Approach to Treatment of Hypophosphatemia

Generalization of regional citrate anticoagulation for continuous renal replacement therapy is not associated with an increased rate of severe complications

BACKGROUND

Contraindications to regional citrate anticoagulation (RCA) for continuous renal replacement therapy (CRRT) have recently been challenged. We aimed to assess the safety of the generalization of RCA to all CRRT sessions.

METHODS

We reviewed all CRRT sessions performed in our ICU during two periods (P1:2018-2019 and P2:2020-2022). RCA was considered as contraindicated in situations at risk of citrate accumulation (lactate >4 mmol/L and/or prothrombin time < 40 %) during P1 but not P2. We reviewed CRRT modality, filter lifespan, and therapy-associated complications including citrate accumulation, electrolyte and acid/base disturbances, and blood transfusion requirements. CRRT efficacy was assessed by serum creatinine and urea kinetics across circuits' lifespan.

RESULTS

We studied 1877 circuits in 467 (P1:245, P2:222) patients. The proportion of patients with risk factors for citrate accumulation was similar between both periods (P1:35 %, P2:32 % p = 0.61). During P2, RCA was used in more circuits (93 vs 66 %, p < 0.001) and filter lifespan was longer (44 vs 32 h, p < 0.001). CRRT efficacy was similar between the two periods. Although risk factors for citrate accumulation were present at first circuit initiation in more RCA circuits during P2 (25 vs 11 %, p = 0.002), the rate of citrate accumulation remained similar (0.3 vs 0.4 %, p = 0.72). There was no increase in the rates of electrolyte disturbances or significant bleeding. There was, however, a higher rate of metabolic acidoses during P2 (13 vs. 9 %, p = 0.01).

CONCLUSION

In an experienced team, generalization of RCA to nearly all patients requiring CRRT extended median filter lifespan without increasing the rate of significant complications.

Loss of LasR function leads to decreased repression of Pseudomonas aeruginosa PhoB activity at physiological phosphate concentrations

The Pseudomonas aeruginosa LasR transcription factor plays a role in quorum sensing (QS) across phylogenetically distinct lineages. However, isolates with loss-of-function mutations in lasR (LasR- strains) are commonly found in diverse settings, including infections where they are associated with worse clinical outcomes. In LasR- strains, the LasR-regulated transcription factor RhlR can also be stimulated by the activity of the two-component system PhoR-PhoB in low-inorganic phosphate (Pi) conditions. Here, we demonstrate a novel link between LasR and PhoB in which the absence of LasR increases PhoB activity at physiological Pi concentrations and increases the Pi concentration necessary for PhoB inhibition. PhoB activity was also less sensitive to repression by Pi in mutants lacking different QS regulators (RhlR and PqsR) and in mutants lacking genes required for QS-induced phenazine production, suggesting that decreased phenazine production is one reason for increased PhoB activity in LasR- strains. In addition, the CbrA-CbrB two-component system, which can be more active in LasR- strains, was necessary for increased PhoB activity in LasR- strains, and loss of the CbrA-CbrB-controlled translational repressor Crc was sufficient to activate PhoB in LasR+ P. aeruginosa. Phenazines and CbrA-CbrB affected PhoB activity independently. The ∆lasR mutant also had PhoB-dependent growth advantages in the Pi-deplete medium and increased virulence-associated gene expression at physiological Pi, in part through reactivation of QS. This work suggests PhoR-PhoB activity may contribute to the fitness and virulence of LasR- P. aeruginosa and subsequent clinical outcomes.IMPORTANCELoss-of-function mutations in the gene encoding the Pseudomonas aeruginosa quorum sensing (QS) regulator LasR occur frequently and are associated with worse clinical outcomes. We have found that LasR- P. aeruginosa have elevated PhoB activity at physiological concentrations of inorganic phosphate (Pi). PhoB activity promotes Pi acquisition as well as the expression of QS and virulence-associated genes. Previous work has shown that PhoB induces RhlR, another QS regulator, in a LasR- mutant in low-Pi conditions. Here, we demonstrate a novel relationship wherein LasR represses PhoB activity through the production of phenazines and Crc-mediated translational repression. This work suggests PhoB activity may contribute to the increased virulence of LasR- P. aeruginosa.

Characterization of serum phosphate levels over time with intravenous ferric carboxymaltose versus placebo as treatment for heart failure with reduced ejection fraction and iron deficiency: An exploratory prospective substudy from HEART-FID

AIMS

Ferric carboxymaltose (FCM) is guideline-recommended for iron deficiency (ID) in heart failure with reduced ejection fraction (HFrEF). Despite a well-established safety profile, the magnitude and clinical significance of FCM-induced hypophosphataemia in HFrEF remains unclear. This pre-specified substudy of HEART-FID evaluated serum phosphate, 1,25-dihydroxyvitamin D, and plasma parathyroid hormone (PTH) subsequent to FCM.

METHODS AND RESULTS

HEART-FID was a randomized, double-blind, placebo-controlled trial of ambulatory patients with HFrEF and ID randomized to FCM versus placebo. This substudy assessed mean change from baseline across eight visits over 6 months for the following endpoints: serum phosphate, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and PTH, in addition to the clinical severity of potential hypophosphataemia. Overall, 133 patients (n = 62 FCM, n = 71 placebo) were prospectively enrolled. Mean age was 68 ± 11 years, 55 (41.4%) were women, and 29 (21.8%) had chronic kidney disease. Phosphate levels decreased in 34 (57.6%) patients in the FCM group compared with 7 (10.3%) in the placebo group. Mean change in phosphate levels reached a nadir at day 21 (-0.36 ± 0.27 mmol/L) subsequent to FCM infusion with 28 (51%) having moderate-to-severe hypophosphataemia. Reductions in 1,25-dihydroxyvitamin D were also observed, whilst PTH increased. These biochemical changes returned to baseline levels by day 91. Serum levels of 25-hydroxyvitamin D remained stable throughout the study. No serious adverse events associated with hypophosphataemia were reported.

CONCLUSIONS

Transient moderate-to-severe hypophosphataemia was frequent subsequent to FCM infusion, accompanied by 1,25-dihydroxyvitamin D decrease and PTH increase. Serum levels of 25-hydroxyvitamin D remained stable. No evidence of symptomatic hypophosphataemia was reported, collectively indicating FCM-related hypophosphataemia to be clinically benign and transient in HFrEF.

Moderate-severe hypophosphatemia, hypomagnesemia, and hypokalemia disturbances in critically ill patients receiving total parenteral nutrition therapy

BACKGROUND & AIMS

Moderate-severe hypophosphatemia (M-SHypoP), moderate-severe hypokalemia (M-SHypoK), and moderate-severe hypomagnesemia (M-SHypoM) are prevalent mineral disturbances in critically ill patients, particularly in the ICU setting. Despite their clinical significance, these disturbances have received limited attention in recent medical literature. This study aimed to investigate their prevalence in critically ill adult ICU patients receiving total parenteral nutrition (PN) compared with non-ICU patients receiving total PN.

