Parathyroid Hormone Suppression Research Articles

Inhibition of the epigenetic suppressor EZH2 primes osteogenic differentiation mediated by BMP2

Bone-stimulatory therapeutics include bone morphogenetic proteins (e.g. BMP2), parathyroid hormone, and antibody-based suppression of WNT antagonists. Inhibition of the epigenetic enzyme enhancer of zeste homolog 2 (EZH2) is both bone anabolic and osteoprotective. EZH2 inhibition stimulates key components of bone-stimulatory signaling pathways, including the BMP2 signaling cascade. Because of high costs and adverse effects associated with BMP2 use, here we investigated whether BMP2 dosing can be reduced by co-treatment with EZH2 inhibitors. Co-administration of BMP2 with the EZH2 inhibitor GSK126 enhanced differentiation of murine (MC3T3) osteoblasts, reflected by increased alkaline phosphatase activity, Alizarin Red staining, and expression of bone-related marker genes (e.g. Bglap and Phospho1). Strikingly, co-treatment with BMP2 (10 ng/ml) and GSK126 (5 μm) was synergistic and was as effective as 50 ng/ml BMP2 at inducing MC3T3 osteoblastogenesis. Similarly, the BMP2-GSK126 co-treatment stimulated osteogenic differentiation of human bone marrow-derived mesenchymal stem/stromal cells, reflected by induction of key osteogenic markers (e.g. Osterix/SP7 and IBSP). A combination of BMP2 (300 ng local) and GSK126 (5 μg local and 5 days of 50 mg/kg systemic) yielded more consistent bone healing than single treatments with either compound in a mouse calvarial critical-sized defect model according to results from μCT, histomorphometry, and surgical grading of qualitative X-rays. We conclude that EZH2 inhibition facilitates BMP2-mediated induction of osteogenic differentiation of progenitor cells and maturation of committed osteoblasts. We propose that epigenetic priming, coupled with bone anabolic agents, enhances osteogenesis and could be leveraged in therapeutic strategies to improve bone mass.

The Beneficial Effect of Paricalcitol (Zemplar) on Secondary hyperparathyroidism Refractory to Calcitriol (Calcijex) and Cinacalcet HCl (Mimpara) in Patients on Maintenance Hemodialysis: A Prospective and Crossover Study

Paricalcitol, 19-nor-1, 25-dihydroxvitamin D2, is a novel 1,25–dihydroxyvitamin D2 analogue, which has greater potential to suppress parathyroid hormone without inducing significant hypercalcemia and hyperphosphatemia. We therefore investigated its role in treatment of patients with moderate to severe secondary hyperparathyroidism (SHPT) who were refractory to conventional therapy with Calcitriol and Cinacalcet HCl. Eight patients were recruited in whom conventional therapy was stable over the past 3 months. After a washout period of 2 weeks, calcijex injections were replaced by Paricalcitol. Paricalcitol induced more suppression of iPTH compared to the conventional therapy without significant hypercalcemia, hyperphosphatemia or side effects. The conversion ratio was approximately 1:2.5 (calcitriol:paricalcitol). In conclusion, injectable Paricalcitol is superior to Calcitriol in treatment of SHPT.
 Keywords: Cinacalcet, Calciferol, hemodialysis, hyperparathyroidism, Paricalcitol.

