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Xue L, Geurts F, Meijer E, de Borst MH, Gansevoort RT, Zietse R, Hoorn EJ, Salih M. Kidney phosphate wasting predicts poor outcome in polycystic kidney disease. Nephrol Dial Transplant 2024; 39:1105-1114. [PMID: 37985930 DOI: 10.1093/ndt/gfad247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Indexed: 11/22/2023] Open
Abstract
BACKGROUND Patients with autosomal dominant polycystic kidney disease (ADPKD) have disproportionately high levels of fibroblast growth factor 23 (FGF-23) for their chronic kidney disease stage, however only a subgroup develops kidney phosphate wasting. We assessed factors associated with phosphate wasting and hypothesize that it identifies patients with more severe disease and predicts disease progression. METHODS We included 604 patients with ADPKD from a multicenter prospective observational cohort (DIPAK; Developing Intervention Strategies to Halt Progression of Autosomal Dominant Polycystic Kidney Disease) in four university medical centers in the Netherlands. We measured parathyroid hormone (PTH) and total plasma FGF-23 levels, and calculated the ratio of tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR) with <0.8 mmol/L defined as kidney phosphate wasting. We analysed the association of TmP/GFR with estimated GFR (eGFR) decline over time and the risk for a composite kidney outcome (≥30% eGFR decline, kidney failure or kidney replacement therapy). RESULTS In our cohort (age 48 ± 12 years, 39% male, eGFR 63 ± 28 mL/min/1.73 m2), 59% of patients had phosphate wasting. Male sex [coefficient -0.2, 95% confidence interval (CI) -0.2; -0.1], eGFR (0.002, 95% CI 0.001; 0.004), FGF-23 (0.1, 95% CI 0.03; 0.2), PTH (-0.2, 95% CI -0.3; -0.06) and copeptin (-0.08, 95% CI -0.1; -0.08) were associated with TmP/GFR. Corrected for PTH, FGF-23 and eGFR, every 0.1 mmol/L decrease in TmP/GFR was associated with a greater eGFR decline of 0.2 mL/min/1.73 m2/year (95% CI 0.01; 0.3) and an increased hazard ratio of 1.09 (95% CI 1.01; 1.18) of the composite kidney outcome. CONCLUSION Our study shows that in patients with ADPKD, phosphate wasting is prevalent and associated with more rapid disease progression. Phosphate wasting may be a consequence of early proximal tubular dysfunction and insufficient suppression of PTH.
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Affiliation(s)
- Laixi Xue
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Frank Geurts
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Esther Meijer
- Department of Nephrology, University Medical Center Groningen, Groningen, The Netherlands
| | - Martin H de Borst
- Department of Nephrology, University Medical Center Groningen, Groningen, The Netherlands
| | - Ron T Gansevoort
- Department of Nephrology, University Medical Center Groningen, Groningen, The Netherlands
| | - Robert Zietse
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Ewout J Hoorn
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Mahdi Salih
- Department of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, Rotterdam, The Netherlands
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Arcidiacono GP, Camozzi V, Zaninotto M, Tripepi G, Fusaro M, Torres MO, Zanchetta F, Cannito M, Cecchinato A, Diogo M, Peleg Falb M, Plebani M, Simioni P, Sella S, Giannini S. Tubular phosphate transport: a comparison between different methods of urine sample collection in FGF23-dependent hypophosphatemic syndromes. Clin Chem Lab Med 2024; 62:1126-1132. [PMID: 38295343 DOI: 10.1515/cclm-2023-1292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/23/2024] [Indexed: 02/02/2024]
Abstract
OBJECTIVES Tubular maximum phosphate reabsorption per glomerular filtration rate (TmP/GFR) is used to evaluate renal phosphate reabsorption and it is a useful tool for the differential diagnosis of hypophosphatemic syndromes. TmP/GFR is typically calculated from fasting plasma and second morning void urine samples, obtained 2 h after the first void (TmP/GFR 2 h). The purpose of this study was to evaluate if TmP/GFR calculated from 24 h urine collection (TmP/GFR 24 h) can be used as an alternative for TmP/GFR 2 h in patients with urine phosphate wasting. METHODS We enrolled adult patients with X-linked hypophosphatemia (XLH) or tumor-induced osteomalacia (TIO). All patients underwent blood and urine sample collections, to calculate TmP/GFR 24 h and TmP/GFR 2 h. RESULTS Twenty patients (17 XLH and 3 TIO), aged 24-78 years, were included. All patients had low TmP/GFR 2 h (0.35 mmol/L, IQR 0.24-0.47 mmol/L) and TmP/GFR 24 h (0.31 mmol/L, IQR 0.22-0.43 mmol/L). The concordance correlation coefficient between TmP/GFR 2 h and TmP/GFR 24 h was 0.86 (95 % CI: 0.69-0.93), with a systematic bias of 0.05 mmol/L (95 % limits of agreement: -0.10 to 0.20). Furthermore, in 70 % (i.e., 14 patients out of 20) and 80 % (i.e., 16 patients out of 20) of cases the difference between TmP/GFR 2 h and TmP/GFR 24 h was within ±30 % and ±35 %, respectively. CONCLUSIONS Despite TmP/GFR 2 and 24 h show a relatively suboptimal agreement, the difference between the two parameters appears to be small and not clinically significant in the setting of adult patients with FGF23-dependent urine phosphate wasting and secondary hypophosphatemia.
