The Ca
-sensing receptor (CaSR) is a dimeric family C G protein-coupled receptor that is expressed in calcitropic tissues such as the parathyroid glands and the kidneys and signals via G proteins and ...β-arrestin. The CaSR has a pivotal role in bone and mineral metabolism, as it regulates parathyroid hormone secretion, urinary Ca
excretion, skeletal development and lactation. The importance of the CaSR for these calcitropic processes is highlighted by loss-of-function and gain-of-function CaSR mutations that cause familial hypocalciuric hypercalcaemia and autosomal dominant hypocalcaemia, respectively, and also by the fact that alterations in parathyroid CaSR expression contribute to the pathogenesis of primary and secondary hyperparathyroidism. Moreover, the CaSR is an established therapeutic target for hyperparathyroid disorders. The CaSR is also expressed in organs not involved in Ca
homeostasis: it has noncalcitropic roles in lung and neuronal development, vascular tone, gastrointestinal nutrient sensing, wound healing and secretion of insulin and enteroendocrine hormones. Furthermore, the abnormal expression or function of the CaSR is implicated in cardiovascular and neurological diseases, as well as in asthma, and the CaSR is reported to protect against colorectal cancer and neuroblastoma but increase the malignant potential of prostate and breast cancers.
Lactation is critical to infant short-term and long-term health and protects mothers from breast cancer, ovarian cancer and type 2 diabetes mellitus. The mammary gland is a dynamic organ, regulated ...by the coordinated actions of reproductive and metabolic hormones. These hormones promote gland development from puberty onwards and induce the formation of a branched, epithelial, milk-secreting organ by the end of pregnancy. Progesterone withdrawal following placental delivery initiates lactation, which is maintained by increased pituitary secretion of prolactin and oxytocin, and stimulated by infant suckling. After weaning, local cytokine production and decreased prolactin secretion trigger large-scale mammary cell loss, leading to gland involution. Here, we review advances in the molecular endocrinology of mammary gland development and milk synthesis. We discuss the hormonal functions of the mammary gland, including parathyroid hormone-related peptide secretion that stimulates maternal calcium mobilization for milk synthesis. We also consider the hormonal composition of human milk and its associated effects on infant health and development. Finally, we highlight endocrine and metabolic diseases that cause lactation insufficiency, for example, monogenic disorders of prolactin and prolactin receptor mutations, maternal obesity and diabetes mellitus, interventions during labour and delivery, and exposure to endocrine-disrupting chemicals such as polyfluoroalkyl substances in consumer products and other oestrogenic compounds.
The extracellular calcium-sensing receptor (CaSR) is a family C G-protein-coupled receptor (GPCR) that is expressed at multiple sites, including the parathyroids and kidneys. The human CASR gene, ...located on chromosome 3q21.1, encodes a 1078 amino acid protein. More than 230 different disease-causing mutations of the CaSR have been reported. Loss-of-function mutations lead to three hypercalcemic disorders, which are familial hypocalciuric hypercalcemia (FHH), neonatal severe hyperparathyroidism and primary hyperparathyroidism. Gain-of-function mutations, on the other hand, result in the hypocalcemic disorders of autosomal dominant hypocalcemia and Bartter syndrome type V. Moreover, autoantibodies directed against the extracellular domain of the CaSR have been found to be associated with FHH in some patients, and also in some patients with hypoparathyroidism that may be part of autoimmune polyglandular syndrome type 1. Studies of disease-causing CASR mutations have provided insights into structure–function relationships and highlighted intra-molecular domains that are critical for ligand binding, intracellular signaling, and receptor trafficking.
This study shows that mutations effecting Gα11 loss of function cause familial hypocalciuric hypercalcemia type 2, and mutations effecting Gα11 gain of function result in autosomal dominant ...hypocalcemia type 2. Important aspects of Gα11 function are also described.
Familial hypocalciuric hypercalcemia, an autosomal dominant disorder, is characterized by lifelong elevations of serum calcium concentrations with low urinary calcium excretion (mean urinary calcium:creatinine clearance ratio, <0.01) and normal circulating parathyroid hormone concentrations in 80% of patients (see Table S1 in the Supplementary Appendix, available with the full text of this article at NEJM.org).
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Patients with familial hypocalciuric hypercalcemia are generally asymptomatic, although pancreatitis or chondrocalcinosis may develop in some affected adults.
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Familial hypocalciuric hypercalcemia is genetically heterogeneous, with three reported variants. Type 1 is due to loss-of-function mutations of the calcium-sensing receptor (encoded by
CASR
), type 2 is . . .
The calcium-sensing receptor (CaSR) is a class C G protein-coupled receptor that responds to multiple endogenous agonists and allosteric modulators, including divalent and trivalent cations, L-amino ...acids,
-glutamyl peptides, polyamines, polycationic peptides, and protons. The CaSR plays a critical role in extracellular calcium (Ca
) homeostasis, as demonstrated by the many naturally occurring mutations in the CaSR or its signaling partners that cause Ca
homeostasis disorders. However, CaSR tissue expression in mammals is broad and includes tissues unrelated to Ca
homeostasis, in which it, for example, regulates the secretion of digestive hormones, airway constriction, cardiovascular effects, cellular differentiation, and proliferation. Thus, although the CaSR is targeted clinically by the positive allosteric modulators (PAMs) cinacalcet, evocalcet, and etelcalcetide in hyperparathyroidism, it is also a putative therapeutic target in diabetes, asthma, cardiovascular disease, and cancer. The CaSR is somewhat unique in possessing multiple ligand binding sites, including at least five putative sites for the "orthosteric" agonist Ca
, an allosteric site for endogenous L-amino acids, two further allosteric sites for small molecules and the peptide PAM, etelcalcetide, and additional sites for other cations and anions. The CaSR is promiscuous in its G protein-coupling preferences, and signals via G
, G
, potentially G
, and even G
in some cell types. Not surprisingly, the CaSR is subject to biased agonism, in which distinct ligands preferentially stimulate a subset of the CaSR's possible signaling responses, to the exclusion of others. The CaSR thus serves as a model receptor to study natural bias and allostery. SIGNIFICANCE STATEMENT: The calcium-sensing receptor (CaSR) is a complex G protein-coupled receptor that possesses multiple orthosteric and allosteric binding sites, is subject to biased signaling via several different G proteins, and has numerous (patho)physiological roles. Understanding the complexities of CaSR structure, function, and biology will aid future drug discovery efforts seeking to target this receptor for a diversity of diseases. This review summarizes what is known to date regarding key structural, pharmacological, and physiological features of the CaSR.