MON-908 Carcinoid Causing Catastrophic Calcemia

Intro: Carcinoid tumors are rare, slow growing, indolent neuroendocrine tumors typically originating from enterochromaffin in the gastrointestinal tract and bronchopulmonary tree1. While often found to be secreting serotonin, many different secretory products have been described2. We present the case of a patient with refractory hypercalcemia due to a carcinoid tumor producing parathyroid hormone related peptide (PTHrP). Case: A 65-year-old male was found to have hypercalcemia of 14.7 mg/dL after presenting for nausea and vomiting. He was treated with Zolendronic acid and intravenous (IV) fluids as initial work-up revealed an appropriately suppressed parathyroid hormone level, no monoclonal spike, and a PTHrP that was dramatically elevated. He refused further work-up initially but was admitted two months later for persistent severe hypercalcemia. Computed tomography imaging showed innumerable liver lesions. Histologic analysis of the largest liver lesion was consistent with carcinoid tumor. For the next two years, he was managed outpatient with Pamidronate, Denosumab, and Sandostatin, along with two liver embolizations. Control of serum calcium levels became more difficult and he had multiple hospitalizations for symptomatic hypercalcemia until chemotherapy, Sunitinib, was initiated. Calcium levels normalized for one year after starting Sunitinib prior to onset of suspected medication-induced pancreatitis. He was switched to Everolimus but did not respond to that and was readmitted mere weeks later for symptomatic hypercalcemia and a combination of Folinic acid, Fluorouracil, and Oxaliplatin (Folfox) was started. He continued to get frequent bisphosphonates and IV fluids along with Folfox but several months later he stopped responding to all medical options. His calcium level climbed to 19.9mg/dL and he underwent a technically complicated surgical procedure in which significant tumor burden was removed from his liver. Since surgery, the patient has remained normocalcemic without additional medical therapy. Discussion: Carcinoid tumors are uncommon with reported incidence of 40 per one million people2. PTHrP is most commonly produced by squamous cell lung cancer, renal cell cancer, gynecologic cancers, and lymphoma3. Carcinoid tumors producing PTHrP with resultant hypercalcemia is rare with a few cases reported in literature4. Our patient had a complex treatment course including IV fluids, anti-resorptive agents, somatostatin analogs, liver embolization, chemotherapeutic agents, and eventual surgical debulking. Surgical intervention is not commonly required for carcinoid tumors5. This patient had a rare tumor, producing an uncommon hormone, and required extensive treatment. This case shows the importance of a multidisciplinary approach in patients with hypercalcemia secondary to carcinoid tumors but refractory to traditional therapy.

SAT-187 Altered Mental Status in a Patient with Bilateral Adrenal Masses

IntroductionPrimary adrenal lymphoma (PAL) is a very rare and aggressive form of Non-Hodgkin’s lymphoma originating from the adrenal glands and with no prior history of lymphoma. It can present with symptoms related to adrenal insufficiency due to tumoral destruction of normal adrenal tissue. Hypercalcemia has also been previously reported as a less common presentation of PAL. We describe here a case of PAL presenting with severe hypercalcemia and adrenal insufficiency.Clinical Case75 year male presented with 50 pound weight loss, fatigue and anorexia for several months. On admission, patient had altered mental status. Further investigation revealed severe hypercalcemia (corrected calcium for albumin =15mg/dl) and AKI (serum creatine=3.45mg/dl, blood urea nitrogen=89). He was started on IV fluids for the hypercalcemia and AKI. Additional work up revealed suppressed parathyroid hormone (PTH) levels of 9 (12 - 88 pg/mL), high normal PTH-related peptide 22 (14-27), low 25-OHD 7.34 (20-120 ng/ml), high normal 1,25-(OH)2-D 63.0 (19.9-79 pg/mL). His ACTH level was elevated ~159 (7.2-63.3 pg/ml) with low normal morning cortisol levels ~10 mcg/dl. Patient was started on IV stress dose steroids for concerns of adrenal insufficiency and calcitonin was also initiated for the treatment of hypercalcemia. CT of the abdomen showed bilateral adrenal masses, measuring 9.8 x 6.4 x 10.8 cm on the right and 9.3 x 5.2 x 9.6 cm on the left with marked retroperitoneal lymphadenopathy. After ruling out pheochromocytoma with negative plasma and urine metanephrines, biopsy of the adrenal mass revealed a highly aggressive diffuse B large cell lymphoma, with BCL2 and MYC overexpression. Concurrent flow cytometric analysis also identified an abnormal population of medium to large B cells expressing bright CD20, CD19, CD38, CD45 without CD10, CD5, CD23 or overt kappa or lambda expression. His calcium levels improved with hydration and steroids. Chemotherapy was later initiated.ConclusionPrimary adrenal lymphoma is rare and aggressive type of NHL. While adrenal insufficiency is expected in this clinical scenario, hypercalcemia from 1,25-(OH)2-D excess is a relatively uncommon presentation. Adrenal insufficiency should be ruled out in bilateral infiltrative adrenal masses. Likely etiologies for hypercalcemia in our case appeared to be secondary to elevated 1,25-(OH)2-D production, humoral hypercalcemia of malignancy and worsened by untreated clinically evident adrenal insufficiency.References(1) Laurent C, Casasnovas O, Martin L, et al. Adrenal lymphoma: presentation, management and prognosis. QJM. 2017 Feb 1;110(2):103-109. doi: 10.1093/qjmed/hcw174(2) Masood A, Tumyan A, Nussenzveig D R., Wakefield D N., Barb D, Ghayee H K., Maalouf N M. The Diverse Clinical Presentations of Adrenal Lymphoma. AACE Clinical Case Reports: Autumn 2017, Vol. 3, No. 4, pp. e307-e312. doi: 10.4158/EP161595.CR

Analyses of risk factors for temporarily inhibited parathyroid hormone secretion of postoperative primary hyperparathyroidism

