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Familial Hypocalciuria Hypercalcemia (FHH) is an inherited disease with autosomal dominant transmission characterized by the presence of usually mild-to-moderate hypercalcemia, hypophosphatemia, hypocalciuria, and normal or moderately increased PTH values. Generally, FFH is asymptomatic although symptoms related to elevated plasma calcium values such as asthenia, intense thirst, polyuria, polydipsia or confusional state may occur. Three types of FHH, which differ in the genetic alterations underlying the condition, are described. The majority of FHH cases are classified as type 1 (about 65 percent of cases), due to mutation in the gene for the calcium-sensitive receptor CASR, expressed on chromosome (Chr) 3q13.3-21, which encodes for a calcium-sensitive receptor G-protein-coupled protein of the plasma membrane. FHH types 2 and 3 are due to GNA11 and AP2S1 mutations, respectively, and other genes involved in the pathogenesis of the disease have likely yet to be identified. Rarely, familial hypocalciuric hypercalcemia may not recognize a genetic cause but be caused by autoantibodies directed against CASR. The frequency of the disease is not known and is estimated, probably by default, because of paucisymptomatic presentation of the disease, to be around 1:80000 cases. Recognition of FHH is especially important for differential diagnosis with primary hyperparathyroidism, which has a much higher incidence, about 1:1000 cases. This allows for the identification of patients at risk for chondrocalcinosis and/or pancreatitis. Clinical suspicion must be raised in cases of hypercalcaemia associated with hypocalciuria, and genetic analysis is fundamental in the differential diagnosis toward forms of primary hyperparathyroidism that might result in unnecessary surgical interventions. We describe a clinical case in which a novel inactivating mutation of CASR leading to FHH type 1 was found., (Copyright by Società Italiana di Nefrologia SIN, Rome,Italy.)

Context: Although a monoallelic mutation in the calcium-sensing receptor ( CASR ) gene causes familial hypocalciuric hypercalcemia (FHH), the functional characterization of the identified CASR mutation linked to the clinical response to calcimimetics therapy is still limited., Objective: A 45-year-old male presenting with moderate hypercalcemia, hypocalciuria, and inappropriately high parathyroid hormone (PTH) had a good response to cinacalcet (total serum calcium (Ca 2+ ) from 12.5 to 10.1 mg/dl). We identified the genetic mutation and characterized the functional and pathophysiological mechanisms, and then linked the mutation to calcimimetics treatment in vitro ., Design: Sanger sequencing of the CASR , GNA11 , and AP2S1 genes was performed in his family. The simulation model was used to predict the function of the identified mutant. In vitro studies, including immunoblotting, immunofluorescence, a cycloheximide chase study, Calbryte™ 520 Ca 2+ detection, and half-maximal effective concentration (EC 50 ), were examined., Results: This proband was found to carry a de novo heterozygous missense I554N in the cysteine-rich domain of CASR , which was pathogenic based on the different software prediction models and ACGME criteria. The simulation model showed that CASR I554N mutation decreased its binding energy with Ca 2+ . Human CASR I554N mutation attenuated the stability of CASR protein, reduced the expression of p-ERK 1/2, and blunted the intracellular Ca 2+ response to gradient extracellular Ca 2+ (eCa 2+ ) concentration. The EC 50 study also demonstrated the correctable effect of calcimimetics on the function of the CASR I554N mutation., Conclusion: This novel CASR I554N mutation causing FHH attenuates CASR stability, its binding affinity with Ca 2+ , and the response to eCa 2+ corrected by therapeutic calcimimetics., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lin, Ding, Huang, Chen, Lee, Sung and Lin.)

Introduction: The occurrence of prolactinomas in sex hormone treated patients with central hypogonadism is extremely rare., Case Presentation: We present a Caucasian male patient who was diagnosed with Kallmann syndrome (KS) at age 15 years. Testosterone treatment was started. At age 26 the patient presented with mild headache. MRI revealed two separate pituitary adenomas along with the absence of the olfactory bulbs. Given the presence of marked hyperprolactinemia (17x upper limit of the reference range) the diagnosis prolactinoma was made and treatment with cabergoline was started which resulted in a complete biochemical response and in marked reduction of both adenomas in size. Hypogonadism persisted and testosterone replacement therapy was continued. Genetic testing of genes associated with pituitary tumors, Kallmann syndrome and idiopathic hypogonadotropic hypogonadism was negative. Mild concomitant hypercalcemia in accordance with familial hypocalciuric hypercalcemia (FHH) prompted mutation analysis of the calcium receptor ( CASR) gene which yielded a pathogenic inactivating variant., Discussion/conclusion: The presence of two separate prolactinomas in a patient with KS has not yet been reported in the literature. The effect of sex hormone treatment of KS patients on the possible development of prolactinoma is unknown at present. The occurance of multiple prolactinomas in our patient suggests increased susceptibility. Although CaSR is expressed in GnRH neurons in mouse brain and CaSR deficient mice have a reduced hypothalamic GnRH neuronal population, the relevance of the CASR gene variant in our patient for the KS phenotype is unclear at present., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jensterle, Janež, Vipotnik Vesnaver, Debeljak, Breznik, Trebušak Podkrajšek, Herman, Fliers, Battelino and Avbelj Stefanija.)