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Affiliation(s)
| | - Valentina Camozzi
- Department of Medicine, Endocrinology Unit, University of Padova, Padova, Italy
| | - Martina Zaninotto
- Department of Medicine, Laboratory Medicine Unit, University of Padova, Padova, Italy
| | - Giovanni Tripepi
- National Research Council (CNR), Institute of Clinical Physiology (IFC), Clinical Epidemiology of Renal Diseases and Hypertension, Ospedali Riuniti, Reggio Calabria, Italy
| | - Maria Fusaro
- National Research Council (CNR), Institute of Clinical Physiology (IFC), Pisa, Italy
| | | | - Francesca Zanchetta
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
| | - Michele Cannito
- Department of Medicine, Endocrinology Unit, University of Padova, Padova, Italy
| | - Alberta Cecchinato
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
| | - Martin Diogo
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
| | - Mor Peleg Falb
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
| | - Mario Plebani
- Department of Medicine, Laboratory Medicine Unit, University of Padova, Padova, Italy
| | - Paolo Simioni
- Department of Medicine, General Medicine and Thrombotic and Hemorrhagic Diseases Unit, University of Padova, Padova, Italy
| | - Stefania Sella
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
| | - Sandro Giannini
- Department of Medicine, Clinica Medica 1, University of Padova, Padova, Italy
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Friedman P, Mamonova T. The molecular sociology of NHERF1 PDZ proteins controlling renal hormone-regulated phosphate transport. Biosci Rep 2024; 44:BSR20231380. [PMID: 38465463 PMCID: PMC10987488 DOI: 10.1042/bsr20231380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 03/07/2024] [Accepted: 03/08/2024] [Indexed: 03/12/2024] Open
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) control extracellular phosphate levels by regulating renal NPT2A-mediated phosphate transport by a process requiring the PDZ scaffold protein NHERF1. NHERF1 possesses two PDZ domains, PDZ1 and PDZ2, with identical core-binding GYGF motifs explicitly recognizing distinct binding partners that play different and specific roles in hormone-regulated phosphate transport. The interaction of PDZ1 and the carboxy-terminal PDZ-binding motif of NPT2A (C-TRL) is required for basal phosphate transport. PDZ2 is a regulatory domain that scaffolds multiple biological targets, including kinases and phosphatases involved in FGF23 and PTH signaling. FGF23 and PTH trigger disassembly of the NHERF1-NPT2A complex through reversible hormone-stimulated phosphorylation with ensuing NPT2A sequestration, down-regulation, and cessation of phosphate absorption. In the absence of NHERF1-NPT2A interaction, inhibition of FGF23 or PTH signaling results in disordered phosphate homeostasis and phosphate wasting. Additional studies are crucial to elucidate how NHERF1 spatiotemporally coordinates cellular partners to regulate extracellular phosphate levels.