METHODS

A historical retrospective cohort analysis was conducted using prospectively collected data from a quaternary hospital over an 8-year period. A total of 736 patients, older than 19 years and receiving PN, were included. Nutritional status (body weight and height) was assessed before starting nutritional support. Serum concentrations of phosphorus, potassium, and magnesium were evaluated within the first 7 days after initiating PN infusion.

RESULTS

Out of 736 patients included in the study, 545 (74 %) were admitted to the ICU. ICU patients had higher rates of surgical procedures (P = 0.009), and mortality (P = 0.001). Laboratory monitoring revealed common phosphorus imbalance in ICU patients, particularly during the first 4 days after PN infusion. ICU participants developed more M-SHypoP when compared to non-ICU (P = 0.002).

CONCLUSION

Prompt detection and treatment of mineral imbalances in ICU patients are crucial. Critically ill patients admitted to ICUs are at a heightened risk of developing hypophosphatemia compared to those not in the ICU. Thus, there is a potential necessity to introduce a novel PN regimen tailored for hypercatabolic patients within the initial 3 days of PN initiation in the ICU.

Severe hypophosphatemia following idecabtagene vicleucel regardless of the severity of cytokine release syndrome

BACKGROUND AIMS

Hypophosphatemia has been recently recognized adverse event in chimeric antigen receptor (CAR)-T cell therapy, complicating 70-75% of patients. Severe hypophosphatemia can cause cytokine release syndrome (CRS)-like symptoms, such as respiratory and cardiovascular dysfunction. Some reports have described the association between inorganic phosphate (iP) and CRS in patients treated with tisagenlecleucel (tisa-cel), lisocabtagene maraleucel (liso-cel), axicabtagene ciloleucel (axi-cel). However, the association between iP and idecabtagene vicleucel (ide-cel) has not been reported and the kinetics of serum iP for each CAR-T cell product have not been compared. We aimed to analyze the kinetics of iP with CAR-T cell products, including ide-cel, and the association between hypophosphatemia and severe CRS.

METHODS

We retrospectively analyzed patients aged ≥ 18 years with B-cell malignancies who received CAR-T cell therapy in our institution. All available laboratory data were collected for 21 days after CAR-T cell infusion; clinical and laboratory data were extracted from electronic medical records.

RESULTS

A total of 108 patients were treated with CAR-T cell therapy (tisa-cel, n = 56; liso-cel, n = 11; axi-cel, n = 28; ide-cel, n = 13). The cumulative incidence of hypophosphatemia and severe hypophosphatemia were significantly higher in the ide-cel group than the other CAR-T products group (92.3% versus 67.5%, P = 0.0045, and 15.4% versus 2.1%, P = 0.017), Patients treated with ide-cel had significantly lower serum iP levels from day -4 to 8 compared to other CAR-T products. As previous reports, the cumulative incidence of hypophosphatemia in the other CAR-T products group was significantly higher in the severe CRS group than in the mild CRS group (84.0% versus 60.0%, P = 0.0002). In contrast, there was no significant difference between the two groups in the ide-cel group (65% versus 100%, P = 0.13).

CONCLUSION

Our results suggest that and that it is important to monitor iP kinetics more carefully because patients treated with ide-cel complicate severe hypophosphatemia, regardless of CRS severity.

Severe Hypophosphatemia Leading to Acute Worsening of Heart Failure and Myopathy: A Case Report

This case highlights a rare instance of severe hypophosphatemia precipitating acute exacerbation of heart failure and myopathy in an 88-year-old male patient residing in a long-term care facility. The patient presented with edema and limb weakness, with a background of chronic heart failure, kidney disease, and vitamin D deficiency. Despite initial treatments targeting anemia and heart failure, the patient's condition did not improve until severe hypophosphatemia was identified and treated with phosphate supplementation, leading to rapid clinical improvement. This case highlights the importance of considering hypophosphatemia in the differential diagnosis of worsening heart failure or myopathy, particularly in frail elderly individuals residing in facilities with a high risk of vitamin D deficiency. It suggests that measuring serum phosphate levels should be considered in cases of heart failure or myopathy in such populations to prevent delays in diagnosis and treatment.

Bone Health ECHO Case Report: Rare Cases of Hypophosphatemia and Low-Traumatic Fractures in Patients with Type 1 Diabetes Mellitus

Bone Health ECHO (Extension of Community Healthcare Outcomes) is a virtual community of practice that has been connecting healthcare professionals online once weekly for the past 10 years. A key component of each ECHO session is presentation and discussion of patient cases with diagnostic and treatment dilemmas. Here we present two wheelchair-bound female patients aged 47 years (Patient 1) and 34 years (Patient 2), both with type 1 diabetes mellitus (T1DM). They were admitted to our hospital due to multiple fractures and muscle weakness. Since age 8 years, both women suffered from T1DM. Patient 1 had extremely poor glycemic control over the whole period of diabetes with frequent cases of ketoacidosis (glycated hemoglobin [HbA1c] varied 10.0-14.2 %), with multiple end-stage complications of DM including anuria requiring hemodialysis from age 37 years. Patient 2 had minimal DM complications and maintained HbA1c within an individual goal (5.0-6.1 %). Both patients had low fasting phosphate and elevated alkaline phosphatase on laboratory evaluation. In the patient with anuria (Patient 1), after careful evaluation of all possible causes of hypophosphatemia, we found the most likely cause to be the effects of constantly repeated intracellular phosphate depletion due to poorly compensated T1DM. While achieving stable glucose control in hospital care, her phosphate levels gradually returned within the reference range. In the younger patient (Patient 2), tumor-induced osteomalacia (TIO) was diagnosed. After tumor removal her symptoms and laboratory results normalized. These cases illustrate two different causes of hypophosphatemia in patients with similar skeletal presentations in association with T1DM.

Using a Built-in Clinical Decision Support to Improve Phosphate Repletion Practice: A Quasi-Experimental Study

BACKGROUND

Inpatient serum phosphate replacement is common, but there is great variability in replacement practice, which leads to overuse. Electronic health record (EHR) interventions with clinical decision support (CDS) can be effective tools to guide clinicians toward best clinical practices. The authors' objective was to use CDS tools to reduce overuse of hypophosphatemia corrections at a large safety-net health care system.

METHODS

The first intervention involved enhancing an existing order set for phosphate repletion by incorporating CDS to guide appropriate repletion orders based on deficit severity and simplifying ordering. The second intervention was a Best Practice Advisory (BPA) that triggered when an intravenous (IV) phosphate repletion was ordered for a patient with mild to moderate phosphate deficiency without an existing nil per os (NPO) order. The primary outcome measure was the number of patients with mild and moderate hypophosphatemia receiving IV replacement without NPO orders per 1,000 patient-days.