Familial hypocalciuric hypercalcemia type 2 (FHH2) and autosomal dominant hypocalcemia type 2 (ADH2) are due to loss- and gain-of-function mutations, respectively, of the GNA11 gene that encodes the G protein subunit Gα11, a signaling partner of the calcium-sensing receptor (CaSR). To date, four probands with FHH2-associated Gα11 mutations and eight probands with ADH2-associated Gα11 mutations have been reported. In a 10-year period, we identified 37 different germline GNA11 variants in >1200 probands referred for investigation of genetic causes for hypercalcemia or hypocalcemia, comprising 14 synonymous, 12 noncoding, and 11 nonsynonymous variants. The synonymous and noncoding variants were predicted to be benign or likely benign by in silico analysis, with 5 and 3, respectively, occurring in both hypercalcemic and hypocalcemic individuals. Nine of the nonsynonymous variants (Thr54Met, Arg60His, Arg60Leu, Gly66Ser, Arg149His, Arg181Gln, Phe220Ser, Val340Met, Phe341Leu) identified in 13 probands have been reported to be FHH2- or ADH2-causing. Of the remaining nonsynonymous variants, Ala65Thr was predicted to be benign, and Met87Val, identified in a hypercalcemic individual, was predicted to be of uncertain significance. Three-dimensional homology modeling of the Val87 variant suggested it was likely benign, and expression of Val87 variant and wild-type Met87 Gα11 in CaSR-expressing HEK293 cells revealed no differences in intracellular calcium responses to alterations in extracellular calcium concentrations, consistent with Val87 being a benign polymorphism. Two noncoding region variants, a 40bp-5'UTR deletion and a 15bp-intronic deletion, identified only in hypercalcemic individuals, were associated with decreased luciferase expression in vitro but no alterations in GNA11 mRNA or Gα11 protein levels in cells from the patient and no abnormality in splicing of the GNA11 mRNA, respectively, confirming them to be benign polymorphisms. Thus, this study identified likely disease-causing GNA11 variants in <1% of probands with hypercalcemia or hypocalcemia and highlights the occurrence of GNA11 rare variants that are benign polymorphisms. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)., (© 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).)

Taking care of patients with parathyroid disorders during pregnancy requires consideration of the physiological fundamental changes in bone and mineral metabolism occurring in these women. Diagnostic and therapeutic procedures regarding primary hyperparathyroidism (PHPT) and hypoparathyroidism significantly differ from the nonpregnant population. PHPT should preferably be cured by parathyroidectomy before pregnancy since in women with hypercalcemic PHPT, maternal and fetal pregnancy complications seem to increase according to the degree of hypercalcemia. Parathyroidectomy, if needed during pregnancy, is preferentially performed in the second trimester. Conservative treatment is recommended for milder cases and is mainly restricted to hydration, with only limited evidence regarding drug treatment. Women with hypoparathyroidism can be informed that there are no major concerns regarding disease-associated infertility and that the risk of pregnancy complications is low if the disease is properly managed. Regular active surveillance is recommended, as requirements for calcium and active vitamin D may change during the course of pregnancy in either direction, with an overall trend for rather reduced doses. Any woman suffering from parathyroid disorders during pregnancy requires further surveillance in the postpartum period and during lactation, as there is an increased risk of hypercalcemia after delivery. Newborns of mothers with parathyroid diseases should, depending on disease severity, be carefully monitored for calcium levels in the first days (to weeks) after delivery since intrauterine exposure to hyper- or hypocalcemia may impact their postnatal regulation of calcium metabolism., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society.)

Parathyroid hormone (PTH) is a hypercalcemic hormone acting on kidneys, bone and intestine. PTH promotes calcium release from the bone, renal calcium reabsorption and phosphate excretion, and conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D-3. Hyperparathyroidism consists in PTH elevation, which may be adapted (secondary hyperparathyroidism) or non-adapted to calcemia levels (primary hyperparathyroidism, familial hypercalcemia/hypocalciuria, tertiary hyperparathyroidism). Primary hyperparathyroidism (PHP) features hypercalcemia and elevated or inappropriate PTH elevation. PHP may be revealed by biological abnormalities such as hypercalcemia and can be accompanied by renal complications (hypercalciuria, nephrolithiasis, nephrocalcinosis) and/or osteoporosis. However, it can also be normocalcemic and calcium loading will be necessary to diagnosis it. The differential diagnosis of PHP is familial hypocalciuric hypercalcemia (FHH), a dominant autosomal disease implicating a calcium sensing receptor-inactivating mutation. It impairs parathyroid cell sensitivity to calcemia elevation and thus induces excessive PTH stimulation, leading to hypercalcemia. Secondary HP (SHP) consists in PTH elevation secondary to a stimulus that needs to be corrected. 25 OHvitD deficiency, kidney failure, renal hypercalciuria, malabsorption and some drugs can induce SHP. Tertiary HP (THP) consists in autonomous PTH secretion by the parathyroid glands after prolonged stimulation under SHP, of whatever cause. This parathyroid autonomy results from the polyclonal hyperplasia observed in SHP progressing toward monoclonal nodular proliferation, leading to nodular hyperplasia or parathyroid adenoma (or, exceptionally, carcinoma), with reduced expression of CaSR and vitamin D receptor. In patients under dialysis, the frontier between SHP and THP is a matter of debate. This review will focus on the pathophysiology of calcium, diagnosis, and management of hyperparathyroidism., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Background: Familial hypocalciuric hypercalcemia (FHH) is a rare autosomal dominant disease, which requires differential diagnosis from relatively common primary hyperparathyroidism (PHPT) in order to avoid unnecessary surgery., Case Presentation: A 16-year-old female had been followed by the department of psychosomatic medicine at our institution. Throughout the follow-up period, her plasma calcium levels were high, plasma Pi levels were relatively low, and plasma intact PTH was relatively high. She was referred to our department to determine the cause of her hypercalcemia. Her 24 h urinary calcium excretion was as low as 100 mg/day, and calcium creatinine clearance ratio was below 0.01. Moreover, she had a family history of hypercalcemia (proband, her brother, and her father). The genetic testing for her family revealed that she, her brother, and her father were definitively diagnosed with FHH type 1 due to the heterozygous calcium-sensing receptor mutation (NM&#95;00388:4:c.164C > T:p.Pro55Leu)., Conclusion: We experienced a 16-year-old female with FHH, in whom genetic testing identified the heterozygous calcium-sensing receptor mutation (NM&#95;00388:4:c.164C > T:p.Pro55Leu) as pathogenic, permitting a definitive diagnosis of FHH type 1. The genetic testing for calcium sensing receptor is beneficial to distinguish asymptomatic primary hyperparathyroidism from FHH., (© 2022. The Author(s).)