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Affiliation(s)
- Peter A. Friedman
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
| | - Tatyana Mamonova
- Laboratory for G Protein-Coupled Receptor Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
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Carnevale V, Nieddu L, Scillitani A, Tinti MG, Eller-Vainicher C, Cosso R, Rendina D, Falchetti A. Calcium-phosphate homeostasis and insulin resistance in men. Nutr Metab Cardiovasc Dis 2024; 34:353-359. [PMID: 37788961 DOI: 10.1016/j.numecd.2023.08.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 08/02/2023] [Accepted: 08/23/2023] [Indexed: 10/05/2023]
Abstract
BACKGROUND AND AIMS Data on P homeostasis in insulin resistance (IR) are still conflicting. We investigated calcium-phosphate homeostasis parameters in men with/without IR. METHODS AND RESULTS 177 volunteers (aged 61.62 ± 12.11), whose body mass index (BMI) was 29.97 ± 6.35, were studied. On fasting blood and spot urine samples, we measured serum creatinine, sodium (sNa), potassium (sK), chloride (sCl), calcium (sCa), phosphate (sP), alkaline phosphatase total activity (ALP), glucose, insulin, parathyroid hormone (PTH), 25-hydroxy-vitamin D [25(OH)D], and urinary electrolytes corrected for creatinine (uNa/Cr, uK/Cr, uCl/Cr, uCa/Cr, and uP/Cr). Through the QUICKI index, we separated subjects with (IR+, n = 68) or without (IR-, n = 109) IR, and their parameters were compared. Associations were assessed by age-adjusted partial correlation, whose coefficients were compared by Fisher's transform. IR + had higher sP (3.54 ± 0.65 vs. 3.35 ± 0.47, p = 0.044) and lower uCa/Cr levels (0.073 ± 0.056 vs. 0.095 ± 0.072, p = 0.047) than IR-. BMI correlated with sP (r = 0.21, p < 0.05) and PTH (r = 0.29, p < 0.01). QUICKI negatively correlated with sCa (r = -0.22, p < 0.05) and positively with uCa/Cr (r = 0.21, p < 0.05), in turn correlating with uNa/Cr (r = 0.45, p < 0.001). In both groups, uCa/Cr correlated with eGFR and uNa/Cr (p < 0.05 to p < 0.001). In IR + only, sP correlated with BMI, PTH with insulin, and uP/Cr (p < 0.05 for all). IR+ and IR-coefficients differed (p < 0.05 to p < 0.001) for the correlation of sP with BMI and of PTH with insulin and uP/Cr. CONCLUSION The higher sP and lower uCa/Cr levels found in men with IR + suggest that IR could modulate calcium-phosphate homeostasis, likely by affecting their renal handling.
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Affiliation(s)
- Vincenzo Carnevale
- Unit of Internal Medicine, "Casa Sollievo della Sofferenza" Hospital, IRCCS, San Giovanni Rotondo (FG), Italy.
| | | | - Alfredo Scillitani
- Unit of Endocrinology, "Casa Sollievo della Sofferenza" Hospital, IRCCS, San Giovanni Rotondo (FG), Italy
| | | | | | - Roberta Cosso
- Unit of Functional and Osteoarticular Rehabilitation, "San Giuseppe" Hospital IRCCS, Istituto Auxologico Italiano, IRCCS, Piancavallo (Milan), Italy
| | - Domenico Rendina
- Department of Clinical Medicine and Surgery, "Federico II" University of Naples, Naples, Italy
| | - Alberto Falchetti
- Experimental Research Laboratory on Bone Metabolism, Istituto Auxologico Italiano, IRCCS, Milan, Italy
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5
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Farrance I, Frenkel R, Choy KW. Uncertainty in measurement and the renal tubular reabsorption of phosphate. Clin Chem Lab Med 2023; 61:2178-2185. [PMID: 37462507 DOI: 10.1515/cclm-2023-0451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 06/29/2023] [Indexed: 10/26/2023]
Abstract
OBJECTIVES The ratio of tubular maximum reabsorption of phosphate to glomerular filtration rate (TmP/GFR) is used to evaluate renal phosphate transport. TmP/GFR is most probably calculated using the formula described by Kenny and Glen or obtained from the nomogram described by Walton and Bijvoet. Even though the calculation itself is well described, no attention has been given to its measurement uncertainty (MU). The aim of this study is to provide a procedure for evaluating the MU of the Kenny and Glen formula; a procedure which is based on the Evaluation of measurement data - Guide to the expression of uncertainty in measurement (GUM). METHODS TmP/GFR is a quantity value calculated from the input of measured values for serum (plasma) phosphate and creatinine, plus measured values of urine phosphate and creatinine. Given the measurement uncertainty associated with these input quantities, the GUM describes the mathematical procedures required to determine the uncertainty of the calculated TmP/GFR. From a medical laboratory perspective, these input uncertainties are the standard deviations of the respective internal quality control estimates for serum and urine phosphate, plus serum and urine creatinine. RESULTS Based on representative measurements for the input quantities and their associated standard uncertainties, the expanded relative uncertainty for a calculated TmP/GFR is approximately 3.0-4.5 %. CONCLUSIONS With the continued relevance of the TmP/GFR procedure and the use of creatinine clearance as an estimate of GFR, the addition of an uncertainty estimate is important as an adjunct to this diagnostic procedure.