RESULTS

Across all hospitals, rate of IV replacement in patients with mild to moderate hypophosphatemia (1.0 to 1.9 mg/dL) without NPO orders decreased from 7.22 to 3.40 per 1,000 patient-days (53.0% reduction, p < 0.001), while the oral replacements in this population increased from 6.39 to 8.87 (38.8% increase, p < 0.001). For patients with phosphate levels ≥ 2.0, IV replacements decreased from 10.66 to 5.36 (49.8% reduction, p < 0.001), and oral replacements from decreased 19.78 to 16.69 (15.6% reduction, p < 0.01).

CONCLUSION

This intervention successfully reduced inpatient IV phosphate replacements by 53.0% in patients with mild to moderate hypophosphatemia using a two-pronged EHR intervention across a large safety-net setting.

Severe and rapidly changing hypophosphatemia in cannabinoid hyperemesis syndrome: a case report

The increasing prevalence of cannabis worldwide requires awareness of a potential, less recognized, paradoxical entity, the cannabinoid hyperemesis syndrome (CHS). This includes cyclic episodes of nausea, vomiting, and compulsive hot water bathing for alleviation in individuals with chronic cannabis use. An 18-year-old male with daily and prolonged cannabis use has excessive nausea and vomiting, is diagnosed with CHS, and is further complicated by severe and rapidly fluctuating hypophosphatemia. He was successfully managed with intravenous (IV) antiemetic (metoclopramide) and IV normal saline in the emergency department. Hypophosphatemia was treated with IV phosphorous. Although hypophosphatemia in CHS is a rare encounter, the authors share their experience to promote broader recognition and insight into successful management.

Non-Classical Effects of FGF23: Molecular and Clinical Features

This article reviews the role of fibroblast growth factor 23 (FGF23) protein in phosphate metabolism, highlighting its regulation of vitamin D, parathyroid hormone, and bone metabolism. Although it was traditionally thought that phosphate-calcium homeostasis was controlled exclusively by parathyroid hormone (PTH) and calcitriol, pathophysiological studies revealed the influence of FGF23. This protein, expressed mainly in bone, inhibits the renal reabsorption of phosphate and calcitriol formation, mediated by the α-klotho co-receptor. In addition to its role in phosphate metabolism, FGF23 exhibits pleiotropic effects in non-renal systems such as the cardiovascular, immune, and metabolic systems, including the regulation of gene expression and cardiac fibrosis. Although it has been proposed as a biomarker and therapeutic target, the inhibition of FGF23 poses challenges due to its potential side effects. However, the approval of drugs such as burosumab represents a milestone in the treatment of FGF23-related diseases.

Exploring the association between serum phosphate levels and mortality in patients hospitalized with infectious diseases: a nationwide study

Objective

The purpose of this study was to examine associations of serum phosphate levels with mortality, target organ damage and length of hospital stay in adults with infectious diseases hospitalized outside of the intensive care unit.

Methods

This nationwide retrospective cohort study comprised patients admitted with infections, to medical and surgical departments in eight tertiary hospitals during 2001-2020. The main exposure variable was the first serum phosphate levels at admission (up to 1 week). The analysis included multivariable logistic regression models and quantile regression.

Results

Of 126,088 patients (49% males, mean age: 69.3 years), 24,809 (19.7%) had decreased phosphate levels, 92,730 (73.5%) normal phosphate levels, and 8,549 (6.8%) elevated phosphate levels on admission. Overall- and in-hospital mortality rates were highest among those with hyperphosphatemia (74.5 and 16.4%, respectively), followed by those with normophosphatemia (57.0 and 6.6%), and lastly the hypophosphatemia group (48.7 and 5.6%); p < 0.001 for all. After adjusting for confounders, the lowest predicted mortality rate was observed in the normophosphatemia group. In the multivariable model, hyperphosphatemia conferred a higher probability of target organ damage (OR [95% CI]: 2.43 [2.06-2.86]), while moderate hypophosphatemia conferred a lower probability (OR [95% CI]: 0.73 [0.65-0.82]), compared to normal phosphate levels and extreme hypophosphatemia showed a non-significant association (OR [95% CI]: 0.87 [0.57-1.28]). The associations were independent of renal failure. In a multivariable model, hyperphosphatemia was associated with a slight increase of 0.33 days in length of stay compared to normal phosphate levels.

Conclusion

A J-shaped relation was found between phosphate levels and prognosis in patients hospitalized with infectious diseases, regardless of their renal function.

A Case of Intractable Hypophosphatemia in a Patient with Guillain-Barré Syndrome and Encephalitis after SARS-CoV-2 Infection

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection attacks the respiratory and nervous systems. Among patients with SARS-CoV-2 infection, cases with simultaneous central and peripheral nervous system damage are rare, and those with intractable hypophosphatemia and hypokalemia complicating the former have not been reported yet.

CASE PRESENTATION

A 59-year-old woman presented to the emergency department with incoherent speech evolving for 3 days. She had tested positive for the SARS-CoV-2 RT-PCR assay 8 days earlier. Her physical examination showed progressive limb weakness with diminished tendon reflexes and normal sensory examination. Cranial MRI revealed multiple abnormal signals in the brain. Cerebrospinal fluid (CSF) analysis and electromyography revealed acute motor axonal neuropathy (AMAN), further diagnosed as encephalitis combined with Guillain.Barré syndrome (GBS). The patient received glucocorticoid therapy, intravenous immune globulin (IVIG), and rehabilitation therapy. The patient experienced an intractable hypophosphatemia and hypokalemia during the treatment period, which was not effectively corrected several times. The symptoms improved after 1 month of treatment.

CONCLUSION

Early diagnosis is important for the management of Guillain-Barré syndrome associated with SARS-CoV-2 infection. Moreover, in order to prevent life-threatening long-term persistent electrolyte disturbances in non-seriously ill patients, clinicians should pay particular attention to their electrolyte status.

Hypophosphatemia in Patients With Multiple Myeloma

Hypophosphatemia is among the most common electrolyte abnormalities, especially among patients with underlying malignancies, and is frequently associated with adverse prognoses. Phosphorus levels are regulated through a number of mechanisms, including parathyroid hormone (PTH), fibroblast growth factor-23 (FGF-23), vitamin D, and other electrolyte levels themselves. Clinically, the findings are nonspecific, and the diagnosis is frequently delayed. This article is a narrative literature review. The PubMed database was searched for relevant articles pertaining to hypophosphatemia causes and consequences in patients suffering from multiple myeloma. We found a variety of causes of hypophosphatemia in patients with multiple myeloma. Tumor-induced osteopenia, although more common among patients with small squamous cell carcinomas, can occur with multiple myeloma as well. Additionally, both light chains themselves and medications can trigger Fanconi syndrome, which leads to phosphorus wasting by the kidney. Bisphosphonates, in addition to being a possible cause of Fanconi syndrome, lead to a decrease in calcium levels, which then stimulates parathyroid hormone (PTH) release, predisposing the patient to significant hypophosphatemia. Additionally, many of the more modern medications used to manage multiple myeloma have been associated with hypophosphatemia. A better understanding of those mechanisms may give clinicians a clearer idea of which patients may need more frequent screening as well as what the potential triggers in the individual patient may be.