Loss-of-function calcium-sensing receptor (CASR) mutations cause mineral metabolism disorders, familial hypocalciuric hypercalcemia, or neonatal severe hyperparathyroidism and increase the risk of femoral fracture, chronic kidney disease, coronary heart disease, and other diseases. In severe cases, CaSR mutations are lethal. Off-label use of the CaSR-positive allosteric modulator (PAM), cinacalcet, corrects hypercalcemia in some patients with CaSR mutations. However, other patients remain unresponsive to cinacalcet, attesting to the need for novel treatments. Here, we compared the effects of cinacalcet to two other clinically approved synthetic CaSR activators, evocalcet and etelcalcetide, as well as a novel PAM, 1-(2,4-dimethylphenyl)-1-(4,5-dimethylthiazol-2-yl)ethan-1-ol (MIPS-VD-836-108) on clinically relevant CaSR mutations. We assessed the compounds in CaSR-expressing HEK293 cells for correction of mutation-induced impairments in intracellular calcium (Ca2+i) mobilization and cell surface expression. While cinacalcet, MIPS-VD-836-108 and evocalcet rescued the signaling of cell surface-expressed mutants, albeit to varying degrees, etelcalcetide was ineffective. Cinacalcet and evocalcet, but not MIPS-VD-836-108 or etelcalcetide, restored the expression of a R680H mutant. However, no compound rescued expression of I81K and C582R mutants or a receptor missing 77 amino acids in the extracellular domain mimicking deletion of CASRexon 5, which impairs CaSR function. These data suggest specific compounds may be clinically effective in some patients with CaSR mutations, but other patients will remain refractory to treatment with currently available CaSR-targeting activators, highlighting the need for new generation drugs to rescue both the signaling and expression of mutant CaSRs.

Background: Primary hyperparathyroidism (PHPT) and familial hypocalciuric hypercalcemia (FHH) are the most important differential diagnosis of parathyroid hormone (PTH)-dependent hypercalcemia. The clinical features of FHH and PHPT can overlap in some cases. Therefore, these two diseases must be differentiated to prevent unnecessary parathyroidectomy. Here, we present a case that was not entirely matched with any of the known differential diagnoses of hypercalcemia., Case Presentation: A 19-year-old girl with no history of any disease presented with persistent hypercalcemia without any specific musculoskeletal complaint. We found persistent hypercalcemia in her routine laboratory data from 3 years ago; while no data was available during the childhood period. Her dietary calcium intake was normal. She did not mention any history of renal stone, bone fracture as well as family history of hypercalcemia. Biochemical features showed normal values of serum creatinine, high normal serum calcium (range, 10.3-11.3 mg/dL; (normal range: 8.8-10.4)), and non-suppressed PTH levels (range, 37.2-58.1 pg/mL; (normal range: 10-65)). Serum 25 OH vitamin D level at the first visit was 16.1 ng/mL that treated by vitamin D supplementation. Since then, all 25 OH vitamin D levels were in the acceptable range. After correction of vitamin D deficiency during the follow-up period the calcium creatinine clearance ratio(s) (CCCR) were calculated in the range of 0.009 to 0.014 (means below 1%). The clinical and laboratory data indicate more FHH rather than PHPT. Genetic studies were negative for the common genes associated with FHH (CASR, GNA11, and AP2S1 genes) and multiple endocrine neoplasia type1 (MEN1). On the other hand, no evidence of autoimmunity was found in her to support an autoimmune FHH-like syndrome. Hence, the case did not match completely to any diagnosis of FHH and PHPT, so we decided to follow her., Conclusion: We presented a patient with FHH phenotype whose common genetic tests were negative. Further research is needed to ascertain other causes leading to similar manifestations., (© 2021. The Author(s).)

Background: In many cases primary hyperparathyroidism (PHPT) remains asymptomatic for years and is only detected by abnormalities in routine diagnostics. While symptomatic disease almost always requires surgical treatment, in symptom-free patients the question of whether and in what form treatment should be carried out is particularly important., Objective: The aim of this review is to summarize the current recommendations regarding the diagnostics and treatment of asymptomatic PHPT, taking the existing evidence into account., Results and Conclusion: The diagnostics of asymptomatic PHPT is the same as for symptomatic disease. The diagnosis is made in the presence of elevated parathyroid hormone and balanced vitamin D levels when a combination of hypercalcemia, hypophosphatemia and hypercalciuria is present. Borderline laboratory findings occur especially in asymptomatic PHPT and the differential diagnosis of familial hypocalciuric hypercalcemia must be considered. Once the diagnosis is made sonography, radiography or computed tomography (CT) is used to search for nephrolithiasis or nephrocalcinosis. Regarding bone mineral density (BMD) measurements, in addition to routine measurements at the lumbar spine and femur, measurement at the distal radius is important as it is the most sensitive site for detecting osteoporosis in PHPT. An indication for parathyroidectomy is confirmed in the case of hypercalcemia > 1.0 mg/dl (>0.25 mmol/l) above the upper limit of normal, hypercalciuria > 400 mg/day (>10 mmol/day), renal insufficiency, proven osteoporosis or age < 50 years. If none of these criteria are fulfilled and surgery is not desired by the patient, annual laboratory check-ups and assessment of BMD every 1-2 years are recommended.

Diagnosing and treating hypercalcemia during pregnancy can be challenging due to both the physiological changes in calcium homeostasis and the underlying cause for the hypercalcemia. During pregnancy and lactation there is increased mobilization of calcium in the mother to meet the fetus' calcium requirements. Here we discuss the diagnostic challenges, management, and patient perspective of hypercalcemia during pregnancy in two particular cases and in other rare conditions causing hypercalcemia.

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.