Objective: To study relative risk factors for temporarily inhibited parathyroid hormone (PTH) secretion after surgery of primary hyperparathyroidism (PHPT). Methods: Seventy-two cases with PHPT from October 2017 to March 2019 in Beijing Chaoyang Hospital were analyzed retrospectively, including 22 males and 50 females aged from 13 to 83 years old. They were reviewed and divided into a complete inhibition group (24 cases, PTH=0 pg/ml), an incomplete inhibition group (23 cases, 0<PTH<12.4 pg/ml), and a non-inhibition group (25 cases, PTH≥12.4 pg/ml) according to the PTH level on the first day after surgery of PHPT. With the Kruskal-Wallis multi-group rank sum test and the Nemenyi test, preoperative and postoperative biochemical parameters and endocrine indexes, including the preoperative serum levels of calcium, phosphorus, PTH, 25-hydroxyvitamin D, and alkaline phosphatase, as well as the levels of PTH 10 min after focal resection, calcium on the first day after surgery, and PTH on the third day after surgery, were compared among three groups to evaluate potential risk factor for postoperative temporary inhabitation of PTH secretion. The predictive values of various risk factors for postoperative temporary inhibition of PTH secretion were evaluated with ROC curve analysis. Results: Preoperative serum PTH, calcium levels, and serum calcium level on the first day after surgery in the complete inhibition group were higher than those in the non-inhibition group,respectively, with statically significant differences [256.5(141.6,585.3) pg/ml vs. 130.2(92.1,256.6) pg/ml, 2.90(2.69,3.22) mmol/L vs. 2.61(2.50,2.75) mmol/L, 2.23(2.08,2.41) mmol/L vs. 2.12(2.05,2.14) mmol/L, χ(2) were 7.17, 11.90, 8.32, respectively, all P<0.05]. When the preoperative serum calcium level was higher than 2.62 mmol/L (AUC=0.698, 95%CI: 0.57-0.83, P=0.006) or the preoperative PTH level was higher than 115.9 pg/ml (AUC=0.697, 95%CI: 0.58-0.82, P=0.007), patients tended to inhibit completely PTH secretion after operation. Conclusions: Preoperative serum calcium and PTH levels are risk factors for postoperative temporary PTH inhibition in PHPT.

PDB12 EFFICACY AND SAFETY OF ETELCALCETIDE IN THE TREATMENT OF SECONDARY HYPERPARATHYROIDISM IN ADULT PATIENTS WITH CHRONIC KIDNEY DISEASE UNDERGOING DIALYSIS: A SYSTEMATIC REVIEW AND META-ANALYSIS

Chronic kidney disease (CKD) is a condition with an irreversible reduction in the number of functioning nephrons, which results in progressive and permanent deterioration in kidney function. There were numerous complications associated with CKD which include secondary hyperparathyroidism. Controlling elevated serum phosphorus levels and directly targeting suppression of intact parathyroid hormone (iPTH) production remain targets. This study aimed to evaluate the efficacy and safety of etelcalcetide in the treatment of secondary hyperparathyroidism in adult patients with CKD undergoing dialysis

Older Age Is Associated with Decreased Levels of VDR, CYP27B1, and CYP24A1 and Increased Levels of PTH in Human Parathyroid Glands.

Parathyroid glands contain the vitamin D receptor (VDR) and 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) and 24-hydroxylase (CYP24A1), which catalyze the production and degradation of 1,25-dihydroxyvitamin D [1,25(OH)2D], respectively. Previous studies have shown that the serum level of intact parathyroid hormone (iPTH) increases with age. We hypothesized that the expression of CYP27B1 or VDR in parathyroid glands decreases with age, which might account for the increased serum levels of iPTH due to decreased suppression of parathyroid hormone (PTH) secretion by 1,25(OH)2D in older people. To test this hypothesis, we examined relative expression levels of VDR, CYP27B1, CYP24A1, and PTH in specimens from parathyroid glands unintentionally removed during thyroidectomy for 70 patients varying in age from 10 to 70 years. The results showed that there was an inverse correlation between age and VDR, CYP27B1, and CYP24A1 expression (p < 0.05). A significant positive correlation between PTH expression levels and age was also observed (p < 0.05). These data indicate that older age is associated with decreased levels of VDR, CYP27B1, and CYP24A1 and increased levels of PTH in human parathyroid glands.

Suppression of Parathyroid Hormone as a Proxy for Optimal Vitamin D Status: Further Analysis of Two Parallel Studies in Opposite Latitudes.