Clinical and Functional Assessment of Digenicity in Renal Phosphate Wasting

Apart from increased fluid intake, patients with kidney stone disease (KSD) due to renal phosphate wasting require specific metaphylaxis. NaPi2a, NaPi2c, and NHERF1 regulate plasma phosphate concentration by reabsorbing phosphate in proximal kidney tubules and have been found altered in monogenic hypophosphatemia with a risk of KSD. In this study, we aimed at assessing the combined genetic alterations impacting NaPi2a, NaPi2c, and NHERF1. Therefore, we screened our hereditary KSD registry for cases of oligo- and digenicity, conducted reverse phenotyping, and undertook functional studies. As a result, we identified three patients from two families with digenic alterations in NaPi2a, NaPi2c, and NHERF1. In family 1, the index patient, who presented with severe renal calcifications and a bone mineralization disorder, carried digenic alterations affecting both NaPi transporter 2a and 2c. Functional analysis confirmed an additive genetic effect. In family 2, the index patient presented with kidney function decline, distinct musculature-related symptoms, and intracellular ATP depletion. Genetically, this individual was found to harbor variants in both NaPi2c and NHERF1 pointing towards genetic interaction. In summary, digenicity and gene dosage are likely to impact the severity of renal phosphate wasting and should be taken into account in terms of metaphylaxis through phosphate substitution.

Postoperative Hypophosphatemia as a Prognostic Factor for Postoperative Pancreatic Fistula: A Systematic Review

Background and Objectives: Postoperative pancreatic fistula (POPF) is one of the most challenging complications after pancreatic resections, associated with prolonged hospital stay and high mortality. Early identification of pancreatic fistula is necessary for the treatment to be effective. Several prognostic factors have been identified, although it is unclear which one is the most crucial. Some studies show that post-pancreatectomy hypophosphatemia may be associated with the development of POPF. The aim of this systematic review was to determine whether postoperative hypophosphatemia can be used as a prognostic factor for postoperative pancreatic fistula. Materials and Methods: The systematic literature review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations (PRISMA) and was registered in the International Prospective Register of Systematic Reviews (PROSPERO). The PubMed, ScienceDirect, and Web of Science databases were systematically searched up to the 31st of January 2022 for studies analyzing postoperative hypophosphatemia as a prognostic factor for POPF. Data including study characteristics, patient characteristics, operation type, definitions of postoperative hypophosphatemia and postoperative pancreatic fistula were extracted. Results: Initially, 149 articles were retrieved. After screening and final assessment, 3 retrospective studies with 2893 patients were included in this review. An association between postoperative hypophosphatemia and POPF was found in all included studies. Patients undergoing distal pancreatectomy were more likely to develop severe hypophosphatemia compared to patients undergoing proximal pancreatectomy. Serum phosphate levels on postoperative day 4 (POD 4) and postoperative day 5 (POD 5) remained significantly lower in patients who developed leak-related complications showing a slower recovery of hypophosphatemia from postoperative day 3 (POD 3) through postoperative day 7 (POD 7). Moreover, body mass index (BMI) higher than 30 kg/m², soft pancreatic tissue, abnormal white blood cell count on postoperative day 3 (POD 3), and shorter surgery time were associated with leak-related complications (LRC) and lower phosphate levels. Conclusions: Early postoperative hypophosphatemia might be used as a prognostic biomarker for early identification of postoperative pancreatic fistula. However, more studies are needed to better identify significant cut-off levels of postoperative hypophosphatemia and development of hypophosphatemia in the postoperative period.

High-Dose Intravenous Iron with Either Ferric Carboxymaltose or Ferric Derisomaltose: A Benefit-Risk Assessment

The intravenous iron formulations ferric carboxymaltose (FCM) and ferric derisomaltose (FDI) offer the possibility of administering a large amount of iron in one infusion. This results in faster correction of anemia and the formulations being better tolerated than oral iron formulations. This triad of logistic advantages, improved patient convenience, and fast correction of anemia explains the fact that intravenous iron formulations nowadays are frequently prescribed worldwide in the treatment of iron deficiency anemia. However, these formulations may result in hypophosphatemia by inducing a strong increase in active fibroblast growth factor-23 (FGF-23), a hormone that stimulates renal phosphate excretion. This effect is much more pronounced with FCM than with FDI, and therefore the risk of developing hypophosphatemia is remarkably higher with FCM than with FDI. Repeated use of FCM may result in severe osteomalacia, which is characterized by bone pain, Looser zones (pseudofractures), and low-trauma fractures. Intravenous iron preparations are also associated with other adverse effects, of which hypersensitivity reactions are the most important and are usually the result of a non-allergic complement activation on nanoparticles of free labile iron-Complement Activation-Related Pseudo-Allergy (CARPA). The risk on these hypersensitivity reactions can be reduced by choosing a slow infusion rate. Severe hypersensitivity reactions were reported in < 1% of prospective trials and the incidence seems comparable between the two formulations. A practical guideline has been developed based on baseline serum phosphate concentrations and predisposing risk factors, derived from published cases and risk factor analyses from trials, in order to establish the safe use of these formulations.

Prevalence and Correlates of Hypophosphatemia Among Type 2 diabetic patients attending the National Center for Diabetes, Endocrinology and genetics (NCDEG)

Objectives

To estimate the prevalence of hypophosphatemia and its associated factors among type 2 diabetic patients attending (NCDEG) in Amman-Jordan, and compare the prevalence of hypophosphatemia between diabetics, nondiabetic subjects.

Patients and methods

A case-control study was carried out at (NCDEG). A total of 1580 diabetic patients (59.7% females, 40.3% males), mean age (SD) of 55.15 ± 15.3 attended this center from January 1st, 2020 till March 31st, 2020 were included. Our study included 2155 non-diabetic from the national population-based multipurpose study in Jordan in 2017, to compare serum inorganic phosphate between diabetic, nondiabetic. Pregnant, those aged <18 or >80 years, GFR below 30 ml/min or those on hemodialysis were excluded. The data included patient's age, gender, smoking and medication, HbA1c. Statistical analysis were performed using the Package for Social Sciences (SPSS) version 21.

Results

The overall prevalence of hypophosphatemia in the diabetic patients was significantly higher (10.5% vs. 3.2%, P-value 0.001). Multivariate logistic regression analysis showed that in diabetic: males, current smokers, diabetic patients with HbA1c between 7 and 9% and >9%, those who on thiazide diuretics were 2, 1.9, 1.8, 1.7, and 1.9 times, more likely to have hypophosphatemia than their counterparts (P-values 0.001, 0.001, 0.006, 0.018 and 0.003), respectively, and it was found those on statin were less likely to have hypophosphatemia.

Conclusion

The prevalence of hypophosphatemia among type 2 diabetic patients is high. Factors independently related to hypophosphatemia in diabetic patients: male gender, smoking, poor glycemic control, taking thiazides and not being on statin.

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The objectives is to estimate the prevalence of hypophosphatemia and its associated factors among type 2 diabetic patients. Also, to compare the prevalence of hypophosphatemia between diabetics, nondiabetic subjects.