Primary hyperparathyroidism (pHPT) is associated with familial syndromes such as multiple endocrine neoplasia type 1 (MEN1), 2A (MEN2A), MEN-like syndromes (CDKN1B), and CDC73-related disorder (hyperparathyroidism - jaw tumor syndrome (HPJT)). Familial hypocalciuric hypercalcemia (FHH) caused by CASR variants is an important differential diagnosis for pHPT. In order to evaluate the contribution of hereditary causes to pHPT in patients encountered in a specialized clinic, we conducted a retrospective study on patients with pHPT that underwent germline genetic testing. We evaluated 46 patients referred to a Cancer Genetics Clinic. Reasons for referral were young age (age < 40) for 29 patients (63%), multi-gland disease for 23 patients (50%), and a positive family history of pHPT for 11 patients (24%). All 46 patients underwent genetic evaluation. A total of 11 rare variants were found (CASR (4), CDC73 (2), MEN1 (2) CDKN1B (1), and RET (2)). One MEN1 variant was classified as pathogenic, and all others were variants of uncertain significance (VUS). All patients with CASR variants had clinical features of FHH and were counselled against parathyroidectomy. Both patients with CDC73 variants were counselled about recurrence of pHPT and parathyroid cancer. Neither of the RET variants were MEN2-associated. The CDKN1B variant was regarded as a true VUS and no action was taken. In this study, genetic testing impacted clinical care in 7 (15%) patients. We suggest that all patients < 40 years of age, with multi-gland disease, single gland disease refractory to treatment, and a positive family history for pHPT or associated tumors should be considered for genetic evaluation.

Familial hypocalciuric hypercalcemia (FHH) is a benign autosomal dominant condition characterized by lifelong asymptomatic hypercalcemia. FHH is typically caused by a heterozygous inactivating mutation of the calcium-sensing receptor (CaSR) and characterized by moderate hypercalcemia, inappropriately normal or elevated serum parathyroid hormone (PTH), and relative hypocalciuria (Fe Ca < 2%) with histologically normal parathyroid glands. FHH should be distinguished from primary hyperparathyroidism so that unnecessary parathyroid surgery is avoided. We report a case that presented with asymptomatic, familial hypercalcemia but low PTH and normal (non-low) urinary calcium excretion found to be secondary to a novel pathogenic inactivating mutation of the CaSR gene. We present an asymptomatic 54-year-old Malaysian woman with incidentally discovered hypercalcemia, intermittent hypophosphatemia, and Fe Ca > 2%. PTH levels were repeatedly below the mean of the reference range (on two separate assays) and sometimes even below the lower reference limit. Two siblings, one niece, and her son had hypercalcemia without nephrolithiasis. Cinacalcet, used as a PTH-suppression test, normalized serum total and ionized calcium after 7 days of cinacalcet 30 mg BID, confirming her hypercalcemia was PTH-mediated. Given her family history, genetic testing was pursued and discovered a novel pathogenic mutation of the CaSR gene confirming the diagnosis of FHH type 1. Our case represents an atypical presentation of FHH1 with low PTH and Fe Ca > 2%. This contributes to the expanding clinical and biochemical spectrum of CaSR inactivating mutations and presents an innovative approach to evaluating biochemically uncertain familial hypercalcemia with cinacalcet before pursuing expensive genetic analysis.

Objective: Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominantly inherited disorder with overlapping biochemistry profile with primary hyperparathyroidism (PHPT), making the correct diagnosis a challenge. The objective of the study was to evaluate the results of the clinical work-up of a large group of hypercalcemic individuals., Design: Cross-sectional study., Patients: Patients undergoing clinical work-up of hypercalcemia., Measurements: Molecular genetic analysis of the CASR gene and exon 2 of the AP2S1 gene. Plasma levels of ionized calcium and PTH as well as calcium creatinine clearance ratio (CCCR)., Results: A rare CASR variant was identified in 38 of 624 index patients (6.1%). A total of 18 CASR variants identified in this study were novel. No variants were identified in exon 2 of the AP2S1 gene. The majority of the variants (N = 16) were classified as likely pathogenic. The level of plasma calcium, plasma PTH and the CCCR was not affected by the type of variant (ie nonsense vs missense) (all P-values >.05). The CCCR was found to be significantly lower for variants in the transmembrane domain compared with variants located in the extracellular domain (P < .05). Plasma levels of calcium and PTH were not associated with the location of the variant (P > .05)., Conclusions: We expanded the spectrum of CASR variants in hypercalcemia with 18 novel variants, and suggest that the location of the CASR variant may affect calcium excretion as determined by the CCCR., (© 2019 John Wiley & Sons Ltd.)

Background: Twenty-four-hour renal calcium-excretion (CE) and calcium/creatinine-clearance-ratio (CCCR), respectively, are widely used to rule out familial hypocalciuric hypercalcemia (FHH) in patients with suspected primary hyperparathyroidism before surgery. The aim was to evaluate the practicability of CE compared to CCCR., Patients and Methods: We analyzed biochemical parameters, surgical treatment, gene mutation results, and long-term follow-up data of 198 patients (including 14 patients with FHH) and the discriminative power of CE and CCCR., Results: Twenty four patients (12.1%) had a low CE and 35 patients (20.2%) had a CCCR indicating FHH. However, eight patients with FHH (57.1%) had a normal or increased CE. Correspondingly, only eight cases of FHH (57.1%) were correctly predicted by CCCR. Sensitivity/specificity were 42.9%/89.9% for CE and 64.3%/79.9% for CCCR, showing no statistical differences (P = 0.482) between both methods., Conclusion: Neither CE nor CCCR was able to distinguish between PHPT and FHH but may help to narrow down potential FHH patients., (© 2018 Wiley Periodicals, Inc.)