Optimal vitamin D status has commonly been defined as the level of 25-hydroxyvitamin D (25(OH)D) at which parathyroid hormone (PTH) concentrations would be maximally suppressed, represented by an observed minimum plateau. Previous findings indicate a large variation in this plateau, with values ranging from <30 nmol/L up to 100 nmol/L. This disparity in values might be explained by differences in study design and methodology, ethnicity, age, gender and latitude. This study aimed to investigate the concentration of 25(OH)D at which PTH concentrations were suppressed in Brazilian women living in opposite latitudes (high vs. low: i.e., UK and Brazil), during wintertime. Using data from the D-SOL study (Interaction between Vitamin D Supplementation and Sunlight Exposure in Women Living in Opposite Latitudes), the association between 25(OH)D status and PTH levels were examined in 135 Brazilian women (56 living in England and 79 living in Brazil, aged 20–59 years old). Mean PTH concentrations for Brazilian women with vitamin D deficiency (<25 nmol/L) were significantly higher compared to those with vitamin D insufficiency (25–49.9 nmol/L) (p < 0.01), vitamin D adequacy (50–74.9 nmol/L) (p < 0.01) and those with optimal vitamin D status (>75 nmol/L) (p < 0.001). Regression modelling was used to investigate the relationship between serum 25(OH)D and PTH for the sample as a whole and for each group separately. A cubic model was statistically significant for the total sample (p < 0.001), whereas a linear model presented the best fit for Brazilian women living in England (p = 0.04) and there were no statistically significant models fitted for Brazilian women living in Brazil. The cubic model suggests that 25(OH)D concentrations above 70–80 nmol/L are optimal to suppress the parathyroid gland in Brazilian women. These findings contribute to a better understanding of the relationship between 25(OH)D and PTH in populations living in a low latitude location and are of great relevance for discussions regarding the estimation of optimal cut-offs for vitamin D levels in the Brazilian population as well as for other low latitude locations.

Obesity and efficacy of vitamin D3 supplementation in healthy black adults.

Results from recent clinical trials suggest that vitamin D efficacy against cancermay be influenced by body mass index. As suppression of parathyroid hormone (PTH) is one indicator of vitamin D efficacy, we examined to what extent doses of vitamin D3 supplementation suppress PTH levels in individuals with and without obesity. A total of 328 healthy African Americans were randomized into the following four groups and treated for 3months: placebo, 1,000, 2,000, or 4,000IU/day of vitamin D3 supplementation. Among the participants, 250 individuals with PTH measurements were included in the analysis. Obese individuals (n = 141) experienced a steep reduction of 3-month PTH from placebo to 1,000IU/day of vitamin D3 supplementation, but no further reduction at 2,000 or 4,000IU/day. For non-obese individuals (n = 109), the reduction of 3-month PTH was approximately linear for increasing vitamin D3 doses. At supplementation of 2,000 to 4,000IU/day, 3-month 25(OH)vitamin D levels were high in both non-obese and obese individuals, but the 3-month PTH levels remained about 10pg/mL higher in individuals with obesity. Our findings suggest that excess adiposity confers resistance to vitamin D efficacy in suppressing PTH levels, even when given at high doses.

Anorexia Nervosa with Markedly High Bone Turnover and Hyperphosphatemia During Refeeding Rectified by Denosumab.

We describe a unique case of hyperphosphatemia associated with a very high bone turnover rate in a 51-year-old postmenopausal woman with undiagnosed anorexia nervosa (AN) who presented with a low-trauma hip fracture. In view of her severely malnourished state, she was not fit for surgery. She was treated according to a refeeding protocol that mandated bed rest. Contrary to expectation, she developed sustained hyperphosphatemia and borderline hypercalcemia. Bone remodelling markers, both resorption and formation, were markedly elevated. Parathyroid hormone (PTH) was low-normal at 1.7pmol/L, C-terminal fibroblast growth factor 23 (FGF23) was high at 293RU/ml, but tubular maximum reabsorption of phosphate (TmPO4/GFR) was elevated at 1.93mmol/L. Denosumab 60mg was administered that was followed by: rapid normalisation of serum phosphate; normalisation of resorption markers, transient hypocalcaemia with secondary hyperparathyroidism, and normalisation of both TmPO4/GFR and C-terminal FGF23. We speculate that prolonged immobilization as part of AN management led to a high remodelling state followed by hyperphosphatemia and high-normal calcium with appropriate suppression of PTH and that marked hyperphosphatemia and high TmP/GFR despite high FGF23 indicates the necessity of PTH adequacy for excess FGF23 to lower TmP/GFR.

The potential effect of vitamin D against bone loss and vascular calcification in ovariectomized rats: possible association with serum nitric oxide.