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The overall prevalence of hypophosphatemia in the diabetic patients was significantly 10.5%.

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The overall prevalence of hypophosphatemia in the non- diabetic patients was 3.2%.

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Factors independently related to hypophosphatemia in diabetic patients included: male gender, smoking, poor glycemic control.

Induction of FGF23-related hypophosphatemic osteomalacia by alcohol consumption

Context

Fibroblast growth factor (FGF) 23 is a hormone that regulates serum phosphate levels, the excess action of which causes chronic hypophosphatemic rickets/osteomalacia. To date, there are only two identified causes of acquired FGF23-related hypophosphatemic osteomalacia: tumor-induced osteomalacia (TIO) and osteomalacia induced by the intravenous infusion of some forms of iron preparations. In the current study, two cases of FGF23-related hypophosphatemia probably induced by chronic alcohol consumption were first introduced.

Case description

Case 1 and case 2 had been drinking high amounts of alcohol for more than twenty years until they were admitted to the hospital. Case 1 was a 43-year-old man with progressive worsening multiple pains and muscle weakness who exhibited chronic hypophosphatemia with increased intact FGF23 levels. A week after admission, the serum phosphate level recovered to the reference range, and the intact FGF23 level declined. Case 1 resumed drinking after discharge, and hypophosphatemia concomitant with high intact FGF23 levels recurred. The alleviation of FGF23-related hypophosphatemia was observed each time he temporarily abstained from drinking for a short period. Case 2 was a 60-year-old man with recurrent fractures and exacerbation of pain in multiple joints who also exhibited hypophosphatemia with increased intact FGF23 levels. After admission, the serum phosphate level gradually increased to the lower limit of the normal range. The intact FGF23 level decreased, but it was still higher than 30 pg/ml, and causative FGF23-producing tumors were not identified even with thorough examinations, including somatostatin receptor scintigraphy, fluorine-18-fluorodeoxyglucose-positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) and systemic venous FGF23 sampling. He completely abstained from alcohol after discharge. Along with the serum phosphate level, intact FGF23 was subsequently decreased and had been normalized for 5 months. Both patients had no genetic mutation related to hereditary FGF23-related hypophosphatemic rickets/osteomalacia, including autosomal dominant hypophosphatemic rickets/osteomalacia (ADHR).

Conclusion

Two cases of FGF23-related hypophosphatemia probably induced by alcohol were first introduced in this study. Identifying this reversible condition among acquired FGF23-related hypophosphatemic osteomalacia is critical to obtain better patient outcomes and save medical resources. This condition is similar to iron infusion-induced FGF23-related hypophosphatemia in terms of the dysregulation of FGF23 due to exogenous factors. Future research to elucidate the precise mechanism of these conditions is warranted.

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Two adults with acquired FGF23-related hypophosphatemic osteomalacia were studied.

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Tumor-induced osteomalacia was suspected initially, but no tumor was identified.

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Cessation of alcohol led to recovery from FGF23-related hypophosphatemia.

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Alcohol is a well-recognized cause of hypophosphatemia, but osteomalacia is uncommon.

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Alcohol-induced FGF23-related osteomalacia is a totally new and distinct phenomenon.

[A complex case of renal phosphate wasting…]

We describe here the case report of a young man of 34-years old suffering from a haemorrhagic rectocolitis and presenting with marked hypophosphatemia secondary to an infusion of ferric-carboxymaltose. The renal phosphate wasting was asserted by a very low renal maximal reabsorption rate of phosphate associated with a high plasma FGF-23 level. Three months later we explored the patient and his father since we learnt that both of them had suffered from kidney stones for years with marked hypercalciuria. Kidney stones were composed of weddellite and carbapatite. We suspected a familial phosphate renal wasting syndrome but however no mutation of the renal phosphate carriers could be identified.

Hyperemesis gravidarum induced refeeding syndrome causes blood cell destruction: a case report and literature review

Background

Hyperemesis gravidarum (HG) is a common complication during pregnancy, however, HG associated simultaneous onset of blood cell destruction due to electrolyte abnormalities is rare. In this case, a woman with refeeding syndrome (RFS) secondary to electrolyte abnormalities caused by severe HG was diagnosed and managed in our hospital.

Case presentation

A 29-year old woman was sent to the local hospitals because of severe HG with appetite loss, weight reduction, general fatigue, and she was identified to have severe electrolyte abnormalities. However, the electrolyte abnormalities were not corrected promptly, and then she had the symptoms of stillbirth, altered mental status, visual hallucination, hemolytic anemia and thrombocytopenia. After transferred to our hospital, we continued to correct the electrolyte abnormalities and the labor induction was performed as soon as possible. The symptoms of blood cell destruction were relieved obviously, and the patient discharged four days later. The electrolyte disturbances and physio-metabolic abnormalities caused by HG helped us diagnose this case as RFS.

Conclusions

This case emphasizes that patients with RFS should be diagnosed appropriately and intervened promptly in order to prevent electrolyte imbalance induced blood cell destruction.

A Pooled Analysis of Serum Phosphate Measurements and Potential Hypophosphataemia Events in 45 Interventional Trials with Ferric Carboxymaltose

Ferric carboxymaltose (FCM) has been shown to achieve rapid replenishment of iron stores and correction of anaemia in various populations with iron deficiency. A decrease in serum phosphate (PO43-) levels, which in most cases is asymptomatic, has been reported with IV iron preparations. Hypophosphataemia (HP) is a known adverse drug reaction with FCM. This post hoc pooled analysis investigates the frequency, duration, risk factors, and clinical signs of HP as reported in interventional clinical trials with FCM. Pooled data from subjects enrolled across 45 clinical trials in different therapy areas were included. A three-step adjudication process was utilised to identify adverse events of HP. Stratified analyses by therapy group and stepwise logistic regression analysis were used to identify predictors of HP. This pooled analysis confirms that FCM is associated with increased rates of serum PO43- lowering, but mean serum PO43- values were seen to recover at Week 4 and further recover at Week 8. Among all subjects receiving FCM therapy (n = 6879), 41.4% (n = 2847) reached a PO43- nadir value <2.5 mg/dL at any point on study and 0.7% (n = 49) reached a nadir <1 mg/dL. Although gastroenterology and women's health subjects were identified to be at higher risk, occurrence of severe HP (<1 mg/dL [0.3 mmol/L]) following FCM administration was not observed to be common among subjects in these studies. Furthermore, there was no correlation between laboratory serum PO43- values and the occurrence of reported adverse events related to low PO43- levels.

Hypophosphatemia and Outcomes in ICU: A Systematic Review and Meta-Analysis

PURPOSE

Hypophosphatemia is reported in up to 5% of hospitalized patients and ranges from 20% to 80% in critically ill patients. The consequences of hypophosphatemia for critically ill patients remain controversial. We evaluated the effect of hypophosphatemia on mortality and length of stay in intensive care unit (ICU) patients.