Familial hypocalciuric hypercalcemia (FHH) causes hypercalcemia by three genetic mechanisms: inactivating mutations in the calcium-sensing receptor, the G-protein subunit α 11 , or adaptor-related protein complex 2, sigma 1 subunit. While hypercalcemia in other conditions causes significant morbidity and mortality, FHH generally follows a benign course. Failure to diagnose FHH can result in unwarranted treatment or surgery for the mistaken diagnosis of primary hyperparathyroidism (PHPT), given the significant overlap of biochemical features. Determinations of urinary calcium excretion greatly aid in distinguishing PHPT from FHH, but overlap still exists in certain cases. It is important that 24-h urine calcium and creatinine be included in the initial workup of hypercalcemia. FHH should be considered if low or even low normal urinary calcium levels are found in what is typically an asymptomatic hypercalcemic patient. The calcimimetic cinacalcet has been used to treat hypercalcemia in certain symptomatic causes of FHH., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Purpose: Patients with familial hyperparathyroidism and low urinary calcium excretion may have familial hypocalciuric hypercalcemia (FHH) with mutations in one of three genes: the calcium-sensing receptor (CaSR) defining FHH-type 1, the adaptor-related protein complex 2 (AP2S1) related to FHH-type 3 or the G-protein subunit alpha11 (GNA11) associated with FHH-type 2. We aimed to evaluate the presence of mutations in these genes and to identify phenotypic specificities and differences in these patients., Subjects and Methods: Selected patients were recruited for genetic evaluation. After informed consent was signed, blood for DNA extraction was obtained and genetic sequencing of CaSR was done. In negative cases, we further performed sequencing of AP2S1 and GNA11., Results: A total of 10 index cases were recruited. CaSR sequencing yielded three missense heterozygous mutations (30%): c.554G > A (p.I32V) previously characterized by our team, c.1394 G > A (p.R465Q) and a novel expected disease-causing mutation c.2479 A > C (p.S827R). We identified 2 additional patients (20%) carrying the deleterious recurrent mutation c.44G > T (p.R15L) in the AP2S1 gene. No GNA11 mutation was found. Clinically, patients with AP2S1 mutations had significant cognitive and behavioral disorders, and higher blood calcium and magnesium levels than patients with FHH1., Conclusion: CaSR and AP2S1 sequencing is worthwhile in patients with familial hyperparathyroidism and phenotype suggesting FHH as it can diagnose up to 50% of cases. GNA11 mutations seem much rarer. Learning disabilities in these patients, associated with higher serum calcium and magnesium levels may suggest the presence of AP2S1 rather than CaSR mutation and may guide the first step in the genetic evaluation.

The calcium-sensing receptor (CaSR) is a G-protein-coupled receptor that plays an essential role in maintaining calcium homeostasis. In the present study, we analyzed the CaSR gene in a Korean family with familial hypocalciuric hypercalcemia (FHH). Genetic studies were performed by direct sequence analysis of the CaSR gene in genomic DNA obtained from peripheral leukocytes. A novel heterozygous G to T substitution at nucleotide position 1711 in exon 6, resulting in the G571W mutation, was identified in the CaSR gene in a 26-year-old female with asymptomatic hypercalcemia, a low calcium/creatinine clearance ratio, and normal intact parathyroid hormone. To study CaSR expression, the mutation was introduced by site-directed mutagenesis into a wild-type (WT) CaSR-expressing pCR3.1 vector, and COS-7 cells were transfected with either the WT or mutant CaSR-containing vector. Transfected cells loaded with Fura-2/AM, a fluorescent indicator of Ca 2+ , were assessed for CaSR function by the change in intracellular calcium [as measured by the 340 nm/380 nm fluorescence intensity ratio (F340/F380)] made in response to challenge with extracellular Ca 2+ . Both WT and G571W cells had equivalent amounts of CaSR protein in the cell membrane. However, after challenge with extracellular Ca 2+ , cells transfected with G571W CaSR responded with a lower F340/F380 ratio than those transfected with WT CaSR and showed decreased sensitivity to extracellular Ca 2+ concentrations. The G571W mutation had therefore impaired the CaSR function. In conclusion, we identified a novel loss-of-function mutation, G571W, in the CaSR gene in a Korean family with FHH.

Germline loss- and gain-of-function mutations of G-protein α-11 (Gα11), which couples the calcium-sensing receptor (CaSR) to intracellular calcium (Ca(2+) i) signaling, lead to familial hypocalciuric hypercalcemia type 2 (FHH2) and autosomal dominant hypocalcemia type 2 (ADH2), respectively, whereas somatic Gα11 mutations mediate uveal melanoma development by constitutively up-regulating MAPK signaling. Cinacalcet and NPS-2143 are allosteric CaSR activators and inactivators, respectively, that ameliorate signaling disturbances associated with CaSR mutations, but their potential to modulate abnormalities of the downstream Gα11 protein is unknown. This study investigated whether cinacalcet and NPS-2143 may rectify Ca(2+) i alterations associated with FHH2- and ADH2-causing Gα11 mutations, and evaluated the influence of germline gain-of-function Gα11 mutations on MAPK signaling by measuring ERK phosphorylation, and assessed the effect of NPS-2143 on a uveal melanoma Gα11 mutant. WT and mutant Gα11 proteins causing FHH2, ADH2 or uveal melanoma were transfected in CaSR-expressing HEK293 cells, and Ca(2+) i and ERK phosphorylation responses measured by flow-cytometry and Alphascreen immunoassay following exposure to extracellular Ca(2+) (Ca(2+) o) and allosteric modulators. Cinacalcet and NPS-2143 rectified the Ca(2+) i responses of FHH2- and ADH2-associated Gα11 loss- and gain-of-function mutations, respectively. ADH2-causing Gα11 mutations were demonstrated not to be constitutively activating and induced ERK phosphorylation following Ca(2+) o stimulation only. The increased ERK phosphorylation associated with ADH2 and uveal melanoma mutants was rectified by NPS-2143. These findings demonstrate that CaSR-targeted compounds can rectify signaling disturbances caused by germline and somatic Gα11 mutations, which respectively lead to calcium disorders and tumorigenesis; and that ADH2-causing Gα11 mutations induce non-constitutive alterations in MAPK signaling., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

The hypercalcemia is defined as a blood calcium range above 2.6 mmol/l. Its prevalence is variable in different studies and it is comprised between 2 and 8/1000 in the general population. The primary hyperparathyroidism (PHP) and cancers are both responsible for about 80 per cent to 90 per cent of causes of hypercalcemia1. The PHP is the first ambulatory cause of hypercalcemia. Contrarily to this, the neoplastic etiology is mainly seen in the hospital settings. The other causes of the hypercalcemia are vitamin D overdose, secondary hypercalcemia due to medications intake and familial hypocalciuric hypercalcemia which will be discussed in this article. The hypocalcemia is defined as a blood calcium range underneath 2.2 mmol/l. The most common etiologies are the postoperative hypopara-thyroidism as a complication of approximatively 1.5 % of thyroidectomies2, the vitamin D deficiency and terminal chronic kidney failure. The other rare causes such as autoimmune hypoparathyroidism, parathyroid agenesis, pseudoparathyroidism and hypomagnesemia will be discussed in this article.