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Affiliation(s)
- Ian Farrance
- Discipline of Laboratory Medicine, School of Health and Biomedical Sciences, RMIT University, Bundoora, VIC, Australia
| | - Robert Frenkel
- 96 Shirley Road, Roseville, NSW, 2069, Australia. Former affiliation: National Measurement Institute, West Lindfield, NSW, Australia
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Pallone SG, Kunii IS, da Silva REC, Lazaretti-Castro M. Use of Teriparatide in Hyperphosphatemic Familial Tumor Calcinosis: Evaluating the Interaction Between FGF23 and PTH on the Phosphaturic Effect. Calcif Tissue Int 2022; 111:102-106. [PMID: 35338393 DOI: 10.1007/s00223-022-00969-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 03/09/2022] [Indexed: 11/02/2022]
Abstract
Hyperphosphatemic familial tumor calcinosis (HFTC) is a rare disease characterized by hyperphosphatemia and calcium and phosphorus crystal deposition. It occurs due to the loss of function of FGF23. Herein, we report a case of a 50-year-old woman diagnosed with HFTC (homozygous variant in the GALNT3 gene, c.803_804 C insertion) with a history of ectopic calcifications in the past 30 years. Laboratory tests on admission were as follows: phosphate (P) 7.1 mg/dL (Normal range (NR) 2.5-4.5 mg/dL), FGF23 c-terminal 2050 RU/mL (NR < 150 RU/mL), and intact FGF23 (iFGF23) 18.93 pg/mL (NR 12.0-69.0 pg/mL). Treatment with acetazolamide, sevelamer, and a phosphorus-restricted diet was started, but phosphatemia remained high and calcifications continued to progress. In an attempt to further decrease P, a 36-day cycle of teriparatide (TPTD) 20 mcg twice daily was added, decreasing P from 6.2 to 5.2 mg/dL and increasing the 1.25(OH)2 vitamin D by 34.2%. As urinalysis was not feasible at the end of the 36-day cycle, a second cycle was performed for another 28 days, producing a similar decrease in P (from 6.4 to 5.5 mg/mL) and an evident decrease in the rate of tubular reabsorption of P (from 97.2 to 85.3%), however, accompanied by a worrying increase in calciuria. The use of TPTD 20 mcg twice daily in a patient with genetic resistance to FGF23 (HFTC) was associated with consistent increase in phosphaturia and reduction in phosphatemia, in addition to an increase in calcitriol. The resulting hypercalciuria precludes the therapeutic use of TPTD in HFTC and suggests an important role of FGF23, not only in phosphate homeostasis but also in avoiding any excess of calcitriol.
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Affiliation(s)
- Sthefanie Giovanna Pallone
- Endocrinology Unit, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil.