METHODS

MEDLINE, EMBASE, Cochrane Library (Reviews and Trials), and PubMed were searched for articles in English. The primary outcome was mortality and secondary outcome was length of stay. The quality of evidence was graded using a modified Newcastle-Ottawa Scale.

RESULTS

Our search yielded 828 articles and ultimately included 12 studies with 7626 participants in the analysis. Hypophosphatemia was associated with increased hospital length of stay (2.19 days [95% CI, 1.74-2.64]) and ICU length of stay (2.22 days [95% CI, 1.00-3.44]) but not mortality (risk ratio: 1.13 [95% CI, 0.98-1.31]; P = .09).

CONCLUSIONS

Hypophosphatemia in ICU was associated with increased hospital and ICU length of stay but not all-cause mortality. Hypophosphatemia appears to be a marker of disease severity. Limited number of available studies and varied study designs did not allow for the ascertainment of the effect of severe hypophosphatemia on patient mortality.

Approach to patients with hypophosphataemia

Phosphate metabolism is an evolving area of basic and clinical research. In the past 15 years, knowledge on disturbances of phosphate homoeostasis has expanded, as has the discovery of new targeted therapies. Hypophosphataemia might be the biochemical finding in several diseases, and its clinical evaluation should initially focus on the assessment of pathophysiological mechanisms leading to low serum phosphate concentrations. Clinical consequences of hypophosphataemia can involve multiple organ systems and vary depending on several factors, the most important being the underlying disorder. This Review focuses on the approach to patients with hypophosphataemia and how underlying pathophysiological mechanisms should be understood in the evaluation of differential diagnosis. We define an algorithm for the assessment of hypophosphataemia and review the most up-to-date literature on specific therapies. Continuous research in this area will result in a better understanding and management of patients with hypophosphataemia.

Phosphate disorders and clinical management of hypophosphatemia and hyperphosphatemia

Serum phosphorus levels range from 2.5 and 4.5mg/dL (0.81-1.45 mmol/L) in adults, with higher levels in childhood, adolescence, and pregnancy. Intracellular phosphate is involved in intermediary metabolism and other essential cell functions, while extracellular phosphate is essential for bone matrix mineralization. Plasma phosphorus levels are maintained within a narrow range by regulation of intestinal absorption, redistribution, and renal tubular absorption of the mineral. Hypophosphatemia and hyperphosphatemia are common clinical situations, although changes are most often mild and oligosymptomatic. However, acute and severe conditions that require specific treatment may occur. In this document, members of the Mineral and Bone Metabolism Working Group of the Spanish Society of Endocrinology and Nutrition review phosphate disorders and provide algorithms for adequate clinical management of hypophosphatemia and hyperphosphatemia.

Disorders of phosphate metabolism

Phosphate in both inorganic and organic form is essential for several functions in the body. Plasma phosphate level is maintained by a complex interaction between intestinal absorption, renal tubular reabsorption, and the transcellular movement of phosphate between intracellular fluid and bone storage pools. This homeostasis is regulated by several hormones, principally the parathyroid hormone, 1,25-dihydroxyvitamin D and fibroblast growth factor 23. Abnormalities in phosphate regulation can lead to serious and fatal complications. In this review phosphate homeostasis and the aetiology, pathophysiology, clinical features, investigation and management of hypophosphataemia and hyperphosphataemia will be discussed.

Hypophosphataemia in confused half-marathon runners: A report of two cases

Introduction:

Severe hypophosphataemia may occur in long distance runners presenting to Accident & Emergency (A&E) department with exertional heat illness.

Case presentation:

A 46-year-old man who collapsed in half marathon race was found to have raised body temperature (38.8°C) and confused with memory loss in the Accident & Emergency department. His amnesia was persistent even after his body temperature was normalized. He was found to have severe hypophosphataemia (0.21 mmol/L; reference range: 0.74 - 1.4 mmol/L). He had a neurological recovery after phosphate replacement. Another 45-year-old female half marathon runner was found to have moderate hypophosphataemia (0.5 mmol/L) co-presenting with exertional heat illness.

Discussion:

Moderate to severe hypophosphataemia complicated the clinical picture of the two cases presented with exertional heat illness. Causes of hypophosphataemia in runners are multifactorial.

Conclusion:

Emergency physician should be alert of profound hypophosphataemia as a complication in heat exertional illness.

Zebrafish and medaka as models for biomedical research of bone diseases

The identification of disease-causing mutations has in recent years progressed immensely due to whole genome sequencing approaches using patient material. The task accordingly is shifting from gene identification to functional analysis of putative disease-causing genes, preferably in an in vivo setting which also allows testing of drug candidates or biotherapeutics in whole animal disease models. In this review, we highlight the advances made in the field of bone diseases using small laboratory fish, focusing on zebrafish and medaka. We particularly highlight those human conditions where teleost models are available.

Roles of Phosphate in Skeleton

Phosphate is essential for skeletal mineralization, and its chronic deficiency leads to rickets and osteomalacia. Skeletal mineralization starts in matrix vesicles (MVs) derived from the plasma membrane of osteoblasts and chondrocytes. MVs contain high activity of tissue non-specific alkaline phosphatase (TNSALP), which hydrolyzes phosphoric esters such as pyrophosphates (PPi) to produce inorganic orthophosphates (Pi). Extracellular Pi in the skeleton is taken up by MVs through type III sodium/phosphate (Na⁺/Pi) cotransporters and forms hydroxyapatite. In addition to its roles in MV-mediated skeletal mineralization, accumulating evidence has revealed that extracellular Pi evokes signal transduction and regulates cellular function. Pi induces apoptosis of hypertrophic chondrocytes, which is a critical step for endochondral ossification. Extracellular Pi also regulates the expression of various genes including those related to proliferation, differentiation, and mineralization. In vitro cell studies have demonstrated that an elevation in extracellular Pi level leads to the activation of fibroblast growth factor receptor (FGFR), Raf/MEK (mitogen-activated protein kinase/ERK kinase)/ERK (extracellular signal-regulated kinase) pathway, where the type III Na⁺/Pi cotransporter PiT-1 may be involved. Responsiveness of skeletal cells to extracellular Pi suggests their ability to sense and adapt to an alteration in Pi availability in their environment. Involvement of FGFR in the Pi-evoked signal transduction is interesting because enhanced FGFR signaling in osteoblasts/osteocytes might be responsible for the overproduction of FGF23, a key molecule in phosphate homeostasis, in a mouse model for human X-linked hypophosphatemic rickets (XLH). Impaired Pi sensing may be a pathogenesis of XLH, which needs to be clarified in future.

Cannabinoid Hyperemesis

Cannabinoid hyperemesis syndrome (CHS) is a paradoxical condition in which a long-term cannabis user suffers an episode of intractable vomiting that may last days separated by longer asymptomatic periods of weeks or months. Cannabinoids are often utilized for their antiemetic properties, so CHS can be a puzzling condition, and the diagnosis of CHS may be disputed by patients. Unlike other cyclic vomiting syndromes, CHS can be relieved by hot showers or topical capsaicin. Abstinence from cannabinoids causes CHS to resolve, sometimes in a matter of days or hours. Marijuana users as well as many clinicians are not aware of CHS, and patients may undergo unnecessary tests, scans, and other procedures to get an accurate diagnosis. Symptoms may be severe enough to require hospitalization. With liberalization of marijuana laws and favorable public opinion about the healing properties of cannabis, CHS may be more frequently observed in clinical practice.