Many epidemiological studies have shown an association between osteoporosis and peripheral vascular disease in postmenopausal women. This work was provided to investigate the possible effect of vitamin D against postmenopausal bone loss and vascular calcification in adult rats. This study was carried on 24 Sprague Dawley female rats. Rats were divided into four main groups (6 rats for each group). Group I : control sham-operated rats. Group II : sham operated rats treated with vitamin D . Group III : control ovariectomized (OVX) rats. Group IV : OVX rats treated with vitamin D. Ovariectomized rats were injected intraperitoneal with active vitamin D (calcitriol) 3 times a week for one month in the form of 0.04 μg/kg calcitriol. Serum level of estradiol, calcium, phosphorus and osteoblastic markers (alkaline phosphatase and osteocalcin) were measured. Serum levels of lipid profile, parathormone and nitric oxide were also evaluated. The bone and the aortic wall were prepared for histopathological study. In comparisons to the ovariectomized rats, active vitamin D caused significant attenuation of the bone loss, biomechanical fragility and delayed the onset of vascular calcification in the aortic wall. Also it improved the lipid profile, serum nitric oxide levels and suppressed parathyroid hormone level. This work suggests that the administration of vitamin D has a beneficial effect on the bone quality and also on delaying the onset of aortic vascular calcification in ovariectomized rats. And suggests a possible association with serum nitric oxide.

Abstract B43: p120 catenin loss drives pancreatic cancer EMT and metastasis through activation of PTHrP-mediated calcium signaling

Abstract Purpose: An unbiased approach to discover candidate cancer genes in pancreatic ductal adenocarcinoma (PDAC) identified the p120 catenin gene (Ctnnd1) as one of the top 20 driver genes, and further analysis revealed that P120CTN loss correlated with reduced survival. Results presented herein used genetically engineered mouse models (GEMMs) to show that P120CTN is a potent metastasis suppressor in PDAC. Methods: We employed orthotopic injection, tail vein metastasis assays, and mouse hospital preclinical trials to show that deletion or pharmacologic inhibition of Parathyroid Hormone Related Protein (PTHrP/PTHLH), a signaling element downstream of P120CTN, delayed tumor development and metastatic outgrowth. Finally, we generated a novel GEMM of Pthlh deletion to demonstrate in the autochthonous KPC model that loss of PTHrP phenocopies anti-PTHrP therapy by blocking both primary and metastatic tumor growth. Results: We have generated a mouse model to delete the gene Ctnnd1, whose gene product p120 catenin (P120CTN) is necessary for E-cadherin stability, resulting in enhanced epithelial-to-mesenchymal transition (EMT) and metastasis in KPC animals. Specifically, we show that KPC-p120ctncKO mice have a dramatically enhanced metastatic phenotype relative to KPC controls, suggesting that P120CTN is a critical factor in metastatic cell dissemination. An unbiased screen of tumor cells isolated from these mice identified misregulated calcium signaling through the Parathyroid Hormone Related Protein (PTHrP) as a previously unappreciated contributor to EMT and metastasis. Genetic deletion of the gene that codes for PTHrP in orthotopic transplantation experiments showed significantly reduced tumor growth and metastasis, establishing PTHrP as an oncogenic and prometastatic secreted peptide. Furthermore, treatment with anti-PTHrP monoclonal antibodies reduced tumor cell proliferation and migration in vitro, demonstrating that anti-PTHrP therapies may be of clinical benefit. Importantly, we generated KPC-PthlhcKO mice and showed that they have significantly reduced primary and metastatic tumor burden and increased survival relative to KPC controls. In parallel experiments, we treated KPC mice in a preclinical trial with anti-PTHrP neutralizing antibodies, which delayed both primary and metastatic tumor growth. Finally, analysis of human samples demonstrated that increased PTHLH expression is associated with significantly decreased survival, and that a subset of patients have PTHLH genomic amplifications. Conclusions: This novel work has demonstrated the importance of the previously unappreciated role that PTHrP-mediated calcium signaling plays in pancreatic cancer cellular plasticity and metastasis, and future studies will look to determine the efficacy of anti-PTHrP monoclonal antibodies with a view towards translation in human clinical trials. Citation Format: Jason R. Pitarresi, Robert J. Norgard, Ben Z. Stanger, Anil K. Rustgi. p120 catenin loss drives pancreatic cancer EMT and metastasis through activation of PTHrP-mediated calcium signaling [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr B43.