| | - Ilda Sizue Kunii
- Endocrinology Unit, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Renata Elen Costa da Silva
- Endocrinology Unit, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Marise Lazaretti-Castro
- Endocrinology Unit, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
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Ovejero D, Hartley IR, de Castro Diaz LF, Theng E, Li X, Gafni RI, Collins MT. PTH and FGF23 Exert Interdependent Effects on Renal Phosphate Handling: Evidence From Patients With Hypoparathyroidism and Hyperphosphatemic Familial Tumoral Calcinosis Treated With Synthetic Human PTH 1-34. J Bone Miner Res 2022; 37:179-184. [PMID: 34464000 DOI: 10.1002/jbmr.4429] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/12/2021] [Accepted: 08/16/2021] [Indexed: 12/27/2022]
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) both influence blood phosphate levels by regulating urinary phosphate reabsorption. Clinical data suggest that adequate renal phosphate handling requires the presence of both FGF23 and PTH, but robust evidence is lacking. To investigate whether the phosphaturic effects of PTH and FGF23 are interdependent, 11 patients with hypoparathyroidism, which features high blood phosphate in spite of concomitant FGF23 elevation, and 1 patient with hyperphosphatemic familial tumoral calcinosis (HFTC), characterized by deficient intact FGF23 action and resulting hyperphosphatemia, were treated with synthetic human PTH 1-34 (hPTH 1-34). Biochemical parameters, including blood phosphate, calcium, intact FGF23 (iFGF23), nephrogenic cAMP, 1,25(OH)2 vitamin D (1,25D), and tubular reabsorption of phosphate (TRP), were measured at baseline and after hPTH 1-34 treatment. In patients with hypoparathyroidism, administration of hPTH 1-34 increased nephrogenic cAMP, which resulted in serum phosphate normalization followed by a significant decrease in iFGF23. TRP initially decreased and returned to baseline. In the patient with HFTC, hPTH 1-34 administration also increased nephrogenic cAMP, but this did not produce changes in phosphate or TRP. No changes in calcium were observed in any of the studied patients, although prolonged hPTH 1-34 treatment did induce supraphysiologic 1,25D levels in the patient with HFTC. Our results indicate that PTH and FGF23 effects on phosphate regulation are interdependent and both are required to adequately regulate renal phosphate handling. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.
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Affiliation(s)
- Diana Ovejero
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.,Musculoskeletal Research Unit, Hospital del Mar Medical Research Institute, Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Barcelona, Spain
| | - Iris R Hartley
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Luis Fernandez de Castro Diaz
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Elizabeth Theng
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Xiaobai Li
- Biostatistics and Clinical Epidemiology Services (XL), National Institutes of Health, Bethesda, MD, USA
| | - Rachel I Gafni
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Michael T Collins
- Skeletal Disorders and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Takashi Y, Toyokawa K, Oda N, Muta Y, Yokomizo H, Fukumoto S, Kawanami D. Combined treatment by burosumab and a calcimimetic can ameliorate hypophosphatemia due to excessive actions of FGF23 and PTH in adult XLH with tertiary hyperparathyroidism: A case report. Front Endocrinol (Lausanne) 2022; 13:1004624. [PMID: 36531500 PMCID: PMC9751939 DOI: 10.3389/fendo.2022.1004624] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 11/15/2022] [Indexed: 12/05/2022] Open
Abstract
INTRODUCTION X-linked hypophosphatemia (XLH) is the most prevalent type of heritable fibroblast growth factor 23 (FGF23)-related hypophosphatemic rickets. Recently, anti-FGF23 antibody, burosumab, has become clinically available. We herein report a patient with adult XLH and tertiary hyperparathyroidism. CASE PRESENTATION The serum phosphate level and tubular maximum reabsorption of phosphate per glomerular filtration rate (TmP/GFR) remained low, despite burosumab treatment. While the influence of the relationship between FGF23 and parathyroid hormone (PTH) on the phosphaturic effect is unclear, it was considered that a high level of PTH due to tertiary hyperparathyroidism remains to suppress renal phosphate reabsorption. A calcimimetic, evocalcet, increased the serum phosphate level and TmP/GFR. DISCUSSION AND CONCLUSION Therefore, it is important to evaluate the presence of secondary-tertiary hyperparathyroidism in patients whose serum phosphate level does not increase with burosumab treatment.