This European expert consensus statement provides recommendations for the diagnosis and management of primary hyperparathyroidism (PHPT), chronic hypoparathyroidism in adults (HypoPT), and ...parathyroid disorders in relation to pregnancy and lactation. Specified areas of interest and unmet needs identified by experts at the second ESE Educational Program of Parathyroid Disorders in 2019 were discussed during two virtual workshops in 2021 and subsequently developed by working groups with interest in the specified areas. PHPT is a common endocrine disease. However, its differential diagnosis of familial hypocalciuric hypercalcemia (FHH), the definition and clinical course of normocalcemic PHPT, and the optimal management of its recurrence after surgery represents areas of uncertainty requiring clarifications. HypoPT is an orphan disease characterized by low calcium concentrations due to insufficient PTH secretion, most often secondary to neck surgery. Prevention and prediction of surgical injury to the parathyroid glands are essential to limit the disease-related burden. Long-term treatment modalities including the place for PTH replacement therapy and the optimal biochemical monitoring and imaging surveillance for complications to treatment in chronic HypoPT need to be refined. The physiological changes in calcium metabolism occurring during pregnancy and lactation modify the clinical presentation and management of parathyroid disorders in these periods of life. Modern interdisciplinary approaches to PHPT and HypoPT in pregnant and lactating women and their newborn children are proposed. The recommendations on clinical management presented here will serve as background for further educational material aimed at a broader clinical audience and were developed with the focus on endocrinologists in training.
Context
Primary hyperparathyroidism is a common condition and results in hypercalcaemia, especially in older women. Thus, it is critical to obtain a robust estimate for the upper limit of the ...reference interval for albumin‐adjusted serum calcium in the general population. The current reference interval in use in the UK (Pathology Harmony range, 2.20 to 2.60 mmol/L) was based on a consensus.
Objectives
To establish a reference interval for albumin‐adjusted serum calcium in men and women.
Design
Cross‐sectional study of men and women who did not have chronic kidney disease or vitamin D deficiency; outliers were identified statistically and then rejected and then a 99% reference interval was calculated.
Patients
502 524 men and women aged 40 to 69 years from the UK Biobank Study.
Measurements
Serum total calcium, albumin, 25‐hydroxyvitamin D, estimated glomerular function (eGFR).
Results
We developed an equation for albumin‐adjusted serum calcium and applied it to 178 377 men and women who did not have chronic kidney disease or vitamin D deficiency. We identified 2962 (1.7%) as outliers, and when excluded, we report a 99% reference interval of 2.19 to 2.56 mmol/L (8.76 to 10.24 mg/dL). We found that for older (55‐69 years) and younger women (40‐55 years) the upper limits were 2.59 mmol/L and 2.57 mmol/L and that for all men, the upper limit was 2.55 mmol/L.
Conclusions
We have established an upper limit of the reference range for older women that would identify all high outliers (2.60 mmol/L and above). The upper limit for young women and for men is lower, at 2.57 and 2.55 mmol/L respectively. The current reference interval in use has to be updated and improved based on these findings. These upper limits may prove helpful for identifying hypercalcaemic disorders like primary hyperparathyroidism in clinical practice.
Hypercalcemic Disorders in Children Stokes, Victoria J; Nielsen, Morten F; Hannan, Fadil M ...
Journal of bone and mineral research,
November 2017, 2017-Nov, 2017-11-01, 20171101, Letnik:
32, Številka:
11
Journal Article
The calcium‐sensing receptor (CaS receptor) plays a pivotal role in extracellular calcium homeostasis, and germline loss‐of‐function and gain‐of‐function mutations cause familial hypocalciuric ...hypercalcaemia (FHH) and autosomal dominant hypocalcaemia (ADH), respectively. CaS receptor signal transduction in the parathyroid glands is probably regulated by G‐protein subunit α11 (Gα11) and adaptor‐related protein complex‐2 σ‐subunit (AP2σ), and recent studies have identified germline mutations of these proteins as a cause of FHH and/or ADH. Calcimimetics and calcilytics are positive and negative allosteric modulators of the CaS receptor that have potential efficacy for symptomatic forms of FHH and ADH. Cellular studies have demonstrated that these compounds correct signalling and/or trafficking defects caused by mutant CaS receptor, Gα11 or AP2σ proteins. Moreover, mouse model studies indicate that calcilytics can rectify the hypocalcaemia and hypercalciuria associated with ADH, and patient‐based studies reveal calcimimetics to ameliorate symptomatic hypercalcaemia caused by FHH. Thus, calcimimetics and calcilytics represent targeted therapies for inherited disorders of the CaS receptor signalling pathway.
Linked Articles
This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc
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