Fatal Hypocalcaemia Due to Hungry Bone Syndrome with Secondary Refractory HyperParathyroidism after Parathyroidectomy: A Case Report

IntroductionHungry bone syndrome (HBS) refers to the rapid, profound, and prolonged hypocalcaemia associated with hypophosphatemia and hypomagnesaemia, and is exacerbated by suppressed parathyroid hormone (PTH) levels, which follows parathyroidectomy in patients with severe primary hyperparathyroidism (PHPT) and preoperative high bone turnover. [1]Case reportThis report concerns a dialysed patient who underwent surgical treatment for secondary refractory hyperparathyroidism. Haemodialysis was carried out pre-operatively, and subsequently, a total parathyroidectomy with auto-transplantation of parathyroid tissue in the sternocleidomastoid muscle (SCM) was performed. Rapid and progressive hypocalcaemia symptoms developed during the second day postoperatively. Acute cardiac symptoms with tachyarrhythmia, haemodynamic instability and finally asystole occurred, which required cardiopulmonary resuscitation (CPR). The ionic calcium level was 2.2 mg/dL being consistent with a diagnosis of HBS. A second cardiac arrest unresponsive to CPR followed an initial period of normal sinus rhythm. Death ensued shortly after. Before death, the ionic calcium was 3.1 mg/dL.ConclusionHBS, after parathyroidectomy in patients with secondary hyperparathyroidism (SHPT), may be severe, prolonged and sometimes fatal. Generally, HBS symptomatology is that of a mild hypocalcaemia. It can, however, include heart rhythm disturbances with haemodynamic alterations requiring intensive care measurements and even cardiopulmonary resuscitation. A close clinical and laboratory post-parathyroidectomy monitoring of dialysed patients is of the utmost importance.

Unexpected complication of a common therapy in a pregnant patient

Background: Pre-eclampsia/eclampsia is a life-threatening disease with considerable risks on maternal and neonatal health. Globally, it affects between 2–8% of all pregnancies. Worldwide, approximately 63,000 pregnant women die each year due to pre-eclampsia/eclampsia. The MAGPIE (Magnesium sulphate for Prevention of Eclampsia) trial stated that the risk of developing convulsions was lowered significantly (58%) in severe pre-eclampsia patients who received magnesium sulfate in comparison to the placebo group.1 The exact mechanism of action of magnesium sulfate (MgSO4) is not completely understood, blocking calcium channels and decreasing availability of calcium for smooth muscle contractions has been suggested. Pritchard advocated that therapeutic concentration of MgSO4 should be between 2-4 mmol/l.2 Despite strong evidence of the effectiveness of MgSO4, concerns have been expressed about the risk of hypocalcemia to the patient when used alone or concomitantly with nifedipine as both of them affect calcium metabolism.3 Hypermagnesemia causes hypocalcemia by inhibiting parathyroid hormone secretion and increases urinary excretion of calcium. Severe hypocalcemia is a life-threatening condition and may lead to focal or generalized tonic muscle cramps, convulsions, arrhythmia, and laryngospasm and stridor which is common in the pediatric population but has also been reported in adults.4 A case of symptomatic hypocalcemia secondary to hypermagnesemia is extremely rare, and to the best of our knowledge, only a few cases have been reported.5 We believe this is the only case in the literature with stridor and potential airway obstruction. Case: A 30-year old black South African woman, gravida 5, para 3+1, presented with severe preeclampsia (BP 215/145 mmHg, proteinuria +2), and preterm premature rupture of membrane at 33 weeks of gestation. General and obstetric examinations were unremarkable. Laboratory parameters on admission showed acute kidney injury, anemia and elevated lactate dehydrogenase and alkaline phosphatase. Other investigations were normal (Table 1). She was admitted to the high dependent unit and received 10 grams of intramuscular MgSO4, followed by continuous intravenous infusion at a rate of 2 g/hour for 24 hours. Her blood pressure dropped to 145/95 mmHg. Three hours post-admission, her blood pressure raised to 186/124 mmHg and was controlled with a labetalol intravenous infusion and nifedipine 10 mg orally. Her blood pressure then dropped to 150/90 mmHg. Six hours post-admission, the patient had an uneventful emergency caesarean section under spinal anesthesia for fetal distress. Nine hours post-admission, the patient had dyspnea, respiratory distress, and inspiratory stridor, and chest examination was unremarkable. While checking her blood pressure, the patient had carpopedal spasm (Trousseau's sign) and masseter muscle spasm (Chvostek's sign). MgSO4 infusion was stopped. She received 10 ml of 10% calcium chloride over 10 minutes and responded dramatically to resuscitation and calcium chloride. Investigations (arterial blood gas, FBC, urea and electrolytes) were performed and showed low ionized calcium 0.89 mmol/l and her magnesium level was 2.74 mmol/l. Conclusion: Although MgSO4 is considered as the treatment of choice for the prevention of convulsions in pre-eclampsia/eclampsia patients, concerns have been raised regarding the risk of severe hypocalcemia, especially when used concomitantly with calcium channel blockers. Prospective studies designed in a controlled fashion are needed to assess the safe combination of magnesium sulfate and nifedipine.