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Affiliation(s)
- Yuichi Takashi
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
- *Correspondence: Yuichi Takashi,
| | - Kyoko Toyokawa
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Naoki Oda
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Yoshimi Muta
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Hisashi Yokomizo
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
| | - Seiji Fukumoto
- Department of Molecular Endocrinology, Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Daiji Kawanami
- Department of Endocrinology and Diabetes Mellitus, Fukuoka University School of Medicine, Fukuoka, Japan
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Nashawi M, Ahmed MS, Amin T, Abualfoul M, Chilton R. Cardiovascular benefits from SGLT2 inhibition in type 2 diabetes mellitus patients is not impaired with phosphate flux related to pharmacotherapy. World J Cardiol 2021; 13:676-694. [PMID: 35070111 PMCID: PMC8716977 DOI: 10.4330/wjc.v13.i12.676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/02/2021] [Accepted: 11/30/2021] [Indexed: 02/06/2023] Open
Abstract
The beneficial cardiorenal outcomes of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in patients with type 2 diabetes mellitus (T2DM) have been substantiated by multiple clinical trials, resulting in increased interest in the multifarious pathways by which their mechanisms act. The principal effect of SGLT2i (-flozin drugs) can be appreciated in their ability to block the SGLT2 protein within the kidneys, inhibiting glucose reabsorption, and causing an associated osmotic diuresis. This ameliorates plasma glucose elevations and the negative cardiorenal sequelae associated with the latter. These include aberrant mitochondrial metabolism and oxidative stress burden, endothelial cell dysfunction, pernicious neurohormonal activation, and the development of inimical hemodynamics. Positive outcomes within these domains have been validated with SGLT2i administration. However, by modulating the sodium-glucose cotransporter in the proximal tubule (PT), SGLT2i consequently promotes sodium-phosphate cotransporter activity with phosphate retention. Phosphatemia, even at physiologic levels, poses a risk in cardiovascular disease burden, more so in patients with type 2 diabetes mellitus (T2DM). There also exists an association between phosphatemia and renal impairment, the latter hampering cardiovascular function through an array of physiologic roles, such as fluid regulation, hormonal tone, and neuromodulation. Moreover, increased phosphate flux is associated with an associated increase in fibroblast growth factor 23 levels, also detrimental to homeostatic cardiometabolic function. A contemporary commentary concerning this notion unifying cardiovascular outcome trial data with the translational biology of phosphate is scant within the literature. Given the apparent beneficial outcomes associated with SGLT2i administration notwithstanding negative effects of phosphatemia, we discuss in this review the effects of phosphate on the cardiometabolic status in patients with T2DM and cardiorenal disease, as well as the mechanisms by which SGLT2i counteract or overcome them to achieve their net effects. Content drawn to develop this conversation begins with proceedings in the basic sciences and works towards clinical trial data.
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Affiliation(s)
- Mouhamed Nashawi
- Department of Internal Medicine, Baylor Scott and White All Saints Medical Center, Fort Worth, TX 76132, United States
| | - Mahmoud S Ahmed
- Division of Medicine-Cardiology, UT Health San Antonio, San Antonio, TX 78229, United States
| | - Toka Amin
- Division of Medicine-Cardiology, UT Health San Antonio, San Antonio, TX 78229, United States
| | - Mujahed Abualfoul
- Department of Internal Medicine, Faculty of Medicine, Cairo University, Dallas, TX 75203, United States
| | - Robert Chilton
- Department of Internal Medicine, Methodist Dallas Medical Center, Dallas, TX 75203, United States
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High bone turnover and hyperparathyroidism after surgery for tumor-induced osteomalacia: A case series. Bone Rep 2021; 15:101142. [PMID: 34901333 PMCID: PMC8640873 DOI: 10.1016/j.bonr.2021.101142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 10/04/2021] [Accepted: 10/07/2021] [Indexed: 11/23/2022] Open
Abstract
Tumor-induced osteomalacia (TIO) is an ultrarare disorder that is caused by renal phosphate wasting due to uncontrolled tumoral production of fibroblast growth factor 23 (FGF23) from phosphaturic mesenchymal tumors. Surgical removal of the tumor is curative. There is limited information on the biochemical changes in mineral metabolism and bone remodeling activity after surgery, but it is reported that surgery is followed by a hungry bone syndrome (HBS) with hypocalcemia and secondary hyperparathyroidism. We report the biochemical response to surgery in two patients, who presented with severe TIO, as manifested by proximal myopathy, multiple stress fractures, high FGF23, low serum phosphate, low maximum renal phosphate reabsorption threshold (TmP/GFR), and low 1,25-dihydroxy-vitamin D (1,25(OH)2D). Prior to surgery, both patients developed secondary hyperparathyroidism and one case had progressed to tertiary hyperparathyroidism. After surgery there was normalization of FGF23, TmP/GFR, and phosphate. High 1,25(OH)2D was recorded. One patient had hypocalcaemia and worsening secondary hyperparathyroidism consistent with HBS; the other patient did not have hypocalcemia but had worsening tertiary hyperparathyroidism that only resolved with cinacalcet. There was a marked increase in bone remodeling markers, both resorption and formation, consistent with a high bone turnover state. There was a different pattern of change in bone specific alkaline phosphatase, reflecting healing of osteomalacia. Biochemical monitoring in the post-surgical management of TIO is warranted for guiding adjustments in medical intervention, both short-term and long-term. Future use of burosumab prior to surgery for TIO may ameliorate the immediate post-surgery effects.
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