Behavioural patterns of electrolyte repletion in intensive care units: lessons from a large electronic dataset

Repletion of electrolytes often depends on provider-specific behavior and hospital policy. We examined the pattern of electrolyte repletion across several intensive care units (ICU) in a large healthcare system from 2010–2015. This included 109 723 potassium repletions, 51 833 magnesium repletions, 2 306 calcium repletions, 8 770 phosphate repletions, and 3 128 249 visit-days over 332 018 visits. Potassium, magnesium, and calcium were usually repleted within the institutional reference range. In contrast, the bulk of phosphate repletion was done with pre-repletion serum level below the reference range. The impact of repletion on post-repletion levels was significant but uniformly small. The pre-repletion serum level had a significant inverse correlation with the post-repletion level of each electrolyte. Potassium, magnesium and phosphate follow-up labs were scheduled in 9–10 hours after their repletion. In contrast, calcium was rechecked in less than 20 minutes. Routine repletion of potassium, magnesium and calcium had no effect on the incidence of tachyarrhythmias. We estimated the expense from electrolyte repletion within the reference range was approximately $1.25 million. Absent a specific clinical indication, repleting electrolytes when the serum concentration are within normative values may represent an avenue for cost savings, staff burden unload and potential reduction in frequency of complications in the ICUs.

Management of inflammatory bowel disease-related anemia and iron deficiency with specific reference to the role of intravenous iron in current practice

Anemia is a common extraintestinal manifestation in patients with inflammatory bowel disease, impacting disease prognosis, morbidity, hospitalization rates and time lost from work. While iron deficiency anemia and anemia of chronic inflammation predominate, combinations of hematimetric and biochemical markers facilitate the diagnosis and targeted therapy of other etiologies according to their underlying pathophysiological causes. Intravenous iron replacement is currently recommended in IBD patients with moderate to severe anemia or intolerance to oral iron. Areas covered: This review examines the impact, pathophysiology and diagnostics of iron deficiency and anemia, compares the characteristics and safety profiles of available oral and intravenous iron preparations, and highlights issues which require consideration in decision making for therapy administration and monitoring. Expert opinion: Modern intravenous iron formulations have been shown to be safe and effective in IBD patients, allowing rapid anemia correction and repletion of iron stores. While traditional oral iron preparations are associated with increased inflammation, negative effects on the microbiome, and poor tolerance and compliance, first clinical trial data indicate that newer oral compounds such as ferric maltol and sucrosomial iron offer improved tolerability and may thus offer a viable alternative for the future.

No difference in mechanical ventilation-free hours in critically ill patients who received intravenous, oral, or enteral phosphate replacement

PURPOSE

To determine the impact on duration of mechanical ventilation (MV) and the need for reintubation after changing from intravenous (IV) to oral phosphate formulations, in response to a national shortage of IV phosphate.

METHODS

A retrospective study was performed in adult patients who required MV for at least 48 hours.

RESULTS

A total of 136 patients were included, with 68 patients in both the restricted phosphate group and unrestricted phosphate groups. There was no difference in the cumulative phosphate supplementation received (IV and oral) between groups (P=.08). The overall mean serum phosphorus concentration in unrestricted vs restricted group was 3.0 vs 2.9 mg/dL, respectively (P=.24), and the phosphorus concentration was not significantly different between groups during the first 21 days of the study (P=.24). The median MV-free hours in the unrestricted group was 462 hours compared with 507 hours in the restricted group (P=.16), and 9 (13.2%) of patients in each group required reintubation (P=.99). There was no significant difference in mortality, or hospital, or intensive care unit (ICU) length of stay.

CONCLUSIONS

No difference in MV-free hours or need for reintubation was observed after a national shortage requiring the restriction of IV phosphate supplementation. Oral phosphate replacement is a safe and an efficient alternative.

Refeeding and weight restoration outcomes in anorexia nervosa: Challenging current guidelines

OBJECTIVE

Cohort study from February 2003 through May 2011 to determine weight restoration and refeeding complication outcomes for patients with anorexia nervosa (AN) treated in an integrated inpatient-partial hospital eating disorder program designed to produce rapid weight gain and weight restoration in the majority.

METHOD

Consecutive admissions (females and males, adolescents and adults; N = 361 patients, 461 admissions) at least 1.8 kg below target weight with AN or subthreshold variants were included. Main outcome measures were rates of hypophosphatemia, transfer to medicine, or death; rates of weight gain and percent achieving weight restoration.

RESULTS

Hypophosphatemia was present in 7.9% of cases at admission and in 18.5% at some point during treatment. Hypophosphatemia was mild to moderate. Lower admission body mass index (BMI), but not rate of weight gain, predicted hypophosphatemia [OR = 0.65; p < .00001 (95% CI 0.57-0.76)]. Five patients (1.1%) were transferred to medicine or surgery, none because of refeeding. There were no deaths. Mean inpatient weight gain was 1.98 kg/week; mean partial hospital weight gain was 1.36 kg/week. By program discharge, 71.8% of adults reached a BMI of 19, 58.5% a BMI of 20. For adolescents, 80.4% came within 2 kg of their target weight; 76.1% came within 1 kg.

DISCUSSION

Refeeding patients with AN using a hospital-based, behavioral protocol may be accomplished safely and more rapidly than generally recognized, weight restoring most patients by discharge. Helpful elements may include the program's integrated, step-down structure; multidisciplinary team approach emphasizing group therapy to effect behavior change; and close medical monitoring for those with BMI < 15.

Etiologic and therapeutic analysis in patients with hypokalemic nonperiodic paralysis

BACKGROUND

Hypokalemic nonperiodic paralysis represents a group of heterogeneous disorders with a large potassium (K(+)) deficit. Rapid diagnosis of curable causes with appropriate treatment is challenging to avoid the sequelae of hypokalemia. We prospectively analyzed the etiologies and therapeutic characteristics of hypokalemic nonperiodic paralysis.

METHODS

Over an 8-year period, patients with hypokalemic nonperiodic paralysis were enrolled by excluding those with hypokalemic periodic paralysis due to acute shift of K(+) into cells. Blood and spot urine samples were collected for the measurements of electrolytes, pH, and biochemistries. Intravenous potassium chloride (KCl) at a rate of 10-20 mmol/h was administered until muscle strength recovered.