Objective: to report a case of familial hypocalciuric hypercalcemia (FHH) in an older patient and highlight the diagnostic challenges in geriatric populations., Case Presentation: We report the diagnosis of FHH in an 88-year-old polypathological patient with hypercalcemia discovered during a check-up for cardiac decompensation. Despite a confusing clinical presentation with gout symptoms, including repeated episodes of knee arthritis, persistent hypercalcemia conducted further investigations. Biological tests excluded primary or hyperparathyroidism and malignancy-related hyperparathyroidism, confirming the diagnosis of FHH through the detection of an inhibitory mutation in the calcium-sensing receptor gene., Conclusion: This case suggests to clinicians the possibility of FHH in older patients with unexplained hypercalcemia. In geriatric patients, the diagnosis is complicated because of the poly-pathology: here hypercalcemia was associated with a confusing gout crisis, which was triggered by diuretic treatment for heart failure.

Chondrocalcinosis is a common disease occasionally associated with hypercalcemia in case of primary hyperparathyroidism. Familial Hypocalciuric Hypercalcemia (FHH) is a rare and almost always asymptomatic condition, due to an autosomal dominant mutation of the calcium-sensing receptor gene. We report the case of a 61-year-old female with chronic hypercalcemia and joint pain. Clinical and biological data revealed chondrocalcinosis associated with FHH. Since primary hyperparathyroidism may mimic FHH, calcium to creatinine clearance ratio should be calculated in every case to avoid a wrong diagnosis and useless parathyroid surgery. The paucity of FFH complications, including chondrocalcinosis, makes their study difficult: additional studies are needed to clearly evaluate the link between FHH and chondrocalcinosis., (Copyright © 2014 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.)

Background: Inactivating mutations of the calcium-sensing receptor (CaSR), of the G-protein subunit α11 (GNA11) and of the adaptor-related protein complex 2, sigma 1 subunit (AP2S1) genes are responsible for familial hypocalciuric hypercalcaemia (FHH). The aim of this study was to analyse prevalence and pathogenicity of CaSR, GNA11 and AP2S1 mutations in patients with an FHH phenotype and to compare them with a sample of patients with primary hyperparathyroidism (PHPT) in order to identify the most useful laboratory parameter for a differential diagnosis., Methods: Patients with an FHH phenotype were studied with polymerase chain reaction amplification and direct sequencing of the entire CaSR, GNA11 and AP2S1 coding sequences. Novel mutations were introduced in a Myc-tagged human wild-type (WT) CaSR cDNA-expressing vector, and functional assay was performed on human embryonic kidney cells evaluating expression and function of mutated proteins., Results: Among 16 FHH patients, none had an inactivating GNA11 or AP2S1 mutation while 3 (18.8%) carried a CaSR mutation and 10 (62.5%) at least one CaSR polymorphism. Within the latter group, 7 of 10 patients had more than one polymorphism (4.1 ± 2.1 per patient). Two novel CaSR mutations [c.2120A>T (E707V) and c.2320G>A (G774S)] were identified: the E707V mutation prevented CaSR expression (western blot), whereas the G774S mutation determined a reduced receptor sensitivity to calcium (IP3 assay). PHPT patients showed significantly (P < 0.001) higher serum calcium, parathyroid hormone, urinary calcium and calcium-creatinine clearance ratio (CCCR) and significantly lower serum phosphate than FHH ones., Conclusions: FHH should be clearly differentiated by PHPT to avoid unnecessary surgery: CCCR could be a useful screening tool while genetic analysis should include the two novel CaSR mutations herein described. The role of multiple polymorphisms deserves further investigation in patients with an FHH phenotype., (© The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

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., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Primary hyperparathyroidism is the main cause of hypercalcemia while familial hypocalciuric hypercalcemia is a rare one. We report a case of a 39-year-old woman followed at our rheumatology outpatient center with the diagnosis of ankylosing spondylitis in which the routine laboratorial analysis demonstrated hypercalcemia with high levels of parathyroid hormone. The ultrasound, scintigraphy, and histology findings confirmed the diagnosis of primary hyperparathyroidism and parathyroid hyperplasia as the underlying cause. After surgery, given the persistence of hypercalcemia in association with a low urinary calcium excretion, a genetic study was carried out which led to the diagnosis of familial hypocalciuric hypercalcemia type 1. The patient had no symptoms or familiar history of hypercalcemia. The authors highlight the rarity of the association of these two conditions in the same patient and the importance of considering familial hypocalciuric hypercalcemia as a possible diagnosis even in patients with an established diagnosis of primary hyperparathyroidism. [ABSTRACT FROM AUTHOR]

Familial hypocalciuric hypercalcemia (FHH) is marked by mild to moderate hypercalcemia, normal-elevated serum PTH levels, and relative hypocalciuria. Cinacalcet, a calcimimetic therapy, has been reported to reduce symptom burden and serum calcium levels in FHH. We report 2 adult males with chronic hypercalcemia, with initial concerns for primary hyperparathyroidism. Urine calcium screening and genetic testing confirmed FHH in both patients. Shortened QTc normalized while on cinacalcet in the first patient and reductions in serum calcium and PTH levels without symptomatic hypercalcemia were noted in the second patient. Calcimimetic therapy can potentially be offered to FHH patients, particularly those with hypercalcemia symptoms, serum calcium levels >1 mg/dL (0.25 mmol/L) above normal or at risk of cardiac arrhythmias. Cinacalcet treatment was overall well tolerated and significantly reduced serum calcium and PTH levels in 2 adult FHH patients over time. Calcimimetic therapy has shown promise in managing persistent hypercalcemia and potential adverse events in FHH patients. Potential barriers include indefinite treatment, cost, and possible adverse effects. [ABSTRACT FROM AUTHOR]