Cinacalcet use in paediatric dialysis: a position statement from the European Society for Paediatric Nephrology and the Chronic Kidney Disease-Mineral and Bone Disorders Working Group of the ERA-EDTA.

Secondary hyperparathyroidism (SHPT) is an important complication of advanced chronic kidney disease (CKD) in children, which is often difficult to treat with conventional therapy. The calcimimetic cinacalcet is an allosteric modulator of the calcium-sensing receptor. It has proven to be effective and safe in adults to suppress parathyroid hormone (PTH), but data on its use in children are limited. To date, studies in children only consist of two randomized controlled trials, nine uncontrolled interventional or observational studies, and case reports that report the efficacy of cinacalcet as a PTH-lowering compound. In 2017, the European Medical Agency approved the use of cinacalcet for the treatment of SHPT in children on dialysis in whom SHPT is not adequately controlled with standard therapy. Since evidence-based guidelines are so far lacking, we present a position statement on the use of cinacalcet in paediatric dialysis patients based on the available evidence and opinion of experts from the European Society for Paediatric Nephrology, Chronic Kidney Disease-Mineral and Bone Disorder and Dialysis Working Groups, and the ERA-EDTA. Given the limited available evidence the strength of these statements are weak to moderate, and must be carefully considered by the treating physician and adapted to individual patient needs as appropriate. Audit and research recommendations to study key outcome measures in paediatric dialysis patients receiving cinacalcet are suggested.

CYP24A1 and SLC34A1 genetic defects associated with idiopathic infantile hypercalcemia: from genotype to phenotype.

Loss of function mutations in the CYP24A1 gene, involved in vitamin D catabolism and in calcium homeostasis, are known to be the genetic drivers of both idiopathic infantile hypercalcemia (IIH) and adult renal stone disease. Recently, also defects in the SLC34A1 gene, encoding for the renal sodium-phosphate transporter NaPi-IIa, were associated with the disease. IIH typically affects infants and pediatric patients with a syndrome characterized by severe hypercalcemia, hypercalciuria, suppressed parathyroid hormone level and nephrolithiasis. In SLC34A1 mutated carriers, hypophosphatemia is also a typical biochemical tract. IIH may also persist undiagnosed into adulthood, causing an increased risk of nephrocalcinosis and renal complication. To note, a clinical heterogeneity characterizes IIH manifestation, principally due to the controversial gene-dose effect and, to the strong influence of environmental factors. The present review is aimed to provide an overview of the current molecular findings on the IIH disorder, giving a comprehensive description of the association between genotype and biochemical and clinical phenotype of the affected patients. We also underline that patients may benefit from genetic testing into a targeted diagnostic and therapeutic workflow.

Parathyroid suppression therapy normalizes chronic kidney disease-induced elevations in cortical bone vascular perfusion: a pilot study.

Patients with chronic kidney disease (CKD) have accelerated bone loss, vascular calcification, and abnormal biochemistries, together contributing to an increased risk of cardiovascular disease and fracture-associated mortality. Despite evidence of vascular pathologies and dysfunction in CKD, our group has shown that cortical bone tissue perfusion is higher in a rat model of high-turnover CKD. The goal of the present study was to test the hypothesis that parathyroid hormone (PTH) suppressive interventions would normalize cortical bone vascular perfusion in the setting of CKD. In two separate experiments, 35-week-old CKD animals and their normal littermates underwent intra-cardiac fluorescent microsphere injection to assess the effect of 10weeks of PTH suppression (Experiment 1: calcium supplementation, Experiment 2: calcimimetic treatment) on alterations in bone tissue perfusion. In Experiment 1, CKD animals had serum blood urea nitrogen (BUN) and PTH levels significantly higher than NL (+ 182% and + 958%; p < 0.05). CKD+Ca animals had BUN levels that were similar to CKD, while PTH levels were significantly lower and comparable to NL. Both femoral cortex (+ 220%, p = 0.003) and tibial cortex (+ 336, p = 0.005) tissue perfusion were significantly higher in CKD animals when compared to NL; perfusion was normalized to those of NL in CKD+Ca animals. MicroCT analysis of the proximal tibia cortical porosity showed a trend toward higher values in CKD (+ 401%; p = 0.017) but not CKD+Ca (+ 111%; p = 0.38) compared to NL. Experiment 2, using an alternative method of PTH suppression, showed similar results as those of Experiment 1. These data demonstrate that PTH suppression-based interventions normalize cortical bone perfusion in the setting of CKD.