RESULTS

We had identified 58 patients with hypokalemic nonperiodic paralysis from 208 consecutive patients with hypokalemic paralysis, and their average K(+) concentration was 1.8 ± 0.2 mmol/L. Among patients with low urinary K(+) excretion (n = 17), chronic alcoholism, remote diuretic use, and anorexia/bulimia nervosa were the most common causes. Among patients with high urinary K(+) excretion (n = 41) and metabolic acidosis, renal tubular acidosis and chronic toluene abuse were the main causes, while primary aldosteronism, Gitelman syndrome, and diuretics were the leading diagnoses with metabolic alkalosis. The average KCl dose needed to restore muscle strength was 3.8 ± 0.8 mmol/kg. Initial lower plasma K(+), volume depletion, and high urinary K(+) excretion were associated with higher recovery KCl dosage. During therapy, patients with paradoxical hypokalemia (n = 32) who required more KCl supplementation than patients without (4.1 ± 0.7 vs 3.4 ± 0.7 mmol/kg, P < 0.001) often exhibited significantly higher plasma renin activity and received a higher volume of normal saline before its appearance.

CONCLUSIONS

Understanding the common etiologies of hypokalemic nonperiodic paralysis may aid in early diagnosis. Patients with initial lower plasma K(+), renal K(+) wasting, and hypovolemia required higher recovery K(+) dosage. Paradoxical hypokalemia is prone to develop in hypovolemic patients even during K(+) supplementation with volume repletion.

Renal control of calcium, phosphate, and magnesium homeostasis

Calcium, phosphate, and magnesium are multivalent cations that are important for many biologic and cellular functions. The kidneys play a central role in the homeostasis of these ions. Gastrointestinal absorption is balanced by renal excretion. When body stores of these ions decline significantly, gastrointestinal absorption, bone resorption, and renal tubular reabsorption increase to normalize their levels. Renal regulation of these ions occurs through glomerular filtration and tubular reabsorption and/or secretion and is therefore an important determinant of plasma ion concentration. Under physiologic conditions, the whole body balance of calcium, phosphate, and magnesium is maintained by fine adjustments of urinary excretion to equal the net intake. This review discusses how calcium, phosphate, and magnesium are handled by the kidneys.

FGF23: mediator of poor prognosis in a sizeable subgroup of patients with castration-resistant prostate cancer presenting with severe hypophosphatemia?

Castration-resistant prostate cancer (CRPC) is an advanced and incurable stage of the second most frequently diagnosed malignancy in men globally. Current treatment options improve survival modestly but eventually fail due to intrinsic or acquired therapeutic resistance. A hypothesis is presented wherein circulating levels of fibroblast growth factor 23 (FGF23), an endocrine member of the fibroblast growth factor family with phosphaturic properties, are proposed as a prognostic and predictive marker to identify CRPC patients with poor prognosis that are amenable to FGF23 antibody therapy (FGF23i) or treatment with fibroblast growth factor receptor inhibitors (FGFRi). With respect to the latter, FGF23 may also serve as a pharmacodynamic marker enabling individualized FGFRi dosing. We recently discovered that the development of severe and sustained hypophosphatemia in CRPC patients undergoing zoledronic acid therapy for bone metastases was associated with markedly worse prognosis compared to patients without or with only mild and transient hypophosphatemia. Severe hypophosphatemia is a typical manifestation of tumor-induced hypophosphatemic osteomalacia (TIO), a paraneoplastic condition mediated by FGF23 overexpression in most instances. While the postulated tumor-promoting role of FGF23 in CRPC or other malignancies has not yet been studied, several lines of evidence suggest that FGF23 may mediate both severe hypophosphatemia (via its endocrine properties) and aggressive CRPC behavior (via autocrine and paracrine activities): (i) FGF23 and the necessary signalling machinery (i.e. members of the fibroblast growth factor receptor [FGFR] family and the essential co-receptor α-KLOTHO [KL]) are highly expressed in a sizeable subgroup of CRPC patients; (ii) FGF/FGFR signalling plays important roles in prostate cancer; (iii) FGF23 can induce its own expression via a positive autocrine feedback loop involving FGFR1; and (iv) this positive feedback loop may be triggered by bone-targeted therapies frequently used for the treatment of CRPC-associated bone metastases. While there is a lack of personalized treatment strategies in the management of CRPC to date, FGF23 targeted therapy has the potential to fill this unmet clinical need in the not-so-distant future. In fact, FGFRi are currently in advanced clinical testing for a number of malignancies such as kidney and lung cancer, but there is a lack of conclusive data on FGFRi therapy in patients selected for FGF/FGFR pathway activation.

The ever-expanding conundrum of primary osteoporosis: aetiopathogenesis, diagnosis, and treatment

In recent years, as knowledge regarding the etiopathogenetic mechanisms of bone involvement characterizing many diseases has increased and diagnostic techniques evaluating bone health have progressively improved, the problem of low bone mass/quality in children and adolescents has attracted more and more attention, and the body evidence that there are groups of children who may be at risk of osteoporosis has grown. This interest is linked to an increased understanding that a higher peak bone mass (PBM) may be one of the most important determinants affecting the age of onset of osteoporosis in adulthood. This review provides an updated picture of bone pathophysiology and characteristics in children and adolescents with paediatric osteoporosis, taking into account the major causes of primary osteoporosis (PO) and evaluating the major aspects of bone densitometry in these patients. Finally, some options for the treatment of PO will be briefly discussed.

Serum phosphate as a risk factor for cardiovascular events in people with and without chronic kidney disease: a large community based cohort study

BACKGROUND

Serum phosphate is a known risk factor for cardiovascular events and mortality in people with chronic kidney disease (CKD), however data on the association of these outcomes with serum phosphate in the general population are scarce. We investigate this relationship in people with and without CKD in a large community-based population.

METHODS

Three groups from an adult cohort of the Quality Improvement in Chronic Kidney Disease (QICKD) cluster randomised trial (ISRCTN56023731) were followed over a period of 2.5 years: people with normal renal function (N = 24,184), people with CKD stages 1-2 (N = 20,356), and people with CKD stages 3-5 (N = 13,292). We used a multilevel logistic regression model to determine the association between serum phosphate, in these groups, and a composite outcome of all-cause mortality, cardiovascular events, and advanced coronary artery disease. We adjusted for known cardiovascular risk factors.

FINDINGS

Higher phosphate levels were found to correlate with increased cardiovascular risk. In people with normal renal function and CKD stages 1-2, Phosphate levels between 1.25 and 1.50 mmol/l were associated with increased cardiovascular events; odds ratio (OR) 1.36 (95% CI 1.06-1.74; p = 0.016) in people with normal renal function and OR 1.40 (95% CI 1.09-1.81; p = 0.010) in people with CKD stages 1-2. Hypophosphatemia (<0.75 mmol/l) was associated with fewer cardiovascular events in people with normal renal function; OR 0.59 (95% CI 0.36-0.97; p = 0.049). In people with CKD stages 3-5, hyperphosphatemia (>1.50 mmol/l) was associated with increased cardiovascular risk; OR 2.34 (95% CI 1.64-3.32; p<0.001). Other phosphate ranges were not found to have a significant impact on cardiovascular events in people with CKD stages 3-5.

CONCLUSIONS

Serum phosphate is associated with cardiovascular events in people with and without CKD. Further research is required to determine the mechanisms underlying these associations.