Context: Although a monoallelic mutation in the calcium-sensing receptor (CASR) gene causes familial hypocalciuric hypercalcemia (FHH), the functional characterization of the identified CASR mutation linked to the clinical response to calcimimetics therapy is still limited. Objective: A 45-year-old male presenting with moderate hypercalcemia, hypocalciuria, and inappropriately high parathyroid hormone (PTH) had a good response to cinacalcet (total serum calcium (Ca2+,) from 12.5 to 10.1 mg/dl). We identified the genetic mutation and characterized the functional and pathophysiological mechanisms, and then linked the mutation to calcimimetics treatment in vitro. Design: Sanger sequencing of the CASR, GNA11, and AP2S1 genes was performed in his family. The simulation model was used to predict the function of the identified mutant. In vitro studies, including immunoblotting, immunofluorescence, a cycloheximide chase study, Calbryte 520 Ca2+, detection, and half-maximal effective concentration (EC50), were examined. Results: This proband was found to carry a de novo heterozygous missense I554N in the cysteine-rich domain of CASR, which was pathogenic based on the different software prediction models and ACGME criteria. The simulation model showed that CASR I554N mutation decreased its binding energy with Ca2+,. Human CASR I554N mutation attenuated the stability of CASR protein, reduced the expression of p-ERK 1/2, and blunted the intracellular Ca2+, response to gradient extracellular Ca2+,(eCa2+,) concentration. The EC50 study also demonstrated the correctable effect of calcimimetics on the function of the CASR I554N mutation. Conclusion: This novel CASR I554N mutation causing FHH attenuates CASR stability, its binding affinity with Ca2+, and the response to eCa2+, corrected by therapeutic calcimimetics. [ABSTRACT FROM AUTHOR]

Context: A germline mutation can be identified in up to 10% of patients with primary hyperparathyroidism (PHPT). In 2017, a high frequency of the GCM2 [(NM_ 004752.4) c.1181A> C; p.Tyr394Ser; rs142287570] variant was reported in PHPT Ashkenazi Jews (AJ). Objective: To evaluate the presence of the GCM2 p.Tyr394Ser variant in Israeli patients addressed for genetic evaluation to characterize their phenotype and clinical management. Method: Patients with PHPT who underwent addressed for genetic screening for suspected familial hypocalciuric hypercalcemia (FHH), a family history of isolated hyperparathyroidism (FIHP), or failed parathyroidectomy with persistent PHPT were recruited. Those with normal initial selected gene sequencing or hyperparathyroid genetic panel completed the GCM2 p.Tyr394Ser variant sequencing. The prevalence of this variant was evaluated using our local genomic database. Results: A total of 42 single individuals from unrelated kindreds were evaluated. A disease-causing mutation was found in 11 (26.1%) patients: 10 were diagnosed with FHH (eight CASR and two AP2S1 mutations), and one patient had a CKN2B mutation. In 28 of the remaining patients, the GCM2 p.Tyr394Ser variant was positive in three (10.7%), and all were AJ. Within AJ (15/28, 53.5%), the rate of the p.Tyr394Ser variant was 3/15 (20%), and of those, two had a history of familial isolated hyperparathyroidism. Multi-glandular parathyroid adenoma/hyperplasia was also observed in two of these patients. No clinical or laboratory findings could discriminate patients with the GCM2 p.Tyr394Ser variant from those with FHH. Cinacalcet normalized the calcium levels in one patient. The prevalence of the GCM2 p.Tyr394Ser variant in 15,407 tests in our local genomic database was 0.98%. Conclusion: In contrast to previous observations, the GCM2 p.Tyr394Ser variantassociated phenotype may be mild in AJ with FIHP, sometimes mimicking FHH. Because surgery may be curative, surgeons should be aware of the possibility of multiple gland diseases in these patients. The clinical spectrum and clinical utility of screening for this variant warrant further investigation. [ABSTRACT FROM AUTHOR]

Between 2% and 10% of patients with primary hyperparathyroidism (pHPT) are diagnosed with hereditary forms of primary hyperparathyroidism (hpHPT). They are more prevalent in younger patients before the age of 40 years, in patients with persistence or recurrence of pHPT and pHPT patients with multi-glandular disease (MGD). The various forms of hpHPT diseases can be classified into four syndromes, i.e., hpHPT associated with diseases of other organ systems, and four diseases that are confined to the parathyroid glands. Approximately 40% of patients with hpHPT suffer from multiple endocrine neoplasia type 1 (MEN-1) or show germline mutations of the MEN‑1 gene. Currently, germline mutations that lead to a specific diagnosis in patients with hpHPT have currently been described in 13 different genes, which enables a clear diagnosis of the disease; however, a clear genotype-phenotype correlation does not exist, even though the complete loss of a coded protein (e.g. due to frame-shift mutations in the calcium sensing receptor, CASR) often leads to more severe clinical consequences than merely a reduced function of the protein (e.g. due to point mutation). As the various hpHPT diseases require different treatment approaches, which do not correspond to that of sporadic pHPT, a clear definition of the specific form of hpHPT must always be strived for. Therefore, before surgery of a pHPT with clinical, imaging or biochemical suspicion of hpHPT, genetic proof or exclusion of hpHPT is necessary. The differentiated treatment approach for hpHTP can only be defined by taking the clinical and diagnostic results of all the abovenamed findings into account. [ABSTRACT FROM AUTHOR]

Familial hypocalciuric hypercalcemia (FHH) is a benign disease associated with heterozygous inactivating mutations in the calcium-sensing receptor (CaSR) gene. This article presents a girl with heterozygous p.Cys575Tyr variation in the CaSR gene. The serum calcium level of a 9.2-year-old girl was 12.4mg/dl in incidental laboratory analysis. On the same occasion, the serum parathyroid hormone (PTH) level was 45 pg/ml, 25(OH) vitamin D level 24.2ng/ml, 1.25 dihydroxy vitamin D level 22pg/ml, and urinary Ca/creatinine ratio A) variation was detected in the patient's CaSR gene, which was reported before, but no clinical manifestations were specified. In children with asymptomatic hypercalcemia, the diagnosis of FHH should be considered if the PTH level is normal or high and the urinary calcium is low. [Med-Science 2022; 11(4.000): 1731-3]

Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant inherited disorder due to inactivating mutations in the calcium-sensing receptor (CaSR), less commonly in the G-protein subunit α11 (GNA11) or the adaptor-related protein complex 2, sigma 1 subunit (AP2S1) genes. It is characterized by mild to moderate hypercalcemia, hypocalciuria, and inappropriately normal or high PTH levels. The disorder is usually asymptomatic, and bone or renal involvement is rare. Adequate differential diagnosis between primary hyperparathyroidism and FHH is important to avoid unnecessary surgery. We report the case of a male patient with FHH showing biochemical heterogeneity to highlight the difficulties of differential diagnosis

Context In the clinic it is important to differentiate primary hyperparathyroidism (PHPT) from the more benign, inherited disorder, familial hypocalciuric hypercalcemia (FHH). Since the conditions may sometimes overlap biochemically, identification of calcium-sensing receptor (CASR) gene variants causative of FHH (but not PHPT) is the most decisive diagnostic aid. When novel variants are identified, bioinformatics and functional assessment are required to establish pathogenicity. Objective We identified 3 novel CASR transmembrane domain missense variants, Thr699Asn, Arg701Gly, and Thr808Pro, in 3 probands provisionally diagnosed with FHH and examined the variants using bioinformatics and functional analysis. Methods Bioinformatics assessment utilized wANNOVAR software. For functional characterization, each variant was cloned into a mammalian expression vector; wild-type and variant receptors were transfected into HEK293 cells, and their expression and cellular localization were assessed by Western blotting and confocal immunofluorescence, respectively. Receptor activation in HEK293 cells was determined using an IP-One ELISA assay following stimulation with Ca++ ions. Results Bioinformatics analysis of the variants was unable to definitively assign pathogenicity. Compared with wild-type receptor, all variants demonstrated impaired expression of mature receptor reaching the cell surface and diminished activation at physiologically relevant Ca++ concentrations. Conclusion Three CASR missense variants identified in probands provisionally diagnosed with FHH result in receptor inactivation and are therefore likely causative of FHH. Inactivation may be due to inadequate processing/trafficking of mature receptor and/or conformational changes induced by the variants affecting receptor signaling. This study demonstrates the value of functional studies in assessing genetic variants identified in hypercalcemic patients. [ABSTRACT FROM AUTHOR]

Familial hypocalciuric hypercalcemia (FHH) is a benign disease associated with heterozygous inactivating mutations in the calcium-sensing receptor (CaSR) gene. This article presents a girl with heterozygous p.Cys575Tyr variation in the CaSR gene. The serum calcium level of a 9.2-year-old girl was 12.4mg/dl in incidental laboratory analysis. On the same occasion, the serum parathyroid hormone (PTH) level was 45 pg/ml, 25(OH) vitamin D level 24.2ng/ml, 1.25 dihydroxy vitamin D level 22pg/ml, and urinary Ca/creatinine ratio <0.01. The ultrasonographic evaluation of the urinary system was unremarkable. The clinical and laboratory findings pointed towards FHD. A heterozygous p.Cys575Tyr (c.1724G>A) variation was detected in the patient's CaSR gene, which was reported before, but no clinical manifestations were specified. In children with asymptomatic hypercalcemia, the diagnosis of FHH should be considered if the PTH level is normal or high and the urinary calcium is low. [ABSTRACT FROM AUTHOR]

Familial hypocalciuric hypercalcemia (FHH) type 1, caused by a heterozygous inactivating mutation of the gene encoding the calcium-sensing receptor (CaSR), is characterized by mild to moderate hypercalcemia, hypocalciuria and inappropriately normal or elevated parathyroid hormone (PTH). FHH must be differentiated from primary hyperparathyroidism (PHPT) because parathyroidectomy is ineffective in the former. Herein, we report a 39-year-old male patient with a 13-year history of asymptomatic PTH-dependent hypercalcemia (mean calcium of 2.88 mmol/l; reference range 2.15-2.55 mmol/l) and calcium-tocreatinine clearance ratio (Ca/Cr) ranging from 0.007 to 0.0198, which is consistent with either FHH or PHPT. Although a family history of hypercalcemia was negative, and PET-CT with fluorocholine was suggestive of a parathyroid adenoma, genetic analysis of the CaSR gene identified a heterozygous inactivating mutation NM_000388.4:c.1670G>A p. (Gly557Glu) in exon 6 and a polymorphism NM_000388.4:c.1192G>A p. (Asp398Asn) in exon 4. The G557E mutation has been previously reported in a Japanese family in which all family members with the mutation had Ca/Cr below 0.01 consistent with FHH. The biochemical profile of FHH and PHPT may overlap. Our FHH patient with a G557E CaSR mutation illustrates that the differential diagnosis can be difficult in an index case with no family history, (false) positive parathyroid imaging and higher calciuria than expected for FHH. Calcium intake, vitamin D status and bone resorption might have contributed to the Ca/Cr variations over a 13-year clinical follow up. This case thus emphasizes the irreplaceable role of genetic testing of the CaSR gene when clinical evaluation is inconclusive. [ABSTRACT FROM AUTHOR]

Background: Neonatal severe hyperparathyroidism (NSHPT) is commonly treated with either parathyroidectomy or pharmacologic agents with varying efficacy and numerous side effects. Reports of using cinacalcet for NSHPT have increased, however, the effective dose for pediatric patients from the onset of symptoms through infancy has not been established. Case presentation: We describe the clinical course of a newborn with a de novo R185Q mutation in the calcium-sensing receptor (CASR) gene, causing NSHPT. The infant received cinacalcet from the first days of life until 1 year of age. Conclusions: Cinacalcet therapy effectively controlled the patient's serum calcium, phosphorus, and parathyroid hormone (PTH) levels without side effects. [ABSTRACT FROM AUTHOR]