Direct bone effects of calcimimetics in chronic kidney disease?

Calcimimetics are widely used in patients on dialysis to treat secondary hyperparathyroidism. Our current view is that bone effects are only indirect through parathyroid hormone suppression. However, because bone cells express the calcium-sensing receptor, direct calcium-sensing receptor-mediated effects are also possible. New experimental data demonstrate direct anabolic bone actions of calcimimetics, independent of parathyroid hormone suppression. Because these effects could be clinically useful, further studies are necessary to confirm the validity of this observation.

Quercetin suppresses the proliferation and metastasis of metastatic osteosarcoma cells by inhibiting parathyroid hormone receptor 1

Osteosarcoma is an aggressive malignant neoplasm and cancerous bone tumor. Quercetin is a well-known flavonoid abundant in vegetables, fruits, grains, leaves, and red onions. In the present study, we evaluated the effects of quercetin-induced inhibition of parathyroid hormone receptor 1 (PTHR1) on proliferation, migration, and invasion in U2OS and Saos-2 cells. Following incubation with quercetin (20, 40, 60, 80, or 100 μM) for 48 h, the cell viability of U2OS and Saos-2 cells were significantly reduced in a dose-dependent manner. Additionally, there were significant decreases in cell adhesion, invasion, and migration as well as reduced cell viability at higher concentrations of quercetin. Furthermore, the mRNA expression levels of matrix metalloproteinases (MMP)-2 and -9 were attenuated, whereas the mRNA expression levels of tissue inhibitors of metalloproteinases (TIMP)-1 and -2 were elevated. Quercetin treatment also significantly reduced the mRNA expression levels of PTHR1 by 0.27-, and 0.55-fold at 80, and 100 μM, respectively, whereas 0.19 and 0.41 folds in Saos-2 cells. PTHR1 protein expression in U2OS cells was reduced by 0.19-, and 0.43-fold at 80, and 100 μM of quercetin, respectively (P < 0.05), whereas 0.17 and 0.35 folds in Saos-2 cells. Immunofluorescence analyses revealed reduced expression of PTHR1 following treatment with quercetin. PTHR1 expression in U2OS cells was reduced by 0.18-, and 0.41-fold at 80, and 100 μM, respectively, whereas 0.15 and 0.38 folds in Saos-2 cells. The knockdown of PTHR1enhanced quercetin-inhibited proliferation and invasion. Taken together, the present findings indicate that quercetin reduced human metastatic osteosarcoma cell invasion, adhesion, proliferation, and migration by inhibiting PTHR1.

Antagonism of Ca2+-sensing receptors by NPS 2143 is transiently masked by p38 activation in mouse brain bEND.3 endothelial cells.

Ca2+-sensing receptors (CaSR) are G protein-coupled receptors which are activated by a rise in extracellular Ca2+. CaSR activation has been known to inhibit parathyroid hormone release and stimulate calcitonin release from parathyroid glands and thyroid parafollicular C cells, respectively. The roles of CaSR in other cell types including endothelial cells (EC) are much less understood. In this work, we demonstrated protein and functional expression of CaSR in mouse cerebral EC (bEND.3). Unexpectedly, CaSR response (high Ca2+-elicited cytosolic [Ca2+] elevation) was unaffected by edelfosine or U73122 but strongly suppressed by SK&F 96365, ruthenium red, and 2-aminoethoxydiphenyl borate (2-APB), suggesting involvement of TRPV and TRPC channels but not Gq-phospholipase C. Acute application of NPS2143, a negative allosteric modulator of CaSR, suppressed CaSR response. However, a 40-min NPS2143 pre-treatment surprisingly enhanced CaSR response. After 4-24h of application, this enhancement faded away and suppression of CaSR response was observed again. Similar results were obtained when La3+ and Sr2+ were used as CaSR agonists. The transient NPS 2143 enhancement effect was abolished by SB203580, a p38 inhibitor. Consistently, NPS 2143 triggered a transient p38 activation. Taken together, results suggest that in bEND.3 cells, NPS 2143 caused acute suppression of CaSR response, but then elicited a transient enhancement of CaSR response in a p38-dependent manner. NPS 2143 effects on CaSR in bEND.3 cells therefore depended on drug exposure time. These findings warrant cautious use of this agent as a CaSR modulator and potential cardiovascular drug.