED AC 2014; 1. [PMID: 26065011 DOI: 10.14800/rci.270] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The calcium-sensing receptor (CaSR) is the principal regulator of the secretion of parathyroid hormone and plays key roles in extracellular calcium (Ca2+o) homeostasis. It is also thought to participate in the development of cancer, especially bony metastases of breast and prostate cancer. However, the expression of CaSR has not been systematically analyzed in prostate cancer from patients with or without bony metastases. By comparing human prostate cancer tissue sections in microarrays, we found that the CaSR was expressed in both normal prostate and primary prostate cancer as assessed by immunohistochemistry (IHC). We used two methods to analyze the expression level of CaSR. One was the pathological score read by a pathologist, the other was the positivity% obtained from the Aperio positive pixel count algorithm. Both of the methods gave consistent results. Metastatic prostate cancer tissue obtained from bone had higher CaSR expression than primary prostate cancer (P <0.05). The expression of CaSR in primary prostate cancers of patients with metastases to tissues other than bone was not different from that in primary prostate cancer of patients with or without bony metastases (P >0.05). The expression of CaSR in cancer tissue was not associated with the stage or status of differentiation of the cancer. These results suggest that CaSR may have a role in promoting bony metastasis of prostate cancer, hence raising the possibility of reducing the risk of such metastases with CaSR-based therapeutics.
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Affiliation(s)
- Jie Feng
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
| | - Xiaojun Xu
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
| | - Bo Li
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA 30322
| | - Edward Brown
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115
| | - Alton B Farris
- Department of Pathology, Emory University, Atlanta, GA 30322
| | - Shi-Yong Sun
- Department of Hematology and Medical Oncology, Emory University School of Medicine and Winship Cancer Institute, Atlanta, GA 30322
| | - Jenny J Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30303
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Christensen SE, Nissen PH, Vestergaard P, Mosekilde L. Familial hypocalciuric hypercalcaemia: a review. Curr Opin Endocrinol Diabetes Obes 2011; 18:359-70. [PMID: 21986511 DOI: 10.1097/med.0b013e32834c3c7c] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE OF REVIEW Hypercalcaemia is a potentially life-threatening condition. Familial hypocalciuric hypercalcaemia (FHH) is a rare, lifelong, benign condition. It is important to separate this condition from other hypercalcaemic states such as hypercalcaemia of malignancy and primary hyperparathyroidism (PHPT). RECENT FINDINGS FHH is caused by inactivating mutations in the calcium sensing receptor (CASR) gene leading to a general calcium-hyposensitivity, compensatory hypercalcaemia and hypocalciuria. The inheritance of FHH is autosomal dominant. Similar to PHPT, FHH is characterized by hypercalcaemia, unsuppressed or elevated plasma parathyroid hormone, and typically normal renal function. The phenotype is normal, and hypercalcaemic symptoms are generally absent. The hallmark is a relatively low urine calcium excretion in contrast to PHPT, in which urine calcium excretion is increased. The vitamin D status as measured by plasma 25-hydroxyvitamin D has been reported to be normal with normal seasonal variations, whereas plasma 1,25-dihydroxyvitamin D has been found slightly increased compared to normal. Bone mineral density Z-scores are normal in spite of a slightly increased bone turnover. Differential diagnoses include mainly PHPT, but in some cases also hypercalcaemia of malignancy and use of thiazide diuretics. SUMMARY In general, FHH does not require treatment. We recommend a two-step diagnostic procedure. First, the calcium/creatinine clearance ratio is measured from a 24-h urine. Second, all patients with calcium/creatinine clearance ratio of 0.020 or less are tested for mutations in the CASR gene. The diagnostic sensitivity of this setup is 98%.
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Affiliation(s)
- Signe E Christensen
- Department of Medicine and Endocrinology, Aarhus University Hospital, Aarhus C, Denmark.
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